Pulsed Steels
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Qin, Rongshan
Rahnama, A.
Zhang, X.F.
Lu, W.J.
Elliott-Bowman, B.
A lecture given by Rongshan Qin, at the Adventures in the Physical Metallurgy of Steels (APMS) conference held in Cambridge University. Short electrical pulses are applied to dramatically modify the structure of steel. Pulsed electric current affects kinetic barrier in non-equilibrium processes and thermodynamic state in non-equilibrium systems. Application of the high density and short duration current pulses in steel processing enables the fabrication of novel microstructure and hence the new property. Our experimental observations have demonstrated the powerful and versatile effects of pulses on microstructure evolution in steels, e.g. pulse-induced grain coarsening, grain refinement, texture control, low temperature transformation and novel phase formation. This reveals significant potential in using electrical pulses to tailor the microstructure of steels. The preliminary theoretical understanding of the observed phenomena has been developed based on the thermodynamic consideration. Kinetic aspect of the effect of the pulses on microstructure transformation, however, is still in its very early stage and requires more attention.
 Ok. The next presenter is Wang Shan Xin from Imperial College London, who will be talking about the applications of his work of electropulsing in steel formation. Thank you very much. I'm interested in cheap steel in extremely short time. The whole short is that if you blink your eye once, I should have done my experiments 1,000 times. That means if you blink your eye, blink your eye, take 0.1 second, and my experiment should take less than 100 microseconds. So I'll firstly show some of the results, and then we'll discuss the mechanics about these. The way I'm using is electric current pulse, because this very short time is a pulse, and I use electric current pass through the steel. So I have quite a few authors here, and I especially should acknowledge those people who are also interested in this very special processing method that is sponsored by the project, and also those people who helped me a lot. So let me first show you some results. This is a piece of steel. It's a commercial pallet steel. We contain 0.8% of carbon. It's a commercial one. You can see it everywhere. So the sample was more than 10 centimeters long, and the diameter is about 2 millimeters. So the max structure, if you look at the max structure, the max goal. So it should be like this, because our cold draw to the steel wire with 60% of reduction at room temperature. Cold draw date. So without any addicting afterwards. So if you look at the max structure, it's something like this. This is a cementite place. The ferrite is actually away. So this is the one. And then I put this steel into my process of facility at room temperature with one pulse. So totally it's less than 100 microsecond. And during the time, you don't see anything happening. You didn't hear a voice, so boom, or something. And you didn't see the steel wire actually become powder or whatever. It's a steel wire, and you didn't see the color of the steel wire change into some others, like red color. And afterwards, I put my finger on the steel wire and didn't feel I can hold my finger for the wire. So that's a kind of phenomenon. However, if you see that steel wire at SEM, you see this is a cementite place. A region was this, now changed into this. Be careful of the scale. Here is 500 nanometer. So in this 10 centimeter steel wire, I choose 12 different points. Exam, and everywhere got exactly the same max structure. So cementite place changed into a particle with average size of 30 nanometers. So when we examined the mechanical property, we found this one, the thickness of this one was about 400. And this one was a little bit higher than this. You know, this is a coated joint without annealing. And this one has already removed all the internal stress, and it is still much harder than this. Another surprising what we found is electrical conductivity of this state is improved 100%. It's almost double. The electrical conductivity of this steel is almost double of this. So that is one situation for palliative steel wire. And then I have another one. This is another steel. We call it trip steel. However, at the moment, it's a hot road steel without any retained austenite, although we call it trip. So if you look at here, we have a lot of ferrite particles here, combined with this complicated max structure. If you look at this, you do not see any anisotropy here, max structure. You don't see that. And again, at room temperature, electrical pulse, this steel, with 3,000 times, passes through 3,000 pulses through this piece of steel at room temperature at a frequency of 1 hertz, which means each second passes through one pulse. And the pulse width at this moment is 20 microseconds. So after 3,000 times, if you put that into optical mass structure, you will see a lot of lines, black lines along the electrocurrent direction. This is an image of SEM, you see this original isotropic property has completely lost. All of these phase change into these, along the electrocurrent direction. So if you use a higher resolution SEM, you will see even inside those lines, the cementite and ferrite lines, are all along the electrocurrent direction. So now we are interested to develop a steel with all the, with this kind of mass structure is everywhere, not only just this. So this is again at room temperature for this steel. So now let me show you another example. So this is a 316L stainless steel. We know this problem with this steel is if you do an anilium, and then secondary phase will fall. So if you anilate at a temperature around 1000 degree, you will see a lot of those white particles, those are secondary phase particles. So this is 316L stainless steel, contains very high chromium, moly and nickel. So if you form these secondary particles, so these secondary particles are very rich in chromium and moly pedinium. In that case, the area throughout these will have a poor chromium and a poor moly. So if these things happen, at that, those poor chromium and a poor moly area will have poor corrosion resistors. So we try not to have these secondary phase particles. However, it's very, very difficult to do. So what we are doing is we put two samples in the furnace, exactly same samples, but one of them linked with electropause in another without. So when we did heat treatment, and then analyzed two samples, one of them is this one. So this is one of the two samples, one is this one, the other is this one. So the secondary phase is not formed. Electropause has suspended the formation of secondary phase. That's one thing. You see much less secondary phase particles at this side. Again, if we analyze the composition inside here, we thought even though we formed some inside, the chromium and molybadinium difference between the particle and the matrix are much, much smaller. So by this one, the electropause has reduced the segregation of this chromium, nickel, and moly in steady-stew. So that's another thing we have done. So now let me tell you another result which we just made very recently, but this has already been published. This is, we use this technology at liquid steel. So it's in liquid state. The sample here is 1.5 centimeter diameter in-galls. We mount that without electropause and a quarter. What we see is inside this steel, we have lot of magnesium sulfur inclusions. So those inclusions are almost round-shaped and distributed everywhere. If you look, examine your cast. Your cast is everywhere. However, if we do the same thing, but connect with our electropousing for 20 minutes. Cast is 20 microseconds, each pass is 20 microseconds, and use a frequency of 1 hertz. And then what we found, things that vary differently, is inside the ingots. Internal ingots is inclusion-free. All the inclusions are gone from inside. However, at a boundary, top, side, and some of the bottom, we have lots of inclusions. All the inclusions are moved from the central part to the outside part. So ideal way is we put the leg or top of that at the collect all the inclusions so that we can make soup clean steels. So this is one thing. So we have expelling inclusions from inside the steel, liquid steel to the surface. Another thing, what we notice at this case, this is almost a spherical particle. Look at it here. All the magnesium sulfur inclusions form this very strange morphology. It's almost everywhere. This is something very strange, and we don't really know what's that. Has electropause affected the interfacial energy? Otherwise, why don't these go to a round shape? Round shape will have much smaller surface area and a little free energy. So that's some of the experiments we have about using the facility. Now let's come into the detail of the technology and analyze what's happening and what can be done further. So firstly, when I talk about passing through high-density electric current to steel, many people immediately think there's a heat there. So now let's calculate what kind of heat has generated by this electric current. It can very easily go through this. I know people don't like the equation, but this equation is very special because they are so easy. And we know them from secondary school. So if we calculate the total energy added by this electropousing, so in my facility, I have two different options. One is I can fix the voltage. Another is I can fix the current, electric current. So suppose I fix the electric current, and this is the current, this is the electrical resistance of the sample, and this is the pulse duration. So use this equation so I can calculate the total energy of this electric current pulse. Now I suppose all those energy has changed into heat and heat up the sample. So in that case, this is the total mass of the sample, this is the specific heat of the sample, and this is the temperature rising. So suppose all of the electric current didn't do anything else, just the heat of the sample. And then this equal to this. From here, I can immediately get the temperature rising due to one pulse is this, just this divided by mc. So here, again, this is the resistance of the sample. I calculate resistance of the sample equals to the density multiplied by the length of the sample divided by the cross-section area of the sample. I have this r. And this is the mass equals the density of the sample, the steel sample, multiplied by the volume of the sample. So it's the length, the cross-section. So if I substitute r to here, m to here, and I get the temperature rising due to one electro-pulse should be this, because current divided by cross-section area is the current in density, so I can actually have this. So you know, it's a very, very simple mathematics, and I have assumed all the electric current energy has to be converted to the heat to heat up the sample. And then let's apply this one to our calculation. I substitute all the parameters of 316L's steady steel-ing, heat capacity, this density, we know 7.8, and its electrical resistivity is this. Now what I need is each pulse is 20 microseconds, and this is current density. Look, this is a astonishing high. Actually what I used to generate those results are not that high. This is 100 times higher than what I used. So it's a ridiculous high. So because I want to do a maximum calculation. So I use a 100 times higher than what I actually used. If you substitute all of that into this, so each pulse can actually increase the temperature of the sample by 0.217 degrees. Okay? It's nothing. And remember, for all the experiments I used, the pulse frequency is 1 hertz. So if I put that in, that means the heat, the heat up rate is 0.217K per second. You know, you know, steel processing, this is a nothing, and it's almost 100 times the high than what I've done. This is average kind. But some people may argue, okay, there's a percolation here. Somewhere I got a high density in the other place, but I already have used 100 times the high than the average. So that's one thing. So the electropulse effect is not a heat effect. Okay? That's one thing. Another. So another thing is some people say, you can do this in your laboratory because your sample is small, but you may not be able to scale up to the industry because industry needs to have a very, very big steel. So can you do that? Let's calculate the energy consumption in the pulse. So the total work in single electropulse is this. Okay? It's the same. So required electric power. Power is a work divided by time. So here I got a pulse frequency. I normally use one hertz. So if we substitute all the parameters we used before in, so each, so get all those of the parameter in, so each pulse actually consumed zero point. The power need to generate this electropulse process is 0.304 watts. That's again nothing. So I can tell you in my laboratory, the facility I used to generate the electropulse is 80 watts. And the electric current was generated at an electrical potential of 20 watts. So for that kind of power, it's nothing because you have a home, we can easily buy the bulb. The power is 100 watts. The mass facility is only 80. So it's very easily to scale up. So but those we know we can apply this, but what is the mechanism? Okay. So there's one thing that's just, it's complicated. I don't believe we have solved this. But one thing is let's analyze this from some dynamics way. So if we have some mass structure change, whether phase transition or just the structure relaxation or whatever, so the total free energy at here is free energy change is a chemical free energy change plus surface energy change plus electric current associated free energy change. Okay. Those two we all know, but what about this term? So this one, fortunately, we know this one can be calculated by this equation. So this equation is a free energy associated with the electropause equals this is a magnetic permavillity at pi. This is the current density distribution after the mass structure evolution. Okay. So this is the current density distribution before the mass structure evolution. And then you have this term which make this calculation very complicated, very, very nonlinear. So what we have done is we have actually developed a software where I able to calculate the current distribution if you have any kind of phase transition or any kind of mass structure change, not only phase transition. For example, if I have a inclusion at the moment, the inclusion is here, but the next moment the inclusion move up to here. So if you look at that case, this chemical free energy difference is the same. You don't have any change because there's no phase transition. This one is the same, but this one is different because if you have an inclusion move from this part to the surface and then you have a completely different electric current distribution. So if you have this completely different electric current distribution, you will have a completely different free energy change. And then because that one, so some of the move will be favored by this electro-pousing, but some of them will not. Okay. So that's the case about inclusion removing. So we tested this against the, so this is a show of analyze for the electric current distribution and we are able to calculate all the free energy change. This is something like our pair line in a layered structure, but that one, all the layers actually the change separate into this small disintegrated part, same at times. And we are able to calculate the current density distribution and again we can get a total free energy. So we will be able to know in this electro-pousing, you actually will let your grace to separate into different several things or you actually will have a cause. So this one, when we calculate, use that equation to calculate the microstructure refinement because sometimes we use that. So we, and this is our theoretical value and this is experimental value not did by ourselves. It's a group here in America. Professor has current as group. So we see as a great, very well and we further predicted and say we can use this electro-pousing to fabricate nanostructure material. Those are required current density. Those are all theoretical work. And again, we found if we use the electro-pousing, we are able to increase the fatigue of life of the material. So we calculated, but if we, for different material, if we use electric current density above a certain value and we are able to hear the crack. So we have done this before and we were able to improve the fatigue of life of low-carbon steel for 34 times. Okay, so those are just my advantage in this steel process. It is a conclusion. Thank you very much. Okay, that's a very novel topic there indeed. And does anyone have any questions? Straight away, yes? See if we can get both our microphones over to this row. Just use that one. Thank you very much for your great presentation. So you show us the microstructure change due to the electric current. So the last part of this presentation, you said just thermodynamic approaches. But to change the microstructure, we must consider the kinetics. So what do you think on that? We did some work and also in literature you can find some work. Pacing electric current can lower the connected barrier of some transformation, but in another group of transformation, you can, electric current can actually increase the connected barrier. So there are some works and we also did some. However, kinetic understanding of this mechanism is very poor at the moment. There are a lot of things we don't understand. Your passing time is very short, I think. So point one second or load one second. If you use one pulse, it's certainly less than 100 microsecond. First time is very short. There are some solid result people found is that the power increase diffusivity many times. That's what people agreed. Another is change the connected barrier. Some of them reduce a lot or even completely remove the connected barrier. Another case you can actually increase the connected barrier. But for rest of things, it's very basic in the early stage. Thank you very much. Okay, Joe. You talked about the, putting this into industry is a limit on the sample size. You said that the power doesn't limit it. Is there a limit imposed by the magnetic skin effect? If you actually want to put a sharp rise and fall of current into something, the current only tends to flow through the surface of the thing. So the skin effect is related to the current frequency. So you can calculate that accurately. If you use that direct current, then you won't have a skin effect at all. You're pulsing it though. Is that not equivalent to a single wave of an AC pulse? Need to calculate it because, for example, a lot of automotive steels. What we are interested is a thin plate or steel wires. For those, you have a few millimeter thickness. You can ignore that. If you calculate about one hertz, if you increase the frequency. Is it not the 20 microsecond period that actually determines the stickling effect? It's a hertz. It's a one hertz. It's a one hertz. So that's what we need though. If you use a very high frequency, for example, 300 hertz, and you see the skin effect. So in that time, there are some of the experiments reported before. People use that to modify the surface property of the material. They can actually generate a morphos at a surface layer of the material. Oh, they deliberately do it. Extremely high frequency. Interesting idea. Thank you. Okay. Yes? Long Shen, thank you for your interesting presentation. I have a very basic question. You did very elementary calculation in the beginning. So if you are going to melt steel with an electrical furnace, normally you spend something around 400 kilowatt hours for tons. So let's say four kilowatt hours, four kilogram. So do you have any number for something on mass of iron, of course, or anything about related moles about your... So how much energy really spent for unit of mass in your process, basically, comparing it to the melting energy, roughly speaking, the entropy of melting we know which is a good number for any metal. So the total amount of energy we spent is extremely small. It's not comparable with your molten material or heat-tub material. So extremely small. What we did to calculate that. So this can be illustrated by our facility. So my facility, the power is only 80 watts. So what can you do with 80 watts facility? If you have a bulb, it's 100 watts. You will not be able to heat up steel by 100 watts. So the energy consumed here is extremely small. If you want to lift up your temperature, you have to use other ways to increase the temperature, not by this. So this is just to induce those amounts of structure, but not heat them, not lift up the temperature. Okay, thank you. Thank you. Okay, I think we just got time for maybe two more questions. So I'll come down to Pedro at the front who's been waiting a while and then we'll go to you at the back. Okay, a very interesting talk. A two-shot question. One is the parameter for liquid processing is the same as the solid state processing. The second question is the ingredients, many kinds of ingredients, some are inextric and conductive, some are not inextric and conductive. Was any results on different kinds of ingredients in steels? We only did this inclusion first of all, Magnus Salfa, because the history is like this. Although I showed you all the experiment firstly, but history is that we got a theory first. So we got the equation and the calculation and then used that to apply for funding. So I got the funding and the high post-doc and that's that experiment. That's the kind of story. So when we did the calculation, we found this removing inclusion by this method is completely different from the existing method of removing inclusion. It exists in methods that use other physical properties like density or size of inclusion or those kind of things. But this is according to the electrical property difference. So in non-metallic inclusion, normally it's not conductive. And your liquid steel has got reasonably good conductivity. So and then when we start the calculation, we can choose, obviously, more important is aluminum inclusion or whatever. But those, Magnus Salfa have relatively high conductivity than aluminum or silica. So we tried the most difficult one and the first try was successful. But we still do other inclusions, remove them and try to optimize the technology. Thank you. Thank you. Okay, one last question, Patrick. You mentioned the refinement of the pearlitic structure associated to a hardness increase. But you didn't mention which one was that. One of your first slides was refinement, the fragmentation of the pearlitic structure. Yeah. And you mentioned there was a hardness improvement. But I couldn't hear which one was that. The other thing is that for that case, I made a quick mental calculation based on 0.2 joules per square meter of inter-facial energy and they came to the staggering amount of 10 to the 4 watts to fragment that microstructure. So am I doing something wrong in the calculation and what is the hardness increase? But only this one, we got a hardness increase because what we found is that because you formed the nanostructure. What is the increase? Marginally increase, this is about 430, this is about 455. But the important thing is this one, you got all the stress here, your thermal stress here. This one, you have completely removed the stress. So this one, you are not able to draw it anymore. But that one, you can draw it to double its stress. So that's the case. So if the inter-laminar spacing is 100 nanometers, you'll have about 10 to the 4, 10 to the 2 meters of inter-facing in a cube of 1 cubic centimeter. That gives you for those pulses 10 to the 4 watts. What is wrong in my calculation? That's all the fault. It could be percolation. So if you, the current can go along the green bond, it's like the moment. The inter-faces are broken or created. So this is interesting. When you talked about the percolation, you talked about it, correct? Yeah. So I agree. Yeah. Remember that you can only do one liter of the inter-faces. Yeah. So you're right. So we did the calculation. When we first done this, we did the calculation. If you just use the original or the surface energy, transform the original surface energy to the particle, what do we find is this size we got is a smaller than your thing. So this size we got is a smaller than your theoretical size. So we should have a big one, but we actually got a smaller one. A problem is that we have put in those extra energy by electro-pousing. Okay. This might run and run and run. You can talk about this afterwards. I'm afraid we have to move on. So thank you very much. Thank you. Thank you. Thank you. Thank you. Thank you. Thank you. Thank you. Thank you.
 Ok.  The next presenter is Wang Shan Xin from Imperial College London, who will be talking about  the applications of his work of electropulsing in steel formation.  Thank you very much.  I'm interested in cheap steel in extremely short time.  The whole short is that if you blink your eye once, I should have done my experiments  1,000 times.  That means if you blink your eye, blink your eye, take 0.1 second, and my experiment should  take less than 100 microseconds.  So I'll firstly show some of the results, and then we'll discuss the mechanics about  these.  The way I'm using is electric current pulse, because this very short time is a pulse, and  I use electric current pass through the steel.  So I have quite a few authors here, and I especially should acknowledge those people  who are also interested in this very special processing method that is sponsored by the  project, and also those people who helped me a lot.  So let me first show you some results.  This is a piece of steel.  It's a commercial pallet steel.  We contain 0.8% of carbon.  It's a commercial one.  You can see it everywhere.  So the sample was more than 10 centimeters long, and the diameter is about 2 millimeters.  So the max structure, if you look at the max structure, the max goal.  So it should be like this, because our cold draw to the steel wire with 60% of reduction  at room temperature.  Cold draw date.  So without any addicting afterwards.  So if you look at the max structure, it's something like this.  This is a cementite place.  The ferrite is actually away.  So this is the one.  And then I put this steel into my process of facility at room temperature with one pulse.  So totally it's less than 100 microsecond.  And during the time, you don't see anything happening.  You didn't hear a voice, so boom, or something.  And you didn't see the steel wire actually become powder or whatever.  It's a steel wire, and you didn't see the color of the steel wire change into some others,  like red color.  And afterwards, I put my finger on the steel wire and didn't feel I can hold my finger  for the wire.  So that's a kind of phenomenon.  However, if you see that steel wire at SEM, you see this is a cementite place.  A region was this, now changed into this.  Be careful of the scale.  Here is 500 nanometer.  So in this 10 centimeter steel wire, I choose 12 different points.  Exam, and everywhere got exactly the same max structure.  So cementite place changed into a particle with average size of 30 nanometers.  So when we examined the mechanical property, we found this one, the thickness of this one  was about 400.  And this one was a little bit higher than this.  You know, this is a coated joint without annealing.  And this one has already removed all the internal stress, and it is still much harder than this.  Another surprising what we found is electrical conductivity of this state is improved 100%.  It's almost double.  The electrical conductivity of this steel is almost double of this.  So that is one situation for palliative steel wire.  And then I have another one.  This is another steel.  We call it trip steel.  However, at the moment, it's a hot road steel without any retained austenite, although we  call it trip.  So if you look at here, we have a lot of ferrite particles here, combined with this complicated  max structure.  If you look at this, you do not see any anisotropy here, max structure.  You don't see that.  And again, at room temperature, electrical pulse, this steel, with 3,000 times, passes  through 3,000 pulses through this piece of steel at room temperature at a frequency of  1 hertz, which means each second passes through one pulse.  And the pulse width at this moment is 20 microseconds.  So after 3,000 times, if you put that into optical mass structure, you will see a lot  of lines, black lines along the electrocurrent direction.  This is an image of SEM, you see this original isotropic property has completely lost.  All of these phase change into these, along the electrocurrent direction.  So if you use a higher resolution SEM, you will see even inside those lines, the cementite  and ferrite lines, are all along the electrocurrent direction.  So now we are interested to develop a steel with all the, with this kind of mass structure  is everywhere, not only just this.  So this is again at room temperature for this steel.  So now let me show you another example.  So this is a 316L stainless steel.  We know this problem with this steel is if you do an anilium, and then secondary phase  will fall.  So if you anilate at a temperature around 1000 degree, you will see a lot of those white  particles, those are secondary phase particles.  So this is 316L stainless steel, contains very high chromium, moly and nickel.  So if you form these secondary particles, so these secondary particles are very rich  in chromium and moly pedinium.  In that case, the area throughout these will have a poor chromium and a poor moly.  So if these things happen, at that, those poor chromium and a poor moly area will have poor  corrosion resistors.  So we try not to have these secondary phase particles.  However, it's very, very difficult to do.  So what we are doing is we put two samples in the furnace, exactly same samples, but  one of them linked with electropause in another without.  So when we did heat treatment, and then analyzed two samples, one of them is this one.  So this is one of the two samples, one is this one, the other is this one.  So the secondary phase is not formed.  Electropause has suspended the formation of secondary phase.  That's one thing.  You see much less secondary phase particles at this side.  Again, if we analyze the composition inside here, we thought even though we formed some  inside, the chromium and molybadinium difference between the particle and the matrix are much,  much smaller.  So by this one, the electropause has reduced the segregation of this chromium, nickel,  and moly in steady-stew.  So that's another thing we have done.  So now let me tell you another result which we just made very recently, but this has already  been published.  This is, we use this technology at liquid steel.  So it's in liquid state.  The sample here is 1.5 centimeter diameter in-galls.  We mount that without electropause and a quarter.  What we see is inside this steel, we have lot of magnesium sulfur inclusions.  So those inclusions are almost round-shaped and distributed everywhere.  If you look, examine your cast.  Your cast is everywhere.  However, if we do the same thing, but connect with our electropousing for 20 minutes.  Cast is 20 microseconds, each pass is 20 microseconds, and use a frequency of 1 hertz.  And then what we found, things that vary differently, is inside the ingots.  Internal ingots is inclusion-free.  All the inclusions are gone from inside.  However, at a boundary, top, side, and some of the bottom, we have lots of inclusions.  All the inclusions are moved from the central part to the outside part.  So ideal way is we put the leg or top of that at the collect all the inclusions so that  we can make soup clean steels.  So this is one thing.  So we have expelling inclusions from inside the steel, liquid steel to the surface.  Another thing, what we notice at this case, this is almost a spherical particle.  Look at it here.  All the magnesium sulfur inclusions form this very strange morphology.  It's almost everywhere.  This is something very strange, and we don't really know what's that.  Has electropause affected the interfacial energy?  Otherwise, why don't these go to a round shape?  Round shape will have much smaller surface area and a little free energy.  So that's some of the experiments we have about using the facility.  Now let's come into the detail of the technology and analyze what's happening and what can  be done further.  So firstly, when I talk about passing through high-density electric current to steel, many  people immediately think there's a heat there.  So now let's calculate what kind of heat has generated by this electric current.  It can very easily go through this.  I know people don't like the equation, but this equation is very special because they  are so easy.  And we know them from secondary school.  So if we calculate the total energy added by this electropousing, so in my facility,  I have two different options.  One is I can fix the voltage.  Another is I can fix the current, electric current.  So suppose I fix the electric current, and this is the current, this is the electrical  resistance of the sample, and this is the pulse duration.  So use this equation so I can calculate the total energy of this electric current pulse.  Now I suppose all those energy has changed into heat and heat up the sample.  So in that case, this is the total mass of the sample, this is the specific heat of the  sample, and this is the temperature rising.  So suppose all of the electric current didn't do anything else, just the heat of the sample.  And then this equal to this.  From here, I can immediately get the temperature rising due to one pulse is this, just this  divided by mc.  So here, again, this is the resistance of the sample.  I calculate resistance of the sample equals to the density multiplied by the length of  the sample divided by the cross-section area of the sample.  I have this r.  And this is the mass equals the density of the sample, the steel sample, multiplied by  the volume of the sample.  So it's the length, the cross-section.  So if I substitute r to here, m to here, and I get the temperature rising due to one  electro-pulse should be this, because current divided by cross-section area is the current  in density, so I can actually have this.  So you know, it's a very, very simple mathematics, and I have assumed all the electric current  energy has to be converted to the heat to heat up the sample.  And then let's apply this one to our calculation.  I substitute all the parameters of 316L's steady steel-ing, heat capacity, this density,  we know 7.8, and its electrical resistivity is this.  Now what I need is each pulse is 20 microseconds, and this is current density.  Look, this is a astonishing high.  Actually what I used to generate those results are not that high.  This is 100 times higher than what I used.  So it's a ridiculous high.  So because I want to do a maximum calculation.  So I use a 100 times higher than what I actually used.  If you substitute all of that into this, so each pulse can actually increase the temperature  of the sample by 0.217 degrees.  Okay?  It's nothing.  And remember, for all the experiments I used, the pulse frequency is 1 hertz.  So if I put that in, that means the heat, the heat up rate is 0.217K per second.  You know, you know, steel processing, this is a nothing, and it's almost 100 times  the high than what I've done.  This is average kind.  But some people may argue, okay, there's a percolation here.  Somewhere I got a high density in the other place, but I already have used 100 times the  high than the average.  So that's one thing.  So the electropulse effect is not a heat effect.  Okay?  That's one thing.  Another.  So another thing is some people say, you can do this in your laboratory because your sample  is small, but you may not be able to scale up to the industry because industry needs  to have a very, very big steel.  So can you do that?  Let's calculate the energy consumption in the pulse.  So the total work in single electropulse is this.  Okay?  It's the same.  So required electric power.  Power is a work divided by time.  So here I got a pulse frequency.  I normally use one hertz.  So if we substitute all the parameters we used before in, so each, so get all those  of the parameter in, so each pulse actually consumed zero point.  The power need to generate this electropulse process is 0.304 watts.  That's again nothing.  So I can tell you in my laboratory, the facility I used to generate the electropulse is 80  watts.  And the electric current was generated at an electrical potential of 20 watts.  So for that kind of power, it's nothing because you have a home, we can easily buy the bulb.  The power is 100 watts.  The mass facility is only 80.  So it's very easily to scale up.  So but those we know we can apply this, but what is the mechanism?  Okay.  So there's one thing that's just, it's complicated.  I don't believe we have solved this.  But one thing is let's analyze this from some dynamics way.  So if we have some mass structure change, whether phase transition or just the structure relaxation  or whatever, so the total free energy at here is free energy change is a chemical free energy  change plus surface energy change plus electric current associated free energy change.  Okay.  Those two we all know, but what about this term?  So this one, fortunately, we know this one can be calculated by this equation.  So this equation is a free energy associated with the electropause equals this is a magnetic  permavillity at pi.  This is the current density distribution after the mass structure evolution.  Okay.  So this is the current density distribution before the mass structure evolution.  And then you have this term which make this calculation very complicated, very, very nonlinear.  So what we have done is we have actually developed a software where I able to calculate the current  distribution if you have any kind of phase transition or any kind of mass structure change,  not only phase transition.  For example, if I have a inclusion at the moment, the inclusion is here, but the next  moment the inclusion move up to here.  So if you look at that case, this chemical free energy difference is the same.  You don't have any change because there's no phase transition.  This one is the same, but this one is different because if you have an inclusion move from  this part to the surface and then you have a completely different electric current distribution.  So if you have this completely different electric current distribution, you will have a completely  different free energy change.  And then because that one, so some of the move will be favored by this electro-pousing,  but some of them will not.  Okay.  So that's the case about inclusion removing.  So we tested this against the, so this is a show of analyze for the electric current  distribution and we are able to calculate all the free energy change.  This is something like our pair line in a layered structure, but that one, all the layers  actually the change separate into this small disintegrated part, same at times.  And we are able to calculate the current density distribution and again we can get a total  free energy.  So we will be able to know in this electro-pousing, you actually will let your grace to separate  into different several things or you actually will have a cause.  So this one, when we calculate, use that equation to calculate the microstructure refinement  because sometimes we use that.  So we, and this is our theoretical value and this is experimental value not did by ourselves.  It's a group here in America.  Professor has current as group.  So we see as a great, very well and we further predicted and say we can use this electro-pousing  to fabricate nanostructure material.  Those are required current density.  Those are all theoretical work.  And again, we found if we use the electro-pousing, we are able to increase the fatigue of life  of the material.  So we calculated, but if we, for different material, if we use electric current density  above a certain value and we are able to hear the crack.  So we have done this before and we were able to improve the fatigue of life of low-carbon  steel for 34 times.  Okay, so those are just my advantage in this steel process.  It is a conclusion.  Thank you very much.  Okay, that's a very novel topic there indeed.  And does anyone have any questions?  Straight away, yes?  See if we can get both our microphones over to this row.  Just use that one.  Thank you very much for your great presentation.  So you show us the microstructure change due to the electric current.  So the last part of this presentation, you said just thermodynamic approaches.  But to change the microstructure, we must consider the kinetics.  So what do you think on that?  We did some work and also in literature you can find some work.  Pacing electric current can lower the connected barrier of some transformation, but in another  group of transformation, you can, electric current can actually increase the connected  barrier.  So there are some works and we also did some.  However, kinetic understanding of this mechanism is very poor at the moment.  There are a lot of things we don't understand.  Your passing time is very short, I think.  So point one second or load one second.  If you use one pulse, it's certainly less than 100 microsecond.  First time is very short.  There are some solid result people found is that the power increase diffusivity many times.  That's what people agreed.  Another is change the connected barrier.  Some of them reduce a lot or even completely remove the connected barrier.  Another case you can actually increase the connected barrier.  But for rest of things, it's very basic in the early stage.  Thank you very much.  Okay, Joe.  You talked about the, putting this into industry is a limit on the sample size.  You said that the power doesn't limit it.  Is there a limit imposed by the magnetic skin effect?  If you actually want to put a sharp rise and fall of current into something, the current  only tends to flow through the surface of the thing.  So the skin effect is related to the current frequency.  So you can calculate that accurately.  If you use that direct current, then you won't have a skin effect at all.  You're pulsing it though.  Is that not equivalent to a single wave of an AC pulse?  Need to calculate it because, for example, a lot of automotive steels.  What we are interested is a thin plate or steel wires.  For those, you have a few millimeter thickness.  You can ignore that.  If you calculate about one hertz, if you increase the frequency.  Is it not the 20 microsecond period that actually determines the stickling effect?  It's a hertz.  It's a one hertz.  It's a one hertz.  So that's what we need though.  If you use a very high frequency, for example, 300 hertz, and you see the skin effect.  So in that time, there are some of the experiments reported before.  People use that to modify the surface property of the material.  They can actually generate a morphos at a surface layer of the material.  Oh, they deliberately do it.  Extremely high frequency.  Interesting idea.  Thank you.  Okay.  Yes?  Long Shen, thank you for your interesting presentation.  I have a very basic question.  You did very elementary calculation in the beginning.  So if you are going to melt steel with an electrical furnace, normally you spend something  around 400 kilowatt hours for tons.  So let's say four kilowatt hours, four kilogram.  So do you have any number for something on mass of iron, of course, or anything about  related moles about your...  So how much energy really spent for unit of mass in your process, basically, comparing  it to the melting energy, roughly speaking, the entropy of melting we know which is a  good number for any metal.  So the total amount of energy we spent is extremely small.  It's not comparable with your molten material or heat-tub material.  So extremely small.  What we did to calculate that.  So this can be illustrated by our facility.  So my facility, the power is only 80 watts.  So what can you do with 80 watts facility?  If you have a bulb, it's 100 watts.  You will not be able to heat up steel by 100 watts.  So the energy consumed here is extremely small.  If you want to lift up your temperature, you have to use other ways to increase the temperature,  not by this.  So this is just to induce those amounts of structure, but not heat them, not lift up  the temperature.  Okay, thank you.  Thank you.  Okay, I think we just got time for maybe two more questions.  So I'll come down to Pedro at the front who's been waiting a while and then we'll go to  you at the back.  Okay, a very interesting talk.  A two-shot question.  One is the parameter for liquid processing is the same as the solid state processing.  The second question is the ingredients, many kinds of ingredients, some are inextric and  conductive, some are not inextric and conductive.  Was any results on different kinds of ingredients in steels?  We only did this inclusion first of all, Magnus Salfa, because the history is like this.  Although I showed you all the experiment firstly, but history is that we got a theory  first.  So we got the equation and the calculation and then used that to apply for funding.  So I got the funding and the high post-doc and that's that experiment.  That's the kind of story.  So when we did the calculation, we found this removing inclusion by this method is completely  different from the existing method of removing inclusion.  It exists in methods that use other physical properties like density or size of inclusion  or those kind of things.  But this is according to the electrical property difference.  So in non-metallic inclusion, normally it's not conductive.  And your liquid steel has got reasonably good conductivity.  So and then when we start the calculation, we can choose, obviously, more important is  aluminum inclusion or whatever.  But those, Magnus Salfa have relatively high conductivity than aluminum or silica.  So we tried the most difficult one and the first try was successful.  But we still do other inclusions, remove them and try to optimize the technology.  Thank you.  Thank you.  Okay, one last question, Patrick.  You mentioned the refinement of the pearlitic structure associated to a hardness increase.  But you didn't mention which one was that.  One of your first slides was refinement, the fragmentation of the pearlitic structure.  Yeah.  And you mentioned there was a hardness improvement.  But I couldn't hear which one was that.  The other thing is that for that case, I made a quick mental calculation based on 0.2 joules  per square meter of inter-facial energy and they came to the staggering amount of 10 to  the 4 watts to fragment that microstructure.  So am I doing something wrong in the calculation and what is the hardness increase?  But only this one, we got a hardness increase because what we found is that because you  formed the nanostructure.  What is the increase?  Marginally increase, this is about 430, this is about 455.  But the important thing is this one, you got all the stress here, your thermal stress here.  This one, you have completely removed the stress.  So this one, you are not able to draw it anymore.  But that one, you can draw it to double its stress.  So that's the case.  So if the inter-laminar spacing is 100 nanometers, you'll have about 10 to the 4, 10 to the 2  meters of inter-facing in a cube of 1 cubic centimeter.  That gives you for those pulses 10 to the 4 watts.  What is wrong in my calculation?  That's all the fault.  It could be percolation.  So if you, the current can go along the green bond, it's like the moment.  The inter-faces are broken or created.  So this is interesting.  When you talked about the percolation, you talked about it, correct?  Yeah.  So I agree.  Yeah.  Remember that you can only do one liter of the inter-faces.  Yeah.  So you're right.  So we did the calculation.  When we first done this, we did the calculation.  If you just use the original or the surface energy, transform the original surface energy  to the particle, what do we find is this size we got is a smaller than your thing.  So this size we got is a smaller than your theoretical size.  So we should have a big one, but we actually got a smaller one.  A problem is that we have put in those extra energy by electro-pousing.  Okay.  This might run and run and run.  You can talk about this afterwards.  I'm afraid we have to move on.  So thank you very much.  Thank you.  Thank you.  Thank you.  Thank you.  Thank you.  Thank you.  Thank you.  Thank you.
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