IMPROVING THE CONTINUOUS CAST BLANK STRUCTURE BY USING MICRO-COOLANTS
Paper intended to clarify some problems regarding the accomplishment of an improved crystalline of the continuously cast blanks using the micro-coolant addition during the continuous casting of the steel. The industrial experiments were made within a metallurgical plant having a continuous casting machine for blooms with a 240x270mm section. Micro-coolants as grains were added in the mould of the continuous casting machine, on a single thread. The conclusions got from analyzing the casting structure of the experimental blanks (with addition of micro-coolants in the mould) in comparison with the common casting structure (witness blank) are presented.
RESPECTS REGARDING THE USAGE MICRO-COOLERS TO CASTING STEEL
Basic problem, which must solve to casting steel, consists in the smooth ingots procurance insurance from chemical point of view, structural and of mechanical ownerships. For the defects mitigation to solidification classic, it is the needed adjustment to an efficient methods exhaust of warmth from the steel under solidification through the administration of micro-cooler under form of grains to casting. Micro-coolers you utilize with the view of process directing of solidification must achieve conditions series: to have a heaved purity respecting the content of oxide inclusions; the wet micro-coolers uttermost 0, 25%; to not have surface oxidant; to have a certain granulometric composition. The work clears the aspects related interaction micro-coolers you deal to casting steel over solidification to this. As parameters, which influence the process of solidification they were taken in the dimensions, study micro-coolers, the specific enlargement of micro-cooler, steel temperature in the enlargement moment while as the influenced parameter steel volume in which they acted microcoolers. Through analysis of regression by the agency of program Excel and Matlab they obtained dependence between meal micro-cooler you utilize to casting ingots from temperature and steel of casting, correlations which they allow the optimal areas establishment variation for temperature of casting, the quantity of micro-cooler dealt respective affected volume percent of cooling to the administration micro-coolers.
A Distortion in Rolled and Heat-Treated Rings
are heat treated (i.e. normalized, quenched and tempered, see Figure 1). Because of this processing, some rings, especially those with a large outer-diameter to wall-thickness ratio, distort and become ovular (out of tolerance). This distortion is not the only problem resulting from this phenomenon. Even if the fi nished rings meet dimensional tolerances and are shipped to the customer, residual stresses resulting from heat treatment may become a problem during subsequent machining, causing additional deformation and distortion. A study on control of distortion and residual stresses in rolled and heat-treated rings is being conducted by the Engineering Research Center for Net Shape Manufacturing (ERC/NSM) in partnership with the Forging Industry Association (FIA/FIERF), Education and Consulting LCC and four forging companies supplying the energy and aerospace industries. Understanding and ultimately solving this problem is a challenging task considering the three triggering mechanisms (thermal, metallurgical and mechanical) that affect the ring during heat treatment and cause the undesired results. In light of the complexity of the problem, most ring-rolling companies approach it with corrective rather than preventive measures. Some manufacture the ring with large tolerances so it can be machined to fi nal dimensions. Others correct the ring distortion by a mechanical method (compression or expansion), which also partially relieves the residual stresses. However, mechanical methods are fairly empirical, and there is a need for a physics-based understanding and methodology to produce rings with minimal distortion at an acceptable cost and lead time.