Preparation of compound wire
O United States Patent 11 1 1111 3,874,066 Lanner 5] Apr. 1, 1975 PREPARATION OF COMPOUND WIRE 3,663,723 5/1972 Persson 156/179 3,777,362 12/1973 Nilsson et al. 29/479 X [75] lnvemor- Lam&#34;, Garphytmn 3,820,229 6/1974 Larker et al. 29/4701 73 A AB G h G h FOREIGN PATENTS OR APPLICATIONS s We yuan 2,007,400 9/1970 France 29/471.1 we 1,261,379 2/1968 Germany 29/4975 22 Filed: Apr. 4, 1973 7/1924 Swede&#34; 209,189 4/1966 Sweden 21 Appl. No.: 347,626  
  Primary Examiner- Francis S. Husar 30 Ford n A cation Prior Data Assistant Examiner-Ronald J. Shore 1 p 11 lggT) g y 4655/7, Attorney, Agent, or Firm-Pierce, Scheffler &amp; Parker 52 us. c1 29/4701, 29/19l.6, 29/480 [57] ABSTFACT 51 1 1m. 01 823k 21/00 For formmg a compound a Core of a We b11191 1S 5 Field of 29/421 E, 4701, 486, 497.5, enclosed within a tubular metallic mantle; the mantle 29/479, 480, 1916 is joined to the core by an explosive joining method; and the resulting composite is worked to a wire of the 5 References Cited desired cross-sectional dimensions. Thus, the exterior UNITED STATES PATENTS of the product may consist of a corrosion-resistant metal (or alloy), whilst the core may be a low alloy 3,167,857 2/1965 Sarto et al. 29/480 X carbon Steel 3,320,666 5/1967 Dion 29/480 X 3,331,121 7/1967 DeMaris et al. 29/475 5 Claims, N0 Drawings PREPARATION OF COMPOUND WIRE The present invention relates to the preparation of a compound wire, i.e. a metal wire consisting of an interior core and an outer cover. having properties not known before.  
  lt frequently, is the case that there are required for a metal wire special surface properties which often cannot be combined with the other material properties of a wire of one single material. Thus, corrosion resistance is often required, and, as a rule, for meeting this requirement it has been necessary to use solid stainless steel throughout, where carbon steel would have been preferred because of its superior mechanical properties and lower price. This is of particular importance as regards wire cables and springs.  
  Moreover, a high scaling resistance is often required of a wire which is used at a high temperature, for instance, on conveyors through furnaces, as resistor elements, etc. To obtain a sufficient scaling resistance, one must in such cases often use ferritic stainless steels or Cr-Ni-alloys which are brittle and expensive and, hence, not ideal.  
  Finally, for many application fields resistance to abrasion is often required from the wire, as in the case of sieve gratings of round wire, or of piston rings or of band saws of flat wire. Steel with high carbide contents must then be used, and these steels have a relatively low ductility and, besides, are expensive.  
  Thus there is a need for a wire material which consists of an inner core of one metal with an outer cover or plating thereon of a different metal. By a suitable choice of metals in the core and the cover it is thus possible to obtain an optimum combination of properties of the finished wire. The cover should then preferably be attached to a core of a wire blank or billet, after which this composite blank is worked to the finished wire by means of known methods, such as hot and cold rolling, drawing, extrusion and the like. It is of course ofthe greatest importance that a complete adhesion be obtained between the core and the cover and that this adhesion be maintained throughout the whole working of the wire blank to the finished wire. This earlier had cause difficulties which are eliminated by means of the method of the present invention.  
  The present invention relates to a method for the preparation of compound wire of metal and is characterized in that a core of a metallic wire blank or billet is surrounded by a tubular mantle of a different metal and is joined to the latter by means of explosive joining or cladding, after which the wire blank further is worked to the finished wire by means of known methods.  
  Methods of explosive joining of different metals have been found to provide a good adhesion between the most various types of metallic materials. It has been found to be suitable that the core material in the finished wire consists of a rolled or forged metallic core or of a wire rolling blank, prepared in some other way, and that the metallic material of the cover or mantle consists of a seamless or welded tube or a plate bent to a tubular shape. After the explosive joining the composite billet is worked to wire or bar having a diameter of 3-20 mm, preferably 5-15 mm, by means of a hot rolling operation or in some other known manner. Further working can be carried out by means of cold rolling, drawing, extrusion or other known methods.  
 LII  
  It previously had been known to prepare compound wires, bars and other elongated metal products by drawing, followed by a heat treatment. Thus, it is known from Swedish Pat. No. 61,563 to prepare such products with an iron or steel core and a copper mantle, wherein a layer of zinc is provided as a binder between the mantle and the core. This method, however, is time-consuming and requires extensive equipment for the drawing and heat treatment. Furthermore, the choice of materials in the core and the mantle is severely limited by their adhesion properties in relation to the binder metal. For example, it would be quite impossible to bond a stainless steel mantle to a core of zinc coated steel. Furthermore, explosive forming or bonding of metals is known from a number of patents, such as Swedish Pats. Nos. 209,189 and 333,860. None of this prior art, however, refers to the explosive joining of a metallic core to a mantle, after which the product obtained is further mechanically worked to a finished wire.  
  By the method of the invention there is obtained as final product a compound wire consisting of a core of one metal with a well adhering mantle of a selected different metallic starting material. The mantle layer is continuous and free from holes or cracks. The mantle is securely joined to the core, throughout the surface area of the core, by explosive joining by the procedure described in US. Pat. No. 3,397,444. The finished compound wire can be shaped to round wire or to narrow bands (flat wire) with a straight edge or with a varying edge radius, using known methods. In the preparation of a corrosion-resistant compound wire according to the invention the mantle of the material can consist of an austenitic stainless steel, a nickel alloy, titanium or titanium alloy or of another corrosionresistant material, while the material of the core consists of an unalloyed or low-alloy carbon steel. If the wire is to be used for the preparation of springs, the core material should consist of a spring steel. Compound wires thus prepared are also suitable for the production of corrosion-resistant wire cables.  
  in the production of a compound wire according to the invention with a high resistance to scaling at elevated temperature, the material of the core preferably consists of a ductile steel or of another ductile alloy, while the material of the mantle consists of a ferritic stainless steel, a nickel-chromium alloy or of another alloy characterized by a high resistance to scaling. In the preparation of a compound wire with a high abrasion resistance the material of the mantle correspondingly consists of a steel or another material with a high abrasion resistance.  
  The invention is illustrated more in detail by the following examples.  
 EXAMPLE:  
  A roller wire blank of carbon steel containing 0.85 percent C and with a diameter of 101 mm was explosion plated with a tube of stainless steel of the 18-8 type. The tube had an interior diameter of 107 mm and the thickness of the material was 3 mm. After joining, the composite billet was rolled to 5.5 mm wire and then drawn, by means of conventional wire drawing technique, to a diameter of 1.9 mm. in all phases from billet to the finished wire the material was controlled and the adhesion between the core and the mantle was found to be excellent.  
  Compound wire of the diameter 3.8 mm was oilhardened by continuous austenitizing, quenching in oil and annealing in a lead bath, and compression springs were prepared from the hardened wire. The compound wire was shaped to springs with fully acceptable values as to straightness, length and pitch.  
  Here the invention had substantially been described with reference to core and mantle materials, which mainly consists of steel and steel alloys. It is. however, obvious to the expert that the invention is not restricted to the use of merely these materials but that also other metallic materials can be fully used in the present process.  
 I claim:  
  1. A process for preparation of a compound metal wire which comprises surrounding a core of a wire billet with a tubular mantle, joining mantle and billet by means of explosive joining or cladding and working the resulting composite wire billet to finished wire.  
  2. The process of claim 1 for the preparation ofa corrosion-resistant compound wire, in which the material of the core consists of an unalloyed or low-alloy carbon steel, and the material of the mantle consists ofa corrosion-resistant material selected from the group consisting of an austenitic stainless steel, a nickel alloy, titanium and a titanium alloy. v  
  3. The process of claim 1 for the preparation of compound wire having pronounced resistance to scaling at elevated temperatures, in which the material of the core consists of a ductile alloy and the material of the mantle consists of an alloy having a high resistance to scaling and selected from the group consisting of ferritic stainless steel and a nickel-chromium alloy.  
  4. The process of claim 1 for the preparation of a compound wire having a high abrasion resistance, in which the material of the core consists of ductile steel, and the material of the mantle consists of some other material having a high abrasion resistance.  
  5. The process of claim 1 wherein the composite wire billet after the explosive joining is hot-rolled in a known manner or is worked in a known manner to a wire or bar with a diameter of 3-20 mm, preferably 5-15 mm.