Composite object out of steel and its method of preparation
FRENCH PATENT REPUBLIC SERVICE iNTELLECTUAL INDUSTRIELLE of the Society, said: E. I. DU PONT AND CO DE [...] residing in the United States of America. [...] no. 943,224 International Classification C [...] 1.366.314 21 Demanded 30 July 1963, to 16m Issued by stopped 1er June 1964. Improvements made to the steel. The stainless steel and other alloys resistant corrosion are expensive in use sheet. Not only, the cost of the material is high, but also the alloys are difficult to [...] work due to hardness. For example, the austenitic stainless steel is usually mapping- [...] in the form of sheet metal by the use of following operations: 1° Bushing of a room or work through a hot rolling mill, to reduce its thickness to about 2.54 mm. 2" Annealing at about 1,065 °C followed by a cooled rapid depth; 3° [...] using mixtures, acid nitric, [...] acid, or by means of hy- [...] sodium; 4° rolling in a rolling mill [...] - becomes to an intermediate thickness; 5° to about 1065 °C New annealing; 6° New descaling such as "3"; 7° New cold rolling in a rolling mill reversible to the final thickness; 8 final ° Annealing about 1,065 °C. The process is not only slow and more steps, but also the need for a [...] - black reversible for the two laminations, or da- dvantage, slows the more than if a rolling mill in tan- dem can be used. One possible method to overcome both during use the cost and the difficulty of working- depicting 100% stainless steel, would be to utilize a base of carbon steel and welding a thin layer of stainless steel. The carbon steel constituting the mass of the plate would be easier work and cheaper. It has been found, -tou however, difficult to obtain a good bond between [...] steel and carbon steel capable to withstand the laminations cold and hot without 64 2191,0 73,417 3-φ- loss of the corrosion resistance of stainless steel and maintaining the workability carbon steel. According to the present invention, a product is obtained which is composite steel sheet comprising a steel base carbon linked integrally to a layer of austenitic steel, whose thickness is less than half and preferably less than a quarter of that of the base layer. The present invention also provides a method of preparation of a piece of steel sheet metal, comprising forming a plate coated with a layer of austenitic stainless steel and a layer of carbon steel base, preheating the coated plate to render it sufficiently foldable for subsequent hot rolling, hot rolling of the plate preheated to a temperature of at least 840 °C, to reduce the thickness of the base part, and the [...] of the workpiece. For the term "coated plate", is designated any composite article (plate, sheet or strip) formed by a coating method wherein the stainless steel is the coating layer and the carbon steel is the base layer. The terms "strip" and "sheet" are used herein in the normal direction that they would have in the field of metallurgical industry, for example, as well as the following table extract of the work "The Making, Shaping and Treating of steel" (the manufacture, shaping and processing steel), seventh edition, of the "United States steel Company" 1957, wherein all dimensions are given in centimeters: The stainless steels are not curable by heat treatment and contain by weight, as main constituent elements, about 16 to 26% chromium, about 6 to 22% nickel, the booklet Price: 2 francs iron and substantially the remainder, but can also include up to 2% of manganese in all grades, 2 to 4% of molybdenum in qualities, small amounts of titanium and niobium in certain qualities, and small amounts of carbon (less than 0.03 The base of carbon steel contains by weight more than 98.5% iron with a maximum of 0.04% phosphorus, of 0.05% sulfur, 0.1 In practice, the stainless steel layer, generally, initially has [...] thickness of 6.35 mm 12.70 mm and the composite part can then be worked to form the products or objects sheet of a depth close to 3.80 mm 0.50. A preferred method of coating, the detonation coating, Patents and Belgian no. 599,918 619,197, respectively of the 2 February 1961 and the 20 June 1962, wherein a metallurgical bond is formed between two layers, or more, metal, by joining the layers by explosion under conditions where a metal jet is formed by. the collision, although other types of coated steels stainless steel can be used, for example the coatings obtained by [...], stainless steel casting on a massive base, or hot rolling. The preheating operation can be carried out in conventional homogenization. The hot rolling may be carried out in a conventional hot rolling mill in which the temperature is to be maintained above 840 °C, after which the workpiece is cooled preferably rapidly, i.e. in about two hours, to less than 485 °C. The one of the reasons prevent continued maintenance in the temperature range ° to 840 °C 485 is to reduce the tendency of the carbon to diffuse and consequently the tendency to form carbides, since the presence of [...] in the austenitic stainless steels reduces the corrosion resistance of the steel. Another object hot rolling at temperatures above 840" G is permit working sufficiently stainless steel for other treatments, i.e. cold rolling without a prior annealing. The hot rolling can be conveniently used to reduce the thickness of the part to about 2.28 mm. The part can be descaled mechanically, that is [...] gravel, sand or shot, or by treatment with a conventional, i.e. a 10% aqueous solution of nitric acid, containing about 4 The base steel is driven more rapidly by an acid bath as stainless steel, so that the pickling time must be carefully adjusted in such circumstances, or at the [...]. carbon is to be protected during descaling the stainless steel. For example, an aqueous sulfuric acid solution heated to 65 °C is used to decarbonize the carbon steel; the carbon steel can then be covered with tape or any other suitable covering material and stainless steel can be de-scaled by means of an aqueous solution of nitric acid and to 15% The descaling sodium hydride is preferably chosen because it does not appreciably attack the carbon steel or stainless steel. The workpiece which can leave the hot rolling mill roll, is immersed in a bath of molten caustic soda to 370 °C, containing 1.5 to 2% of sodium hydride If two workpieces have been laminated together with heat (rolling "sandwich"), the surfaces of the elements which are in contact and protected from the atmosphere that generally require no appreciable descaling, although it is still necessary to decarbonize the outer surfaces oxidized. It has been found that the chemical descaling of parts or composite structures containing carbides in the stainless steel layer is capable of giving a poor ductility and defects in the form of stitching, so that it is particularly important to avoid the formation of carbides or eliminate any carbide would be formed before the chemical descaling. Carbides that form can in general be redissolved by annealing at 900-950 °C and in particular carbides that may exist at the surface of the stainless steel, which is a region which is critical with respect to the corrosion resistance. Any further reduction in the thickness of the workpiece can be conveniently performed by cold drawing conventional, in a reversing mill or a roll mill in tandem, the latter being preferred due to its faster rate. When a final thickness greater than about 1.78 mm is desired, any cold rolling is generally carried out to improve the uniformity of the surface and the resulting cold working reaches about 2% at least, in which case it n ' cst required additional treated. Furthermore, if the plate or strip is cold rolled to more than 2%, annealing will be usually the case, to provide sufficient ductility for any subsequent forming operation. Following the cold rolling, annealing any conventional 5 minutes between 790 and 950 °C is suitable, the precise temperature being determined in accordance with each base steel, for example, a temperature of less than about 900 °C for steel rimmed, and temperatures of up to about 950 °C for killed steel, followed by cooling to below 485 °C within less than two hours, to avoid harmful carbide precipitation. If the annealing is performed to the air, a further descaling is generally necessary while, if it is carried out under an inert atmosphere such as argon, cracked ammonia, or vacuum, it is not necessary to apply final treatment descaling. The method of the present invention is much faster and less complicated that the known process in practice and described for the work of the austenitic stainless steel. For metal sheets of a thickness greater than 1.78 mm, when the state of the surface does not have a critical, a coated plate may be in principle simply cold rolled and descaled. For roles thinner also require cold rolling, a rolling mill can be used and the annealing temperatures, compared to previous techniques, are substantially reduced. The importance of the use of a base steel, low carbon spring of the following table, that highlights the diffusion of the carbon of the various steels in a stainless steel containing 0,025 Migration distances expressed in centimeters are those on which the carbon content of the stainless steel has been supported above a level of 0.03 as a result of diffusion of carbon from the steel base. On these distances from the face of separation, carbides can form, even if the workpiece is worked according to standards preferred. It is desirable to limit the carbide region to less than about 2/3 or even 1/3 of the total thickness of the stainless steel layer, so that carbides do not penetrate to the surface. Table On above, and taking into account the initial thickness of the stainless steel layer, it is possible to calculate the maximum carbon content desirable in a base steel any, for example, an average content less than about 0.12% and a carbon content to the lower surface to about 0.06 Thus that it has been specified above, it was further found that the holding part of a hot rolled between 485 and 840 °C for a period of time causes the diffusion-appreciable planne d A composite sheet comprising a carbon steel backing having an average carbon content of less than 0.12% and an austenitic stainless steel cludding of thickness less than half that of the backing and containing less than 0.03% carbon for at least a third of its thickness is formed by explosive bonding followed by hot rolling at at least 1550 DEG C. A rimmed, killed or semi-killed carbon steel backing of composition:- 98.5% min. iron 0.04% max. phosphorus 0.05% max. sulphur 0.1% max. silicon 0.025 - 0.9% manganese 0.12% max. carbon is clad with an austenitic stainless steel of composition 16 - 26% chromium 6 - 22% nickel 0 - 2% manganese 0.03% max. carbon traces of sulphur, phosphorus and silicon and optionally 2 - 4% molybdenum small quantities columbium and titanium balance iron by explosive bonding. The backing layer preferably has a carbon content at the surface of less than 0.06%. After heating to say 2200 DEG F. for one hour the composite slab is hot rolled, cooled to at least 900 DEG F. in less than two hours and descaled after annealing at 1650-1750 DEG F. if desired. Two workpieces may be simultaneously hot rolled together in sandwich form. If further reduction is required it is effected by cold rolling in a reversing mill or a tandem mill. A reduction of more than 2% entails subsequent annealing at 1450-1750 DEG F. followed by cooling to below 900 DEG F. in less than two hours. Within the range 1450 DEG -1750 DEG F. annealing temperatures are under 1650 DEG F. for rimmed steel and up to 1750 DEG F. for killed steel. Annealing may be carried out in air or, to avoid further descaling, in an inert atmosphere, e.g. argon or cracked ammonia, or in a vacuum. The descaling may be mechanical or chemical by use of an agent such as 10% nitric acid-4% hydrofluoric acid, an aqueous sulphuric or nitric acid electrolytic pickling bath, or a melted salt or sodium hydride bath. Thus e.g. the work in the form of a coil may be immersed in molten caustic soda at 700 DEG F. containing 1.5 - 2% sodium hydride produced in situ by reacting sodium and hydrogen. This may be followed by a dip in 10% nitric 1 DEG % hydrofluoric acid for twenty minutes. Alternatively the carbon steel portion may be descaled by treatment in 10% sulphuric acid at 150 DEG F. for 30 minutes and covered with vinyl tape while the stainless steel portion is immersed in 15% nitric and 2% hydrofluoric acid at 150 DEG F. for 10 minutes. 1° The side stainless steel has no pinholes after exposure to a spray of salt during 100 hours; 2° The sheet can be folded in of a circle, the spokes are 1,2 and 4 times greater than its thickness, without cracking; 3° In [...] of the "Olsen cup", which comprises punching of the sample to make a hollow 1.91 cm, to determine the depth of the trough which can be produced without cracking, the plate forms a basin of a height of 10.2 mm prior to the occurrence of a crack. The process described above is repeated exactly as before, with the exception that the sheet is descaled in a bath of molten sodium hydroxide containing 2% of sodium hydride to 370 °C, followed by a brief immersion in an acid in a mixture of 10% HN03, 1% HF for 20 minutes. SUMMARY A. composite article characterized by the following features, alone or in combinations: 1° II comprises a base layer of carbon steel, welded integrally to a layer of austenitic stainless steel having a thickness of less than a half of that of the base layer; 2° The carbon content of the stainless steel layer is lower, to 0.03% by weight to a depth of at least one third of the thickness of the stainless steel; 3° The steel base an average carbon content less than 0.06% by weight; 4° The base steel is killed steel or [...] ; 5° The base steel is a killed steel having on the surface a carbon content of less than 0.06% by weight; B. A method of preparing a structure steel sheet, characterized by the following features, alone or in combinations: 1° The method forms a coated plate from a layer of austenitic stainless steel and a base layer carbon steel, to preheating the coated plate to make it sufficiently pliable for a subsequent hot rolling, to the hot rolling at a temperature of at least 840 °C to decrease the thickness of the work and [...] the work; 2° The plate is covered or clad [...] by a detonation coating; 3° The workpiece is cooled below 485 °C within two hours after the hot rolling; 4° The descaling is carried out using sodium hydride; 5° After descaling, the work is annealed between 900 and 950 °C to re-dissolve all carbides at the surface of the stainless steel; 6° The work is cold rolled as modulation of- subsequently coating; 7° The work is annealed after the cold rolling; 8" The carbon content to the surface of the neck- che is less than 0.06 by weight; C. Objects B obtained according to the method of above or any other equivalent method. Society said: E. I. DU PONT DE [...] AND CO. For proxy: [...], & Blundell [...] For the sale of the fascicles, be directed to I ' [...] Nationale, 27, the street Convention, Paris (15 *). Ministry of industry
Steel composite article and process for its preparation.
Width 0,584 and 0,5S4 0,516 0,516 0,457 0,457 0,144 0,144 0,114 Up to 8.9 mm Bar Bar Hinge Hinge Hinge to 15.2 mm 8,9 mm Bar Bar Hinge Hinge Hinge 15,2 mm to 30.5 mm Plate Hinge Hinge Hinge Hinge 30,5 mm to 122 mm Plate Sheet Sheet Sheet Sheet More of 122 mm Plate Plate Plate Sheet Sheet Carbon content [...] base Distance migration % 0,04 0,122 0,300 0,421 0,462 0,487 0,539 0,06 0,10.. 0,12 0,15 0,20