KR860000125B1 - Method for producing accumulated steel pipe - Google Patents

Abstract

An accumulated steel pipe contains a carbon steel on the outer layer and a stainless steel on the inner layer. A metallic foil(5) is inserted between the carbon steel(1) and the stainless steel(2). An intermediate material is obtained by a cold drawing. A hot working makes a product by heating the intermediate material to an appointed temperature. The circumferential plane of the inner layer(2) is attached spirally by a metallic foil(5). Grinding, shot blasting or an acid wash treatment is used as a preparation treatment for the circumferential plane of the tube(2) or the rod(12) and the inner plane of the outer tube(1).

Description

Manufacturing method of laminated steel

1 is an explanatory diagram showing the main part of the process by the method of the present invention in the case of laminated steel pipe production.

2 is an explanatory diagram showing a cold drawing state.

3 is a photograph of a metal microscope capturing the joint in the side cross-section of the laminated steel pipe obtained by the method of the present invention.

4 is an explanatory diagram showing a state in which a metal foil is rolled up and attached.

FIG. 5 and FIG. 6 are metal micrographs which captured the junction part in the axial cross section of a laminated steel pipe, when metal foil was used as a medium.

7 is an explanatory diagram showing an important part of the process according to the method of the present invention in the case of manufacturing a laminated steel pipe by a method including a step of manufacturing a laminated bloom as cold drawing.

8 is an explanatory diagram showing the present cold drawing state.

9 is a metal microscope photograph of the joint portion in the axial end surface of the laminated steel pipe obtained by the present invention.

10 is an explanatory view showing important parts of the manufacturing process of the laminated steel by the method of the present invention.

11 is an explanatory diagram showing the cold drawing state.

12 is a metal micrograph of the axial cross section of the laminated steel wire.

Fig. 13 is an explanatory diagram showing an important part of the manufacturing process of the laminated steel wire in another method of the present invention.

14 is an explanatory diagram showing the cold drawing state.

FIG. 15 is a fastening micrograph of the axial cross section of the laminated steel wire.

Figure 16 is a longitudinal cross-sectional view of the steel pipe material for explaining a conventional method for manufacturing a laminated steel pipe.

The present invention relates to a method for producing a steel pipe or rod-shaped steel or steel wire formed by laminating two or more kinds of metals. Laminated steel pipes formed by laminating an outer layer with carbon steel and an inner layer with stainless steel are widely known.

The laminated steels represented as such laminated steel pipes are used under special conditions by imparting corrosion resistance, hydrogen sulfide resistance, and abrasion resistance by using a composite material (usually a quantitatively small layer. In this example, stainless steel of the inner layer). A base material (usually quantitatively high in number) which is generally inexpensive in terms of price, for the purpose of making it possible to adapt to special use under severe conditions, etc. In the above example, the carbon steel of the outer layer It is prepared to bind to).

As a method of manufacturing the laminated steel pipe as described above, for example, the following method is known as the prior art.

In other words, as shown in FIG. 16 of the accompanying drawings, a tubular body 2 'made of stainless steel is fitted into a thick tubular body 1 made of carbon steel and placed in the tubular body 1 ( 2 ') are welded continuously over their entire circumference.

On the outer circumferential surface of the tube 2 ', nickel plating of 80-130 mu m thickness is applied to prevent the diffusion of carbon when the tube is joined metallurgically.

In addition, the outer diameter of the tube 2 'is about 1/16 inch smaller than the inner diameter of the tube 1 so as not to cause any trouble when the two are fitted together.

At the end of the tubular body 1, a gas discharge hole 1a 'is formed which leads to a gap between the tubular bodies 1 and 2'.

Such an assembly is called a tubing material, that is, a billet, which is heated through a rotary forge mill with the gas discharge hole 1a 'as the bottom after heating it to a predetermined condition.

Such a method or a method similar to the above is difficult for machining such as gas discharge holes 1a ', difficult to weld after joining the cores of the internal and external bodies 2', 1, Since the pipes are bent to each other, it is difficult to assemble long steels, which impairs the improvement of production efficiency of billet production.

In addition, there is a press-fit method for assembling the laminated billet, but since the press required to press the inner tube 2 'into the outer tube 1 has a limited stroke, a long material can be obtained. I can't.

Also, a heat shrink fitting method can be considered, but in the case of heat treatment fitting fixation, a scale (coating of thick metal oxide) is generated on the inner circumferential surface of the tube 1 so that the metallurgical bonding property can be obtained when the tube is manufactured. It is bad and thus causes a decrease in product inspection pass rate.

In addition, in order to prevent the generation of scale during rolling during hot working, a method of replacing air between the tubular bodies 1 and 2 'with an inert gas such as argon is also carried out. In the laminated steel pipe having a total length of about 7m, the upper 2m and the lower 0.5m may be discarded due to poor metallurgical bonding.

Thus, there are various difficulties in the method which is said to be highly practical compared with the explosive cladding method etc. which are conventionally used.

The present invention has been made to solve the above-described problems possessed by the prior art, and the present invention is obtained by using a cold drawing technique as a middle material of a laminated billet or laminated bloom of a hollow or non-porous shape. It is a method to obtain required product by hot processing intermediate material.

In addition, an object of the present invention is to provide a method for producing a steel pipe with high production efficiency and high product inspection pass rate, and another object of the present invention is a bar-shaped steel, steel wire, etc. in a laminated state that has not yet been put to practical use. However, the present invention also provides a manufacturing method which can perform the excellent metallurgical bonding between the base material and the material with high production efficiency and recovery rate.

It is still another object of the present invention to provide a method for producing laminated steel which is excellent in metallurgical bonding and does not require large-scale facilities for carburizing.

That is, the present invention relates to a method for manufacturing a laminated steel obtained by laminating two or more kinds of metals, in which a core made of a metal to form an inner layer is directly or in a tube made of a metal to form an outer layer thereof. The outer peripheral surface of the tube body (one or more) made of the metal which will form the intermediate layer and the core body made of the metal which will form these inner layers and / or the metal body which will form the intermediate layer is the metal foil which is diffused to the metal in contact with it The material is loosely fitted through the one to which it is wound and attached, and cold fitting is carried out at the same time to obtain the intermediate material closely contacted with the core, and the intermediate material is heated to a predetermined temperature, and then heated to form the required product. It is characterized by performing a process.

Although a detailed description will be made later as a representative embodiment, first of all, a supplementary description of the main features of the present invention described above will be given to clarify the technical scope of the present invention.

First, the product of the present invention is a steel pipe and rod-shaped steel or steel wire.

These laminated steels generally have the same two-layer structure as the above-mentioned known laminated steel pipes, but when used in a place where both the inner and outer layers are exposed to a highly corrosive atmosphere, they are made of a corrosion resistant metal as a mixture. Steel pipes having a three-layer structure held on the outer circumference are preferable.

Moreover, also in steel wires, it is possible to arrange | position a base material in a center part, and the some mixture material in a surface layer.

That is, the steel pipe and the steel wire of the present invention are made of two or more kinds of metals, and are not limited to the case where the base material occupies the outer layer, but also include the case of occupying the inner layer or the middle car.

Next, when the product to be manufactured, such as a steel pipe, has a two-layer structure, the raw material to be fitted is a combination of two tubes or one tube and one rod body.

In the case where the product has a structure of three or more layers, the raw material to be fitted is a combination of three or more tubes or two or more tubes and one rod.

In addition, the core refers to the tube or rod to be located in the innermost layer.

In the following description of the materials used, carbon steel, alloy steel, stainless steel, or nickel base alloys are selected. As stainless steels, martensitic, ferritic, austenite, and other hardenable deposits Including chromium manganese, and nickel base alloys include Inconel.

As the material, wear-resistant steel, stainless steel, nickel and alloys thereof, titanium and alloys thereof, copper and alloys thereof, chromium and alloys and aluminum and alloys thereof are selected. Abrasion manganese steel.

First, the case where the method of the present invention is applied to steel pipe production having a two-layer structure will be described.

When manufacturing laminated steel pipes made of stainless steel with an inner layer and carbon steel, a large diameter tube made of carbon steel and a small diameter tube or rod made of stainless steel are prepared.

These tubes (or rods) fit the small diameter tubular body 2 or the rod 12 into the large diameter tubular body 1, as shown in FIG. 1 (a), and then cold-draw it. The inner diameter of the tubular body 1 and the outer diameter of the tubular body 2 (or the diameter of the rod body 12) may be set to such an extent that there is no problem in fitting the two.

That is, it is good to select so that a fitting may be carried out to such an extent that a fitting operation can be performed smoothly, without having to fit in a close state.

The outer diameter, thickness, inner diameter of the tubular body 2, and thickness (or diameter of the rod body 12) of the tubular body 1 may be appropriately set as far as the cold drawing process for producing the laminated billet is concerned. In this case, the laminated billet is set in accordance with the processing conditions in the production process of the material. In addition, it is preferable that the tubular bodies 1 and 2 are pipes without a joint part, but are not necessarily limited thereto.

In addition, the inner surface of the outer tube 1 and the outer surface of the inner tube 2 (or the outer surface of the rod 12) must be treated cleanly before the fitting of both, so that the polishing process is preferable, but instead of polishing Therefore, short blasting may be performed on both surfaces, or acid pickling may be performed.

In other words, it is sufficient as a pretreatment to remove the scale, and nickel plating is preferably applied to one side in order to prevent diffusion of carbon between the materials of the inner and outer layers.

In addition, other metal plating may be performed with the same effect. The method of using metal foil instead of plating will be described later.

In this way, the fitting bodies 1, 2 (or the fitting bodies 1 and the rod 12) are plastically deformed by pressing the opening, and then a hydraulic or chain drawing machine is used. Cold drawing to obtain a hollow laminated billet 3 (or non-porous laminated billet 13), which is an intermediate material, as shown in FIG. 1 (b).

2 (a) to 2 (d) schematically show the manufacturing conditions of the laminated billets (3) and (13), and the tubular bodies (1) (2) ( Or the cross section of the tubular body 1 and the rod body 12 is shown, the longitudinal cross section of the raw material which passes through the inside of a drawer in the center, and the cross section of the laminated billet 3 and 13 are shown in the right side.

Fig. 2 (a) and Fig. 2 (b) show the case of manufacturing hollow hollow billet 3, and Fig. 2 (a) shows the extraction of the metal core using the floc 51 and the second (b). In Fig. 2, the drawing state is shown only by the dice 52 without the flocks.

FIG. 2 (c) and FIG. 2 (d) show the case where the non-porous laminated billet 13 is manufactured. In FIG. 2 (c), the rod 12 of small diameter is used, and the inner layer is laminated. A laminated billet suitable for the production of laminated steel pipes, and a thin-walled pipe body 1 having a second thickness (d) is used, and a laminated laminated billet suitable for the production of laminated steel pipes having an outer layer as a material is obtained. Mandrel may be used to withdraw the metal core, and the drawing number may be about one time, but may be two or more times.

In regard to the degree of work, the inner tube 2 or the rod 12 may be reduced in diameter by an appropriate amount relative to the outer tube 1, and even a few percent of the standard may be sufficient, but it is desired that the inner tube or rod may be It is better to use a workability that even reduces the cross-sectional area.

The laminated billet (3) (or 13) produced in this way is the tubular body 1, 2 (or the tubular body 1 and the rod body 12) mechanically and firmly in close contact, so that no air remains between them. It is in a state.

Subsequently, this laminated billet (3) 13 is sheared to a set length, put into a heating furnace, and heated to a predetermined temperature.

In the case of the method according to the present invention and the tubular body 1 (2) (or the tubular body 1 and the rod body 12) constituting the laminated billet (3) (13), but firmly in close contact, the thermal expansion of the inner and outer metals Due to the difference in coefficients, there is no possibility that a small gap may occur between inner and outer layers in some cases.

For this reason, even if the above-mentioned minute clearance gap is generated by welding the thickness portion along the boundary line of the inner and outer layers, as shown in Fig. 1 (c) on the end faces of the laminated billets 3 and 13, It is desirable not to intrude.

As a result, even when the above-mentioned gap is generated, no scale is generated in the gap, and there is no fear that the inner and outer tubes or the tube and the rod are separated from each other during the subsequent production process. However, the coefficient of thermal expansion of the inner metal, such as when the inner tube (2) or rod (12) is carbon steel and the outer tube (1) is ferritic stainless steel, or the former is austenitic stainless steel, and the latter is carbon steel If the value is larger than that of the outer metal, there is no possibility that a gap is generated between the two by the heating of the laminated billet, so that the above-mentioned welding is unnecessary, but in other cases, the difference in the coefficient of thermal expansion of the inner and outer metals is remarkably large. This welding is not necessary unless the length of the laminated billet is short to some extent. When the required heat treatment is finished, the laminated billet is transferred to the tube making process.

Production can be performed using a rolling mill, or by a press method.

As a rolling mill, a rotary mill, a plug mill, an axel mill, a mandrel mill, a pilger mill or a reducer is used. In the case of hollow laminated billets, the rolling mill is stretched and rolled. You can make it.

In the case of non-hollow laminated billets, first, the punching mill, ie, rotary piercer or press piercing mill, is used to drill holes, and then the rolling mill is the same as in the case of the hollow laminated billets described above. Stretch-rolling is carried out in accordance with the present invention.

As a result, the desired laminated steel pipe 4 as shown in FIG. 1 (d) is obtained, and the laminated steel pipe obtained in this way may be cold worked if necessary.

In case of press method, extrusion method such as Yudin Senryu method, Zinger press method, or push-pull method such as Elhard Pushbench method is appropriately adopted, and the hollow laminated billet completed with the required dimensions by internal dimension (3) It may be sent to a horizontal press process by an extrusion press of Yudin Senryu after heating. However, a non-porous laminated billet 13 or a hollow laminated billet 3 having an inner diameter of about a guide hole may be used in a vertical press. It is sent to a horizontal press process after carrying out the perforation process by the process.

The non-porous laminated billet 13 is, of course, subjected to guide holes or conical processing before being put into a heating furnace.

Further, before the heat treatment, the hole may be processed by a horizontal press by machining.

In the case of the Elhard push bench method, the non-porous laminated billet 13 is used, and after heating, it is processed into a hollow tube having a bottom by an Elhard press and then pressed by a tindam die method or a single die method. Work is done.

In addition, when the manufacturing process in the method of the present invention is the Elhard push bench method, the non-porous lamination billet is not limited to the circular billet shown in the drawing, but may be a square billet.

As described above, the laminated steel pipe 4 (first (d) diagram) obtained as a press method may be finished by cold working thereafter as necessary.

Next, the Example at the time of manufacturing the laminated steel pipe which made the inside mixture into an austenitic stainless steel by the method of this invention is demonstrated.

Example 1

As the outer tube 1, an outer diameter of 214 mm, an inner diameter of 151 mm, and a thickness of 31.5 mm made of carbon steel with a carbon content of 0.20% was used. The inner tube (2) had 0.07% carbon, 8.5% nickel and 18.0% chromium. Austenitic stainless steels with an outer diameter of 148 mm, an inner diameter of 122 mm and a thickness of 12.5 mm were used.

Grinding the inner surface of the outer tube 1 and the outer surface of the inner tube 2 and pressing them together to crimp the opening to form a plastic deformation process, and then cold drawing as the shape of FIG. To obtain a hollow laminated billet (3) having an outer diameter of 205 mm, an inner diameter of 121 mm, and a thickness of 42 mm (outer layer 30 mm + inner layer 12 mm).

Thereafter, the laminated billet was cut into a predetermined length and welded to the inner and outer layer boundaries at both ends, and heated at 1,170 ° C. for 100 minutes in a rotary furnace heating furnace. Subsequently, this billet was provided to a rotary rolling mill, and stretched to an outer diameter of 223 mm, an inner diameter of 198 mm, and a thickness of 12.5 mm, and then stretched again to an outer diameter of 217 mm, an inner diameter of 196 mm, and a thickness of 10.5 mm as a floc mill. It is 230mm, inner diameter 209.5mm, thickness 10.25mm, and finally, it is rolled to the selected diameter by plastic processing as the precision between 6 stands, and obtained laminated steel pipe with outer diameter of 219mm, inner diameter of 198mm and thickness of 10.5mm (outer layer of 8mm + internal resistance of 2.5mm). .

The laminated steel pipe was subjected to ultrasonic damage inspection over its entire length and its entire circumference.However, except for 20cm of the top and 5cm of the bottom of the tube about 7.7m, it was completely metallurgically joined to the base material of the outer layer and the mixture of the inner layer. It is obvious that you are doing.

As mentioned above, the incomplete part of the metallurgical joint is confirmed at the top and the bottom part because both ends of the steel sheet are encroached into the inner surface of the tube when the tube is manufactured, and has nothing to do with the characteristics of the method of the present invention. .

FIG. 3 is a 100 times metal microscope photograph of one end surface close to the tube end of the laminated steel pipe obtained as described above, with the carbon steel of the base material (upper part: puerlite structure) and the stainless steel of the mixture (lower part of picture: It is evident that the austenitic structure) is completely joined together in a metallurgical manner.

In the case of such a method of the present invention, the following effects are obtained.

(1) The laminated billet, which is a raw material in the production process, is obtained by drawing two or more tubes or rods together by cold drawing, so that air is not completely left in the gap between the joining surfaces.

For this reason, there is no scale generation inside the billet during heating, and the inner and outer layers are completely joined metallurgically by the production of hot tubing.

In addition, since it is not necessary to consider the discharge of air in hot work, there is no need for machining to form a gas discharge cavity as in the prior art, and there is no fear that the inner and outer layers will peel off during hot work.

(2) It is possible to manufacture long laminated billets, and it is only necessary to cut them to the required length, so the efficiency of billet production is high.

(3) Since the base material and the composite material inside and outside of the billet are completely in close contact with each other, the pass rate of the quality inspection of the product is very high because it is completely metallurgically joined from the normal to the bottom part after stretching rolling by hot working or after hot pressing. It becomes high.

(4) In the production of laminated billets, the treatment of the inner and outer tubes is not necessarily required for grinding, but may be a simple treatment such as washing with acid due to the removal of scale, which is sufficient. The pretreatment process is simplified.

As described above, the present invention is cold drawn to obtain hollow or non-porous billets made of steel pipe materials, that is, a technique that can be said to be out of the common sense in the processing technology of steel products to be installed before the hot working process. By adopting this, excellent effects are obtained.

By the way, in the case of a steel sheet steel pipe made of carbon steel and stainless steel, nickel plating is performed on the outer circumferential surface of the tubular body 2 (or the rod 12) with a thickness of 30-50 μm in order to prevent carbon diffusion or carburization.

However, the equipment cost for the plating equipment and its auxiliary equipment is extremely high and a lot of manpower is required for the material preparation for the plating. Furthermore, the plating costs are high because the plating is performed by electrolysis. Since the size is limited, the length of the laminated billet cannot be lengthened because the length of the laminated billet is constrained in manufacturing the laminated billet as described above, and it has been a factor that increases the manufacturing cost per unit weight.

In order to solve this problem, the present invention proposes a method of winding a thin foil of metal (hereinafter referred to as metal foil) instead of plating. That is, as shown in FIG. 4 (a) or FIG. 4 (b), the metal foil 5, for example, nickel foil having a suitable thickness is spirally formed on the outer circumferential surface of the tubular body 2 or the rod body 12 that will constitute the inner layer. The wound is fitted into the tube 1 to form the outer layer.

Thereafter, as described above, cold drawing is performed to obtain a hollow or non-porous laminated billet, and then hot working.

Moreover, in the case of a structure of three or more layers, a metal foil is wound up also on the outer peripheral surface of the tubular body which comprises an intermediate | middle layer as needed.

The pretreatment of the portion wound on or opposite to the metal foil, that is, the outer circumferential surface of the tube body 2 or the rod body 12 of FIG. 4 and the inner circumferential surface of the outer tube body 1, may be polished, shot blasted or pickled. Used.

Winding the above-described metal foil 5 may be wound in a spiral shape so that the side edges of the metal foil tape overlap each other little by little so as to cover the entire main surface of the tubular body 2 or the rod 12.

It is preferable to use 20-80 micrometers in thickness as this metal foil tape, and when the reduction rate is large in a later process, a comparatively thick thing is selected.

As mentioned above, it is preferable to select the thing of 30 micrometers or more from a workability at the time of winding up a metal foil, and 40 micrometers or more from an economic view.

Next, the Example at the time of winding up such metal foil is demonstrated.

Example 2

As the base material 1 constituting the outer layer, the outer diameter 214 mm, inner diameter 151 mm, and thickness 31.5 mm made of 0.18% carbon guild steel is 0.06% carbon, and nickel is the material mixture 2 constituting the inner layer. An outer diameter of 148 mm, an inner diameter of 122 mm, and a thickness of 13 mm made of an austenitic stainless steel of 8.2% and chromium 18.2% were used.

The inner surface of the tube body 1 and the outer surface of the tube body 2 are polished, and the outer surface of the tube body 2 is spirally formed so that the ends thereof slightly overlap each other with nickel foil having a thickness of 50 μm on the outer surface of the tube body 2. After wrapping the entire side surface as if it were covering, fitting the pipes (1) and (2), crimping the openings to perform plastic deformation processing, and then cold drawing with a 200t hydraulic press, 205mm outside diameter, 121mm inside diameter, 42mm thickness The hollow-phase laminated billet (3) of (outer layer 30mm, inner layer 12mm) was obtained.

The laminated billet 3 is cut to a certain length, and a circumferential weld is applied to the inner and outer boundary portions in both cross sections, and this is heated in a rotary furnace heating furnace for 1,170 ° C. for 100 minutes, and then the billet of this fixed length is rotated. As a rolling mill, it is drawn and rolled to an outer diameter of 223 mm, an inner diameter of 198 mm and a thickness of 12.5 mm, and then stretched into a floc mill with an outer diameter of 217 mm, an inner diameter of 196 mm and a thickness of 10.5 mm. Finally, the opening was crimped with the precision between 6 stands, and plastic deformation processing was performed, and the sheet was rolled to a set shape to obtain a laminated steel pipe having an outer diameter of 219 mm, an inner diameter of 198 mm, and a thickness of 10.5 mm (outer layer of 8 mm and inner layer of 2.5 mm). .

5 is a 100 times metal microscope photograph of one end surface close to the tube end of the laminated steel pipe obtained as described above, and the carbon steel of the base material (upper part: pearlite structure) and the stainless steel (lower part of the picture: oh) of the base material. It is evident that the stenitite structure is integrally bonded completely metallurgically through the nickel layer 3 (intermediate thin layer in the photograph).

Example 3

As the outer tube 1, an outer diameter of 252 mm, an inner diameter of 149 mm, and a thickness of 51.8 mm made of low-alloy steel of carbonaceous 0.11%, silicon 0.38%, manganese 0.46%, chromium 4.78%, molybdenum 0.48%, and the inner tube (2) ), An outer diameter of 145 mm, an inner diameter of 98 mm, and a thickness of 23.5 mm of austenitic stainless steels of carbon 0.04%, nickel 12.5%, chromium 17.7%, molybdenum 2.6%, and titanium 0.41% were used.

The inner surface of the outer tube 1 and the outer surface of the inner tube 2 are polished, and a nickel foil having a thickness of 80 μm is formed on the outer circumferential surface of the tube 2 so that the edges thereof overlap each other slightly without spiraling. The inner tube (2) was inserted into the outer tube (1), and the opening was pressed to perform plastic deformation processing. In this state, a cold drawing was carried out using a 200t hydraulic press to obtain an outer diameter of 248.5 mm and an inner diameter of 97.9. A hollow laminated billet (4) having a thickness of 75.3 mm (outer layer 51.75 mm + inner layer 23.55 mm) was obtained.

Subsequently, the laminated billet 4 was cut into a predetermined length, and circumferential welding was performed on the inner and outer boundary portions at both end surfaces thereof, and this was heated at 1,130 ° C. for 30 minutes in an induction heating furnace.

In addition, a laminated steel pipe having an outer diameter of 114.3 mm, an inner diameter of 92.6 mm, and a thickness of 10.85 mm (outer layer of 8.55 mm + inner layer of 2.30 mm) was obtained by Yudin Sen-ryu extrusion press.

FIG. 6 is a 100 times photograph of a metal microscope of one end surface close to the end between the laminated steel pipes obtained as described above, and the austenitic stainless steel of the base metal and the low alloy steel (the upper part of the photo: martensite structure) The state where steel (the lower part of a photograph: an austenite structure) interposed the nickel layer (intermediate part in a photograph) between them and can fully confirm metallurgical integration.

Thus, when adopting the method of winding up the metal foil as a material to prevent the coal

(1) Since the metal foil is wound spirally on the outer circumferential surface of the tubular body or rod forming the inner layer and fitted to the tubular body forming the outer layer, it is cold drawn. There is no need for plating equipment, so there is no expense.

(2) By adopting the method of rolling and attaching the metal foil, it is possible to produce a long billet without limiting the length and size of the tube or rod, etc. Compared with the size, length and length of the pipe, the cost per unit weight is extremely low, and the quality pass rate of the pipe is extremely high.

(3) The price of the metal foil is extremely low compared to the plating cost, and moreover, even in view of the manpower required for rolling and attaching, it is only about several% of the plating. Is obtained.

Next, a method of manufacturing a laminated steel pipe slightly different from the above method will be described.

In this method, the intermediate material is also cold drawn and falls within the scope of the method of the present invention in the same manner as in each of the embodiments described above. Bloom (hereinafter, referred to as a bloom body) is used as a rod to form an inner layer. As a result, the intermediate material obtained by cold drawing becomes a lamination bloom, and accordingly, the process for manufacturing a non-porous lamination billet by heating and pulverization rolling is added.

The method is described below.

First, a tube and a bloom body for producing a laminated billet according to a desired structure are selected. For example, in the case of a laminated steel pipe having an inner layer of carbon steel and an outer layer of stainless steel, a bloom body made of carbon steel and a stainless steel The tube is ready.

As the bloom body, for example, a bloom obtained by continuous casting may be used, and as the pipe body, a pipe or a welded pipe without a connecting portion may be used.

And as shown in FIG. 7, for example, the rectangular bloom material 22 is fitted to the rectangular tubular body 21 so that the cross-sectional shape of both is not limited to the rectangular shape, but the circular control and the rectangular ( Or a combination with a circular bloom.

In addition, the relative dimension relationship between the inner dimension of the tubular body 21 and the cross-sectional dimension of the bloom body 22 only needs to be set so that it may be performed satisfactorily when fitting both.

In addition, the outer dimension of the tubular body 21, the thickness, and the cross-sectional dimension of the bloom body 22 itself may be appropriately set as far as the cold drawing process for producing the bloom is carried out. It is determined in consideration of processing conditions in.

In addition, the inner surface of the tubular body 21 and the surface of the bloom body 22 are polished prior to the fitting of the two, so that shot blasting may be performed on both surfaces instead of polishing, and only pickling may be performed. good.

In order to prevent diffusion of carbon between the materials of the inner and outer layers, nickel plating may be applied to one surface or the foil foil may be rolled and attached to the bloom element 22.

These points are the same as in the foregoing embodiment.

The fitting body 21 and the bloom body 22 thus fitted are subjected to plastic working on the tube body 21, and then cold drawn using a hydraulic or chain drawing machine, and the like shown in FIG. 7 (b). As described above, the laminated body 23 in which the tubular body 21 and the bloom element 22 are mechanically in close contact with each other is obtained.

8 (a), 8 (b), and 8 (c) show the manufacturing conditions of the laminated bloom 3 and the tubular body 21 and bloom which are fitted to the left side in each drawing. The cross section of the raw material 22 is shown in the center, the longitudinal cross section of the raw material passing through the inside of the drawing machine, and the cross section of the laminated room 23 is shown on the right side.

FIG. 8 (a) shows the case where both the bloom and the tubular body are rectangular, and FIG. 8 (b) shows the case where the bloom and the tubular body are circular and the tube body is circular, and FIG. have.

Reference numeral 52 in the drawing indicates a dice.

In addition, about the degree of work, the tubular body 21 may be reduced relative to the bloom body 22 by an appropriate amount, and the standard of about several% may be sufficient.

In addition, the number of times is preferably one, but may be two or more times.

The laminated bloom 23 produced in this way is in a state where the tubular body 21 and the bloom element 22 made of the raw material are firmly in close contact with each other, and no air remains between them.

Subsequently, this laminated room 23 is cut to a predetermined dimension, put into a crack furnace, and heated to a required temperature.

Even in this case, in order to prevent scale generation due to gap formation due to a difference in thermal expansion coefficient of the inner and outer layer metals, the laminated room 23 is formed at the boundary line of the inner and outer layers as shown in FIG. According to the welding, when the difference in the coefficient of thermal expansion of the inner and outer layer metals is remarkable, it is not really necessary except for the case where the length of the cut laminated bloom is particularly short.

After the required heat treatment is completed, the laminated bloom is hot rolled into a steel piece cracking mill such as a reversible steel piece cracking mill or the like, for example, a round cylindrical laminated billet 24 as shown in Fig. 7 (d). Get) The laminated billet 24 is subjected to an inter-hot processing, that is, a rolling process, and in addition, since no air remains between the inner and outer layers of the metal, both layers are completely metallurgically joined.

The laminated billet 24 thus obtained is cut and processed into a predetermined length to be a material of a limited process, and is then sent to a manufacturing process. As the manufacturing process, a Mannes mann plug mill method, a Mannesmann assembly method, The so-called incline rolling method such as Mannesmann mandrel mill method or Mannesmann peeler mill method, or extrusion method such as Yudinsen-type method, singer press method, or press method such as Elhardt push punch press plate method is the product use, material, actual cost condition Etc. are appropriately adopted.

For example, in the Mannesmann force mill method, the laminated billet 24 is cut into a predetermined length and heated as a rotary furnace type heating furnace, followed by rotary peering, rotary rolling mill, prader mill, liller, and steel making in the order of order. .

Thus, the desired laminated steel pipe 25 (the seventh (e) degree) is obtained, and may cold-work after that as needed.

In addition, in the case of the press piercing mill or the push-out method of Elhard's push punch, the square billet may be produced by the rolling and may be provided as a cleansing agent.

Next, the Example at the time of manufacturing the laminated steel pipe which made the outer layer material into the austenitic stainless steel by the method mentioned above is demonstrated.

Example 4

As the outer tube 1, a rectangular tube having an outer diameter of 500 mm, an inner diameter of 408 mm, and a thickness of 46 mm made of austenitic stainless steel of 0.07% carbon, 8.5% nickel, and 18.0% chromium, or the inner bloom element 22 ) Was used as a continuous casting bloom of 400 mm ψ made of a carbon steel of 0.20% carbon.

After grinding the inner surface of the tube body 21 and the surface of the bloom body 22, they are fitted with Aries, and the opening of the tube body 21 is pressed to perform plastic deformation processing. As shown in the figure, cold drawing was carried out to obtain a laminated bloom 23 of 492 mm ψ (but the bloom element 22 remains 400 mm ψ).

Thereafter, the laminated bloom 23 was cut to a predetermined length, and the inner and outer layer boundary portions were agglomerated at both end surfaces, and were heated at 1,250 ° C. for 180 minutes in a cracking furnace.

As a heating type rolling mill, the laminated bloom 23 was rolled annually to 285mmψ (thickness of the outer layer 27mm, cross-sectional dimension of the inner layer 231mmψ), and then, as a continuous stand mill of 6 stands, 197mmψ outer layer thickness 18.5mm, inner layer diameter 160mm Circular laminated billet (24) was obtained.

The laminated billet 24 was heated at 1,170 ° C. for 100 minutes in a rotary furnace common sense heating furnace, and was produced by Mannesmann floc mill method.

The dimension (unit mm) of the pipe in the exit side of the mill to this piping process is as follows.

Ultrasonic breakage test was carried out on the laminated steel pipe from the sizer, over its entire length and its entire circumference, but metallurgical bonding was completed with the inner base material and the outer layer of the material except for 20cm of the top and 20cm of the top of the length of the pipe. It is clearly confirmed that there is.

As mentioned above, the incomplete part of the metallurgical joining is observed at the top and the bottom part because it is rolled into the inner surface of the tube when both ends of the steel sheet are produced and have nothing to do with the characteristics of the method of the present invention.

9 is a 100 times metal micrograph of a cross section close to the end of the laminated steel pipe obtained as described above, and the carbon steel of the base material (the lower part of the photograph: the pearlite structure) and the stainless steel of the composite material (the upper part of the photograph: It can be clearly seen that the yoyosterite structure) is completely metallurgically integrated and bonded.

Also in the case of the above-described method, since the extremely characteristic method of obtaining the laminated bloom as an intermediate material as cold drawing is used, the following effects are obtained.

(1) Since the laminated bloom is obtained by extracting the tubular body and the bloom element by cold drawing, the air in the joining surface gap is not completely left.

Therefore, there is no scale generation inside the laminated room even when heated for the hot rolling, and thus the laminated metal billet is completely metallurgically bonded, and thus, the metallurgical laminated pipe is completely metallurgically bonded, and the inner and outer layers are peeled off during hot working. There is no concern.

In addition, since the inner and outer layers are closely adhered to each other by cold drawing, it is not necessary to consider the discharge of residual air during hot working, and thus, no machining is required, such as the formation of gas discharge holes, as in the case of obtaining the laminated steel pieces as described above. .

(2) The production efficiency of the billet production is high because the processing for lamination is carried out at the manufacturing stage of the bloom which is the material of the billet used as the raw material in the manufacturing process.

In addition, long steel slabs and long pipes can be easily obtained.

(3) In the stage of BLUM, the base metal and the composite material are completely in close contact with each other mechanically, so that after hot rolling, they are completely joined metallurgically from the top to the bottom.

Therefore, the pass rate of product quality test is extremely high.

(4) Prior to the production of laminated bloom, pretreatment does not necessarily require grinding, only removal of scale is sufficient, and simple processing such as pickling may be sufficient, thus making the aforementioned machining unnecessary and pretreatment. This is enlightened and streamlined.

Next, a method of manufacturing a laminated steel wire rod will be described.

In the case of steel wire manufacturing, it is basically characterized in that the intermediate material is obtained by cold drawing as in the case of steel pipe manufacturing, but as a core of the inner layer, of course, the rod (including the BLUM material as described above) is Used.

And it can be roughly divided into the case of manufacturing a laminated billet as cold drawing, and the case of manufacturing a laminated billet by manufacturing a laminated bloom, and then heating-dividing rolling.

First, the former case will be described.

First, as shown in FIG. 10 (a), the small diameter cylinder 32 is fitted into the large diameter tube 31. As shown in FIG.

The inner diameter of the tube body 31 and the diameter of the rod body 32 should be appropriately set so that the fitting between them will not interfere and the number of cold drawing will not be unnecessarily increased (preferably as one time). In addition, clean cleaning of the inner surface of the tube body 31 and the outer surface of the rod body 32 prior to the fitting thereof is the same as in the case of steel pipe manufacturing, and nickel plating is applied to the surface of the rod body 32 as necessary. Conduct.

Moreover, you may roll up and attach nickel foil.

The fitted tube body 31 and the rod body 32 are subjected to plastic deformation processing by pressing the opening against the tube body 31, and then simultaneously cooled and drawn out using, for example, a hydraulic machine or a chain machine. As shown in FIG. 10 (b), the inner surface of the tubular body 31 and the outer surface of the rod body 32 are formed of a non-porous laminated billet 33 in close contact with each other.

11 (a) to 11 (c) show roughly the manufacturing conditions of various laminated billets. In each of the drawings, longitudinal sections of the tubular body and the rod body fitted to the left side are shown, and a die 52 in the center thereof. Longitudinal cross sections of the tube body and the rod body passing through the inside) are shown on the right side, and a cross section of each laminated billet obtained by cold drawing.

That is, FIG. 11 (a) shows the case where the laminated billet 33 of a non-porous circular cross section is obtained from the tubular body 31 and the rod 32 of circular cross section, and FIG. 11 (b) shows the tubular body of circular cross section. The case where the laminated billet 33 of the same non-hollow interspace cross section is obtained from 31 and the bar 32 of a square cross section is shown, and FIG. 11 (c) shows the tubular body 31 and the rod 32 of a cross section. Similarly, the case where the laminated billet 33 of non-porous rectangular cross section is obtained is shown, respectively.

In addition, the number of times is preferably one, but may be two or more times.

The degree of work may be such that the outer tube 31 is relatively reduced with respect to the inner rod 32, or may be a standard of several percent. However, the rod 32 is also preferably used to increase the adhesion between them. It is good to make it adhere to the tube body 31 in the state which reduced the cross section area slightly.

The laminated billet 33 thus produced is in a state in which the tube body 31 and the rod body 32 are firmly in close contact with each other mechanically so that no air remains between them.

Next, the laminated billet 33 is heated to a predetermined temperature through a heating furnace as it is.

Also in this case, before heating, the boundary line of the inner and outer layers is welded at the end surface of the laminated billet to prevent air intrusion into the gap velocity between the inner and outer layers.

After completion of the required heat treatment, the laminated billets (3) (31) and (32) are transferred to the stretching rolling process in the hot treatment.

In the stretching and rolling process, the rollers are rolled as ball rollers by the following processes suitable for the intended products.

The hot rolled steel bars are each cut to the appropriate length after cooling and, if required, calibrated and heat treated.

In the case of the wire 34, as shown in FIG. 10 (c), the coil is wound into a coil shape after cooling and completed by performing necessary heat treatment.

Next, an example is given taking the case of a laminated bar as an example.

Example 5

As the base rod 32, a non-boiling steel roll having a diameter of 191 mm made of a killed steel containing 0.16% carbon, and a steel sheet 31 having 0.06% carbon, 9.5% nickel, and chromium 19.0 An outer diameter of 216 mm, an inner diameter of 206 mm, and a thickness of 5 mm made of% austenitic stainless steel were used.

The main surface of the rod body 32 and the inner circumferential surface of the tube body 31 are polished, and a nickel foil having a thickness of 80 μm is plated on the main surface of the rod body 32 as a plating material, and the end edges of the rod body 32 are slightly overlapped with each other to roll in a spiral without gaps. After attaching the rod 32, the rod 32 is inserted into the tube 31 and subjected to plastic deformation at both ends, and cold drawn using a 200 ton hydraulic press to make the outer diameter of the tube 31 200 mm and the diameter of the rod 32 190.5. mm and a laminated steel piece 33 having an outer layer thickness of 4.75 mm was obtained.

The laminated steel piece 33 cut | disconnected this to predetermined length, and welded the junction part of an inner and outer layer over the periphery in both end surfaces, and heats it for 90 minutes at 1,160 degreeC in the heating furnace, and the preparation heat 1-8 stand, Through the mill to produce continuous rod-shaped steel of medium row 9-12 stands and finished row 13-16 stands, rod-shaped steel having an outer diameter of 22 mm, an inner diameter of 20.95 mm and an outer layer thickness of 0.525 mm was obtained.

After descaling the rod-shaped steel using superfluoric acid, lubricating the surface with a mixture of Philel Bond and Bon Diryube, and plastic deformation processing were completed. The bar was cold drawn to obtain a laminated bar having an outer layer outer diameter of 19 mm, an outer layer inner diameter of 18.1 mm, and an outer layer thickness of 0.45 mm.

FIG. 12 is a 100-time photograph of metal microstructure of one end surface close to the distal end portion of the laminated bar obtained as described above, and the outer layer of austene in which the inner layer of carbon steel (the lower part of the photograph: the pearlite structure) is laminated. It has been confirmed that the nit stainless steel (upper part of the photograph: austenite structure) is sandwiched by a nickel layer interposed therebetween and completely joined together metallurgically.

In such a method, the production of high quality laminated rod-shaped steel that is completely metallurgically bonded and a long length of laminated steel are obtained, resulting in high production efficiency, high product pass rate, and easy pretreatment. In the case of the present invention, the same effect as in the case of the present invention is obtained. In particular, the method of the present invention brings about the fact that industrial manufacture of laminated rod-shaped steel and laminated steel wire, which has not been found in the past, has become possible. .

Next, in the production of laminated rod-shaped steel, a method of manufacturing a laminated bloom by cold drawing, obtaining a non-porous laminated steel piece by induction rolling, and then preparing a preparation by stretching rolling will be described.

For example, in the case of manufacturing laminated steel using carbon steel as the inner layer as the base material and stainless steel as the outer layer as the base material, a tubular body having a square cross section made of carbon steel and a stainless steel made of a square cross section made of carbon steel, for example, is prepared. .

As a bloom body, what is obtained by continuous casting may be used as it is, or cut and cut to an appropriate length, and a pipe body may be manufactured according to a bloom body by welding, or a pipe or welded tube without a joint part may be provided.

Of course, the cross-sectional shapes of the tubular body and the bloom body may be circular or other shapes other than squares.

Next, as shown in FIG. 13 (a), when the bloom body 42 is fitted into the pipe body 41 and cold drawn thereafter, the cross-sectional area of the pipe body 41 and the cross-sectional area of the bloom body 42 are shown. And just set it so that the fitting of both will not interfere.

However, if the difference between them is too large in actual work, the number of PS increases, so it is desirable to keep the difference between them as small as possible within the range where the fitting is performed without any problems.

In addition, before fitting the blooms 42 into the pipes 41, the inner surface of the pipes 41 to be joined to each other and the outer surface of the blooms 42 have metallurgical bonding properties between the pipes 41 and the blooms 42. In order to increase, polishing for removing scales or the like is performed.

Instead of polishing, for example, a cleaning treatment for cleaning the surface by shot blasting or pickling may be performed.

Further, on the inner surface of the tubular body 41 or on the outer surface of the bloom body 42, carbon diffuses from the bloom body 42 to the tubular body 41 in the case where the bloom body 42 is carbon steel, the tubular body 41 is stainless steel, or the like. Nickel plating should be applied to the required thickness (usually 30-50 µm) on either side to prevent this.

Of course, you may roll up and attach nickel foil.

The pipe body 41 and the bloom body 42 in the fitted state are pressed against the pipe body 41 and subjected to plastic deformation processing, and then passed through the die by means of a hydraulic drawing machine or a chain drawing machine, for example. It is cold drawn, and it shape | molds into the non-porous laminated bloom 43 in which the inner surface of the tubular body 41 and the surface of the bloom body 42 were in close contact as shown in FIG. 13 (b).

Figures 14 (a) to 14 (c) show the process of manufacturing a laminated bloom by combining a tubular body and a bloom body having all different cross-sectional shapes, each of which is fitted on the left side. The cross section of the tubular body and the bloom material is shown at the center, and the cross section of the tubular body and the bloom element being cold drawn by the die 52 at the center, and the cross section of the laminated bloom obtained by cold drawing at the right side.

Fig. 14 (a) shows a case where a laminated bloom 43 of a rectangular section is obtained from a tubular body 41 of a rectangular cross section and a bloom element 42 of a non-hollow rectangular cross section, and Fig. 14 (b) shows a circular cross section. Fig. 14 (c) shows a case in which a laminated bloom 43 of a rectangular section is obtained from a tubular body 41 and a bloom element 42 of a non-pore rectangular cross section. The case where the laminated bloom 43 of a circular cross section is obtained from the bloom element 42 of a circular cross section is shown, respectively.

PS is preferably one, but may be more than one.

Further, the degree of work is to reduce the cross-sectional area of the tubular body 41 so that the inner surface thereof is brought into close contact with the outer surface of the bloom body 42, that is, a few% of the tubular body 41 being relatively reduced relative to the bloom body 42. Although a standard of degree may be sufficient, it is preferable to make it into the processing degree which reduces to the cross-sectional area of a bloom element preferably.

The laminated bloom 43 thus produced is in a state in which the tubular body 41 and the bloom element 42 are firmly in close contact with each other mechanically so that no air remains between them.

Subsequently, this laminated room 43 is put into a heating furnace as it is and heated to predetermined temperature.

Prior to this heating, the boundary lines of the inner and outer layers on the end face of the laminated room 43 are closed by welding as necessary in order to prevent air intrusion when a gap occurs in the same manner as stated.

When the laminated bloom 43 is heated up to the required temperature, the laminated bloom 43 is hot rolled into a steel flake rolling mill such as a reversible steel crushing mill or a continuous steel crushing mill, and metallurgically joined to form a metal sheet. The laminated steel piece as shown in the figure is obtained.

The laminated steel piece 44 is subjected to hot pores, i.e., a hot rolling process, and since no air is present between the metals of the inner and outer layers, oxides such as scale are not produced, and both metals are joined metallurgically.

The laminated steel piece 44 obtained in this way is supplied to the manufacturing process of a raw material so that it may become raw materials, such as a rod-shaped steel and a wire rod.

In the manufacturing process of a steel bar and a wire rod, it rolls as a ball roller by the following process suitable for the cross-sectional shape of a steel bar and a wire rod, respectively.

For example, after the laminated steel piece 44 is heated to a required temperature in a heating furnace, it is stretched and hot rolled by a ball roller to obtain a laminated steel material having a required shape as shown in Fig. 13 (d).

Next, the Example at the time of manufacturing the laminated wire whose outer layer was made of the austenitic stainless steel by the method of this invention is demonstrated.

Example 6

The outer tube 41, which is a mixture, has a circular tube of outer diameter 646 mm, inner diameter 566 mm, and thickness 46 mm, made of austenitic stainless steel of 0.08% carbon, 7.35% nickel, and chromium 17.8%. As the bloom body 42, a continuous casting bloom of 400 mm? Made of carbon steel of 0.17% carbon was used.

After polishing the inner surface of the tube and the surface of the bloom body 42, the two are fitted together, and the opening of the tube 41 is crimped to perform plastic deformation processing. As shown in the figure, cold drawing was carried out to obtain a laminated bloom of 480 mm ψ (but the diameter of the bloom material portion remains 400 mm ψ).

Thereafter, the laminated bloom was cut to a predetermined length, and the inner and outer boundary lines were welded and closed on both end faces, and this was subjected to a heat treatment for 180 minutes at 1,250 占 폚 in a crack furnace.

The rolled bloom was hot rolled using a reversible cracking rolling mill to form 240 mm ψ (thickness of the outer layer 20 mm, cross-sectional dimension of the inner layer 200 mm ψ), followed by 115 mm ψ (thickness of the outer layer 9.75 mm, thickness of the inner layer 95.5) as a continuous continuous rolling mill of six stands. mm) square rectangular steel pieces were obtained.

The laminated steel pieces were heated at 1,150 ° C. for 90 minutes in a heating furnace, and the laminated steel pieces heated at 1,150 ° C. in a heating furnace were taken out and stretch rolled as a continuous wire mill of 1-7 stands of prepared heat and 8-15 stands of intermediate heat. It is made of 17.5mm shipbuilding material, and then the shipbuilding material is passed through a continuous block mill of 16-25 stands, and the finished wire is 5.5mm outside diameter, 4.6mm outside layer thickness and 0.45mm outside layer thickness. Got.

After descaling the finished wire using superfluoric acid, lubricating the surface with a mixture of Pelbond and Bonderyube, compressing the opening to perform plastic deformation processing, and drawing the finished wire from cold To obtain a steel wire having an outer layer outer diameter of 3.0 mm, an outer layer inner diameter of 2.5 mm, and an outer layer thickness of 0.25 mm.

FIG. 15 is a 100-fold metal microscope combined photograph of one end surface close to the distal end portion of the laminated wire obtained as described above, and the ferrite stainless steel of the outer layer, which is laminated with carbon steel of the inner layer (the lower part of the photograph: the pucklite structure). It can be seen that the steel (upper part of the photo: austenite structure) is completely metallurgically bonded together.

According to the method of the present invention as described above, the following effects are obtained.

(1) The laminated bloom is obtained by pulling the tubular body and the bloom body together as a cold draw and bringing the two into close contact with each other. Therefore, no air remains between the interface between the two surfaces. The metallurgical fully bonded laminated steel piece which does not generate scale, and the laminated pipe material which were fully metallurgically bonded by this are obtained, and there is no fear that the inner and outer layers may peel off during hot working. In addition, since both inside and outside layers are completely adhered by cold drawing, it is not necessary to consider the discharge of residual air during hot processing, and therefore the assembly cost of BLUM can be extremely inexpensive.

(2) Since the processing is performed for lamination at the manufacturing stage of BLUM, which is the material of the steel sheet to be used in the manufacturing process of the laminated steel, the production efficiency of the steel sheet is high, and the long steel strip or the long steel wire material is easy. You can get it.

(3) At the stage of BLUM, the base metal and the composite material are completely in close contact with each other mechanically, and after the hot rolling in the hot treatment, the metallurgical perfect joint is obtained from the top to the bottom.

Therefore, the product pass rate is very high.

(4) As a treatment before producing the laminated bloom, it is not necessarily necessary to remove the scale, it is sufficient to remove the scale, and a simple treatment such as pickling may be necessary. Therefore, the above machining is unnecessary and the pretreatment process is simplified. The same effect as the manufacturing method of steel pipes and crude materials as described above is obtained.

As described in detail above, the present invention adopts a method contrary to the conventional technical common knowledge that the material of hot working is manufactured as cold drawing, and thus, production of steel pipe, section steel, etc. as a product with high production efficiency and high quality. It is possible to provide high quality steel pipes, section steels, etc. with excellent metallurgical bonding.

Particularly, rod-shaped steels and steel wires, which did not exist in the past, were industrially produced by the present invention and could be provided for new applications.

In addition, in the case of using a metal foil as a medium for preventing carburization, the present invention exhibits excellent effects, such as easily manufacturing a carburized laminated steel without requiring a large-scale plating facility.

Claims (1)

In the method for producing a laminated steel formed by laminating two or more kinds of metals, in the tube 1 made of the metal to form the outer layer, the core 2 made of the metal to form the inner layer is directly or On the outer circumferential surface of the tube body made of the metal to form the intermediate layer and the core body made of the metal to form the inner layer or the metal to form the intermediate layer, the metal foil 5 diffused on the metal in contact with it is wound and attached. It fits loosely through and cold-draws the fitting at the same time to obtain an intermediate material in which the tubular body and the core are in close contact with each other, and heat the intermediate material to a predetermined temperature, and then perform hot working to form the required product. Method of manufacturing laminated steel.

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