JPH01107985A - Manufacture of clad steel - Google Patents

Abstract

PURPOSE:To prevent unremovable oxidizing scale of titanium and stainless steel from occurring by putting a ply metal on a parent steel material, putting a thin steel material on it, welding the circumference, sealing the internal part, performing hot rolling and forming a thin surface layer of steel material. CONSTITUTION:A ply metal 2 of titanium and stainless steel is put on the surface of the parent steel material 1, the thin steel material 6 is put thereon, the circumference is welded 5, the internal part is sealed and hot rolling is performed. In this case, hot oxidized scale generated on the surface layer of a thin steel material 6 is removed in a pickling device for common steel material 6 to perform cold working. Thereafter, after a heat treatment carried out in the atmosphere, a thin layer of steel material on the hot oxidized scale and the ply metal is removed and then a slight cold treatment is executed. Then, it is possible to obtain clad steel having a homogeneous and nice surface of metallic luster and prescribed mechanical properties.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention inexpensively produces a clad steel material in which a thin metal layer having different and excellent properties is provided on the surface layer of a steel base material by a hot pressure welding method. It is about the method.

(Prior Art) Steel has great strength and is the most commonly used metal material, but it is highly chemically reactive and gradually oxidizes even in the atmosphere, causing rust. For this reason, various rust prevention measures have been devised since ancient times. For example, applying rust preventive oil, painting, plating,
Organic lining, hand cladding etc. Many methods have been proposed in the past for producing so-called clad steel, in which titanium or stainless steel is laminated in order to improve the surface characteristics of steel materials with excellent corrosion resistance.

Typical conventional techniques for manufacturing titanium and stainless steel clad steel include steel ingot casting, hot pressure welding, and explosion pressure welding. (Stainless Steel Handbook, published by Nikkan Kogyo Shimbun) The steel ingot casting method produces clad steel by casting the base material or composite material into a molten state in a mold, solidifying it, and then processing it by rolling etc. be. In this method, either metal is joined in a molten state, which causes the movement of component elements in the steel and the formation of intermetallic compounds, maintaining the excellent properties of the clad metal, and creating a thin cladding with a uniform thickness on the surface layer. It is difficult to form layers. In addition, the explosive bonding method is a method in which plywood is stacked on top of a base material, an explosive is placed on top of the plywood, and an explosive is detonated from the negative end to cause the metals to collide at high speed and join together. This method has disadvantages in that it detonates explosives, so it is limited by space, is unsuitable for large-area materials, and cannot be mass-produced. In the hot welding method, a composite material and a back-up material are stacked on the surface of a base material, or a composite material is stacked on the surface of a base material, the end faces are sealed by welding, and then clad steel is manufactured by hot rolling.

In this method, it is necessary to take measures to prevent the formation of oxides that inhibit bonding at the interface between the thick steel material and the composite material during heating before hot rolling. As shown in Fig. 3, a typical method for assembling materials before hot rolling is to stack the composite material 2 on the surface of the thick steel material 1 and seal the surrounding area with back-up material 3 by welding 5. A separator 4 is inserted to prevent the two from joining. (Titanium Zirconium Vol.1.
35-1, page 24) Furthermore, as a method of omitting the back-up material, an assembly method has been devised in which the back-up material 3 is used only on the side surface of the thick steel material 1, as shown in FIG. (Unexamined Japanese Patent Publication 1986-
203377 Publication) In the method shown in Fig. 3, since heat conduction is blocked by the separator 4, the back-up material is It is normal that the thickness of the steel material 3 is greater than the thickness of the thick steel material 1. Therefore, the assembly cost increases. Furthermore, after hot rolling, the periphery is cut to separate the clad steel and the back-up material. Furthermore, when cold working, it is usual to perform heat treatment in a reducing or non-oxidizing atmosphere after cold working to obtain predetermined mechanical properties. On the other hand, the fourth
The method shown in the figure does not use back-up materials on the top and bottom surfaces, so the assembly cost is low, but scale is generated on the surface of the composite material during hot rolling. Therefore, since clad steel produced by this method must be scaled with strong acids such as hydrofluoric acid or nitric acid, it cannot be used in combination with conventional pickling equipment used for ordinary steel materials. Usually, the acid used to remove scale from ordinary steel is hydrochloric acid or sulfuric acid, which is easy to handle, and the selection of materials for pickling equipment can be inexpensive. Furthermore, the treatment of hydrofluoric acid and nitric acid waste liquid is not as simple as that of hydrochloric acid and sulfuric acid, so it is desirable to avoid using them as much as possible.

Furthermore, when cold working, heat treatment is required in a reducing or non-oxidizing atmosphere, similar to the method shown in FIG. These methods require backup materials that are more than twice as large as the thick steel materials, use highly toxic special acids to remove scale during hot rolling, and maintain a non-oxidizing atmosphere during heat treatment. This requires special equipment and special gas.

These are some of the factors that make the cost of clad steel high, and are also one of the reasons why the spread of clad steel is delayed.

(Problems to be Solved by the Invention) The present invention eliminates the thick back-up material, which is one of the causes of increased costs in the conventional method of manufacturing clad steel using the hot pressure welding method, and removes the thick back-up material that is generated on the surface of titanium and stainless steel. This method prevents the formation of a scale layer that is difficult to generate, does not use highly toxic special acids, and also eliminates the special atmosphere environment during heat treatment after cold working to produce inexpensive titanium and stainless steel clad steel. This is what I am trying to do.

(Means for solving the problem) In order to prevent the formation of high-temperature oxide scale on the surface layer of titanium and stainless steel clad steel, it is necessary to It is necessary to take measures to prevent the surface from coming into contact with the atmosphere, and a thick back-up material is usually used.

The same applies to heat treatment after cold working, and the heat treatment is usually performed in a reducing or non-oxidizing atmosphere. However, these measures increase the cost of clad steel and hinder its widespread use.

As shown in FIGS. 1 and 2, the present invention involves stacking a composite material 2 of titanium and stainless steel on the surface of a thick steel material 1, superimposing a thin steel material 6 on top of the composite material 2, and welding the periphery 5 to internally seal the material. After sealing and hot rolling, high-temperature oxidation scale that has formed on the surface layer of the thin steel material is removed using ordinary steel pickling equipment, and after cold working,
After heat treatment in the atmosphere, the high-temperature oxide scale and thin steel layer on the composite material are removed, and then mild cold working is performed to create a homogeneous and clean surface with a metallic luster and the desired mechanical properties. It was confirmed that clad steel could be obtained.

The thick steel materials used in the present invention are low carbon steel, high carbon steel, and stainless steel, and the composite material is stainless steel and titanium. Further, the composite material may be IN or two or more layers may be stacked. The thickness (diameter) of thick steel material 1 is usually 20cm to 20011I! Use one from l. The surface of thick steel materials is subjected to grid blasting to remove scale on the surface and at the same time give an appropriate roughness. This surface roughness is Hma
x50 μm or more is appropriate. This roughness is effective in suppressing movement of the constituent elements of the thick steel material and composite material due to contact during heating in the heating furnace. Due to the grid blasting process, fine blasting material adheres to the surface layer of the thick steel material, so it must be removed using a means such as a wire brush just before assembly and welding.The surface of the composite material 2 is also treated in the same way as the thick steel material. The surface treatment of 0 or more, which is more preferable, is applied only to the surface that will be the joint surface between the thick steel material and the composite material, and no special surface treatment is required for other surfaces. The thickness of the composite material depends on how thick it will be after the final cold rolling, but the thickness used is about 20 countries or less.

The thickness of the thin steel material 6 is determined in consideration of the thickness reduced by oxidation in the heating furnace before hot rolling, oxidation during hot rolling, and oxidation during heat treatment after cold working.

A thickness of approximately 0.5 m to 2 mm is sufficient. If this thickness is too large, internal gas expansion during heating before hot rolling may cause the weld to fail and oxidize the joint surface, and the steel material to be removed before final cold working may For this thin steel material, it is preferable to use a steel material that is as close to pure iron as possible and contains no added elements, in order to reduce the effect of element migration to the composite material.The surface treatment of thin steel materials is particularly important. It is not necessary, and it is sufficient if the surface is clean. However, in the present invention, a separator is not interposed between the composite material 2 and the thin rope material 6.

The materials made as described above are arranged as shown in FIG. 1 or 2, and the periphery is joined by welding so that the inside is sealed.

The welding method is not particularly limited, but since it is a thin steel material, TIG welding, seam welding, etc. are suitable.

Although the method shown in Figure 2 is more time-consuming than the method shown in Figure 1, it only requires welding of the same materials, and there are no problems associated with welding dissimilar materials.
At this time, in the production of clad steel using the conventional hot pressure welding method, good joint strength between the thick steel material and composite material could not be obtained unless the interior was placed in a vacuum state or the surrounding area was welded in a vacuum. In the method of the present invention, even if the internal gas expands during heating before hot rolling, the steel material is thin and will not deform and break the welded part, so welding can be carried out in the atmosphere, and the inside is especially vacuum-vacuumed. After welding, the material is heated to a predetermined temperature in a heating furnace. In the case of titanium clad steel, this temperature is suitably between about 800"C and 1100°C or less. In the case of stainless steel clad steel, it is preferably about 1000 to 1200°C. The heating time is such that the temperature is quickly raised to the specified temperature. As soon as the entire material reaches the same temperature, consideration must be given to hot rolling as quickly as possible.In hot rolling, the amount of reduction during the first pass is particularly important; It is preferable to set the thickness to about 8 am or more for steel, and about 12 mm or more for stainless steel clad steel. This is because the thin steel material in the outermost layer of the rolled material is destroyed during the first pass of hot rolling, and the internal airtightness is lost. The thick steel material and composite material must be joined during the first pass.For this reason, it can be said that the amount of reduction during the first rolling pass holds the key to the success of cladding.The clad steel produced in this way Since the outermost layer of the steel is made of ordinary steel, the high-temperature oxide scale generated during hot rolling can be removed using ordinary steel pickling equipment before cold working. Heat treatment is performed as it is without passing it through electrolytic cleaning equipment to remove dirt. Heat treatment does not need to be carried out in a normal reducing or non-oxidizing atmosphere and can be carried out in the air. The oxide scale layer and dirt are completely removed from the outermost thin steel layer in the next step.

That is, the thin steel material 6 shown in FIG. 1 or FIG. 2 has the function of preventing high-temperature oxidation before hot rolling, and the scale generated during hot rolling can be removed by pickling treatment similar to that of ordinary steel.
Furthermore, the surface cleaning step after cold working and the provision of a special atmosphere to prevent surface oxidation during heat treatment can be omitted.

If heat treatment is not performed, the outermost thin steel layer is also removed in the pickling process after hot rolling, cold rolling is performed, and the product is used as is. Grinding or blasting may be used in combination as a means for removing the thin steel layer. The final step is to perform mild cold working to smooth the surface to a uniform roughness and ensure a predetermined mechanical strength.

Examples will be shown to further specifically explain the method of the present invention.

(Example) Example I A JIS standard 5PCD slab steel material (thickness: 100mm, width: 250mm, length: 400mm) was cleaned by grid blasting on both sides, and then surface treated with a wire brush. 0 plywood 5US304 (thickness 4 [l
11l, width 240mm, length 390mm) was treated in the same way, layered on both sides of the thick steel material, and then a 0.8mm cold rolled steel plate (width 250mm + length 400aa) was layered on top of this. The rolled steel plate and the thick steel material were joined by seam welding as shown in Fig. 1. At this time, the surface roughness of the thick steel material and plywood is Hmax, 7
It was 5 μm. After holding the material thus obtained at 1100°C for 1 hour in an electric heating furnace, it was hot rolled to a thickness of 3.
It was rolled to III11. At this time, the amount of reduction in the first pass was 20 mm. The hot-rolled material was subjected to a hydrochloric acid pickling method for ordinary steel materials to remove oxidized scale, and then cold-rolled to a plate thickness of 1 mm.

After annealing at 780°C in the air, the thin steel layer on the outermost surface was removed by pickling with hydrochloric acid, and rolled at a reduction rate of about 3% in a temper rolling mill to obtain a stainless clad steel plate with a thickness of about 0.971111. was manufactured.

The thickness of the stainless steel surface layer was approximately 37 μm. In order to investigate the bondability between this stainless steel and thick steel material, we used a cylindrical deep drawing tester with an inner diameter of 40mm to draw to a depth of 60mm, cut the processed part, and examined the boundary using a microscope, but we could not find any peeling points. Ta.

Example 2 A JIS standard 5pcc steel slab (thickness 1QQmm, width 300mm, length 500m+) was used as a thick steel material, and a Ti plate was used as plywood (thickness 6mm, width 250ml1, length 450m).
0.21111 N between the thick steel material and the Ti plate.
After inserting the i-plate, a cold-rolled steel plate (thickness 0.4 t
300mm wide, 500mm long) were stacked and the periphery was joined by TIG welding as shown in Figure 2. The material prepared as described above was held in a heating furnace at 900"C for 1 hour, and then hot rolled to two shells. The oxide scale on the surface and the outermost thin steel layer were removed using hydrochloric acid pickling equipment. After removing it, it was cold rolled to a thickness of 0.4 mm to obtain a Ti clad steel plate with a Ti layer of about 20 μm thick.

The bondability of the Ti layer of this Ti-clad steel plate was examined for peeling of TiN after a 90-degree bending test, but no abnormality was found.

Example 3 As a thick steel material, a JIS standard 5US304 round bar (diameter 8
After grid-blasting the surface of the 0-wall, 900 mm long) to Hmax of 50 μm and cleaning it with a wire brush, a Ti tube with a thickness of 6I with the inner surface treated in the same manner was stacked on top of it, and a low- Welded carbon steel pipes were stacked, cold-rolled steel plates were applied to both end faces, and the inside was sealed by TIG welding.

The material thus obtained was heated in a heating furnace at 950°C for 30 minutes.
After holding for a minute, it was hot rolled into a clad wire with a normal diameter of 10φ. After removing the oxidized scale on the surface by pickling with hydrochloric acid, the wire was drawn to a diameter of 6φ by cold wire drawing and annealed in an oxidizing atmosphere at 900°C. After removing the outermost thin steel layer by pickling with hydrochloric acid, the wire was drawn to a diameter of 5.0 φ using a cold wire drawing machine to produce a clad wire with a Ti layer of about 320 μm. After winding this clad wire around a 2-inch diameter tube, the adhesion of the Ti layer was examined by observing the appearance and cross section of the clad wire, but no abnormality was found.

(Effects of the Invention) As explained above, the present invention provides a method for manufacturing titanium and stainless steel clad steel by providing a thin steel material as the outermost layer to prevent the formation of oxidized scale that is difficult to remove on titanium and stainless steel. It is characterized by prevention.

This makes it possible to omit a thick back-up material when producing clad steel, and to replace the oxidized scale generated during hot rolling with steel scale, allowing the pickling equipment to be installed on the surface side.

Further, the heat treatment after rolling can be performed in an oxidizing atmosphere.

Therefore, by applying the present invention, it becomes possible to manufacture clad steel at a lower cost than the conventional clad steel manufacturing method, and the effect is very large.

[Brief explanation of the drawing]

3 and 4 are diagrams showing the assembly of the material before hot rolling according to the conventional method, and FIGS. 1 and 2 show the assembly of the material before hot rolling according to the present invention. 1...Base steel material 2...Mixture material 3...Backup material 4...Separator 5...Welding part 6...Thin steel material Fig. 1 Fig. 2

Claims (1)

[Claims] After covering the surface of the cleaned base steel material 1 with composite material 2 and covering the surface with thin steel material 6 without using a separator, the end faces are welded and joined, the inside is kept airtight, and the material is clad by hot rolling. A method for producing clad steel, which is characterized by removing a thin steel layer and performing cold working.