JPH0811306B2 - Method for producing titanium clad steel sheet by hot rolling - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a titanium clad steel sheet by hot rolling.

[0002]

2. Description of the Related Art Generally, a method for producing a titanium clad steel sheet by hot rolling comprises a base material made of any one of iron-based metals such as carbon steel, low alloy steel or stainless steel, and titanium or titanium alloy. The assembled slab composed of the laminated material is heated to a temperature around 1050 ° C., and the heated assembled slab is hot-rolled at a rolling temperature of 950 to 1000 ° C. to press-bond the base material and the titanium laminated material to each other to form a titanium clad. It manufactures steel sheets.

In the method for producing a clad steel sheet by hot rolling, the cleanliness of the joint surface of the laminated material, the rolling reduction ratio of the assembled slab, and the compressive stress and rolling temperature are the main factors that influence the progress of pressure bonding.

Regarding the rolling temperature, in a titanium clad steel sheet produced by hot rolling, a brittle intermetallic compound of Fe—Ti is formed at the joint interface between the base material and the laminated material by hot rolling. This intermetallic compound increases as the heating temperature and rolling temperature of the slab increase, and reduces the joint strength and bendability of the joint interface between the base material of the titanium clad steel plate and the laminated material.

Further, the carbon diffused from the base material at the joint interface between the base material and the laminated material forms titanium carbide at the joint interface. Helps reduce sex.

As one measure, Japanese Patent Laid-Open No. 59-22029
No. 3 and JP-A-60-213378,
A method of heating a slab at a low temperature of 950 ° C. or lower and hot rolling is disclosed.

However, in the method of heating at a temperature of 950 ° C. or lower and hot rolling, mutual diffusion of metal atoms between the base material and the laminated material, that is, at the bonding interface is less likely to occur, and the bonding of the base material and the laminated material Unbonded porosity remains at the interface. Therefore, conversely, this causes a decrease in the joint strength and bending workability of the joint portion between the base material and the laminated material.

As another measure, there is proposed a method of inserting an intermediate material between the base material and the laminated material. Japanese Patent Laid-Open No. 60-647
No. 86 discloses an intermediate material made of copper or Ni.
In JP-A 0-124483, an intermediate material made of ferritic or martensitic stainless steel is disclosed in
In JP-A-170586, a composite intermediate material made of copper and nickel is inserted, and in JP-A-60-261683, a composite intermediate material made of copper and molybdenum or nickel and molybdenum is inserted.

However, in the case of an intermediate material made of copper or nickel, Fe-T is formed at the bonding interface between the intermediate material and the base material.
It is not good because it forms an intermetallic compound that is weaker than i.
Further, in the case of a composite intermediate material composed of copper and molybdenum or nickel and molybdenum, the workability of molybdenum is poor,
Molybdenum breaks during hot rolling.

In the case of an intermediate material made of stainless steel or a composite intermediate material made of chromium and nickel or chromium and copper,
Since the price of the intermediate material is high, there is a cost disadvantage in industrial production. Therefore, in order to solve the problems of the method of inserting the intermediate material as described above, a method of manufacturing a titanium clad steel sheet as disclosed in JP-A-63-56370 has been proposed.

Here, a thin intermediate material made of low carbon steel having a carbon content of 0.01% by weight or less is inserted between the base material plate and the laminated material, and the intermediate material and the laminated material are 0.1-
An assembly slab was prepared with a gap of 8.0 mm, and the assembly slab was rolled at a rolling temperature of 650 to 850 ° C. and a compression index of 80. The hot rolling is performed under the above conditions.

On the other hand, the following proposals have been made regarding the cleanliness of the joining surface of the laminated material.

In JP-A-56-122681, the surface oxide film is removed by chemical means such as pickling or electrolytic polishing or mechanical means such as grinder polishing, and the surface oxide film is sufficiently removed by acetone or trichloroethylene. It is described that the surface is degreased to be a clean surface.

Japanese Patent Application Laid-Open No. 60-203377 also describes that after buffing, the surface is degreased with acetone to obtain a clean surface.

In Japanese Patent Laid-Open No. 62-9786, collision of nickel particles destroys a thin oxide film, and nickel plating prevents reoxidation in a slab heating furnace.

In Japanese Patent Laid-Open No. 62-9788, the oxide film is removed by mechanical polishing or pickling with nitric acid, and then nickel plating is applied to prevent reoxidation.

The following proposals have also been made regarding the rolling reduction ratio and the compressive stress of the assembled slab. JP-A-6 mentioned above
In Japanese Patent Application Laid-Open No. 3-56370, in order to solve a bonding failure caused by uncompressed porosity, a vertical compressive stress acting on a base material and a laminated material during hot rolling is increased to form a metal between the base material and the laminated material. It discloses a method of promoting mutual contact of atoms, and describes that a titanium clad steel sheet equivalent to or better than the explosive-bonded material can be obtained even by a manufacturing method by hot rolling.

[0018]

However, there are the following problems with the techniques described in the above items 1 and 2.

With respect to the above, the method for producing a titanium clad steel sheet as disclosed in Japanese Patent Laid-Open No. 63-56370 can be expected to have some effect. However, even in this case, an oxide film may be formed at the joining interface of the titanium clad steel plates.

For details, see JP-A-56-122681.
Although the method as shown in Japanese Patent Publication can remove a thick surface oxide film that can be visually confirmed, a thin oxide film formed by pickling or a thin oxide film formed by heat generated by dry buffing or dry grinder polishing, etc. It is difficult to visually confirm the presence or absence of an oxide film on the film, and the surface oxide film cannot be removed. Further, the electrolytic polishing method is disadvantageous in terms of industrial production cost.

The method disclosed in Japanese Patent Laid-Open No. 62-9786 is to perform nickel plating in order to prevent reoxidation of the joining surface of the joining material during heating of the slab, which requires a costly plating step. Since it is added, there is a cost disadvantage in industrial production.

The presence of the oxide film as described above becomes a major obstacle to the formation of a new surface of the laminated material in the initial rolling stage. The term "new surface" as used herein means the surface of an active laminated material that is newly formed as the laminated material expands. It is considered that this active surface greatly contributes to the bonding at the interface.

Regarding the method, the method as disclosed in JP-A-63-56370 is expected to have some effect.
However, in recent years, the demand for extremely thick titanium clad steel plates and wide titanium clad steel plates has increased, and there is a tendency to manufacture large titanium clad steel plates. In this case, it is necessary to manufacture a large assembly slab.

However, in the above method, the size of the assembly slab is restricted due to the restrictions of the rolling mill, and only the method of controlling the vertical compressive stress stabilizes the bonding strength and bending workability of the bonding interface between the base material and the laminated material. It may not be possible to maintain.

In order to solve the above-mentioned problems, the present inventors have based on a method for producing a titanium clad steel sheet having an intermediate material as disclosed in JP-A-63-56370.
The present invention has been achieved through repeated studies.

That is, according to the present invention, regardless of whether the titanium clad steel sheet is large or small, a titanium clad steel sheet having high joint strength and bending workability at the joint interface between the base material and the laminated material is manufactured by hot rolling. The purpose is to provide a method.

[0027]

In order to achieve the above object, one of the present inventions is a combination of a base material made of an iron-based metal such as carbon steel, low alloy steel or stainless steel, and titanium and a titanium alloy. In a method for manufacturing a titanium clad steel plate by pressing the material and the material together by hot rolling, a thin intermediate material made of a low carbon steel having a carbon content of 0.01% by weight or less is inserted between the base material and the laminated material. , The intermediate material and the laminated material are joined together. The surface of the laminated material to be joined, which is to be joined, is surface-finished by wet high count polishing.
This is a method for producing a titanium clad steel plate, in which an assembled slab having a space of 0 mm is manufactured, and the assembled slab is hot rolled at 650 to 850 ° C.

Two of the present inventions are one of a thin first intermediate material made of a low carbon steel having a carbon content of 0.01% by weight or less between a base material and a laminated material, and copper, nickel, or copper and a nickel alloy. And a thin second intermediate material consisting of two to form a thin laminated intermediate material, and the second intermediate material is inserted so that it is on the base material side,
The surface to be joined of the laminated material is finished by wet high count polishing to manufacture an assembled slab with a gap of 0.1 to 8.0 mm between the laminated intermediate material and the laminated material.
A method for producing a titanium clad steel sheet hot-rolled at 50 to 850 ° C.

[0029]

According to the present invention, since the intermediate material is inserted between the base material and the laminated material, carbon diffused from the base material to the laminated material via the intermediate material can be prevented. Therefore, titanium carbide is not formed at the joint interface between the intermediate material and the laminated material.

Further, since an appropriate gap is provided between the intermediate material and the laminated material, contact between the intermediate material and the laminated material is prevented when the assembly slab is heated, and Fe- at the interface between the intermediate material and the laminated material is prevented. The Ti intermetallic compound layer is not formed.

The present invention requires wet high count polishing. By applying the wet high count polishing, it is possible to suppress the residue of the abrasive and the formation of the oxide film based on the experimental result described later. Wet high count polishing according to the present invention is intended for use with abrasives of size 150 and above.

That is, when removing the oxide film formed by hot rolling of the laminated material, when a low-count (less than 150) coarse-grained abrasive is used, foreign matter is brought into the joint interface, Shear strength decreases. Therefore, high count polishing is required to make the polishing surface roughness fine.

Next, the reason for limiting the numerical values of the present invention will be described. In the present invention, the carbon content of the low carbon steel constituting the intermediate material is set to 0.01% by weight or less, because when the carbon content exceeds 0.01% by weight, diffusion of carbon from the intermediate material occurs. Because it cannot be ignored. The thickness of the thin intermediate material is preferably 0.5 to 2 mm, and the thickness of the thin intermediate material after hot rolling is preferably about 50 to about 400 μm.

When it is necessary to more effectively prevent the diffusion of carbon from the base metal at the joint interface between the intermediate material and the laminated material, it is preferable to use a low carbon steel containing less than 0.01% by weight of carbon.
The intermediate material and a second intermediate material made of any one of copper, nickel, and an alloy of copper and nickel are laminated to form a thin laminated intermediate material, and the second intermediate material is interposed so that the second intermediate material is on the base metal side. Insert. It is not preferable to insert only the thin second intermediate material made of copper, nickel, or a copper-nickel alloy because an intermetallic compound that is more brittle than the Fe-Ti intermetallic compound is formed.

In the present invention, the assembled slab is manufactured by providing a gap of 0.1 to 0.8 mm between the intermediate material and the laminated material, because the hot rolling is performed when the gap size exceeds 8.0 mm. In order to obtain a predetermined shear strength and workability, the base material, the intermediate material, and the composite material require a large reduction ratio for pressure bonding.

On the other hand, when the size of the space is less than 0.1 mm,
When exhausting the air present in the space after welding the assembled slab, the exhaust resistance becomes too large and it takes a long time. Therefore, this interval is set in the range of 0.1 to 0.8 mm. The interval between the intermediate material and the laminated material is preferably a method of inserting spacers at the four corners between them.

In the present invention, the hot rolling temperature of this material is set in the range of 650 to 850 ° C. because the rolling temperature is 850 ° C.
If it exceeds, the formation of a brittle intermetallic compound of Fe-Ti at the bonding interface is promoted, while if it is less than 650 ° C, the rolling pressure required for a predetermined rolling reduction increases, which is not preferable.

In the present invention, the reason why the surface finishing is limited to wet high count polishing is due to the results of various tests on the polishing method of the laminated material.
The test method is shown in Table 1.

[0039]

[Table 1]

That is, assembling slabs (method A) in which the lapping method of the joining surface of the laminated material was changed were manufactured, titanium clad steel plates were manufactured by hot rolling, and shear tests and bending tests were performed on the titanium clad steel plates. The relationship between the polishing finish method of the joint surface of the laminated material and the shear test and bending test was investigated. The result is shown in FIG.

FIG. 2 is a diagram showing the relationship between the final finish of the surface of the laminated material and the shear strength and workability. In FIG. 2, the mark ○ indicates that the titanium laminated material and the base metal did not peel off in the bending test, and the mark ● indicates that the titanium laminated material and the base metal peeled off in the bending test, indicating that it was defective. Shows.
The dotted line indicates the JIS standard lower limit value.

In the pickling method, although the oxide film visually observed is removed by pickling, a thin oxide film is formed by the reaction between the pickling solution and titanium, and the shear strength is low.

In the wet low count belt polishing method, water cooling prevents the formation of an oxide film due to heat generation during polishing, but since the abrasive remains on the rough polishing surface, the shear strength is low.

In the dry high count polishing method, since the polishing roughness is fine, the residue of the polishing material is prevented, but a thin oxide film is formed by the frictional heat caused by the polishing and the shear strength is low.

In the wet high count belt method or the wet high count grindstone polishing method, high shear strength can be obtained because the retention of an abrasive and the formation of an oxide film that reduce the shear strength are prevented.

From the above, as shown in FIG. 2, it was found that it is preferable to perform wet high count polishing as the final finishing method of the surface of the joining material to be joined. The polishing count is preferably 150 or more. Usually, number 200 is used in terms of cost.

[0047]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. A typical assembly slab system for carrying out the present invention is shown in FIGS. 1 (a) and 1 (b).

In FIG. 1, (a) is an assembly slab system for producing two titanium clad steel plates at the same time (hereinafter referred to as A).
Method), (b) is an assembly slab method for producing one titanium clad steel plate (hereinafter referred to as method B),
A method or B method is selected according to the number of products produced.

Alternatively, as the product becomes thicker, the thickness of the assembled slab becomes thicker, and the method A cannot be used because of the relationship with the maximum slab capable of rolling (about 500 mm). In that case, the method B is selected.

In FIG. 1, 1 is a base material, 2 is a laminated material,
Reference numeral 3 is an intermediate material (including a laminated intermediate material), 4 is a release material (for example, zirconia oxide powder), and 10 is a joining surface polished by a wet high count grindstone.

The peeling material 4 is applied to the surfaces of both mating materials 2 which are separation surfaces in the A method, and is applied to the surfaces of the mating material 2 and the cover material 8 which are separation surfaces in the B method.

In method A, a spacer 5 is inserted between both base materials 1 in order to supplement the thicknesses of the joining material 2 and the intermediate material 3,
The base material 1 and the spacers 5 are welded at the welded portions 6 by arranging them at the four corners of the assembly slab 9. A gap 7 is provided between the laminated material 2 and the intermediate material 3.

In the B method, the cover 8 is used to prevent the surface of the laminated material 2 opposite to the surface to be joined from being oxidized during heating / rolling.

The inside of the manufactured assembly slab 9 has a ^{size of} 10 ^-2.
A high vacuum of Torr or less is preferable. Therefore, after welding the peripheral welded portion 6 of the assembly slab 9 in the atmosphere, the interior of the assembly slab 9 is suctioned to a high vacuum by a diffusion pump (not shown), After the temporary welding is performed in the atmosphere, the inside of the assembly slab is evacuated to a high vacuum in the vacuum chamber, and then the welded portion 6 around the assembly slab 9 is electronically welded.

According to the method of the present invention, the A type titanium clad steel plate of the present invention example (1) is Nos. 1 to 6, the B type titanium clad steel plate of the present invention example (2) is Nos. 9 to 11 and A.
The titanium clad steel plate of Comparative Example (1) of the method is No. 7 or 8
The titanium clad steel plate of Comparative Example (2) of method B and method No.
12 to 16 were manufactured, and accuracy tests such as ultrasonic flaw detection tests were performed.

Assembling slab methods are two methods A and B shown in FIGS. 1 (a) and 1 (b), and Table 2 shows conditions such as specifications and dimensions of the base material in each method.

[0057]

[Table 2]

The titanium clad steel plate of the present invention (N
Table 3 shows the manufacturing conditions of titanium clad steel plates (Nos. 7 and 8 and Nos. 12 to 16) for comparison with Nos. 1 to 6 and Nos. 9 to 11).

[0059]

[Table 3]

Table 4 shows the results of these accuracy tests.

[0061]

[Table 4]

As shown in Tables 3 and 4, in the present invention, the results of ultrasonic flaw detection are good regardless of the A method and the B method.
A titanium clad steel sheet having a shear strength of kgf / mm ² or more and good bending workability was obtained.

[0063]

According to the present invention, it is possible to easily manufacture a titanium clad steel sheet having high joint strength and bending workability regardless of the size of the titanium clad steel sheet.

[Brief description of drawings]

FIG. 1 is a view showing a cross section of an assembly slab of a titanium clad steel plate showing an embodiment of the present invention, (a) is a view showing a cross section of an assembly slab of two titanium clad steel plates at the same time,
(B) is a figure which shows the cross section of the assembly slab of one titanium clad steel plate .

FIG. 2 is a graph showing the relationship between the final finishing method, the shear strength and the bending work of the titanium composite material according to the present invention.

[Explanation of symbols]

 1 Base Material 2 Laminated Material 3 Intermediate Material (Including Laminated Intermediate Material) 4 Separation Material 5, 6 Welded Area 7 Interval Between Laminated Material and Intermediate Material 8 Cover 9 Assembly Slab 10 Polished with Wet High Count Grindstone Planned joining surface

Claims (2)

[Claims] 1. A titanium clad steel plate is produced by press-bonding a base material made of an iron-based metal such as carbon steel, low alloy steel or stainless steel, and a laminated material made of titanium or a titanium alloy to each other by hot rolling. In the method, a low-carbon steel thin intermediate material having a carbon content of 0.01% by weight or less is interposed between the base material and the laminated material, and the joining surface of the laminated material to be joined with the intermediate material is wet high count. The assembled slab is manufactured by finishing the surface by polishing and further providing a space of 0.1-8.0 mm between the intermediate material and the laminated material.
A method for producing a titanium clad steel sheet by hot rolling, which comprises hot rolling at 0 to 850 ° C. 2. A titanium clad steel plate is manufactured by press-bonding a base material made of an iron-based metal such as carbon steel, low alloy steel or stainless steel, and a laminated material made of titanium or a titanium alloy to each other by hot rolling. In the method, a thin first intermediate material made of a low carbon steel having 0.01% by weight or less of carbon between the base material and the laminated material and a thin first intermediate material made of any one of copper, nickel and a copper-nickel alloy. 2 Intermediate material is a thin laminated intermediate material, the second intermediate material is inserted so that the second intermediate material is on the base metal side, and the joining surface of the mating material is surface finished by wet high count polishing. 0.1 between the and the laminated material
A method for producing a titanium clad steel sheet by hot rolling, characterized in that an assembled slab provided with an interval of ~ 8.0 mm is produced, and the assembled slab is hot rolled at 650 to 850 ° C.