JPH0811307B2 - 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 shear strength and bending workability of the joint interface between the base material of the titanium clad steel plate and the laminated material. In addition, 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, which reduces the shear strength and bending workability of the joint interface between the base material and the laminated material. Is promoting.

As one countermeasure, JP-A-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 bonding material, that is, at the bonding interface is less likely to occur, and the bonding between the base material and the bonding material Unbonded porosity remains at the interface. For this reason, conversely, this causes a decrease in the shear strength and bending workability of the joint portion between the base material and the laminated material.

As another measure, there has been 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 0-124483 discloses, an intermediate material made of ferritic or martensitic stainless steel, JP 60
In JP -170586, a composite intermediate material made of copper and nickel, in JP-A-60-261683, are interposed a composite intermediate material made of copper and molybdenum or nickel and molybdenum.

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 a chemical means such as pickling or electrolytic polishing or a 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 Unexamined Patent Publication 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, mechanical oxidation or pickling with nitric acid is used to remove the oxide film 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. In the above-mentioned Japanese Patent Laid-Open No. 63-56370, in order to solve the bonding failure caused by the non-bonding porosity, the vertical compressive stress acting on the base material and the laminated material during hot rolling is increased to form the base material and the laminated material. It discloses a method for promoting mutual contact of metal atoms between the two, and describes that a titanium clad steel sheet equivalent to or better than the explosive-bonded material can be obtained even by the manufacturing method by hot rolling.

Further, the above-mentioned hot rolling is generally performed only in a single direction. In that case, when the deformation resistance of the laminated material is higher than that of the base material, the base material in the front and rear end regions of the laminated material is largely deformed, and as a result, the thickness of the front and rear end regions of the laminated material is thicker than other regions. Become. On the contrary, when the deformation resistance of the laminated material is lower than that of the base material, the base material in the front and rear end regions of the laminated material is slightly deformed, and as a result, the thickness of the front and rear end regions of the laminated material becomes thinner than other regions. .

As a measure against this, Japanese Patent Laid-Open No. 19114/1987.
There is a so-called cross rolling method as shown in Japanese Patent No.
Here, as an example, a method of manufacturing a clad steel plate by using SUS304 stainless steel as a laminated material and dividing the rolling direction into two substantially orthogonal directions and rolling is described.

[0019]

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.

[0021] For the details, see Japanese Patent Application Laid-Open No. 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. 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 compression 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.

Also for cross rolling, in the case of titanium clad steel sheet, there is a problem that the method for producing a clad steel sheet as disclosed in JP-A-62-191141 cannot be applied as it is.

In order to solve the above-mentioned problems, the inventors of the present invention are based on a method for producing a titanium clad steel sheet with 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 a stable joint strength at the joint interface between the base material and the laminated material and a high bending workability is obtained by hot rolling. It is intended to provide a method for manufacturing.

[0029]

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 producing a titanium clad steel plate by press-bonding each other with hot rolling, a thin intermediate material made of low carbon steel containing 0.01% by weight or less of carbon 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 sheet, in which an assembled slab provided with a space of 0 mm is manufactured, and the assembled slab is hot rolled at 650 to 850 ° C. including cross rolling.

Two of the present invention 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.
This is a method for producing a titanium clad steel sheet that is hot-rolled including cross-rolling at 50 to 850 ° C.

[0031]

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 during heating of the assembly slab, 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 is premised on wet high count polishing. 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 a defect. Shows. The dotted line is the JIS standard lower limit value and the shear strength is 14 kgf / mm.
² is shown.

The pickling method, the wet low count belt polishing method, and the dry high count polishing method all reduce the shear strength.
And, a titanium alignment material and the base material is separated in a bending test, is poor.

On the other hand, the wet high count polishing achieves a shear strength of 20 kgf / mm ² or more regardless of belt polishing and grindstone polishing. Wet high count polishing according to the present invention is intended for use with abrasives of size 150 and above.
Usually, number 200 is used in terms of cost. 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 bonding interface, and the shear strength decreases. Therefore, high count polishing is required to make the polishing surface roughness fine.

In the present invention, in addition to the wet high count polishing described above, it is necessary to hot-roll the assembled slab at 650 to 850 ° C. including cross rolling.

The rolling temperature of the hot rolling is set within the range of 650 to 850 ° C. because the rolling temperature at the joining interface exceeds 850 ° C.
The formation of brittle Fe-Ti intermetallics is promoted, while 65
This is because if the temperature is lower than 0 ° C., the rolling pressure required for the predetermined rolling reduction increases, which is not preferable.

The hot rolling including the cross rolling is performed as shown by the solid line in order to eliminate the large variation in the shear strength caused by the straight rolling in addition to the wet high count polishing shown by the dotted line in FIG. In addition to such wet high count polishing,
This is because when cross rolling is performed, higher stable shear strength can be obtained.

Here, hot rolling including cross rolling means hot rolling in the longitudinal direction and the width direction with respect to the longitudinal direction of the assembled slab.

Even if the wet high count polishing is performed until the end of rolling in only one direction, the extension of the titanium clad steel sheet is not uniform, and the extension of the titanium clad sheet is delayed by a new surface. Formation will be delayed. In the case of rolling including cross rolling, variations in shear strength are reduced as described above. It is considered that this is because the whole laminated material spreads uniformly and the formation of new surfaces is promoted evenly, and as a result, the bonding at the interface becomes sound over the entire region.

Next, another 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 0.01 wt% or less,
If the carbon content exceeds 0.01% by weight, the diffusion of carbon from the intermediate material 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, the first carbon material is made of a low carbon steel containing 0.01% by weight or less 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 should be noted that inserting only the thin second intermediate material made of copper, nickel, or a copper-nickel alloy is not preferable because an intermetallic compound that is more fragile than the Fe-Ti intermetallic compound is formed.

In the present invention, the assembled slab is manufactured with a space of 0.1 to 0.8 mm provided between the intermediate material and the laminated material, because the hot rolling is performed when the size of the space 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. Regarding the space between the intermediate material and the laminated material, it is preferable to insert spacers at the four corners between them.

[0045]

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 (hereinafter referred to as A system) for simultaneously manufacturing two titanium clad steel plates.
(B) is an assembly slab system (hereinafter referred to as B system) for manufacturing one titanium clad steel plate, and the A system or B system is selected according to the number of produced sheets.

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 the method A, a spacer 5 is inserted between both base materials 1 in order to supplement the thicknesses of the laminated 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 is 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.

Next, the results of experiments conducted on the method of the present invention will be described in detail. Here, hot rolling with various rolling directions is performed to produce titanium clad steel plates, and ultrasonic waves in that case are used.
The flaw detection result , the shear strength and the bending test result were obtained. Table 1,
Table 2 shows the manufacturing conditions.

[0053]

[Table 1]

As shown in Table 1, the assembling method is the A method,
The method is roughly classified into the B method, and rolling including straight rolling and cross rolling (cross rolling in the table) is performed.

[0055]

[Table 2]

As Example 1 of the present invention, No. 1 to 5 titanium clad steel plates according to the A method are shown, and as No. 8 to 10 titanium clad steel plates according to the B method as Example 2 of the present invention.
Indicated by. Comparative example (1) is wet low count polishing (No. 120)
Then, the titanium clad steel plate by method A is No6, No.
7, the comparative example (2) is wet low count polishing (120
No.), the titanium clad steel plate by the B method is No 11 to
13, the comparative example (3) is wet high count polishing (200
No.) , No. 14-
It is indicated by 16.

The titanium clad steel plates manufactured under the conditions shown in Tables 1 and 2 were subjected to accuracy tests such as ultrasonic flaw detection tests. Table 3 shows the results of these accuracy tests.

[0058]

[Table 3]

As shown in Table 3, in the present invention, the A method and the B method are used.
Regardless of the method, it was possible to obtain a shear strength with a small variation of 30 kgf / mm ² or more. On the other hand, as shown in Comparative Example (3), the shear strength was lower than that of the present invention when straight-rolled even after wet high count polishing .

[0060]

According to the present invention, regardless of whether the titanium clad steel sheet is large or small, a titanium clad steel sheet having a stable joint strength at the joint interface between the base material and the laminated material and high bending workability is hot-rolled. Can be manufactured by.

[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 including cross 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 including cross rolling at 650 to 850 ° C.