JPH0811308B2 - 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--Ti is formed at the bonding interface between the intermediate material and the base material.
It is not good because it forms a more brittle intermetallic compound.

Further, in the case of a composite intermediate material composed of copper and molybdenum or nickel and molybdenum, the workability of molybdenum is poor and the molybdenum is damaged 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 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 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 the bonding failure due to the non-compression bonding porosity, the vertical compressive stress acting on the base material and the laminated material at the time of hot rolling is increased so that the metal between the base material and the laminated material is increased. 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.

[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.

Since the titanium clad steel plate cannot be heated at a high temperature on this new surface, the influence of the surface roughness of the joint interface between the base material and the laminated material is important. This phenomenon can be explained by the relationship between the ease of plastic flow prior to the formation of the new surface and the unevenness of the surface.

That is, in the case of high temperature heating such as a stainless clad steel plate, since plastic flow is easy,
Plastic flow occurs according to the unevenness of the surface, and the formation of a new surface is started in the process. As a result, both materials at the bonding interface easily reach mechanical bonding, which promotes the formation of a subsequent new surface.

However, since the titanium clad steel plate requires low temperature heating, plastic flow is difficult, and in order to form a new surface, it is unavoidable that the titanium clad steel plate itself loses the unevenness due to extension. As can be seen from this, the disappearance of the unevenness is considered to be an important factor for rolling the titanium clad steel sheet.

In the polishing method as a countermeasure for this, except for the case of an extremely smooth surface obtained by the electrolytic polishing method, a belt polishing method using industrially inexpensive abrasive grains or a grinding stone polishing method is used. The surface irregularities hinder the formation of the new surface.

Regarding the method, the method 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.

In order to solve the above-mentioned problems, the present inventors 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, the joining strength and bending workability of the joining interface between the base material and the laminated material are improved by using the polishing method suitable for the actual operation. An object of the present invention is to provide a method for producing a high titanium clad steel plate by hot rolling.

[0032]

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 joining surface of the joining material, which joins the intermediate material and the joining material, is polished by wet high count polishing in a direction in which the rolling direction and the angle are changed as the polishing direction,
The assembled slab is manufactured by finishing the uneven surface of the planned joining surface so that it can be eliminated, and further providing a space of 0.1 to 8.0 mm between the intermediate material and the laminated material. The method is for producing a titanium clad steel sheet that is hot rolled at 850 ° C.

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 joining surface of the joining material that joins the intermediate material and the joining material is polished by wet high count polishing in a direction in which the angle is changed from the rolling direction as the polishing direction so that the irregularities on the joining surface can be eliminated. Of a titanium clad steel plate, which is surface-finished and further has an interval of 0.1 to 8.0 mm provided between the laminated intermediate material and the laminated material, and which is hot rolled at 650 to 850 ° C. This is a manufacturing method.

[0034]

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. The Ti intermetallic compound layer is not formed.

In the present invention, the joining surface of the laminated material is polished by wet high count polishing in a direction different in angle from the rolling direction as a polishing direction, and surface finishing is performed so that the irregularities of the joining surface can be eliminated. is necessary.

The present invention is premised on wet high count polishing. FIG. 3 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. 3, ○ indicates that the titanium composite material and the base metal did not separate in the bending test and was good, and ● indicates that the titanium composite material and the base material separated in the bending test and the product was defective. 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, in the wet high count polishing, the shear strength of 20 kgf / mm ² or more is obtained regardless of the belt polishing and the 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 this case, in the present invention, when performing wet high count polishing, polishing is performed in a direction in which the angle is changed from the rolling direction as the polishing direction, and the surface finish is formed so that the irregularities of the planned joining surface can be eliminated.

Polishing in a direction in which the angle is changed from the rolling direction is used as the polishing direction. In addition to the wet high count polishing as shown by the dotted line in FIG. 3, when the polishing is performed in the same direction as the rolling direction, shearing occurs. In contrast to the large variation in strength, in addition to the wet high count polishing as shown by the solid line, when polishing was performed in the direction in which the rolling direction and the angle were changed, the variation in shear strength was small and the stability was higher. This is because the shear strength can be obtained.

When the polishing is carried out only in the same direction as the rolling direction, it is not possible to eliminate the concavo-convex portion of the planned joining surface. The direction of changing the angle with respect to the rolling direction as the polishing direction is practically about 45 °, or at a right angle, or cross polishing. In FIG. 3, polishing was carried out in the direction of 45 ° and the direction of right angle.

However, the angle is not limited to the above as long as it is an angle capable of eliminating the irregularities on the surfaces to be joined.

Next, the reason for the numerical limitation of the present invention will be described in detail. 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 material at the joint interface between the intermediate material and the laminated material, the first carbon material is 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.

If only a thin second intermediate material made of copper, nickel or a copper-nickel alloy is inserted, Fe-
It is not preferable because an intermetallic compound that is more brittle than the intermetallic compound of Ti is formed.

In the present invention, the assembled slab is manufactured with a gap of 0.1 to 8.0 mm provided between the intermediate material and the laminated material, because when the gap size exceeds 8.0 mm, hot rolling is performed. 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, if the size of the interval 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.

[0050]

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 is not possible because of the relationship with the maximum slab capable of rolling (about 500 mm). In that case, 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, alumina powder), and 10 is a planned 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 10 to be joined from being oxidized during heating and 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.

FIGS. 2A, 2B and 2C are views schematically showing the direction of changing the angle with respect to the rolling direction as the polishing direction of the joining surfaces of the present invention, and FIG. Figure showing polishing in a right angle direction, Figure (b) shows polishing in the direction of 45 °,
FIG. 6C is a diagram showing cross polishing. Here, the thick arrow indicates the rolling direction, and the arrow indicates the polishing direction.

Practically, polishing is carried out in a direction of about 45 ° and at a right angle, and cross polishing is carried out. However, the angle is not limited to the above as long as it is an angle that can eliminate the uneven portion of the planned joining surface.

In FIG. 7A, the joining surface 10 of the laminated material 2 is polished in the direction indicated by the arrow perpendicular to the rolling direction indicated by the thick arrow.

In FIG. 6B, the joining surface 10 of the laminated material 2 is polished in the rolling direction indicated by the thick arrow and the direction indicated by the 45 ° arrow.

In FIG. 7C, the joining surface 10 of the laminated material 2 is polished in the direction indicated by the arrow crossing the rolling direction of the thick arrow. By these polishing, when the assembled slab is hot-rolled in the subsequent step, the uneven portion of the joining surface 10 can be eliminated.

According to the method of the present invention, the titanium clad steel plate according to the A method is No. 1 to 7, the titanium clad steel plate according to the B method is No. 10 and 11, the titanium clad steel sheet according to the A method is No. 8 and 9 for comparison, and the titanium clad steel plate according to the B method. No. 12 to 14 Titanium-clad steel plate No. 15 to which the wet high count polishing was performed in the direction parallel to the rolling direction.
17 was manufactured and the accuracy test such as the ultrasonic flaw detection test was performed.
The assembly slab method is A, B shown in FIGS. 1 (a) and 1 (b).
Table 1 shows the standards such as the base material and the conditions such as dimensions in each of the two methods.

[0063]

[Table 1]

Titanium clad steel plate (No. 1) of the present invention example (1) of method A by wet high count (200) polishing of the present invention
7), (No. 10, 11) of the present invention example (2) of the B method and the titanium clad steel plate (No. 8, 9) by the wet low count (No. 120) polishing of the comparative example (1) of the A method, the B method Comparative example
Titanium clad steel plate (No. 12 to 14) by wet low count (No. 120) polishing of (2) and titanium subjected to wet high count (No. 200) polishing of Comparative example (3) of method A in a direction parallel to the rolling direction. Table 2 shows the manufacturing conditions for the clad steel plates (No. 15 to 17).

[0065]

[Table 2]

Table 3 shows the results of these accuracy tests.

[0067]

[Table 3]

As shown in Tables 2 and 3, when the wet high count polishing was performed, the ultrasonic flaw detection result and the bending test result were better than those of the wet low count polishing, and the shear strength was high. A high value was obtained. However, even when wet high count polishing is performed, when polishing is performed in the direction of the rolling direction of the present invention at 45 ° or at a right angle, or when cross polishing is performed, the same direction as the rolling direction is obtained. Compared with the comparative examples (Nos. 15 to 17) that were ground into No. 1, the shear strength was high, and the variation was small.

From the above examples, the present invention can manufacture a titanium clad steel sheet having high joint strength and bending workability at the joint interface between the base material and the laminated material by hot rolling.

[0070]

According to the present invention, it is possible to easily manufacture a titanium clad steel sheet having stable joint strength and high 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 diagram showing a rolling direction and an angle changing direction in wet high count polishing according to the present invention.

FIG. 3 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 Grinding with a count polishing in a direction in which the angle with the rolling direction is changed as the polishing direction, the surface finish is made so that the irregularities of the planned joining surface can be eliminated, and 0.1-8 between the intermediate material and the laminated material. Manufacture an assembly slab with a space of 0.0 mm,
A method for producing a titanium clad steel sheet by hot rolling, which comprises hot rolling at 50 ° 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 laminated to form a thin laminated intermediate material, the second intermediate material is inserted so that the second intermediate material is on the base material side, and the joining surface of the mating material is used as the polishing direction by the wet high count polishing in the rolling direction. The surface is polished so that the concavo-convex portion of the surface to be joined can be eliminated by polishing in the direction in which the angle is changed.
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.