JPH05138370A - Production of rolled clad material - Google Patents

Abstract

PURPOSE:To effectively produce an extremely thick steel plate by previously joining slabs by a liquid phase diffusion joining method. CONSTITUTION:The clad material is produced by rolling. The slabs are previously joined by the liquid phase diffusion joining method in the production thereof. An Ni-B alloy is used as an insert material in the case of executing the liquid phase diffusion joining. The liquid phase diffusion joining is executed by using the Ni-B alloy as the insert material and maintaining the vacuum degree at the boundary at <=1X10<-1>Torr, then subjecting the materials to heating and hot rolling. As a result, the good joining property is obtd. at <=3 reduction ratio.

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 rolled clad material, which has a good weldability due to a relatively small rolling ratio and is capable of appropriately obtaining an extremely thick clad steel. An attempt is made to provide a method for manufacturing a material.

[0002]

2. Description of the Related Art Although there are hot rolling method, build-up welding method, explosive welding method, and cast-girth method as a method for producing clad steel, the hot rolling method is comprehensively judged from economical efficiency and productivity. The best. However, in the case of producing a clad steel by this hot rolling, in order to obtain good bondability, in the case of SUS304, which is a general-purpose γ-stainless steel, the rolling ratio is 4 or more, and the high ratio typified by Hastelloy alloy. For Ni alloys, a reduction ratio of 5 or more is required.

Regarding the production of such a clad steel, the base material and the laminated material are previously joined (hereinafter referred to as pre-joining) at the stage of slab assembly, and then hot rolling is performed. Proposals for three groups have been made. (1) Using a hot press (JP-A-57-134287,
57-112985) (2) Using a hot isostatic press (HIP) (JP-A-56)
-122682) (3) What is brazed (JP-A-57-109588, 57-11298)
Five)

[0004]

In the conventional hot rolling method described above, it is difficult to secure such a reduction ratio because there is a limit to the slab thickness in the production of extremely thick clad steel having a plate thickness of 100 mm or more, It is difficult to manufacture extremely thick clad steel.
That is, although steel is manufactured by continuous casting in recent years, the thickness of the sukubu produced by such a method is about 250 mm. Therefore, in order to secure the reduction ratio 4, the maximum thickness of the product is about 60 mm. Become.

The method of using the hot press of (1) proposed as described above is generally described as follows: "Insert material is inserted at the interface to be joined and covered with a retort, and the inside of the retort is depressurized (or non-reduced). After changing to an oxidizing atmosphere)
This is a method of “pressing while heating”, in which the so-called solid phase bonding is performed, in which the insert material is not melted and bonding is performed in the solid phase. According to these methods,
Although good bonding is maintained, the complicated process is complicated. That is, the retort must be used first, and the retort becomes scrap after one use, which is a major obstacle in providing an inexpensive clad. Also, applying pressure while heating requires a large-scale facility, which is an obstacle to achieving the above-mentioned object. The size of a normal slab is about 2000 mm x 3000 mm (maximum 210
It has a large area of 0 mm x 4500 mm),
It goes without saying that a huge amount of equipment is required to press this. By the way, the size of the object to be joined by such hot pressing is usually 1000 mm x 1500
It is about mm, which is much smaller than the slab size made by conventional steel manufacturers.

These disadvantages are due to the proposal of (2) above.
When it comes to HIP processing, it gets even worse. That is, the example disclosed in JP-A-56-122682 is a slab having a length and width of 54 mm, which is out of the laboratory scale (from the viewpoint of a person who manufactures clad steel at a steel manufacturer). Absent. About 2000mm x 3000mm (2100 at maximum)
It is almost impossible to make a slab (mm x 4500 mm). Unless it is very expensive, it will be meaningless industrially.

From this point of view, the brazing of the above (3) is advantageous. That is, it is a great advantage that pressurization is basically unnecessary. Also, when assembling the above slab, only the heating furnace is sufficient as the equipment. Atmospheric pressure can be achieved by devising the assembly method. Then, the equipment owned by the steel manufacturer can be reused, and new capital investment need not be made. However, the brazing of (3) is a melting phenomenon during reheating and rolling. That is, brazing basically melts the brazing filler metal and solidifies the brazing filler metal to perform joining, but when the brazing filler metal is heated again, it is melted again at the melting point of the brazing filler metal. The melting phenomenon during rolling is extremely inconvenient for making clad steel. There is a risk that the melt may jump out during the rolling process and break the equipment, but since it is not joined at all, pre-joining cannot be performed and it is not possible to contribute to joining from the first pass. According to the results of the study by the present inventors, it is important that they are joined at the start of rolling, and rolling must be performed within a temperature range in which the brazing material does not remelt. It is also easily inferred that the bonding strength becomes low near the melting point of the brazing material (on the solid phase side), and our purpose cannot be achieved. Even when the example of JP-A-57-112985 is seen, the joining is performed at 1100 ° C. and the rolling is 850.
It is performed at a temperature as low as ˜740 ° C. In other words, as long as brazing is performed, the rolling temperature must be lower than the melting temperature of the brazing material, and must be significantly lower than the melting point in order to secure the bonding strength, which is a major operational limitation. Become.

Japanese Patent Laid-Open Nos. 57-112985 and 57-109588 are
In the content described in the detailed invention, it is nothing but brazing, and it cannot be said to be liquid phase diffusion bonding.
In other words, diffusion bonding is premised on the fact that the elements contained in the insert diffuse into the base material or the composite material during the bonding process, raising the melting point and "causing isothermal solidification", but these are not described. By the way, it cannot be said that such a phenomenon has occurred, and the Cu f
Since oil does not cause isothermal solidification in metallurgical consideration, it cannot be brazed.If Cu is used as an insert material in this way, molten metal cracking may occur, that is, it may penetrate into the base metal grain boundaries during heating. It is likely to be broken.

[0009]

The present invention has been studied to solve the technical problems in the conventional ones described above, and has been studied to obtain a thick clad steel. As a result of considering which process is important for joining although not joined, it was estimated as follows. (1) The interface (between the base material and the laminated material) of the assembled slab is initially not joined. (2) This is heated and starts rolling, but at the initial stage of rolling, the interface between the base material and the laminated material slips. When this slippage phenomenon occurs, the mating material and the base material extend separately. That is, a material having a small deformation resistance (in many cases, a base material) extends largely, and a material having a large deformation resistance (in many cases, a composite material) extends little. (3) Such a tendency is small in the center of the rolled plate, and becomes remarkable in the vicinity of the end face of the plate. (4) The "new surface" is the key to joining in the rolling process. That is, the "new surface" formed on the surface of the mating material and the surface of the base material are formed at the same time, and the new surface is firmly connected only when the new surfaces are in contact with each other. (5) However, the slip phenomenon described above delays the formation of a new surface on one side (often a laminated material). That is, the new surface of the base material is formed more and more, but the formation of the new surface of the mating material of the other party is delayed, so that even if the new surface of the base material is formed, the proportion of contribution to the bonding is reduced. (6) Therefore, in this initial rolling process, the reduction ratio contributing to metal joining is reduced. (7) This tendency is remarkable at the edge of the rolled plate, and the edge tends to peel off. If the interface is not joined at the end, it will become a notch and will peel off. (8) When the rolling progresses to some extent, local joining occurs and this slip phenomenon is suppressed (these joints have a function of stopping with a pin). Then, in the subsequent rolling, the entire metal joining is likely to occur. That is, the "new surface" of the mating material and the base material are formed at the same ratio, which effectively contributes to metal bonding.

The present invention based on the results of such studies is as follows. (1) In the method for producing a clad material by rolling,
A method for producing a rolled clad material, which comprises joining the slabs in advance by a liquid phase diffusion bonding method.

(2) When performing liquid phase diffusion bonding, a Ni-B type alloy is used as an insert material.
The method for producing a rolled clad material according to item.

(3) When performing liquid phase diffusion bonding, Ni-B alloy is used as an insert material, and the degree of vacuum at the interface is 1 × 10 ^-1 To.
The method for producing a rolled clad material as described in the item (1), wherein heating and hot rolling are performed after the temperature is set to rr or less.

[0013]

In the method of manufacturing the clad material by rolling, the slab is preliminarily joined by the liquid phase diffusion joining method, so that proper joining can be obtained at the slab stage and the first slip phenomenon between the base material and the laminated material is suppressed. By reducing the initial slip in such a condition that the initial slip is suppressed, the ratio of the reduction contributing to the joining is increased, and the clad is properly joined.

By adopting liquid phase diffusion bonding, the bonding strength at the rolling temperature is secured and the pressure at the time of bonding is unnecessary,
Effective joining can be obtained without requiring special equipment.

When performing the above-mentioned joining, by using an Ni-B type insert material, the diffusion of B into the base material and the laminated material is rapid, and the soaking of B from the liquid phase is performed by soaking for a relatively short time. Diffuse to complete the liquid phase diffusion bonding.

By setting the degree of vacuum at the slab interface to 1 × 10 ^-1 Torr or less, the base material and the composite material are prevented from being oxidized when the slab is heated, and the bonding force at the time of liquid phase diffusion bonding is increased, followed by rolling. Aim to join effectively.

The technical relationship of the present invention as described above will be described in more detail. In FIG. 1, 10 mm ^t of SUS304L (steel 1) having the components shown in the following Table 1 is used as a composite material, and 190 mm ^t of 5 is used.
Table 2 below using 0 kgf / mm ² class high tensile strength (steel 2) as the base material.
Two kinds of intermediate materials having a thickness of 40 μm showing
After inserting it between the laminated material and the base material, assemble the slab with the open type and evacuate it to 1 × 10 ^-1 Torr so that the laminated material is on the lower side. Bonding rate and interface shear strength when rolled to 100 mm ^t at a reduction ratio of 2 after soaking at ℃ for 3 hours (U in both cases)
(Evaluation by ST) is shown (in the figure, the case where a Ni-P system is used as an insert material is also shown, but for the description of the Ni-P system, see the next section). For comparison, the results when no intermediate material was inserted were also added. Cu as intermediate material
When the foil and the intermediate material were not inserted, after rolling at a reduction ratio of 2, the joining did not occur at all and the joining rate was 0%, so that the shear test could not be performed. On the other hand, with intermediate materials
When the Ni-B alloy was used, the bonding rate was 100%, and the shear strength of the interface was 408 MPa, which was as good as the case where the reduction ratio of 4 or more was secured in the normal process.

[0018]

[Table 1]

[0019]

[Table 2]

Further, material combined SUS304L 10mm thick showing the components in Table 1 in FIG. 2 (steel 1), 50 of 230 mm ^t
kgf / mm ² class high-strength steel was used as the base material (steel 2), and two types of Ni-B alloys having the components shown in Table 3 below were used as intermediate materials, and the area ratio of the intermediate materials during slab assembly was varied. The drawing shows the joining ratio and the shear strength of the interface when the material is soaked at 1150 ° C. for 3 hours and then rolled to 120 mm at a reduction ratio of 2 × 10 ⁻² Torr. In any of the intermediate materials, when the area ratio during slab assembly is 50% or more, the bonding ratio after rolling is 100%, and the shear strength of the interface is 350%.
It is as good as MPa or more. On the other hand, the area ratio of the intermediate material is 2
In the cases of 0% and 40%, a significant decrease in shear strength occurs. Thus, it is not necessary to pre-bond the entire surface of the slab bonding interface. It is only necessary that the slip phenomenon does not occur from the first rolling.

[0021]

[Table 3]

The reason why the Ni-B type insert material is preferable is shown in FIG. That is, FIG. 1 also shows the case where a Ni-P alloy is used as an insert material. It can be seen that the Ni-P alloy is inferior in joining property to the Ni-B alloy. .. Considering the reason for this, the present invention focuses on achieving the above-mentioned object without lowering productivity as compared with the conventional method for producing rolled clad steel, so that the normal soaking time is within 3 hours. After the intermediate material is melted, it is necessary to solidify at that temperature. As shown in FIG. 1, the Ni-B alloy is the most suitable as the intermediate material, and the Ni-P alloy and the pure Cu used in JP-A-57-109588 and 57-112985 are not necessarily preferable. .. This is because in the case of Ni-B alloys, B diffuses quickly into the base material and the laminated material, so that B diffuses from the liquid phase within the soaking time of 3 hours, and liquid phase diffusion bonding is completed. Is. On the other hand, the diffusion of P is slow in the Ni-P alloy and the diffusion of Cu is slow in the pure Cu, so that the pre-bonding is not completed within the soaking time and the action like that of the Ni-B alloy cannot be obtained. ..

The technical details of the degree of vacuum at the interface will be described below. In FIG. 3, the components shown in Table 3 above and having a thickness of 10 mm are shown.
Ni-based alloy (Hastelloy alloy) as a composite material, 190 mm ^t 4
The characteristics change when 0 kg steel is used as a base material and the Ni-B alloys whose components are shown in Table 2 are used as an intermediate material and an open type slab is assembled and the degree of vacuum is changed are shown. As for heating, the laminated material was soaked at 1200 ° C. for 3 hours, and then rolled at a rolling ratio of 2 to 100 mm. When the degree of vacuum during clad assembly is 1 × 10 ^-1 Torr or higher, 350 is obtained under all conditions.
Good shear strength of MPa or more can be obtained, but no joining occurs at 1 Torr or less. When the degree of vacuum at the interface of the slab exceeds 1 × 10 ^-1 Torr, it is not joined even if the subsequent rolling is performed. The reason is that the surfaces of the base material and the laminated material are oxidized during heating of the slab and joining during liquid phase diffusion joining It is considered that the force was weak and the interface was peeled off by the subsequent rolling.

As explained above, the slab was assembled by inserting at least 50% by area ratio of the Ni-B based alloy at the interface between the base material and the laminated material, and the slab was made to have a vacuum degree of 1 × 10 ^-1 Torr or less. rear,
It is confirmed that it is possible to produce a rolled clad steel having good bondability at a reduction ratio of 3 or less by performing hot rolling.

As described above, according to the present invention, mild steel, non-tempered high-strength steel (for example, 50 to 70 kg grade), tempered high-strength steel, and other general steel (mild steel, low alloy steel) are used as the base material. It is also possible to employ a wide range of materials such as austenitic stainless steel in general, duplex stainless steel, cupronickel, monel, titanium and high nickel alloys.

[0026]

EXAMPLES Specific examples of the present invention are described below. (Example 1) Table 4 below shows the components of the laminated material (steel 5) and the base material (steel 6) used.

[0027]

[Table 4]

In addition to the above-mentioned mating material and base material of Table 4, the intermediate materials of A to G shown in Table 5 below were used, and the interface between the mating material and the base material was also prepared by the same assembly method as shown in Table 5. , And then evacuated to 3 × 10 ^-2 torr, and heated to 1150 ° C for 2.
After soaking for 5 hours, the result of rolling to a size of 150 mm with a reduction ratio of 2 is shown in the right side of Table 5.

[0029]

[Table 5]

That is, as is clear from the results of Table 5, A using the Ni--B type alloy of the present invention as an intermediate material,
For the B and C materials, a bonding rate of 100% was obtained after hot rolling, and a shear strength of 400 MPa or more was obtained. On the other hand, D material using Ni-P alloy and E using pure Cu
In the case of the material, solidification of the intermediate material is not completed at the time of heating, so that no joining occurs after hot rolling. As is clear from the comparison of materials A, B, and C, in the case of Ni-B alloys, Cr, Co, M
Even if the alloy contains any of o, Fe, W, and Si, good bondability can be obtained after hot rolling. The material F is the result of the sacrificial material type, but since the material satisfies the conditions of the present invention, good bondability is obtained like the open type. All of materials A to F are the result of heating with the laminated material on the lower side, but the sandwich type with the laminated material on the inner side and the base material on the outer side also satisfies the conditions of the present invention as shown in G material. If so, good bondability can be obtained even at a reduction ratio of 2. The present invention is particularly effective in the production of extremely thick clad steel for which it is difficult to secure a reduction ratio of 4 or more, but it is also effective for rolled clad steel of ordinary thickness to be G material (70 + 5 mm). It is also clear from the results for clad steel.

(Example 2) Table 6 below shows the components of the laminated material (steel 7) and the base material (steel 8) adopted in this example. 81% Ni-15% Cr-4.0% B alloy was used as an intermediate material, and a slab was assembled under the conditions of a base material of 192 mm large and a laminated material of 8 mm large.
After heating for an hour, rolling was performed.

[0032]

[Table 6]

The manufacturing conditions and results are as shown in Table 7. As shown in Table 7, the H, I and J materials satisfying the area ratio and vacuum degree of the intermediate material under the conditions of the present invention are hot. A good shear strength of 350 MPa or more after rolling is obtained in each case. On the other hand, in the example in which the condition of the area ratio of the intermediate material is not satisfied, in the case of the L material which does not satisfy the condition of the vacuum degree, sufficient joining does not occur.

[0034]

[Table 7]

(Example 3) Table 8 shows a laminated material having a size of 10 mm,
Assemble a slab using 81% Ni-15% Cr-4.0% B alloy as an intermediate material at the composition of the base material of 190 mm size and the interface between the base material and the composite material, and ^{1x10 -2} torr After making the vacuum degree of No. 3, after heating the laminated material to 1200 ° C. for 3 hours,
The result of rolling to 100 mm at a reduction ratio of 2 is shown. M material combining carbon steel and γ-type sunteres steel, N material combining carbon steel and duplex stainless steel, O material combining carbon steel and Y-type stainless steel, P combining carbon steel and Ni-based alloy In any case of the Q material, the Q material, and the R material in which the Y-based stainless steel and the Ni-based alloy are combined, the conditions of the present invention are satisfied, so that any clad steel can obtain a good shear strength of 400 MPa or more. ing.

[0036]

[Table 8]

[0037]

As described above, according to the present invention, pre-bonding using liquid phase diffusion bonding is performed at the time of clad rolling heating of the base material and the laminated material, and then hot rolling is performed, whereby a reduction ratio of 3 is obtained. Good bondability can be obtained below, and it was possible to effectively achieve the production of extremely thick clad steel, which had to be difficult to produce by the rolling method because a sufficient reduction ratio could not be secured in the past. It is an invention that is highly effective.

[Brief description of drawings]

FIG. 1 is a chart showing a change in a joining state depending on a type of an intermediate material.

FIG. 2 is a table summarizing changes in the bonding state with the area ratio of the intermediate material.

FIG. 3 is a table summarizing changes in the bonding state with the degree of vacuum at the interface.

Claims (3)

[Claims] 1. A method for producing a clad material by rolling, wherein a slab is preliminarily joined by a liquid phase diffusion joining method. 2. The method for producing a rolled clad material according to claim 1, wherein a Ni-B alloy is used as an insert material when performing liquid phase diffusion bonding. 3. When performing liquid phase diffusion bonding, a Ni-B alloy is used as an insert material, the degree of vacuum at the interface is set to 1 × 10 ⁻¹ Torr or less, and then heating and hot rolling are performed. The method for producing a rolled clad material according to claim 1.