JPH0484682A - Production of clad material having high base metal toughness - Google Patents

Abstract

PURPOSE:To produce the clad material having high base metal toughness by disposing cladding metals having the deformation resistance higher than the deformation resistance of base materials on the outer side of the base metals disposed on both sides of a separator and forming an assembled slab, then rolling the slab. CONSTITUTION:The base metals 1, 1 are disposed on both sides of the separator and the clad metals 2, 2 are disposed on the outer side of the base metals 1, 1. The peripheral edges are then welded. The clad steel plate is formed by an ordinary method using the assembled slab. The rolling shape ratio is increased in this way, by which the toughness of the base metals of the clad steel plate is improved.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is a method of manufacturing a cladding material by hot rolling assembled slabs, and in particular a cladding material that can increase the toughness of the base material. It relates to a method of manufacturing materials.

(Prior Art) As a means of inexpensively supplying corrosion-resistant materials that can withstand various corrosive environments, cladding materials that are made of thin-walled corrosion-resistant materials and are made of inexpensive carbon steel as a base material are attracting attention.

In recent years, high strength and high toughness have been required for the base material of this clad steel.

As a method to meet this demand, for example, JP-A-60-2
In Publication No. 16984, a so-called thermal processing control method is applied, in which a sandwich-type assembled slab in which two sheets of laminated material are inserted between two base materials is heated to a predetermined temperature, and then rolling and accelerated cooling conditions are controlled. A technique has been disclosed that attempts to increase the strength and toughness of the base material by doing so.

In the production of clad steel plates using this sand inch type assembly slab, as shown in Fig. 1, the cladding materials 2 and 2 are sandwiched between the base materials 1.1 and the peripheral edges are welded (3 is the welded part). Since a bottom symmetrical assembly slab is used, there is an advantage that even if accelerated cooling is performed after rolling, there is no concern that the slab will warp due to the difference in thermal conductivity between the base material and the laminate, which is a problem in the case of asymmetric assembly.

However, in sandwich type assembled slabs,
Since the sheet thickness during rolling is twice that of normal rolling, the amount of reduction applied to each clad steel plate is only 2 under the same amount of reduction, and the improvement in strength and toughness due to controlled rolling is not necessarily sufficient. That's hard to say.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method for improving the toughness of a cladding material manufactured from vertically symmetrical Zandwich-type assembled slabs (symmetrical assembled slabs).

(Another means to solve the problem) It is known that increasing the rolled shape ratio in (1) 2 below is effective in improving the toughness of the center of thick-walled materials ( For example, [Tetsu to Haganeko 62 (+9
76) P, 1708).

However, to: Plate thickness before rolling Li: Plate thickness after rolling R; Roll radius The present inventors have studied applying this to the rolling of symmetrically assembled slabs to improve the toughness of the base material of the cladding material. Overlapping,
The present invention has been accomplished.

The gist of the present invention is to produce a cladding material with high base material toughness, which is characterized by rolling an assembled slab in which a laminate material having higher deformation resistance than the base material is arranged on the outside of the base material with a separating agent sandwiched therebetween. method”.

The base material is carbon steel, low alloy steel, etc., and the mating material having higher deformation resistance than the base material is austenitic stainless steel, Ni-based alloy, etc.

FIG. 2 is a block diagram of a symmetrical assembled slab used in the method of the present invention. As shown in the figure, the base material 1.
1, and a bonding material 2.2 is placed on the outside of the base materials 1 and 1, and the peripheral edges are welded.

Using this assembled slab, a crane and a
It is set as iiiui.

(Function) The structure of the symmetrical assembly slab has been changed from the conventional structure in which the cladding material is arranged in the center and sandwiched between the base materials to the structure in which the laminate material is arranged outside the base material (the symmetrical assembly slab used in the method of the present invention). composition)
The fact that the rolling shape ratio determined by the above formula (1) increases by changing to is supported by trial calculations based on the model below.

FIGS. 3 and 4 are schematic diagrams showing changes in plate thickness before and after rolling of a symmetrical assembled slab used in the method of the present invention and a conventionally used symmetrical assembled slab.

In these figures, to: Total plate thickness before rolling the: One side plate thickness of the base material before rolling th: Total thickness of base material before rolling t: Total plate thickness after rolling tjl: One side thickness of base material after rolling tj: Total thickness of base material after rolling tsz laminated material plate thickness R: Roll radius It is.

Now, assuming that the plate thickness (ts) of the laminated material, which has higher deformation resistance than the base material, does not change before and after rolling, the rolled shape ratio is determined based on the above equation (1).

In the case of the symmetrical assembled slab used in the method of the present invention, as shown in Fig. 3, the radius of the roll is apparently R, but the thickness (ts) of the laminate in contact with the roll is different before and after rolling. Therefore, it can be seen as essentially R+ts. Therefore, (in calculating the rolled shape ratio based on formula 11, R+ts is used instead of R, t is used instead of to)
If tj is used instead of h and L, th=to~2
ts, tj=t, -2ts Then, by substituting these into equation (1), it becomes th +tj to+tI-4tS.

On the other hand, in the case of conventionally used symmetric assembled slabs, the roll radius is R, as shown in Figure 4, and a laminate material whose plate thickness (ts) does not change is inserted in the center of the assembled slab. Therefore, if we exclude this, we get the following equation, and when we substitute these into equation (1), we get the rolled shape ratio.

Comparing Equations (2) and (3) above, the rolled shape ratio is larger in the case of the symmetrical assembled slab used in the method of the present invention in Equation (2), and the roll diameter is larger by an amount equivalent to the thickness of the laminated material. The same effect would occur if

Therefore, in the production of clad steel, a laminate material with higher deformation resistance than the base material (
By using a symmetrical assembled slab made of austenitic stainless steel, Ni-based alloy, etc., it is possible to increase the rolling shape ratio and improve the toughness of the clad steel plate.

In addition, according to the method of the present invention, regardless of the chemical composition of the base material,
Although it is possible to achieve higher toughness than when using conventional symmetrically assembled slabs, it goes without saying that it is necessary to design the components according to the required performance.

(Example) Using base materials having the chemical components shown in Table 1, stainless steel was used as the mating material for these base materials (A, B, and C). 8 (SO5316), Incoloy (product name)
and stainless steel mcsUs 304), an assembled clad steel plate was manufactured by applying the method of the present invention. Also,
For comparison, a clad steel plate was similarly produced using the same base material and cladding material, and by a method of rolling a symmetrical assembled slab constructed with the cladding material arranged in the center. Table 2 shows the assembled slab thickness, manufacturing conditions, final product dimensions, and rolled shape ratio of the bus.

Mechanical tests were conducted on the base material of these clad steel plates, and
The yield point (YS), tensile strength (TS), and fracture surface transition temperature (vTs) were determined.

The mechanical test results are also shown in Table 2. As is clear from the results in Table 2, in the inventive examples, the rolling shape ratio in the first pass was larger than in the comparative examples for all steel types, and the fracture surface transition temperature (vTs) of the base metal was significantly improved. You can see that

(Hereinafter, blank space) (Effects of the invention) In the production of assembled clad steel plates using vertically symmetrical sandwich-type assembled slabs, the method of the present invention is applied using assembled slabs in which a laminate with high deformation resistance is arranged on the outside of the base material. By doing so, the rolling shape ratio can be increased, and the toughness of the base material of the clad steel plate can be improved.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing the structure of a sandwich-type assembled slab; FIG. 1 is a diagram of a conventionally used assembled slab; and FIG. 2 is a diagram of an assembled slab used in the method of the present invention. be. Figures 3 and 4 are schematic diagrams showing changes in plate thickness before and after rolling of symmetrical assembled slabs. Figure 3 is for the assembled slab used in the method of the present invention, and Figure 4 is for the conventionally used slab. This is the case for assembled slabs.

Claims (1)

[Claims] A method for producing a cladding material having a high base material toughness, which comprises rolling an assembled slab in which a laminate material having higher deformation resistance than the base material is arranged on the outside of the base material with a separating agent sandwiched therebetween.