JPS60141390A - Production of clad steel plate - Google Patents

Abstract

PURPOSE:To produce a clad steel plate at a high yield without generating defecting joining by passing the thinner plate material to a high speed roll side in different circumferential speed rolling in which the circumferential speeds between an upper roll and a lower roll are different in a specific range. CONSTITUTION:A base metal and a clad metal are subjected to different circumferential speed rolling in which the circumferential speeds of an upper roll 5 and a lower roll 6 are different in a >=10% and <=30% range in the stage of producing a clad steel plate by joining the base metal and the cladding metal by hot rolling. The blank material having the thinner thickness of the base metal and the cladding metal is passed to the high speed roll 5 side in the stage of performing such different circumferential speed rolling. A large slip deformation is thus generated on the roll 5 side. A large slip deformation is therefore generated with the joint surfaces by which the base metal and the cladding metal are more strongly joined.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a clad steel plate by hot rolling.

Clad steel plates, which are made by laminating and bonding high-grade steel plates etc. (hereinafter referred to as laminates) with the required properties to low-profile ordinary steel plates (hereinafter referred to as base materials), have corrosion resistance, Because it can impart properties such as heat resistance and abrasion resistance,
In recent years, demand as an industrial material has increased, and its production has also increased.

There are various types of clad steel sheets, including stainless clad steel, nickel and nickel alloy steel, copper and copper alloy clad steel, and various manufacturing methods including hot rolling. Various materials and methods are used depending on the purpose of the clad steel sheet to be obtained.

Among the various manufacturing methods mentioned above, the production of clad steel by hot rolling involves hot rolling the base material and the laminate, and moving the constituent atoms of the base material and the laminate at a distance that allows them to exert an attractive force on each other in the atomic distance. This hot rolling method has traditionally been applied to the production of large clad steel sheets because it is advantageous for mass production of large products. However, when producing clad steel sheets by hot rolling, oxides of base metals and additive elements are generated on the joint surfaces of the base metal and laminate when they are heated, and oxides of base metals and additive elements are formed on the surface of the material. A partial carburized layer may be formed, resulting in the following disadvantages.

In other words, most of the oxides generated at the joint between the base material and the laminate during heating are destroyed and worn away during the subsequent rolling process, but the remaining oxides, etc. In this case, bonding defects such as peeling and variations in bonding strength occur, resulting in a high number of defective products and a decrease in yield. Therefore, in order to eliminate such bonding defects at the joint between the base material and the laminate material and to improve the yield, various measures have been conventionally taken when heating the material, as described below.

For example, measures are taken such as welding the periphery of the joint between the base material and the cladding material, evacuating the gap between the joint surfaces, filling it with argon, or degassing with a light compressor. Countermeasures have been taken, such as inserting a metal foil between the base material and the laminate, or plating at least one of them and then hot rolling. However, with these conventional methods of producing clad steel sheets by hot rolling, although yields are certainly improved, bonding defects have not yet been sufficiently eliminated for the following reasons. As a result, a problem arises in that the bonding strength of the bonded portions of the resulting cladding plates varies.

In other words, it is known from thermodynamics that various oxides are generated even at low oxygen partial pressures that cannot be achieved industrially. It is not possible to completely prevent the formation of oxides, and at least small amounts of oxides remain or are newly formed. In addition, these fine oxides cannot be completely destroyed even during the rolling process after heating, and therefore, these fine oxides are present in the joints of the rolled rolled steel sheets. Microscopic bonding defects occur in the intervening portions, and even if peeling does not occur, variations in bonding strength occur.

The present invention has been made in view of the above-mentioned conventional circumstances, and is intended to reduce bonding defects, particularly microscopic bonding defects, between base materials and laminate materials, thereby eliminating variations in bonding strength at bonded parts of products. It is an object of the present invention to provide a method for producing a clad steel sheet that can improve combing and yield.

In order to achieve the above object, the inventors of this invention conducted experiments and studies from time to time, and found that if a strong sliding deformation is applied to the base material and the laminate material during rolling after heating the base material and the laminate material, the base material and the laminate material will be mutually compatible. The inventors have discovered that the above-mentioned object can be achieved by sufficiently destroying microscopic oxides, etc. existing on the bonding surface, and furthermore hastening the shrinkage and disappearance of voids in the bonding surface, leading to the creation of this invention.

As a means of imparting strong sliding deformation inside a material during rolling, so-called different circumferential speed rolling has been conventionally used.

This rolling at different circumferential speeds makes it possible to reduce the rolling load, so it can also be used when rolling with a large reduction ratio or when applying shear strain to the rolled material to refine the recrystallized grains after rolling. Traditionally used. In addition, regarding the manufacture of clad steel sheets in particular, see JP-A-52-130457,
A method is described for producing warp-free clad steel sheets by passing the harder material with poor stretchability between the base material and the cladding material through the high-speed roll side, thereby equalizing the amount of deformation of the base material and cladding material to be joined. There is -C. However, this method applies rolling at different circumferential speeds in order to equalize the elongation of the product only when the laminated material is made of a material that is more convenient than the base material, so its scope is limited and Nor was it intended to solve the conventional problems mentioned above.

In other words, the method for manufacturing a clad steel sheet of the present invention, in manufacturing a clad steel sheet by hot rolling, involves rolling the plate at different circumferential speeds in which the circumferential speeds of the upper roll and the lower roll are different in the range of 10% to 30 inches. This method is characterized in that the thinner plate material passes through the high-speed roll side.

This invention will be explained in more detail below.

In this invention, when manufacturing a clad steel plate by joining a base material and a cladding material by hot rolling, different circumferential speed rolling is performed in which the circumferential speeds of the upper roll and the lower roll are different in the range of 10 inches or more and 30 inches or less. Let's do it. Here, the reason why the different peripheral speed ratio of the upper roll and the lower roll, that is, the different peripheral speed ratio is 10% or more and 30% or less, is that if the different peripheral speed ratio is less than 10%, in addition to the material As a result, the effect of improving the joint strength between the base material and the composite material after rolling is small, and if the different circumferential speed ratio exceeds 30%, the effect of performing different circumferential speed rolling is saturated. Moreover, there is a risk that the base material and the laminate material will not be joined and become two plates, or that large warping deformation will occur.

As an example to show this, Figure 1 shows the different circumferential speed ratios obtained when rolling at different circumferential speeds is performed using low carbon steel with a thickness of 80cm as the base material and cupronickel steel with a thickness of 20+1011 as the laminated material. The relationship with the shear strength of clad steel is shown. As shown in Figure 2, the slab is made by combining a base material 1 with a cladding material 3 that has been nickel-plated 2, and then adding cladding materials 3 and 4 together along the edges of the laminate material 3. Formed by welding. 4 is a build-up bath contact part. The shear strength of the clad steel obtained by heating the slab thus formed to 950°C and finishing it at 700°C to a thickness of 25% is 100%).
When is less than 10%, the shear strength is low and its variation is large.

Still, in this invention, when performing the above-mentioned different circumferential speed rolling, the thinner material of the base material and the laminate material passes through the high speed roll side. Figure 3 shows the circumferential speeds V and v2 of the upper roll 5 and lower roll 6, respectively, during hot rolling.
FIG. 3 is a schematic diagram showing the state of sliding deformation of the rolled material 7 when performing normal rolling where v is set at a constant speed, and mixed circumferential speed rolling where v2 is set larger than v2. As shown in Fig. 3 (4), in the case of normal rolling, the neutral point 8 is located at almost the same position on both the upper and lower roll sides, and the rolled material 7 undergoes almost the same degree of sliding deformation on both the upper and lower roll sides. However, as shown in FIG. 3(B), in the case of rolling at different circumferential speeds, larger deformation occurs on the high speed roll 5 side. Therefore, as mentioned above, if the material with the thinner plate thickness is placed on the high-speed roll side, a large deformation will occur on the joint surface, and the base material and the laminate material will be joined more strongly. Conversely, if the base material is thinner than the laminate material, the base material should be placed on the high-speed roll side, and if the cladding ratio is 50150, both the base material and the laminate material should be placed on the high-speed roll side in terms of adhesion. Also good. However, in order to make the elongation deformation of the steel sheet more uniform and to perform stable rolling, it is desirable to use the side with higher deformation resistance on the high-speed roll side.

The shrinkage and disappearance of voids is due to the diffusion of vacancies and atoms, so performing rolling at different circumferential speeds at the circumferential temperature in the initial stage of hot rolling has a greater effect in eliminating voids, and also helps prevent product rebound deformation. Therefore, it is effective to carry out rolling at the beginning of hot rolling when the material is at a high temperature and the amount of deformation is still small.Therefore, it is desirable to carry out rolling at different circumferential speeds for at least 1 bus up to the third pass of the hot rolling process. Preferably, the first pass is rolled at different circumferential speeds.

Examples of this invention are described below.

Example co, io%, Si 0.25%, Mn 1.
2 (using 801111111 thick low carbon steel with a composition of 1% as the base material, Ni 92%, Fe 1.7 fb
, P O, 003%, Cu 88.3% When producing a clad steel plate made of 20cm thick keep-pro nickel steel as a laminate material, the mating surfaces of the base material and the laminate material were ground and cleaned, and the laminate material was A 180 μm 2y Kel plating was applied to the joints, and as shown in FIG. 2, they were overlapped and bath-bonded on the entire periphery to form an assembled slab with a thickness of lQQwn.

Next, the product was heated to 950°C, and hot rolling was performed at a finishing temperature of about 700°C to obtain a product with a thickness of 258°C.

The first pass of the hot rolling was different circumferential speed rolling with a different circumferential speed rate of 15'%.

In Comparative Examples and other examples, clad steel plates were manufactured by hot rolling at a constant circumferential speed in the same manner as in the above-mentioned Examples.

When ultrasonic testing was performed on the clad steel plates obtained in the Examples and Comparative Examples, the inspection yield in the Comparative Examples was approximately 75%, while that in the Examples was 90%. The test yield was extremely high.

Furthermore, a shear strength test was conducted in accordance with KJISGO601 to examine the adhesive strength of the joint between the base material and the laminate. Fourth
The figure shows the sample sampling positions from the clad steel plates obtained in Examples and Comparative Examples. As shown in the figure, the shear strength test was carried out by taking nine samples from both widthwise sides and the center of the rolling tip 9, intermediate portion IO1, and rear end 11 of the clad steel plate. The test results are shown in Table 1.

Table 1 Unit = Kg 4 As described above, according to the present invention, the clad steel plate is manufactured by hot rolling at different circumferential speeds, in which the upper roll and the 'F' roll have different circumferential speeds. By applying sliding deformation to the inside of the material during rolling, the oxide film and oxides existing on the contact surface between the base material and the laminate are sufficiently destroyed.
By abrading and further shrinking and eliminating voids on the bonding surface, it is possible to firmly bond the mutual bonding surfaces of the base material and laminate, producing clad steel plates at a high yield without causing bonding defects. can do.

[Brief explanation of the drawing]

Figure 1 shows the different circumferential speed rates and shear strength of the obtained clad steel plate when rolling was performed at different circumferential speeds using 80 mm thick low carbon steel as the base material and 20 mm thick key pro nickel steel as the laminated material. FIG. 2 is a schematic diagram showing the test piece used in the test shown in FIG. 1. FIG. 3 is a schematic diagram showing the sliding deformation that occurs in the material during hot rolling. Figure (4) shows the case of normal rolling, and Figure 3 (B) shows the case of different circumferential speed rolling. Moreover, FIG. 4 is a schematic diagram showing the sampling positions from the clad steel plates obtained in the examples of the present invention and the comparative examples thereof. ■... Base material, 2... Nickel plating, 3... Laminating material. 4...Overlay welding part. Patent attorney representing applicant Kawasaki Steel Corporation! & Takehisa Ta (and 1 other person)

Claims (2)

[Claims] (1) When producing clad steel sheets by hot rolling, the circumferential speed of the upper roll and the bottom roll is 10% or more.
A method for manufacturing a clad steel sheet, characterized in that rolling at different circumferential speeds in a range of 0° or less is performed such that the thinner sheet material passes through the high speed roll side. (2) The method for manufacturing a clad steel sheet according to claim 1, characterized in that at least one pass from the first pass to the third pass is rolled at different circumferential speeds.