JPS5911394B2 - Manufacturing method of clad steel plate with excellent bonding strength - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a clad steel plate with excellent joint strength.

Clad steel plates have been used in many fields, but recently there has been a demand for clad steel plates with particularly high joint strength and excellent performance.

Conventionally, there are many methods for manufacturing clad steel sheets, among which the representative ones used industrially include cold welding rolling, hot welding and rolling, and explosion welding. In the production of clad steel plates, which are bonded by diffusion of alloying elements between the base material and composite material using the pressure rolling method, depending on the combination with the composite material, the peel strength at the interface may decrease due to the formation of an alloy layer due to diffusion. To prevent this, there is a method of plating either the composite material or the base material with nickel or the like, but this has the drawback of high cost as described below. In other words, applying a medium metal such as 2x5 to either the plating material or the base material requires plating equipment, which increases the initial equipment cost and requires manpower to handle the base material or composite material to be plated. In addition to requiring additional equipment for this purpose, there are restrictions on the size of the plating tank, and therefore there are restrictions on the size of the base material or composite material to be plated, and since it is not possible to plate large items, the per unit weight of the slab is The plating cost will inevitably increase. Furthermore, it is difficult to increase the thickness of the plating, which limits the degree of processing in the hot rolling process, and the plating cost per unit weight increases by 2.
5 Not only are prices increasing, but the plating process is often
Since it is done by electrolysis, the running cost is extremely high, and it has drawbacks that make it unprofitable in terms of cost. The present invention improves such drawbacks and improves the composite material and base material steel plate 30.
Metal foil (thickness of 20 μm or more and less than 200 μm) as a medium that diffuses into both and forms a mutually strong alloy bonding layer, nickel alloy foil containing nickel, molybdenum, alloys thereof, and nickel in a weight ratio of 50ql7 or more, etc. By inserting one type or a combination of two or more of these 35 types of metal foil between the composite material and the base material and performing hot rolling, a clad steel plate with lower cost and higher performance than the medium made by plating can be produced. 1. Metal foil is inserted as a medium between the base material and composite material whose mating surfaces have been cleaned by chamfering or polishing, and when the periphery of the mating surfaces is welded and fixed, the entire circumference is During welding, a small amount of air remaining between the mating surfaces is expelled through the air holes by cold processing such as light cold rolling or cold press pressing, leaving a part unwelded as air holes. The air holes are repaired by welding and the entire circumference is welded to create an assembled slab, and the assembled slab is heated to a predetermined temperature and then hot rolled to a predetermined thickness to prevent carburization from the base material to the composite material, and at the same time remove the medium metal. The feature is that a metallurgically strong alloy bonding layer is formed by diffusing the foil component to both sides of the composite material and the base material.

In this way, the present invention requires no special equipment by simply laying metal foil on the base material and layering the composite material on top of it, so the initial cost is zero and there are no restrictions on the size of the assembled slab. Since there is no carburization from the base material to the composite material, the cost per unit weight of the slab is extremely low, and since the thickness of the medium can be made thicker compared to the plating layer, it is possible to further prevent carburization from the base material to the composite material. If the thickness of the foil is made thicker, it is possible to carry out high-deformation rolling in the hot rolling process, and the cost per unit weight of the slab becomes lower and lower. Moreover, metal foil is available at a low price compared to the plating cost, and it has the advantage that slabs can be assembled at approximately a few percent of the plating method if the handling costs are taken into account. Generally, if a metal foil is inserted between the base material and the composite material, the metal foil will move freely between the mating surfaces of the base material and composite material during hot rolling, so that the metal foil will move in accordance with the elongation of the base material and composite material. It was unthinkable in common sense that the foil would stretch uniformly, but
The experimental results showed that the components of the metal foil had already begun to diffuse to both ends of the base material and composite material during heating, and as hot rolling progressed, the components of the metal foil continued to diffuse to both sides, causing them to merge with the base material. The materials are rolled together through a medium called metal foil,
As a result, it was found that the metal foil was also stretched uniformly.

In addition, metal foil always contains inclusions, and although it was not common sense that it could be rolled to a thin thickness due to the size of the inclusions, the above mechanism allows the metal foil to be rolled to a thickness of about 4 μm. It has been found that the foil can be stretched without breaking. This is a completely new finding, and the present invention is based on this finding. As mentioned above, the present invention uses two media as a medium.
By using a metal foil with a thickness of 0 μm or more but less than 200 μm, it is possible to manufacture a clad steel sheet with superior performance at a lower cost than a plated sheet. After that, when welding and fixing the periphery of the mating surfaces, leave some parts unwelded as air holes.
After expelling a small amount of air remaining between the mating surfaces through air holes by cold processing such as light rolling or cold press pressing, the air holes are repaired by welding and the entire circumference is welded. The slabs are assembled by girth welding, but if the paired slabs are heated and then hot-rolled, joint failures due to oxidation of the mating surfaces can be reliably prevented, which is compatible with the aforementioned prevention of carburization and diffusion of the medium metal. All in all, a clad steel plate with excellent performance and yield can be obtained.

The thickness of the metal foil as a medium is 20mm or more 2001tm
The reason why it is less than 20 μm is because the reduction ratio is generally 3 to 3.
4 or more, and therefore the thickness of the metal foil after rolling is not uniform, which may cause breakage, or carburization (movement of carbon from the base material).
The thickness was set to 20 μm or more in order to prevent this.

Further, the thickness of less than 200 μm is preferable for preventing carburization (migration of carbon from the base material) as the medium becomes thicker, but it is not preferable because the thicker the medium, the lower the shear strength. Therefore, the thickness of the medium was less than 200 μm. Figure 5 shows the shear strength (JISGO6O
The results are shown below.

When a carbon steel plate is used as a base material and stainless steel or an alloy containing nickel such as Cypronickel is used as a composite material, it is preferable to use nickel as the medium metal foil.

Example As shown in Table 1 below, a metal foil is inserted between the base material and composite material whose mating surfaces have been ground, and when the periphery of the mating surfaces is welded and fixed, some of the unwelded parts are used as air holes. After that, the air is vented by cold rolling under light pressure or cold pressing, and the small amount of air remaining between the mating surfaces is expelled through the air holes, and then the air holes are repaired by welding and assembled by welding all around. The slab was then heated and hot rolled.

Table 2 shows the results of ultrasonic testing, shear strength and side bending tests for this clad product. Additionally, as comparative examples, test results are also shown in Table 2, in which no metal foil was inserted between the mating surfaces and no air bleed process was performed, or in which no air bleed process or metal foil was inserted.

Furthermore, regarding the clad products numbered 1 and 11, E. P
．． M. A. The diffusion status of the metal foil to the base material and composite material side was investigated.

It was found that in the product No. 1, the Ni component of the medium reliably diffused and penetrated to both sides, resulting in a metallurgically strong bond. In Figure 3, E. P. M. A. The measurement results are shown. In addition, fillet welding tests were conducted, and it was reconfirmed that a metallurgically strong joint could be obtained without peeling from the mating surfaces due to welding distortion, and because the Ni foil was inserted, the composite material could be separated from the base material. The carburization phenomenon was also reliably prevented, and FIG. 4 shows the microstructure. Regarding the area where the bonding of the clad product with reference numeral 11 has been obtained, E. P. M. A. The diffusion status of the Ni medium to the base material and composite material side was investigated, and it was found that the Ni medium was definitely diffused and permeated to both sides. In Figure 1, E. P. M. A. Shows the measurement results. Moreover, FIG. 2 shows the microstructure.

[Brief explanation of the drawing]

Figure 1 shows the E.I. of a clad steel plate made of stainless steel.
P. M. A. A chart showing the measurement results, Fig. 2 shows a microscopic photograph of the cross section of the same steel plate, and Fig. 3 shows the E.I. P. M. A diagram showing the measurement results, Figure 4 shows a microscopic photograph of the cross section of the steel plate,
FIG. 5 is a chart showing the results of shear strength according to the thickness of Ni foil used as a medium.

Claims (1)

[Claims] 1. Insert a metal foil of 20 μm or more and less than 200 gm as a medium between the base material and composite material whose mating surfaces have been cleaned, and when welding and fixing the periphery of the mating surfaces, use some of them as air holes and leave them unwelded. After the air remaining between the mating surfaces is expelled through the air holes by cold working under light pressure, the air holes are repaired by welding to form an assembled slab with all-around welding, and the assembled slab is heated and then hot-processed. Bonding strength characterized by preventing carburization from the base material to the composite material by rolling, and at the same time, diffusing the metal foil component of the medium to both sides of the base material and composite material to form a metallurgically strong bonding layer. An excellent manufacturing method for clad steel sheets.