JPS63281786A - Production of clad material - Google Patents

Abstract

PURPOSE:To save a fuel cost and to improve a product quality by evacuating the inner part of an assembly slab, coating the surface of a clad material by a protection material and executing hot rolling after heating by a continuous type heating furnace. CONSTITUTION:The surfaces of a base metal 10 and clad material 12 are cleaned and an assembly slab is formed as well with boxing welding. The upper and lower faces of this assembly slab are coated by the protection stock 20 of an iron plate, etc. to heat the slab by charging it into a continuous type heating furnace. A composite clad material is formed by subjecting the assembly slab after heating to hot rolling. In this case, the assembly slab is reduced at its surface heating speed due to the interposition of the protection material 20 to cause relaxation heating effect. The cavity generation between the base metal 10 and clad material 12 is therefore prevented because of its becoming of the heating similar to a batch type heating furnace. Owing to using a continuous type heating furnace the fuel cost is saved and yet the product quality is improved as well.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing kraft materials, such as thick clad steel plates, which have excellent heating fuel consumption and rolling efficiency.

In particular, the present invention relates to a method for producing clad steel sheets, which comprises forming assembled slabs, continuously heating them, and then hot rolling them.

(Prior art) Conventionally, the method for manufacturing cladding materials using the hot rolling method involves overlapping the mating surfaces of the cleaned base material and cladding material, welding them all around to form a slab, and then hot rolling. It was rolling.

However, when performing cladding of four-circumference welded assembled slabs, especially plates of plates with significantly different coefficients of linear expansion, if the assembled slabs are charged into a continuous heating furnace prior to hot rolling, the base material and laminate plate The amount of deformation due to thermal expansion becomes non-uniform due to the non-uniform heating speed due to the difference in thickness, and for example, as shown in FIG. Even after rolling, this cavity 1
Part 4 cannot be crimped.

Therefore, conventionally, it is impossible to heat assembled slabs using a continuous heating furnace, which has a fast temperature rise speed.
It had no choice but to heat in a batch-type heating furnace, which has a slow temperature rise speed. For this reason, the batch method is limited in the amount of steel that can be heated at one time, and consumes a large amount of heating fuel.
A decline in production efficiency and an increase in costs were unavoidable.

(Problems to be Solved by the Invention) The general object of the present invention is to provide a novel method for manufacturing rudd material that solves the problems of the prior art.

A specific object of the present invention is to enable heating in a continuous heating furnace to be carried out relatively easily, to significantly improve rolling efficiency, and to save fuel due to the continuous heating method. It is an object of the present invention to provide a method for producing cladding materials, especially kraft steel materials.

Note that kraft material is a broad term that includes clad steel plates, but in the following, the most common of these, raft steel plates, will be explained as an example.

(Means for Solving the Problems) The inventors of the present invention have found that there is a method that enables continuous heating, and have completed the present invention. .

Therefore, the gist of the present invention is to stack the mating surfaces of the base material and the mating material as clean surfaces, seal-weld the peripheries of the mating surfaces, vacuum the inside, and assemble the entire circumference welding slab. The cladding is characterized in that at least the outer surface of the assembled slab is covered with a protective material, then charged into a continuous heating furnace, heated to a predetermined temperature, and then hot rolled to form a kraft. This is a method of manufacturing the material.

The above-mentioned seal welding refers to welding that is performed to isolate the periphery of the mating surface between the mating material and the base metal from the outside air. In this case, a part is left unwelded, and the air remaining on the mating surface is vacuum-suctioned from there. and remove it. Finally, the vacuum suction port is also sealed by welding to complete the sealing of the mating surfaces.

In this way, in the present invention, when charging the slab into a continuous heating furnace, the above-mentioned iron plate is placed on the surface of the slab as a protective material, and if desired, the same iron plate is placed on the back side (as a protective material), and charging heating is performed. By using such a simple means, unexpected problems arise due to differences in linear expansion coefficients of the metal materials that make up the slabs, or due to rapid heating of only the laminated materials to high temperatures. It is possible to prevent cavities from being formed between the base material and the laminate due to the expansion of the material.

Thus, the invention allows continuous rolling of welded assembled slabs prior to hot rolling, and thus:
This makes it possible to manufacture the cladding material on a continuous line, improving production efficiency, and furthermore, since continuous heat treatment is performed, it is possible to reduce fuel consumption.

(Operation) Next, the present invention will be described in more detail with reference to the accompanying drawings.

As already mentioned, FIG. 1 schematically shows the formation of cavities in the conventional method, and in the figure, the differences in the amount of expansion seen between metal plates 10 and 12 with different coefficients of linear expansion cause The formation of cavities 14 is unavoidable in the case of continuous rapid heating. In other words, in the case of a laminated material whose four circumferences are welded and fixed, when rapidly heated, the welded fixed part (four circumferential parts) and the unfixed part (the non-fixed parts) The deformation behavior during thermal expansion is markedly different between the entire surface of the slab and the full surface of the slab. In other words, the four peripheral parts are affected by the thermal expansion of the base material slab, and if the board is thick, it will not expand for a while, so it will not expand immediately, but the non-fixed part is thin, so it will expand quickly. As a result, a difference in deformation behavior as shown in FIG. 1 is observed, and a cavity 14 is formed.

In a continuous heating furnace, the furnace atmosphere temperature is quite high at 1000° C. or more, so the assembled slabs charged into the furnace are subjected to extremely rapid heating, and the above-mentioned tendency is even more noticeable.

Therefore, conventionally, in order to avoid such rapid heating, slow heating is performed as a bunch method.

However, as shown in FIG. 2, in the present invention, at least the surface of the laminate material, that is, the top and bottom surfaces of the assembled slab, is covered with a protective material 20 called a bottom plate or cover, and then the continuous heating furnace is loaded. Since the thermal energy in the heating furnace is first received by the protective material 20, the heat is then gradually transferred to the laminate material 12. In other words, while using a continuous heating furnace, the heating rate is set to give an appearance of slow heating, similar to the batch method.

Here, the protective material may be the same material as the base material or the laminate material, a different metal, or a non-metal such as ceramic. In short, there are no particular restrictions as long as the surface of the laminate is rapidly heated by the surrounding atmosphere when charged into a continuous heating furnace, and it acts as a buffer to prevent rapid heating. be. However, since such a protective material must be easily removed prior to the subsequent hot rolling process, it is specifically limited to the types described above.

Since the above-mentioned protective material used in the present invention is not welded and fixed to the assembled slab, the entire surface can freely and uniformly expand even if it is rapidly heated. There is no cavity formation as described above, and there are no particular restrictions on the installation form of the protective material, but it may be sufficient to simply place it on the slab surface, or it may be necessary to prevent free expansion during heating so that the protective material does not shift. It may be possible to weld at appropriate locations to prevent the damage from occurring, or it may be sealed by welding along the seams after wrapping the whole. Furthermore, these protective materials may be hot rolled Descaling is performed prior to the removal.

In this way, since the slab is covered with a protective material, the heating rate of the slab surface is considerably moderated, resulting in the slow heating effect seen in batch systems. However, unlike the batch type heating furnace, long-term heating is not required, and the required heating time is about 2 to 6 hours, which is about 1/3 to 115 hours compared to the batch type heating furnace.

Regarding the cause of this effect in the present invention, firstly, in the conventional case, it was thought that the high temperature atmosphere inside the furnace came into direct contact with the slab surface, resulting in cavities, but in the case of the present invention, the high temperature atmosphere inside the continuous heating furnace It is thought that no cavities are formed in the laminate because energy is once received by the protective material and then gradually transferred to the laminate. The protective material acts as a buffer against rapid heating.

Next, the present invention will be explained in more detail with reference to examples thereof.

EXAMPLE A mild steel plate (thickness: 240a+a) was used as a base material, and stainless steel plates (thickness: 3 mm, 5LIS304) were used as a laminating material on both sides, and a craft steel plate was produced by hot rolling according to the present invention.

First, the mating surfaces of both the base material and the mating material were made clean by, for example, mechanical polishing, and then one side was assembled into a slab by four-circle welding, and the inside was vacuumed by suctioning air from inside the mating surfaces. Next, in the same manner, another mating material was laid on the mating surface on the opposite side of the base material, and four-circumference welding was repeated to form an assembled slab.

Next, a steel plate cover made of a SS41 steel plate with a thickness of 0.5 ma + 0) was placed on the upper surface of the assembled slab obtained in this way, and on the other hand, the same steel plate with a thickness of 5 + s +++ was placed as a bottom plate on the lower surface of this clad steel plate. I laid it. Preferably, the size of these protectors is slightly larger than the size of the assembled slab.

The assembled slabs prepared in this manner by four-circle welding were placed in a continuous heating furnace. At this time, the heating rate, heating temperature, and heating time (furnace time) were measured and compared with the conventional batch method, and continuous heating was performed under the same conditions without using the protective material according to the present invention. As a comparative example, we considered a case in which a clad assembly was charged into a furnace.

Figures 3(a) and (b) show the heat pattern in the furnace in this example.The maximum heating temperature was 1250°C in both cases, but the time required for this was different from the batch method shown in Figure 3(a). It was 15 to 23 hours, and 3.0 to 4.8 hours in the continuous system shown in FIG. 3(b). In addition, the temperature increase rate in these cases is approximately 0°44 to 0.83°C in batch mode.
/Hram, 1.23-2.05℃/I(r
It was vs.

The results are summarized in Table 1, and as is clear from the results, continuous heat treatment of assembled slabs became possible for the first time with the present invention.

Table 1 (Effects of the Invention) The present invention has been described in detail above, and as is clear from these, the following effects can be obtained according to the present invention.

(Since it is 11 continuous type, fuel is saved.

(2) Since the heating slabs are continuously charged (
Rolling efficiency is greatly improved.

(3) Since the upper and lower surfaces of the assembled slab do not come into direct contact with the furnace atmosphere, the surface condition is good.

(4) Since it has become possible to roll a large amount at once, it has also become possible to reduce manufacturing costs.

[Brief explanation of drawings]

Fig. 1 is a schematic explanatory diagram illustrating the formation of cavities observed when continuous heat treatment is performed by a conventional method; Fig. 2 is a schematic cross-sectional diagram of a welded assembled slab according to the present invention; Fig. 3 ( a) and (b) are graphs showing the heat patterns of a batch heating furnace and a continuous heating furnace, respectively.

Claims (1)

[Claims] The mating surfaces of the base material and the cladding material are placed on top of each other as clean surfaces, the peripheries of the mating surfaces are sealed and welded, and the inside is vacuum-sucked to form a full-circumference welded assembled slab, and at least the outside of the cladding material of the assembled slab is A method for manufacturing a cladding material, which comprises covering the surface with a protective material, charging the material into a continuous heating furnace, heating it to a predetermined temperature, and then hot rolling to form a cladding material.