JPS6356032B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing clad steel with good operability and with less equipment.

Clad steel plates, in which metals with different properties are layered and bonded on the steel plate surface to exhibit a variety of composite properties, have applications in a variety of fields, and various interesting proposals have been made regarding their manufacturing methods. The rolling joining method, in which a strip or sheet metal skin is superimposed on a strip or sheet steel plate and then rolled, is a typical method for producing clad steel plates because of its mass productivity. Conventionally, in the production of clad steel plates using this roll joining method, it has been considered extremely important to clean the joint surfaces and expose the clean metal surface in order to increase the adhesive strength. Since steel sheets are susceptible to surface oxidation, it has been considered essential to take some measure to prevent or remove the formation of oxide films. For example, gas sealing the steel plate with non-oxidizing atmospheric gas until the rolling joining process (especially in the case of warm or hot pressure welding),
It was considered common sense to increase the amount of deformation by setting the rolling reduction rate as high as 65% or more in order to increase the joint strength.

However, preventing or removing such an oxide film on steel sheets requires large-scale equipment and operation becomes complicated, and rolling with a high reduction ratio requires increasing the capacity of the rolling mill, which requires larger equipment. There were many disadvantages in actual operation, such as these, which were obstacles to the provision of inexpensive cladding materials.

The present invention goes beyond the conventional method of manufacturing clad steel sheets, which requires a non-oxidizing atmosphere gas seal and a high pressure reduction rate for the purpose of cleaning the surface of the steel sheet, and is capable of manufacturing clad steel sheets under heating conditions in an atmospheric atmosphere. This method provides an equipment-saving and easy-to-operate manufacturing method for clad steel plates that can obtain sufficient bonding strength in the process. When overlapping and rolling rolled metal strips or sheets, the steel plates are heated in advance to a temperature of 55 to 250°C in an atmospheric atmosphere before rolling and joining. 30 to 65% of skin metal at room temperature is rolled in one roll while keeping the temperature of at least the surface of the roll at 50℃ or higher.
We have developed a manufacturing method for clad steel sheets that is extremely advantageous in actual operation and is characterized by rolling at a reduction rate of .

In other words, the temperature of the work rolls for rolling joining is heated to at least 50°C, the temperature of the steel plates to be welded is heated to 55 to 250°C, and the reduction rate in one rolling is 30 to 65%. With a combination of three conditions,
It was found that sufficient adhesion strength could be obtained without causing any practical problems. One of the characteristics of the method of the present invention is that the steel plate is heated in an atmospheric atmosphere, and even when heated in an atmospheric atmosphere, the heating temperature of the steel plate, work roll temperature, and rolling reduction ratio are within the above conditions. Within this range, a good product can be obtained without the expected adhesion failure due to surface oxidation. However, it is necessary to clean the surface of the steel plate to be heated in the atmospheric environment by a surface cleaning treatment such as ordinary degreasing, pickling, or mechanical brushing as necessary.

This heat treatment of the steel plate at 55 to 250° C. in the atmosphere is preferably carried out by an internal heating method, such as induction heating. This enables mass production on a continuous line and eliminates the need for a special atmospheric furnace as in the past. Although a slight oxide film is formed by such heat treatment of the steel plate, it does not impair adhesion. When heated at a temperature exceeding 250° C., the amount of oxide film produced is such that adhesive strength is insufficient under the work roll temperature and rolling reduction ratio, and a good quality product cannot be obtained. Furthermore, if the temperature is lower than 55°C, the adhesion will be unstable under the work roll temperature and rolling reduction ratio mentioned above, and even if the rolling reduction ratio is increased above the above range, poor adhesion will be observed and the product will not be of good quality. . Therefore, it is necessary to heat the steel plate above 55℃ and below 250℃, but even if a slight oxide film is formed on the surface layer by heating the steel plate in this range in the atmosphere, heating above 55℃ is necessary. By work role
Rolling at a reduction rate of 30 to 65% causes relative slippage between the steel plate and the skin material, and as a result, the temperature of the steel plate further increases due to frictional heat, which easily destroys the oxide film of that extent, resulting in a clean surface. It is considered that at the same time as the metals are exposed, partial interdiffusion between the metals takes place, resulting in good adhesion.

Figure 1 shows the results of the investigation of the bonding strength between the skin material and the core material of steel plates after pressure welding, with the work roll temperature set at 95±5°C and the rolling reduction rate and core material temperature varied. It is. At that time, the core material before pressure welding,
The thickness of the skin material and the pretreatment conditions were determined as follows.

(1) Core material: 1.2mm thick mild steel plate (rimmed steel)
Alkaline degreasing (sodium orthosilicate 5%, 85
°C, immersion for 2 minutes), washed with water, then pickled (10% hydrochloric acid)
wt, immersed at room temperature, immersed for 10 seconds), washed with water, and dried (completely dried using a hot air blower), which was used as a core material.

(2) Skin material: The skin material was made of a JIS1100 material with a thickness of 0.3 mm and cleaned with trichloroethane spray.

In addition, in the joint strength determination test, the test piece 2 after pressure welding was fixed in a vise 1 as shown in FIG. 2, the bending angle of 90° was repeated as shown in FIG. 2, and the peeling condition was observed. The criteria for this determination are as shown in FIG. From this figure 1, it is understood that when the core material temperature is 55℃ or higher, sufficient adhesive strength can be obtained even with a relatively low reduction rate of 30%, and when the temperature exceeds 250℃, the adhesive strength decreases. can. From the above points, it can be seen that the appropriate core material temperature is 55 to 250℃ and the pressure reduction ratio is preferably 30% or more.Other than these, what is preferable for product quality is an extremely high reduction ratio of over 65% at room temperature. . In other words, by maintaining the temperature of the core material in the range of 55 to 250°C, which is higher than room temperature, an aluminum-clad steel sheet with excellent adhesive strength can be obtained at an industrially possible rolling reduction of 30 to 65%. .

Maintaining the temperature of the work rolls above 50°C is also an important means for the purpose of the present invention. According to experiments conducted by the present inventors, poor adhesion was observed in the clad steel plate at the beginning of production. It was found that this was due to the low work roll temperature. After doing some research, I found that the work roll temperature was determined under the above steel plate heating temperature and rolling reduction rate.
It was found that maintaining the temperature above 70°C was necessary to prevent adhesion failure. Since the work roll is at room temperature at the start of production, it is necessary to preheat the work roll to 70°C or higher. When production is started using this preheating roll, the surface temperature of this work roll can be maintained at 70° C. or higher during rolling due to the heated steel plate and the frictional heat during rolling. If continuous operation continues for a long time, the surface temperature of the work rolls may rise to an undesirable level. For example, if the work roll temperature of the skin material rises to a temperature exceeding 350°C, operational problems such as breakage of the skin material, seizure of the skin material to the roll, and poor sheet thickness accuracy will occur. For this reason, it is necessary to control the surface temperature of the work roll to be below 350°C of the skin material and above 50°C. For example, it is best to control the temperature so that it does not rise excessively by using rolling oil paint or cold air.

Figure 3 shows the results of manufacturing an aluminum-clad steel sheet by combining the core material temperature at 60±5℃ and the pressure roll (work roll) temperature conditions at two levels: the lower limit of 30% and the upper limit of 55%. The adhesive strength of the obtained pressure-welded plate was investigated by the test method shown in FIG. 2, and the relationship between work roll temperature and adhesive strength was investigated. From this figure 3, the work roll temperature
The adhesive strength rapidly increased at 50°C, and it is clear that this effect is significant. Furthermore, when the work roll temperature approaches 100°C, the adhesive becomes almost completely bonded, and the adhesive strength does not change further up to 350°C, and there are no particular problems in manufacturing.
However, if the temperature exceeds 350°C, the roll itself will become severely oxidized, which may cause flaws on the product surface (i.e., the skin material), the skin material becoming unwrapped around the work roll, and the skin material often breaking. Workability,
This will cause quality problems and cannot be considered a practical manufacturing area. From the above points, it can be seen that the work roll temperature is preferably at least 60°C to 350°C.

By heating the steel plate and controlling the temperature of the work rolls based on the above conditions, it is possible to produce a clad steel plate with sufficient adhesive strength even if the reduction ratio in one rolling joint is kept to 65% or less. Rolling reduction rate is 65% as before.
Although it is possible to set the rolling mill at a higher location, this requires a large rolling mill and does not meet the purpose of the present invention. In the present invention, the lower limit of this rolling reduction rate is 30
%. If the rolling reduction is lower than this, sufficient adhesive strength cannot be obtained.

The clad steel sheet rolled and welded in this manner is subsequently heat treated to impart properties depending on the intended use and use. For this heat treatment, softening annealing by heating at a temperature higher than the recrystallization temperature of the steel, diffusion annealing to further increase the adhesive strength, etc. is adopted as appropriate depending on the material. These temperature conditions vary depending on the type and use of the steel and skin material, but for example, when the skin material is aluminum, the temperature is 480 to 600
℃, and in the case of diffusion heating, the temperature range is preferably 350 to 480℃. In other words, recrystallization of steel begins to occur at temperatures above about 480°C, but at temperatures above 600°C, the formation of intermetallic compounds becomes significant due to the reaction between aluminum and iron, which causes peeling, so softening annealing within the above range is not recommended. During annealing and diffusion annealing, the steel is heated at a temperature below 480°C, at which recrystallization does not occur, and at a temperature above 350°C, which is the temperature necessary for interdiffusion of metals to occur. Diffusion annealed materials are used as hard materials. Even when the skin material is other metal, the type and conditions of these heat treatments can be appropriately determined depending on the application based on the characteristics of the metal.

Various materials can be used as the skin material for the clad steel plate according to the present invention. As shown in the examples below, examples include aluminum, copper, titanium, or alloy elements added to these, but are not limited to these. Can be combined with steel plate.

Example 1 Manufacture of aluminum clad steel plate A rimmed steel plate with a thickness of 2.0 mm was used as the core material, and it was degreased (soda orthosilicate 5% wt, 85°C, immersion for 2 minutes).
After that, wash with water, then pickle (hydrochloric acid 10% wt, room temperature 10
(soaked for seconds), then washed with water and dried. This steel plate was heated to 200°C by induction heating in the atmosphere at a position 2 m in front of the pressure roll, and then a 0.5 mm thick aluminum plate (JIS1100) that had been previously solvent-degreased (trichloroethane spray cleaning) was placed on both sides of the steel plate. The aluminum clad steel sheets were produced by stacking them on top of each other and pressing them into a pressure roll having a temperature of 80°C with a pressure reduction ratio of 35%. During this period, the speed of the steel plate up to the pressure roll was 30 m/min.

When the clad steel plate after pressure welding was fractured in a repeated bending test, there was no peeling of aluminum on the fracture surface at all. Therefore, it was confirmed that a complete clad steel plate was obtained.

Example 2 Manufacture of aluminum-clad steel plate Using the same material as in Example (1), the steel plate was treated under the same pretreatment conditions, and then heated to 90°C by induction heating in the atmosphere at a position 2 m in front of the pressure roll as described above. rear,
Aluminum plates 0.5mm thick are stacked on both sides of this steel plate, and pressed into a pressure roll at a temperature of 120℃.
An aluminum clad steel plate was manufactured with a pressure reduction of 59%. During this period, the speed of the steel plate up to the pressure roll was 20 m/min. The clad steel plate after pressure welding was fractured in repeated bending tests, and when the fractured surface was observed, there was no peeling at all, and it was confirmed that the clad steel plate was completely integrated. When this clad steel plate was subsequently softened and annealed by heating at 520° C. to 540° C. for 8 hours in an annealing furnace, the steel plate hardness was Hv98, and an excellent soft aluminum clad steel plate with sufficient resistance to processing was produced.

Example 3 Manufacture of copper-clad steel plate A rimmed steel plate with a thickness of 2.0 mm was used as the core material, and after the same pretreatment as in Example 1, the material was heated by induction heating in the atmosphere at a position 22.0 m immediately before the pressure roll. , 180
After heating to ℃, a 0.3 mm thick copper plate with 99.9% purity, which had been previously solvent-degreased with trichloroethane, was placed on both sides of the heated steel plate, and then put into a pressure welding roll (temperature 340℃) to determine the pressure welding reduction rate. 55% copper clad steel plate was produced. During this period, the speed of the steel plate up to the pressure roll was 43 m/min. The clad steel plate after pressure welding was broken by repeated bending, and when the fractured surface was observed, there was no peeling at all, and a completely integrated clad steel plate was obtained. Subsequently, this clad steel plate was annealed and heated at 650°C for 2 hours to obtain a soft copper clad steel plate. In addition, the steel plate hardness is
Hv92, and a good product was obtained with no peeling of the copper layer during bending.

Example 4 Manufacture of titanium clad steel plate A rimmed steel plate with a thickness of 2.0 mm was used as the core material, and after the pretreatment was performed in the same manner as in Example 1, it was heated to 130°C by induction heating in the atmosphere at a position 2 m in front of the pressure welding roll. After heating, a titanium plate with a thickness of 0.4 mm, which has been pretreated under the same conditions as the core steel plate and whose surface has been cleaned, is placed on both sides of the heated steel plate, and then placed on a pressure roll (temperature 280℃). Pressure reduction rate of 48
% titanium clad steel plate was produced. During this period, the speed of the steel plate up to the pressure roll was 15 m/min.
It was hot. The clad steel plate after pressure welding was broken by repeated bending, and the fracture surface was examined, and it was found that there was no peeling at all, and there was complete adhesion. Subsequently, this clad steel plate was softened and annealed at 680°C for 2 hours to produce a soft material. The steel plate hardness of this soft material was Hv90, and an excellent titanium clad steel plate was obtained that could be bent extremely easily and did not peel off during bending.

As described above, according to the method of the present invention, a clad steel sheet with excellent adhesion can be produced without the need for special equipment such as an atmospheric furnace or brushing device, or a special rolling machine to obtain a high rolling reduction. With its mass production and highly operable line, it is able to provide low-cost, high-quality clad steel sheets.

[Brief explanation of the drawing]

Figure 1 is a diagram of the relationship between the core material temperature and rolling reduction of the clad steel plate, Figure 2 is a cross-sectional view of the vise used in the pressure welding strength determination test, and Figure 3 is the relationship between the work roll temperature and the adhesive strength of the clad steel plate. It is a diagram.

Claims (1)

[Claims] 1. In a method for producing clad steel plates in which a strip or sheet-shaped skin metal whose joint surface has been previously cleaned is overlaid on a strip-shaped or sheet-shaped steel plate whose joint surface has been cleaned in advance and then rolled and joined, The steel plates are heated in the air to a temperature of 55 to 250℃, and the surface temperature of the work rolls used for rolling and joining is maintained at at least 50℃, and the sheet metal at room temperature is rolled for 30℃ in one rolling process.
A method for producing clad steel sheets by rolling joining, characterized by pressure welding at a rolling reduction of ~65%.