JP2783170B2 - Method for producing clad plate of aluminum and stainless steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a clad plate of aluminum and stainless steel having excellent press formability and bonding property.

[0002]

2. Description of the Related Art In recent years, clad plates that combine metals having different properties such as mechanical properties, corrosion resistance, and electrical properties and have the advantages of each other have been found to be widely used in recent years. Has become. Among them, the most widely used clad plate is a clad plate made of a combination of aluminum and stainless steel.

[0003] As a method for producing these clad plates,
Conventionally, there is an explosion pressure bonding method using explosion energy and the like, but a rolling joining method is often used as a method for producing a low-cost and inexpensive clad plate.

Various proposals have been made for a method of rolling and joining a clad plate of aluminum and stainless steel, but each has the following problems.

[0005] For example, in Japanese Patent Application Laid-Open No. Hei 1-266981, an aluminum or aluminum alloy and stainless steel are superposed to form a combined material.
There has been proposed a method for producing a clad material made of aluminum or an aluminum alloy and stainless steel, which is roll-welded at a reduction rate of 10 to 30% after heating at a temperature of 500 ° C. for a predetermined time. However, in this manufacturing method, it is necessary to coat stainless steel in advance with pure aluminum in order to obtain a clad material having a high bonding strength, so that complicated material treatment is required, and an inexpensive clad material cannot be manufactured.

In Japanese Patent Application Laid-Open No. 3-204185, when manufacturing a clad steel sheet using aluminum or an aluminum alloy as a composite material and steel as a base material, the joining surface of the base material having an aluminum sprayed film formed thereon is required to be joined. After heating to a temperature T (° C.) of 350 ° C. or less, depending on the temperature T, a reduction is applied under the condition that the total rolling reduction R ≧ −0.1 T + 50, and the aluminum having a finished rolling temperature of 150 ° C. or more A method of manufacturing a clad steel sheet is disclosed, and the feature of this manufacturing method is to increase the shearing force of the clad steel sheet.

However, in the manufacturing method disclosed herein, since the heating temperature and the total draft are too wide, it is difficult to control the temperature of the raw material in actual operation, and poor bonding to the clad steel sheet occurs. There is a problem that it easily occurs. That is, at the time of actual rolling, the material temperature decreases due to heat radiation to the atmosphere between the heating furnace and the rolling mill, heat radiation to the table roll during transportation, and furthermore, to heat removal by the deflector roll in the case of a coil. I do.
At this time, the temperature of the material significantly changes depending on the thickness of the plate, and the temperature distribution varies greatly depending on the material. At this time, if the material is rolled and joined under the processing conditions of low temperature and low rolling reduction, the surface to be joined becomes unjoined, or even if it becomes joined, it peels or cracks during subsequent press working. , Resulting in a so-called weak bonding state.

[0008]

SUMMARY OF THE INVENTION The present invention overcomes the above-mentioned problems of the conventional rolling joining technology, eliminates the material treatment corresponding to the pre-treatment of the clad plate production, and has the formability capable of withstanding the press working after the production. The object of the present invention is to establish a method for manufacturing a clad plate of aluminum and stainless steel having excellent bonding properties.

[0009]

Means for Solving the Problems The inventors of the present invention established a method for manufacturing a clad plate excellent in press formability and joining property, when a rolling roll bites a clad material in actual rolling joining or when the rolling roll bites the clad material. The relationship between the conditions of the raw material temperature and the rolling reduction immediately before, and the press formability and bonding properties was examined in detail. As a result, it has been found that by controlling the raw material temperature and the total draft just before the roll biting, a clad plate of aluminum and stainless steel that can withstand the subsequent press working can be manufactured with stable quality. In addition, according to this method, a complicated pretreatment of the material is not required before the roll joining.

The present invention has been completed based on the above findings, and the gist is as follows.

[0011] That is, "when rolling and joining aluminum and stainless steel by heating, respectively, the rolling temperature T _A (° C.) of aluminum and the rolling temperature T of stainless steel.
Aluminum and stainless steel with excellent formability and bonding characteristics, characterized in that both _S (° C) are rolled under the temperature range of 100 ° C or higher to 450 ° C or lower and satisfy the following formula (1). Production method of clad plate ”.

[0012] _{log r ≧ (-0.001 T A +0.71} ) log T S + (-0.003 T A +3.12) ... (1) where, r represents a total reduction ratio (%).

Here, aluminum refers to pure aluminum such as A1100 and A1050 specified in JIS H4000 or A3
Includes aluminum alloys such as 003 and A3004. Further, the rolling temperature means a raw material temperature immediately before a mill gap, that is, immediately before being caught by a rolling roll.

Furthermore, as a criterion for determining press formability,
The limit drawing ratio (LDR) of the cylindrical drawing is used. Specifically, clad plates of various diameters are drawn into a cylinder with a punch, and the maximum diameter of the clad plate that can be drawn without cracking is determined. The case where the ratio of the maximum diameter of the clad plate / punch diameter is 1.8 or more is obtained. It is determined that the moldability is excellent. This is because if the limit drawing ratio is higher than this, there is no problem as to the formability of general pressed products. In addition, the criterion for determining the bondability was the presence or absence of cracks due to end face peeling or local peeling of the clad plate by press working, and the case where no cracking occurred was considered good.

The joining material used in the method of the present invention is as follows:
The invention is not limited to stainless steel and aluminum, but can be applied to high Ni alloys and aluminum alloys.

[0016]

The present invention is characterized by maintaining a raw material temperature immediately before a mill gap (hereinafter referred to as a rolling temperature) at a predetermined temperature in order to produce a clad plate excellent in press formability and bonding property. And rolling at a required reduction ratio, thereby eliminating the need for complicated pretreatment of the material before rolling and joining.

As described above, the rolling temperatures (T _A and T _S ) of aluminum and stainless steel as joining materials are defined as the temperatures of aluminum and stainless steel immediately before the mill gap. The material temperature measured at the time of passage through the gap or within 10 seconds before that shall be used. As described above, the temperature of the heated material decreases due to heat radiation to the atmosphere, heat radiation to the table roll during transportation, and the like. However, as described above, by limiting the measurement range of the rolling temperature to the time when passing through the mill gap or within 10 seconds before it, even if the temperature of the material decreases, the decrease is small and the joining of the clad plate is small. This is because it does not adversely affect the strength.

The present inventors measured the material temperature from 10 seconds before the material passed through the mill gap to the material passing through the material gap using a thermocouple welded to the material, and then measured the temperature change state up to the material gap. As a result, the temperature drop within 10 seconds was 5 to 5 for both aluminum and stainless steel.
It stays in the range of 15 ° C. Further, when the temperatures at 10 seconds and 6 seconds before the material passed through the mill gap were measured with radiation thermometers installed above and below the table on the front of the rolling mill, the measurement results differed from the measurement results obtained using the aforementioned thermocouple. Did not. Therefore, it is determined that such a small amount of temperature decrease is considered to be industrially acceptable and negligible in view of the error of the thermometer and the like. Therefore, before actually passing through the mill gap
The measured value of the radiation thermometer within 10 seconds was represented as the rolling temperature.

The rolling temperature, T _A and T _S are set to a condition of 100 ° C. or more and 450 ° C. or less.

When T _A or T _S is less than 100 ° C., it is the same as ordinary cold rolling, and the joining requires a high pressure, which causes problems such as cracking during press forming due to hardening of the material. Further, under the condition that T _A or T _S exceeds 450 ° C.,
Due to heating in the air atmosphere, an excessive oxide layer is formed on the stainless steel surface, while grain growth (Gleng loss) occurs in aluminum, and a clad plate with excellent press formability and bonding properties is obtained. Absent. Therefore, each rolling temperature was limited to a range of 100 ° C or higher and 450 ° C or lower.

In order to improve the joining strength of the material, it is necessary to secure a total draft (r) in joining rolling.
Here, a total rolling reduction, the thickness of the sum of the thickness of the material (t _1), manufactured with cladding plates _{(t 2), r = {} (t 1 -t 2)
/ T ₂ ｝ × 100 (%).

From the basic experiments of the present inventors, the conditions of the rolling temperature and the total rolling reduction that satisfy all the evaluation criteria for the press formability and the joining property described above were obtained.

FIG. 1 shows the lower total rolling reduction that can satisfy all of the evaluation criteria for formability and bondability when the rolling temperature of aluminum and stainless steel is changed in the range of 100 ° C. to 400 ° C., respectively. FIG. As is apparent from FIG. 1, the lower limit of the total rolling reduction is determined according to the rolling temperature, and the rolling temperature (T _A , T _S ) and the total rolling reduction at this time are determined.
When the relationship with (r) is arranged, the following equation (2) is obtained.

Log r = (− 0.01 T _A +0.71) log T _S + (− 0.03 T _A +3.12) (2) From the basic experiment and the results of the examples described later, T _A , T
_{By making S a} high temperature within the above-mentioned temperature range of 100 ° C. to 400 ° C., or increasing r, the progress of diffusion between the base metals is further promoted, and the press formability and bondability of the clad plate are improved. It turns out that it becomes. That is, in order to stably produce a clad plate excellent in press formability and joining property, rolling may be performed under conditions satisfying the above-mentioned formula (1) according to the rolling temperature of aluminum and stainless steel.

Further, a feature of the method of the present invention is that a clad plate having good press-formability and bonding properties can be manufactured without complicated material processing. This is achieved by adopting an appropriate temperature range in which material oxidation and material hardening can be prevented, that is, a temperature range of 100 ° C to 450 ° C.

[0026]

[Example] As joining materials, stainless steel (SUS 304 2D material) having a thickness of 0.5 mm and a width of 100 mm and a thickness of 2 mm and a width of 100 mm
Roll joining was performed using aluminum (pure Al: A1100 · H24).

These materials were separately heated in an electric furnace in an atmosphere, taken out of the furnace, and superimposed on each other within about 15 seconds after leaving the furnace. These rolling joining was performed using a two-high rolling mill having a roll diameter of 330 mm at a rolling speed of 10 m / min.

At this time, the rolling temperature of each of stainless steel and aluminum was measured with radiation thermometers installed above and below the front table of the rolling mill. This radiation thermometer was installed at a position 400 mm away from the center of the roll in front of it. From the superposition of the materials to the mill gap, the material was conveyed at a low speed of about 4 m / min on the roller table so that there was no deviation between the two materials.
After a second, it will pass through the mill gap.

As described above, in order to confirm the reduction in the rolling temperature (T _A , T _S ), a thermocouple was separately welded to both materials, and the temperature drop from the temperature measurement point to the mill gap was measured. In each case, it was in the range of 5 to 15 ° C.

The total rolling reduction (r) in the joining rolling was calculated by measuring the thickness of each material before rolling and the thickness of the rolled clad plate with a micrometer.

In evaluating press formability and bondability, a rolled clad plate was machined to a diameter of 48 to 66 mm.
Cut out a disk every 4mm to 32mm and punch it 32m in diameter
Pressing was performed with a small cylindrical drawing machine with a m and a die diameter of 38 mm. In this case, stainless steel is used as the outside of the cylinder, and a 30 μm thick polyethylene film is stretched between the die and the die surface.
Used as a lubricant.

FIG. 2 is a diagram showing the relationship between the stainless steel rolling temperature (T _S ) and the total draft (r) when the aluminum rolling temperature (T _A ) in the cylindrical drawing is kept constant at 420 ° C. In the figure, the results of evaluation of press formability and bondability are indicated by the following symbols.

：: LDR ≧ 1.8 No peeling Δ: LDR <1.8 or peeling during pressing ×: Unbonded or peeling during machining As is apparent from FIG. 2, the stainless steel rolling temperature (T _S ) and the total rolling reduction ( As r) increases, press formability and bonding properties become better, and the desired clad plate can be obtained. Further, when the temperature is out of the temperature range of T _S defined by the present invention and is in the range of T _S <100 ° C. and T _S > 450 ° C., there is an influence of the oxidation of the material, etc. doing. In the figure, the lower limit total rolling reduction (r) line at which excellent press formability and bonding properties can be secured is shown. In this case, the total rolling reduction (r) is log r = −
Expressed as 0.29 log T _S +1.86.

Similarly, the evaluation of press formability and bondability of the clad plate was performed by setting the aluminum rolling temperature (T _A ) to 325 ° C.
The test was performed when the temperature was changed to 230 ° C and 125 ° C.

FIG. 3 shows the case where T _A is 325 ° C.
FIG. 5 is a diagram showing the relationship between the stainless steel rolling temperature (T _S ) and the total draft (r) when T _A is 125 ° C. when _A is 230 ° C. In each case, the same result as the evaluation shown in FIG. 2 was obtained. Further, the lower limit total reduction rate (r) line shown in each case is, in each case, the above-mentioned line.
It can be expressed by equation (2).

In the embodiment, the method of manufacturing the clad plate by the sheet method has been described. However, when the method of the present invention is adopted in the coil method, continuous and stable quality can be obtained, so that it is more effective. Have confirmed.

[0037]

According to the method of the present invention, a clad plate of aluminum and stainless steel excellent in formability and bonding property capable of withstanding press working after manufacture can be stably manufactured at low cost without complicated material processing. Can be manufactured.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing a lower total rolling reduction that can satisfy all evaluation criteria for formability and bondability when rolling temperatures of aluminum and stainless steel are respectively changed.

FIG. 2 is a diagram showing a relationship between a stainless steel rolling temperature (T _S ) and a total rolling reduction (r) when an aluminum rolling temperature (T _A ) in a cylindrical drawing is 420 ° C.

FIG. 3 is a graph showing the relationship between the stainless steel rolling temperature (T _S ) and the total draft (r) when the aluminum rolling temperature (T _A ) in a cylindrical drawing is 325 ° C.

FIG. 4 is a diagram showing the relationship between the stainless steel rolling temperature (T _S ) and the total draft (r) when the aluminum rolling temperature (T _A ) in the cylindrical drawing is 230 ° C.

FIG. 5 is a diagram showing the relationship between the stainless steel rolling temperature (T _S ) and the total draft (r) when the aluminum rolling temperature (T _A ) in a cylindrical drawing is 125 ° C.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-8587 (JP, A) JP-A-4-13488 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B23K 20/04 C22C 21/00

Claims (1)

(57) [Claims] When rolling and joining aluminum and stainless steel by heating, respectively, the rolling temperature T _A (° C.) of aluminum and the rolling temperature T _S (° C.) of stainless steel are both 100 ° C. or more and 450 ° C. or less. A method for producing a clad plate of aluminum and stainless steel having excellent formability and bondability, characterized in that rolling is performed at a temperature in the range described above and under the conditions satisfying the following expression (1). _{log r ≧ (-0.001 T A +0.71} ) log T S + (-0.003 T A +3.12) ... (1) where, r represents a total reduction ratio (%).