JP2541392B2 - Clad steel manufacturing method - 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 industrially stably producing a clad steel material having excellent joint performance.

[0002]

2. Description of the Related Art In recent years, carbon steel (C content: 0.01 to 0.30% by weight of steel, etc.), which has a stable supply and is very advantageous in terms of formability, weldability, cost, etc., is used as a base material. However, there is a tendency that the demand for a clad steel material in which a dissimilar metal composite material (for example, SUS304 or the like) is superposed on this, regardless of the type of thick steel plate, thin steel plate, steel pipe, flat steel, or the like.

Conventionally, as a typical means for producing the above-mentioned clad steel material, the base material and the laminated material (hereinafter referred to as "composite material") are superposed, and the four circumferences of the surfaces to be joined are excluding air vent holes. After welding and encapsulating it, cold rolling or pressing it under light pressure to expel the air existing between the joint surfaces, and then welding and sealing the air vent holes to assemble the composite slab and then heat it. A method of rolling into a clad product has been known (see Japanese Patent Publication No. 57-26870, Japanese Patent Publication No. 59-11394, etc.).

However, this method requires a large amount of equipment (cold rolling equipment, press equipment, etc.) for venting air at the time of assembling the composite slab, and the surface of the obtained composite slab to be joined (vacuum degree). ) Becomes incomplete due to individual technical differences when welding / sealing the air vent hole, resulting in interfacial peeling during heating / rolling, peeling at the product joint surface and ultrasonic defects (detected by ultrasonic inspection). There is a problem in that it is easy to generate defects.

However, when the above method is applied, an air absorbing material (for example, zirconium or zircaloy) is interposed between the surfaces to be joined so as to strengthen the degree of vacuum at that portion during heating. Proposal (Japanese Patent Publication Sho 59-3
No. 0517) was also made, but the adverse effect on the cost cannot be ignored because the air absorbing material itself is relatively expensive, and the above-mentioned problems regarding equipment problems and variations in air vent hole welding / sealing technology remained. Therefore, the practical effect was not sufficient.

On the other hand, the surfaces to be joined of the respective material metals are cleaned and superposed, and the four circumferences of the superposed surfaces (the surfaces to be joined) are electron beam welded or laser beam welded. There is a method of assembling a composite slab for hot-bonding and rolling by sealing it by high energy beam welding (see Japanese Patent Publication No. 55-6498). As we all know,
Since high energy beam welding is performed in a vacuum chamber,
According to the method of assembling the composite slab described above, if the four laps of the superposed surfaces are sealed by high energy beam beam welding,
The surfaces to be joined are inevitably kept in a high vacuum, and not only cold rolling equipment and press equipment for air venting are required, but also welding and sealing operations for air venting holes are unnecessary.

However, the following problems have been pointed out even with a composite slab to which high energy beam welding is applied. That is, when the composite slab is heated in order to be subjected to hot rolling, the thermal stress at that time may cause the fracture of the welded portion and the airtightness of the surfaces to be joined may not be maintained, and the desired joining strength cannot be obtained. Is a problem. Therefore, from the viewpoint of preventing such inconvenience, the Japanese Patent Publication No.
In the proposal related to No. 6498, "to secure a penetration depth that exceeds the specified amount that affects the strength of the sealed weld portion of the composite slab" is an essential condition.

However, since the hermetic sealing welding at the time of assembling the composite slab is a dissimilar material welding, thermoelectromotive force is apt to be generated, and it is also considered that there is residual magnetism, but the electron beam and the laser are also present. The beam and the like are apt to be bent due to these influences, and therefore the welded portion is deflected as shown in FIG. 4 and it is difficult to secure a necessary penetration depth. Moreover, in the actual work of joining and rolling, stable joining performance is ensured unless a sufficient penetration depth is secured so that it is not broken by not only the thermal stress at the time of heating the composite slab but also the deformation stress at the time of rolling. It became clear that it was not possible. Therefore, in practice, the above-mentioned "method proposed as JP-B-55-6498", in which it is difficult to secure the necessary penetration depth, cannot be said to be sufficiently satisfactory industrially.

In view of the above, the object of the present invention is to provide a means for stably and inexpensively producing a clad steel material having excellent joint performance, without the need for complicated steps and particularly expensive equipment. Was to establish.

[0010]

The present inventor has obtained the following knowledge as a result of earnest studies to achieve the above object. (A) In order to stabilize the joint performance of the product clad steel at a high level, in addition to "Countermeasures against weld fracture due to thermal stress during composite slab heating", "Airtightness due to weld fracture due to deformation stress during joint rolling""Measures against being broken" are necessary. That is, in order to stably produce a laminated composite metal material with desired performance by the joining rolling method, it is of course important to take measures against weld fracture due to thermal stress, but at the same time, the initial pass of joining rolling (until the joining progresses due to rolling) It is an important factor to secure sufficient weld strength (penetration depth) in the composite slab to withstand the deformation stress that occurs during (between). However, when high energy beam welding, which facilitates vacuum sealing of the surfaces to be joined, is used as the sealing means, it is not possible to secure a sufficient penetration depth as described above, but joining is performed. High energy beam only for temporary attachment for mere sealing of the power surface
Welding means (for example, arc welding in the atmosphere, etc.) that can easily obtain a sufficient penetration depth before applying heat welding and rolling while taking out this from the vacuum chamber. If the main welding is performed, it is easy to seal the surfaces to be joined in a vacuum, and it is also possible to easily and reliably secure the predetermined sealed weld penetration depth necessary for stabilizing the joint performance to a high level. Become. Further, in this case, it is not necessary to use the vacuum chamber for a long time, which is advantageous in cost.

(B) Further, the stress state due to the plastic deformation of the welded portion due to the joint rolling has a close relation with the degree of joint progress in the initial rolling pass, and the problem of fracture of the welded portion during rolling can be alleviated if the joint progresses quickly. It Therefore, for example, Japanese Patent Publication No. 59-
By utilizing the "method of accelerating the joining between the surfaces to be joined in the rolling process by inserting a metal foil medium contacting material such as Ni foil between the joining surfaces of the composite slab" proposed in Japanese Patent No. 11394, etc., The prompt joining of the materials at the beginning of rolling promotes the plastic deformation of the welded portion due to rolling, and the shear stress applied to the welded portion is reduced, so the required penetration depth of the sealed welded portion is also reduced. It Furthermore, depending on the type of mixture, an alloy layer may be formed in the clad joint due to diffusion and the peel strength at the interface may be reduced. It is possible to manufacture a high-quality clad material that can be applied to high-quality members.

The present invention has been completed based on the above findings and the like. "When manufacturing a clad steel material by joint rolling, first, Ni foils are formed between a plurality of material metals whose surfaces to be joined are cleaned. Insert a medium contact material made of metal foil, etc., and stack them together, and temporarily seal the four sides of the surfaces to be joined by high energy beam welding in a vacuum to seal them, and then perform the main welding of the four sides. After performing the above process to form a composite slab with a predetermined weld penetration depth, hot- or warm-bonding the composite slab to stably bond clad steel with excellent joint performance at low cost. It has a major feature in that it can be manufactured in.

Here, the metal foil used as the medium contact material is Ni
The material is not limited to foil, but is well known depending on the type of material and other conditions (for example, Japanese Patent Publication No. 59-1139).
(See Japanese Patent Publication No. 4)) and the like. Also,
High energy beam welding means electron beam in a vacuum chamber,
Needless to say, it is a generic term for welding performed by irradiating a high energy beam such as a laser beam. Since this high-energy beam welding is a temporary welding that focuses on ensuring the degree of vacuum, there is no problem even if the penetration depth is shallow. For example, FIG. 1 is a graph showing the result of investigation of "penetration depth required to secure vacuum degree" in electron beam tack welding of a composite slab made of stainless steel (base material is carbon steel). However, it can be confirmed from FIG. 1 that the penetration depth may be very small in tack welding. As the main welding, arc welding (for example, MIG welding) in normal atmosphere where a sufficient penetration depth can be easily obtained
Is appropriate. In the main welding, "thermal stress during heating"
And it is necessary to secure a penetration depth that gives strength to the welded part that does not break even by "deformation stress during rolling".
This is the thickness of the composite material, the width of the composite material or base material at room temperature, the length of the composite material or base material at room temperature, the clad ratio, the rolling roll diameter, the rolling amount per pass during rolling, etc. It may be calculated based on experimental data or the like in consideration of.

Next, the present invention will be described with reference to examples.

[Carbon steel base material]

 Carbon content: 0.05% by weight, dimensions: 250 mm thickness x 2200 mm width x 4000 mm length. [Stainless steel mixture] Material: SUS304, Dimensions: 30mm thickness x 2200mm width x 4000mm length. [Ni foil medium contact material] Material: pure Ni, thickness: 0.1 mm.

When assembling the composite slab,
First, the joint surfaces of the base material and the composite material are polished and cleaned, then Ni foil is inserted between the joint surfaces, and the vacuum chamber (vacuum degree 10 ^-2 to 10 ^-5 To
rr), the bonding surface was vacuum-sealed by performing temporary welding on the four circumferences of the bonding surface by electron beam irradiation. The penetration depth in this tack welding was 5 mm.

Next, after the air was supplied to the vacuum chamber to create an air atmosphere, main welding of the welded portion temporarily attached by MIG welding was performed. The penetration depth after this main welding was 25 mm. Then, the composite slab assembled as described above was heated to 1250 ° C., and was then joint-rolled with a rolling machine having a roll diameter of 1000 mm to produce a clad steel plate having a thickness of 20 mm + 2.5 mm.

The obtained clad steel sheet had an ultrasonic inspection yield of 100% and a high shear strength of 37 kgf / mm ² at the joint interface.

Example 2 The following carbon steel base material, stainless steel composite material and Ni foil medium contact material were prepared and assembled into a composite slab as shown in FIG. [Carbon steel base material] Carbon content: 0.05% by weight, dimensions: 100 mm thickness x 2200 mm width x 4000 mm length. [Stainless steel mixture] Material: SUS304, Dimensions: 30mm thickness x 2150mm width x 3950mm length. [Ni foil medium contact material] Material: pure Ni, thickness: 0.1 mm.

When assembling the composite slab,
First, the joint surfaces of the base material and the composite material are polished and cleaned, then Ni foil is inserted between the joint surfaces, and the vacuum chamber (vacuum degree 10 ^-2 to 10 ^-5 To
rr), the bonding surface was vacuum-sealed by performing temporary welding on the four circumferences of the bonding surface by electron beam irradiation. The penetration depth in this tack welding was 5 mm.

Next, after the air was supplied to the vacuum chamber to create an air atmosphere, main welding of the welded portion temporarily attached by MIG welding was performed. The penetration depth after this main welding was 28 mm. The composite slab assembled as described above was heated to 1250 ° C., and was then joint-rolled with a rolling machine having a roll diameter of 1000 mm to produce a clad steel plate having a thickness of 12 mm + 2.5 mm.

The obtained clad steel sheet had an ultrasonic inspection yield of 100% and a high shear strength of 35 kgf / mm ² at the joint interface.

[0022]

[Summary of Effects] As described above, according to the present invention, it is possible to produce a clad steel material having excellent joint performance easily, inexpensively, and stably, which is an extremely useful effect in industry. Is brought about.

[Brief description of drawings]

FIG. 1 is a graph showing a required penetration depth in tack welding during assembly of a composite slab.

FIG. 2 is a schematic diagram showing a composite slab assembly state in an example.

FIG. 3 is a schematic diagram showing an assembled state of a composite slab in another example.

FIG. 4 is a schematic view showing a beam deflection state in high energy beam welding.

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Claims (1)

(57) [Claims] 1. In the production of a clad steel material by joint rolling, first, a medium contact material made of a metal foil is inserted and superposed between a plurality of material metals whose surfaces to be joined are cleaned, and the surfaces to be joined are joined together. High energy in a vacuum on four laps
After temporarily attaching by beam welding and sealing, and then performing the main welding of the four rounds to form a composite slab in which a predetermined weld penetration depth is secured, the composite slab is joined hot or warm. A method for producing a clad steel material, which comprises rolling.