JPH0726192B2 - Manufacturing method of high Al content stainless steel plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is capable of molding at room temperature and has excellent high-temperature oxidation resistance, corrosion resistance, and electric heat resistance, and the heat generation of an electric heater and polluted gas. TECHNICAL FIELD The present invention relates to an industrial manufacturing method of a high Al stainless steel alloy plate suitable for a catalytic metal substrate for treating aluminum.

[Conventional technology]

Since stainless steel sheets are excellent in oxidation resistance and corrosion resistance, they are widely used in various industrial fields by taking advantage of this characteristic. However, in order to impart further oxidation resistance, it is effective to add Al to the steel. Is. However, the addition of a large amount of Al makes the material very brittle, making it difficult not only for cold rolling but also for hot rolling.
It is extremely difficult to manufacture a stainless steel plate. For this reason, high-Al stainless steel sheets have high electrical resistance, and although they are materials with excellent oxidation resistance and corrosion resistance, their productivity is extremely poor, so they have not been fully utilized.

[Object of the Invention]

An object of the present invention is to establish a method for easily producing such a useful high Al stainless steel sheet, and to contribute to the widespread use of the high Al stainless steel sheet.

[Structure of Invention]

The object of the present invention to achieve the above-mentioned object is to provide a stainless steel sheet containing 0.01 to 0.8% of C ≦ 0.03%, Cr ≦ 30%, one or more of Ti, Nb, V or Mo. Alternatively, at least one surface of the steel strip is overlaid with Al plates or thin strips in a ratio corresponding to the amount of Al to be contained, and this is passed between rolls to form a laminated pressure welding plate. In some cases, after further rolling to the target sheet thickness (it is advantageous to perform intermediate annealing at 250 to 550 ° C before or during rolling), the Al layer is formed at a temperature in the range of 600 to 1300 ° C. The present invention resides in a method for producing a high Al-containing stainless steel plate or steel strip, which is characterized by performing a diffusion treatment under the condition of alloying without melting.

Further, according to the present invention, a laminated pressure-bonded plate, an annealing pressure-bonded plate or a rolled plate obtained during the above-mentioned manufacturing method is used as a raw material to form a product shape or an intermediate product shape according to the application, and this processed product Or, to manufacture a processed or semi-processed product of Al-containing stainless steel, characterized by subjecting the semi-processed product to a diffusion treatment under the condition that the Al layer does not melt and alloys at a temperature in the range of 600 to 1300 ° C. A method is provided.

According to the method of the present invention, a stainless steel sheet containing 3% or more of Al, which is difficult in the past, and in some cases, 10% or more of Al can be industrially produced. Moreover, industrial production as a steel strip is possible as in the case of producing ordinary stainless steel sheets. The high Al content stainless steel sheet obtained by the method of the present invention is an alloy steel sheet having a uniform concentration in the thickness direction in which Al is uniformly diffused, depending on the degree of diffusion treatment,
High Al stainless steel sheets with different Al concentration distributions in the thickness direction, with a special structure having a layered alloy layer interposed or an outermost surface layer having an oxide film of Al or Cr, can be manufactured. The feature is that it is relatively easy to manufacture a product suitable for the purpose. Further, it is possible to easily manufacture a processed product or a semi-processed product made of high Al stainless steel having a complicated shape, which was difficult to manufacture in the past.

In particular, the present invention uses a stainless steel sheet containing C ≦ 0.03%, Cr ≦ 30%, and one or more of Ti, Nb, V or Mo as 0.01 to 0.8% as a stainless steel sheet as a starting material. This is because the stainless steel plate of this composition system is used as the steel plate during the diffusion treatment of the pressure contact plate.
Voids and cracks that may occur near the interface with the Al plate are prevented, and it is possible to manufacture high-quality high Al-containing stainless steel sheets with even higher heat resistance.

[Detailed Description of the Invention]

The present invention starts with a stainless steel plate or steel strip (hereinafter collectively referred to as a steel plate) containing 0.01 to 0.8% of C ≦ 0.03%, Cr ≦ 30%, one or more of Ti, Nb, V or Mo. Used as a material. When the C content of the stainless steel plate used is large, voids are easily generated near the interface between the pressure-bonded plate of the steel plate and the Al plate, and this causes cracks at the interface. Therefore, the C content is preferably as low as possible, but 0.03% is acceptable. On the other hand, if the Cr content exceeds 30%, the workability becomes poor and cracks tend to occur during pressure welding, making it difficult to obtain a good pressure-bonding plate, so it is necessary to set it to 30% or less. Ti, N
When b, V or Mo is contained in the steel in an appropriate amount, it is possible to prevent the occurrence of voids and cracks near the interface between the steel layer and the Al layer during the diffusion treatment of the pressure contact plate. If the content of one or more of these components is less than 0.01%, the effect is not recognized. On the other hand, even if a large amount is contained, the effect is saturated and the workability deteriorates, making it difficult to obtain a pressure contact plate, so the content is limited to 0.8% or less. It is not always clear why the inclusion of these components can prevent voids and cracks near the interface, but it is believed that these components are associated with the fixation of C and the formation of stable carbides. I can think of it.

On the other hand, the Al plate (usually a thin plate or a thin strip) used in the method of the present invention is preferably a pure Al plate, but the normal Al plate contains some Fe, Si and the like. Since these elements are also contained in the stainless steel sheet, therefore, there is no problem even if such an element is contained in particular, and an Al plate containing up to 3% of such an element is also included in the present invention. It can be used to advantage.

In the present invention, one or both sides of the stainless steel plate
The Al plates are superposed so as to have a target Al content and pressed against each other using a roll. In both of them, it is desirable to clean the superposed surfaces. In the pressure welding process of the laminated plate by this roll, the pressure reduction ratio is 30
If it is less than%, it is usually difficult to obtain a good pressure-welded state between stainless steel and Al. Therefore, the press contact reduction rate is 30
% Or more is required, and a laminated pressure welding plate of stainless steel and Al can be obtained.

It is preferable to perform an annealing treatment to improve the adhesiveness of the laminated pressure-bonded plate. This annealing treatment is not necessary for all, but when the thickness of the pressure contact plate exceeds about 1.5 mm,
In the subsequent process, when cold rolling is performed to reduce the plate thickness, or in some cases, when forming into a product shape or a semi-finished product shape, peeling may occur on the adhesive surface. To prevent this, It is advantageous to subject the sheet to annealing. This intermediate annealing is not effective unless a temperature of 250 ° C or higher is adopted. However, if the temperature exceeds 550 ° C, the alloy layer develops thickly at the interface between the stainless steel layer and the Al layer of the pressure-bonded plate, and cracks occur near this alloy layer during cold rolling in the next process, which may cause delamination. . As the annealing method for this intermediate annealing, batch annealing with a tight coil can be used. In this case, the annealing time should be about 1 to 20 hours. Other annealing methods may be used, but in any case, it is necessary to carry out in the temperature range of 250 ° C to 550 ° C in order to prevent peeling during cold rolling.

In this way, a laminated pressure-bonded plate that has undergone the pressure-bonding process, an annealing pressure-bonded plate that has undergone intermediate annealing, or a cold-rolled pressure-bonded plate that has been cold-rolled with or without intermediate annealing with a target Al content Once manufactured, it is then diffusion treated.
This diffusion treatment is a treatment for mutually diffusing the stainless steel layer and the Al layer, and must be performed in the temperature range of 600 to 1300 ° C. If the diffusion treatment temperature is less than 600 ° C, the diffusion of Al does not proceed sufficiently, and if it exceeds 1300 ° C, a molten layer occurs in the diffusion alloy layer. It should be noted that the heating rate during this diffusion treatment was increased to increase the Al
When heated rapidly to a temperature above the melting point of
l Layer may melt. When this Al layer melts, it causes the concentration of Al to change in the plate surface direction due to sagging and accumulation. Therefore, it is necessary to prevent such melting of the Al layer as much as possible. For this reason, heating at a temperature below the melting point of Al, for example, to a temperature of 550 to 680 ℃
It is preferable that the Al layer is made into an alloy layer having a high melting point by holding for at least a minute and then heated to a higher temperature to perform sufficient diffusion treatment. That is, it is necessary to perform diffusion treatment under the condition that the Al layer is alloyed without melting at a temperature in the range of 600 to 1300 ℃.

By selecting the diffusion treatment temperature and diffusion treatment time and adjusting the atmosphere, steel sheet products of various configurations can be manufactured.
In other words, if sufficient diffusion is performed in a non-oxidizing atmosphere, a stainless steel sheet with a high Al content that has a uniform Al concentration in the plate thickness direction can be manufactured, and if the treatment is completed on the way to sufficient diffusion. A high Al content stainless steel plate having a high Al concentration in the surface layer can be manufactured. Also, if diffusion annealing is performed without avoiding surface oxidation, a special high-Al stainless steel sheet for heat resistance, which has a rich oxide layer such as Al and Cr in the surface layer, can be manufactured. If the surface of the steel sheet becomes inferior in quality after the diffusion treatment, the surface can be made in good condition by removing the strain by light cold rolling, or by polishing or polishing the surface.

In this way, according to the method of the present invention, it is possible to industrially manufacture a high Al stainless steel plate, which is difficult to manufacture by the ordinary steel plate manufacturing method. In particular, it is difficult to roll not only cold rolling but also hot rolling on stainless steel containing a high amount of Al, but according to the method of the present invention, a stainless steel plate and an Al plate having good workability are welded in a pressure-welded state before Al is alloyed. Alternatively, since the plate thickness is reduced by rolling after pressure welding, it is possible to satisfactorily cold-roll down to the target thin plate, and in some cases, cold-work into a product shape or semi-finished product shape. The content can be 10% or more as required. Therefore, not only for special applications, such as electric resistance heating materials and catalyst-supporting metal substrates used at high temperatures, but also highly Al-containing stainless steel sheets or strips having excellent heat resistance and corrosion resistance can be manufactured at low cost. The oxidation resistance of the high Al content stainless steel obtained by the method of the present invention is sufficient even under severe conditions such as heating at 1200 ° C. for 2000 hours as shown in the examples below, and C is 0.03% or less and 0.01-0.8% Ti, Nb, V or Mo
It is possible to prevent the occurrence of voids and cracks at the interface between the steel layer and the Al layer during diffusion treatment by using a stainless steel plate containing one or more of it can. Conventionally, it has been attempted to achieve this by repeating rolling and annealing of stainless steel containing Al for the purpose of imparting further oxidation resistance to the stainless steel. Is 3
It will be appreciated how useful the method of the present invention is in view of being limited to less than or equal to%.

Typical examples of the present invention will be described below to show how excellent the heat resistance of the steel sheet obtained by the method of the present invention is.

[Example 1] Table 1 shows the chemical composition value (% by weight) in Table 1 with a plate thickness of 1.0 mm.
JIS stainless steel plate No. 10 with a thickness of 0.2 mm is used as the core material
A skin material was prepared by spray-defatting 50 Al plates with trichloroethane.

The skin material is laminated on both sides of this core material under the plate thickness configuration shown in Table 2 and is inserted into a 4-high rolling mill, and pressed to the plate thickness shown in Table 2 at the indicated reduction rate. It was rolled and wound on a coiler. The rolling speed was 10 to 30 m / min. The obtained pressure-bonded plate coil was placed in a batch annealing furnace, subjected to intermediate annealing at 350 ° C for 10 hours, and then cold-rolled to a plate thickness of 0.30 mm. A 60 mmφ disc-shaped sample was sampled from the obtained cold-rolled cold-rolled sheet, and the disc-shaped sample was heat-treated at 650 ° C for 1 hour and then heated to 1100 ° C and 1200 ° C in air. The oxidation test of heating at was carried out. The results are shown in Table 2.
Samples No. 1 and N after heat treatment at 1100 ° C × 25 hours
O.5 samples were taken and their cross-sections were observed under a microscope. The photographs are shown in FIGS. 1 and 2.

As is clear from Table 2, sample No. 6, which is a comparative material, shows an oxidation increase of 10 mg / cm ² or more in an oxidation test of 1100 ° C. for 25 hours, while sample No. 1 and No. 1 according to the present invention. 2, No. 3 and No. 4 show good oxidation resistance with an increase in oxidation of less than 10 mg / cm ² even at an oxidation test of 1100 ° C. for 1200 hours.

Also, sample No. 5 of the comparative material containing no Ti, Nb, V or Mo shows little oxidation increase and good oxidation resistance, but as shown in the photograph in Fig. Voids and cracks occur near the interface. On the other hand, when the stainless steel plate having the components specified in the present invention is used, voids and cracks are not seen and the interface becomes uniform as seen in the photograph of FIG. The Al of the cold-rolled welded sheet was uniformly diffused during the oxidation test at high temperature under the condition of 1100 ° C for 2 hours.

[Example 2] The pressure-bonded rolled plates of Samples No. 2 and No. 5 in Example 1 had a plate thickness of 0.
Cold-rolled to 3mm, heat treated at 650 ℃ for 1 hour, followed by diffusion treatment at 1100 ℃ for 2 hours in vacuum.
A high-Al stainless steel plate in which l was uniformly diffused. After that, light cold rolling with an elongation of 1.0% was performed to correct the shape of the sheet. A 60 mmφ disc-shaped specimen was sampled from the obtained high-Al stainless steel sheet, and heated at 1100 ° C and 1200 ° C in the atmosphere to perform an oxidation experiment. The results are shown in Table 3.

In this example, the oxidation resistance of a high Al stainless steel plate in which Al of the pressure contact plate was uniformly diffused was examined. As is clear from Table 3, the SUS430 steel sheet of sample No. 6, which is a comparative material, has an oxidation temperature
It shows an oxidative increase of 10 mg / cm ² or more in less than 25 hours at 1100 ° C. and 1200 ° C., whereas in Sample No. 2a according to the present invention, it is 10 mg / cm ² even at 1100 ° C. × 1200 hours or more and 1200 ° C. × 2000 hours. Oxidation weight increase of less than cm ² shows good oxidation resistance.

It should be noted that, in Comparative Material Sample No. 5a, which uses a stainless steel sheet containing no Ti, Nb, V, or Mo, the oxidation increase is small and good, but when the cold-rolled cold-rolled sheet is subjected to diffusion treatment, it is near the interface between the steel layer and the Al layer. Voids and cracks (as in Fig. 2) occur easily during light cold rolling performed to correct the shape of the plate after diffusion treatment, and cracks occur during processing such as punching and bending. To do.

[Brief description of drawings]

Figure 1 is a metallographic micrograph showing the metallographic structure of the steel sheet cross-section after diffusion treatment using a stainless steel sheet containing Ti as the core material, and Figure 2 is a stainless steel sheet containing no Ti, Nb, V, Mo as the core material. 3 is a metallographic micrograph showing a metal structure of a steel plate cross section after the diffusion treatment.

Front page continuation (72) Inventor Tetsumitsu Midomaru 2-3-1 Tsuiya, Amagasaki City, Hyogo Prefecture Nisshin Steel Co., Ltd. Osaka Works Kanzaki Manufacturing Division (72) Inventor ▲ Makimoto Mamoru Amagasaki City, Hyogo Prefecture Ya 2-3-1 Nisshin Steel Co., Ltd. Osaka Works Kanzaki Manufacturing Division (56) Reference JP-A-50-11942 (JP, A) JP 54-9985 (JP, B2)

Claims (3)

[Claims] 1. Corresponding to the amount of Al contained in at least one surface of a stainless steel plate containing 0.01 to 0.8% of C ≦ 0.03%, Cr ≦ 30%, one or more of Ti, Nb, V or Mo. Al plates are stacked so that the ratio becomes a ratio, and this is passed between rolls to form a laminated pressure welding plate.
A method for producing a high Al-containing stainless steel sheet, which comprises subjecting a diffusion treatment to a temperature in the range of 1300 ° C under the condition that the Al layer is not melted but alloyed. 2. Corresponding to the amount of Al contained in at least one surface of a stainless steel plate containing 0.01 to 0.8% of C ≦ 0.03%, Cr ≦ 30%, one or more of Ti, Nb, V or Mo. Al plates are superposed so as to have a ratio, and the plates are passed between rolls to form a laminated pressure-bonded plate. The obtained laminated pressure-bonded plate is further rolled to a target plate thickness, and then at a temperature in the range of 600 to 1300 ° C. A method for producing a high Al content stainless steel sheet, which comprises subjecting a diffusion treatment to a condition in which an Al layer is alloyed without melting. 3. A stainless steel plate containing 0.01 to 0.8% of C ≦ 0.03%, Cr ≦ 30%, one or more of Ti, Nb, V or Mo and corresponding to the amount of Al contained on at least one surface. Al plates are superposed so as to have a ratio, and these are passed between rolls to form a laminated pressure-bonded plate, and the obtained laminated pressure-bonded plate is further rolled to a target plate thickness, before or during this rolling. Intermediate anneal at 250-550 ℃, then 600-1
A method for producing a high Al-containing stainless steel sheet, which comprises subjecting a diffusion treatment to a temperature in the range of 300 ° C under the condition that the Al layer is not melted but alloyed.