JPH0313559A - Production of ferritic stainless steel sheet with high al content or formed part of the same - Google Patents

Abstract

PURPOSE:To easily obtain the steel sheet having superior high-temp. oxidation resistance and corrosion resistance and capable of forming at ordinary temp. by subjecting a sheet of a ferritic stainless steel with a specific composition and the prescribed Al sheet to pressure welding and then carrying out diffusion treatment under specific conditions. CONSTITUTION:An Al sheet having a thickness corresponding to the amount of Al to be incorporated is laid at least on one side of a sheet of a ferritic stainless steel having a composition which contains, by weight, <=0.03% C, <=30% Cr, and 0.01-0.8% Ti and in which 0.01-0.5% of one or more kinds among rare earth elements, such as Ce and La, are further added. Subsequently, the resulting laminated sheets are passed through rolls and subjected to rolling reduction at >=30% draft so as to be formed into a clad sheet, and then, the above clad sheet is subjected to diffusion treatment at 600-1300 deg.C under the conditions where the Al layer is not melted but alloyed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention can be molded at room temperature and has excellent high-temperature oxidation resistance, corrosion resistance, and electric heating properties, and is suitable for use in the heating zone of electric heaters and polluting gases. The present invention relates to an industrial manufacturing method of a high Al-containing ferritic stainless steel alloy plate suitable for use as a catalytic metal substrate for processing.

[Prior art] Stainless steel sheets have excellent oxidation and corrosion resistance, and are widely used in various industrial fields to take advantage of these characteristics. It is effective to add However, adding a large amount of Al makes the material extremely brittle, making cold rolling and even hot rolling difficult, making it extremely difficult to produce high-Al stainless steel sheets by a combination of ordinary rolling and annealing. It is. For this reason, although high-Al ferritic stainless steel sheets have high electrical resistance and are excellent in oxidation and corrosion resistance, they have very poor manufacturability and are therefore not fully utilized. Therefore, the present inventors have developed a method for easily producing a high-Afi stainless steel plate, which involves applying a diffusion treatment to a stainless steel plate and an Al plate after pressure bonding. With this method, voids and cracks may occur near the interface between the steel plate and the Al plate during the diffusion process, so Nb
It was necessary to add expensive alloying elements such as , V, and No.

[Purpose of the invention]

The purpose of the present invention is to establish a method for easily manufacturing such a useful high AΩ ferritic stainless steel sheet, and to contribute to the widespread use of high Al stainless steel sheets.

[Structure of the invention]

The present invention achieves the above object, C50.03%, C
r530%, Ti; Contains 0.01-0.8%, C
A thickness corresponding to the amount of Al to be contained on at least one side of a ferritic stainless steel plate or steel strip to which 0.01 to 0.5% of one or more rare earth elements such as e, La, Pr, and Nd are added. Al plates or thin strips are stacked together and passed between rolls to form a laminated press-welded plate. Depending on the case, the resulting laminated press-welded plate is further rolled to the target thickness (in this case, before rolling Alternatively, it is advantageous to perform intermediate annealing at 250 to 550°C)
Provided is a method for producing a high i-containing ferritic stainless steel plate or steel strip, which is characterized by performing a diffusion treatment at a temperature in the range of 600 to 1300° C. under conditions in which the like layer is alloyed without melting.

According to the present invention, the laminated press-welded plate, annealed press-welded plate, or rolled plate obtained during the above manufacturing method is used as a raw material to be formed into a product shape or an intermediate product shape according to the application, and this processing is performed. 600-1300 for goods or semi-processed products
Provided is a method for producing a processed or semi-finished product of high Al-containing ferritic stainless steel, characterized in that the i-layer is subjected to a diffusion treatment at a temperature in the range of °C under conditions in which it alloys without melting. .

According to the method of the present invention, an Al layer of 3% or more, which was conventionally used,
In some cases, stainless steel sheets containing 10% or more of Al can be manufactured industrially. Moreover,
It can be manufactured industrially as a copper strip in the same way as ordinary stainless steel sheets.

Depending on the degree of diffusion treatment, the high Al-containing stainless steel sheet obtained by the method of the present invention can be an alloy steel strip with a uniform concentration in the thickness direction in which Aρ is uniformly diffused, or an alloy steel strip with a uniform concentration of Al in the thickness direction. In some cases, a layered alloy layer may be present, or the outermost surface layer may contain Afl or Cr.
It is possible to produce a high AΩ stainless steel plate with a special structure that has an oxide film, and it is characterized in that it can be produced relatively easily to suit the application.

In addition, high A
l It can be easily manufactured into processed or semi-finished products made of stainless steel.

In particular, the present invention uses stainless steel sheets as starting materials, C50.03%, Cr530%, Ti; 0.01
It contains 0.8% of one or more rare earth elements such as Ce, La, Pr, and Nd. O1~0.
A major feature is that a ferritic stainless steel sheet containing 5% Ti is used, and by using this ferritic stainless steel sheet containing Ti, voids that may occur near the interface between the steel sheet and the Aff plate during the diffusion treatment of the pressure welding plate. In addition, Ce,
By adding rare earth elements such as La, Pr, and Nd, the peeling resistance of oxide scale is ensured, so it is possible to produce a high Aρ-containing ferritic stainless steel sheet with excellent heat resistance. .

The present invention has C50.03%, Cr530%, Ti;0.
Contains 0.01 to 0.8% of one or more rare earth elements such as Ce, La, Pr, and Nd.
．． A ferritic stainless steel plate or copper strip (hereinafter collectively referred to as steel plate) containing 5% additive is used as a starting material.

If the C content of the stainless steel plate used is high, the steel plate and A
When the ρ plate is subjected to the diffusion treatment, voids are likely to be generated near the interface between the two, which causes cracks to occur at the interface. Therefore, it is desirable that the C content be as low as possible, but a C content of up to 0.03% is acceptable. On the other hand, if Cr exceeds 30%, workability is poor and cracks are likely to occur during press-welding, making it difficult to obtain a good press-welded plate, so it is necessary to keep the content below 30%. Ti
When a suitable amount of Al is contained in the steel, it is possible to prevent the generation of voids and cracks near the interface between the steel layer and the Al2 layer during the diffusion treatment of the press-welded plate. If the Ti content is less than 0.01%, the effect will not be recognized.On the other hand, if it is contained in a large amount, the effect will be saturated and the processability will deteriorate, making it difficult to obtain a press-welded plate. .8% or less. Although it is not necessarily clear why the inclusion of Ti can prevent voids and cracks occurring near the interface, it is thought to be related to the fact that Ti fixes C and forms stable carbides. Ca, La,
The addition of rare earth elements such as Pr and Nd can ensure the peeling resistance of oxide scale @Ce, La,
Addition amount of rare earth elements such as Pr and Nd is 0.01%
If the content is less than 0.5%, the effect will not be observed, whereas if it is contained in a large amount, the effect will be saturated and it will become expensive, so a range of 0.5% or less is appropriate.

On the other hand, the Aρ plate (usually a thin plate or ribbon) used in the method of the present invention is preferably a pure Al plate, but ordinary Al
The plate contains some amount of Fe, Si, etc. These elements are also contained in stainless steel sheets, so there is no problem even if such elements are contained, and even Aρ sheets containing up to 3% of these elements can be used in the present invention. can be used.

In the present invention, an Al plate is stacked on one or both sides of the stainless steel plate so that the target An content is achieved, and is pressed using a roll. In any case, the stacked surfaces are purified. It is desirable to keep it. In the pressure welding process of stacked plates using rolls, if the pressure reduction ratio is less than 30%, it is usually difficult to obtain a good pressure contact state between the stainless steel plate and Al1. Therefore, it is necessary to set the pressure reduction ratio to 30% or more, and thereby a laminated pressure-welded plate of a stainless steel plate and Al1 can be obtained.

It is desirable to perform an annealing treatment to improve the adhesion of this laminated pressure bonded plate. Although this annealing treatment is not necessary for all cases, in cases where the thickness of the press-welded plate exceeds approximately 1.5 mm, when further cold rolling is performed in the next process to reduce the plate thickness,
Further, in some cases, peeling may occur on the bonded surface during molding into a product shape or semi-finished product shape, and it is advantageous to perform annealing to prevent this. This intermediate annealing is not effective unless a temperature of 250°C or higher is used.However, if the temperature exceeds 550°C, a thick alloy layer will develop at the interface between the stainless steel plate and the Al plate of the press-welded plate. Cracks occur near this alloy layer during rolling, which may cause peeling. This intermediate annealing may be batch annealing using a tight coil. In this case, the annealing time is preferably about 1 to 20 hours. Other annealing methods may be used, but in any case, in order to prevent peeling during cold rolling, it is necessary to carry out the annealing in a temperature range of 250°C to 550°C.

In this way, the laminated press-welded plate that has undergone the press-welding process, the annealed press-welded plate that has been subjected to intermediate annealing, or the cold-rolled press-welded plate that has been further cold-rolled with or without intermediate annealing can be adjusted to the target AIl amount. Once manufactured, it is then subjected to a diffusion treatment. This diffusion treatment is a treatment for mutually diffusing the stainless steel tN layer and the Al1 layer, and must be performed at a temperature range of 600 to 1300°C.

If the diffusion treatment temperature is less than 600°C, the diffusion of Al will not proceed sufficiently, and if it exceeds 1300°C, a molten layer will be formed in the diffusion alloy layer. In addition, if the heating rate during this diffusion treatment is increased to a high temperature higher than the melting point of Al, the temperature will reach approximately 700°C.
The AI1 layer may melt nearby.

When this Aβ calendar melts, it causes a concentration change in the thickness direction of i due to sag or accumulation. therefore,
It is necessary to prevent such melting of the Al layer,
For this purpose, the Al1 layer is heated to a temperature below the melting point of Al and maintained at a temperature of 550 to 680°C for more than 1 minute to turn the Al1 layer into an alloy layer with a high melting point, and then heated to a higher temperature to obtain a sufficient temperature. Diffusion treatment is recommended. That is, it is necessary to perform the diffusion treatment at a temperature in the range of 600 to 1300° C. under conditions in which AI is alloyed without melting.

Steel plate products of various configurations can be manufactured by selecting the diffusion treatment temperature and diffusion treatment time, and further by adjusting the atmosphere.

That is, if sufficient diffusion is performed in a non-oxidizing atmosphere,
A high-I content stainless steel plate with a uniform A4 concentration in the thickness direction can be manufactured, and a high-Al content stainless steel plate with a high An concentration in the surface layer can be manufactured if the treatment is completed before sufficient diffusion occurs. . Furthermore, if diffusion annealing is performed without particularly avoiding surface oxidation, a special heat-resistant high-Al content stainless steel sheet can be produced in which a large number of oxide layers such as Al and Cr are present in the surface layer. If the surface properties of the steel sheet become poor after the diffusion treatment, the surface properties can be improved by removing the distortion by light cold rolling or by polishing or polishing the surface.

In this way, according to the method of the present invention, high-Al stainless steel sheets, which are difficult to manufacture using ordinary steel sheet manufacturing methods, can be manufactured industrially. In particular, high Al-containing stainless steel is difficult to roll, not only by cold rolling but also by hot rolling.
The plate thickness is reduced in the welded state before alloying or by rolling after press welding, so it is possible to cold-roll the target thin plate, and in some cases, it is possible to cold-roll into a product shape or semi-finished product shape. Moreover, the Afl content can be increased to 10% or more if necessary.

Therefore, in addition to special applications such as materials for electrical resistance heating and metal substrates for holding catalysts used at high temperatures, high AM-containing ferritic stainless steel sheets or copper strips with excellent heat resistance and corrosion resistance can be produced at low cost. . The oxidation resistance of the high Afl-containing stainless steel obtained by the method of the present invention is sufficient even under severe conditions such as heating at 1100°C for 400 hours, as shown in the examples below, and the C content is 0.
0.03% or less and contains 0.01 to 0.8% Ti,
Furthermore, by adding 0.01 to 0.5% of one or more rare earth elements such as Ce, La, Pr, and Nd and using a ferritic stainless steel plate, the interface between the steel layer and the Al layer during diffusion treatment is improved. Since the generation of voids and cracks is prevented, and the peeling resistance of oxide scale is ensured, a high-quality layer can be obtained. Conventionally, attempts have been made to achieve this by repeatedly rolling and annealing stainless steel to which Al is added for the purpose of imparting further oxidation resistance to stainless steel. Considering that the content is limited to 3% or less, it will be understood how useful the method of the present invention is.

[Specific disclosure of the invention]

Typical examples of the present invention are listed below to show how excellent the heat resistance properties of steel plates obtained by the method of the present invention are.

Example 1 Plate thickness 0.4 mm whose chemical composition (weight %) is shown in Table 1
The core material is a ferritic stainless steel plate polished on both sides with a wire-brushed roll, and the plate thickness is 0.1 m.
The skin material was prepared by spray degreasing an Al plate of JIS alloy number 105o with 1~lichlorethane.

Table 1 Layer skin materials on both sides of this core material with the plate thickness configuration shown in Table 2, and roll them in a 4-high rolling mill until the thickness shown in Table 2 is achieved at the indicated rolling reduction. The material was pressure-rolled and wound on a coiler. The rolling speed was 10-30 m/min. The obtained press-welded plate coil was placed in a batch annealing furnace and heated at 350°C x 1
After performing intermediate annealing for 0 hours, the plate thickness was 0 except for sample NQ3.
．． It was cold rolled to a thickness of 10 mm. Then, a disk-shaped specimen of 606IIlφ was taken from the obtained cold-rolled sheet, and this disk-shaped specimen was subjected to heat treatment at 650°C for 30 minutes, and then an oxidation experiment in which it was heated to a temperature of 1100°C in the air. was carried out. The results are shown in Table 2.

As is clear from Table 2, the comparison material sample Na 6
Then, in the oxidation test at 1100℃ x 2S time, Q, 78
In contrast, samples Na 1, N(12, N(L 3, Na 4, and Ha 5) of the present invention exhibit good oxidation resistance of 0.52 mg/d or less. This is considered to be because the addition of rare earth elements such as Ce, La, Pr, and Nd improved the removability of oxide scale.

Claims (4)

[Claims] 1. C:≦0.03%, Cr:≦30%, Ti:0.0
Al to be contained on at least one side of a ferritic stainless steel sheet containing 1 to 0.8% and further adding 0.01 to 0.5% of one or more rare earth elements.
Al plates with a thickness corresponding to the amount of aluminum are stacked, passed between rolls and reduced by 30% or more to form a laminated press-welded plate, and the obtained laminated press-welded plate is heated at a temperature in the range of 600 to 1300°C. A method for producing a high Al-containing ferritic stainless steel sheet, which comprises performing a diffusion treatment under conditions where the Al layer is alloyed without melting. 2. C:≦0.03%, Cr:≦30%, Ti:0.0
Al to be contained on at least one side of a ferritic stainless steel sheet containing 1 to 0.8% and further adding 0.01 to 0.5% of one or more rare earth elements.
Al plates with a thickness corresponding to the weight are stacked, passed between rolls and rolled down by 30% or more to form a laminated press-welded plate.The obtained laminated press-welded plate is further rolled, and then rolled to 600 to 130
A high Al-containing ferritic stainless steel sheet which is subjected to a diffusion treatment at a temperature in the range of 0°C under conditions such that the Al layer is alloyed without melting. 3. C:≦0.03%, Cr:≦30%, Ti:0.0
An Al plate having a thickness corresponding to the amount of Al to be contained on at least one side of a stainless steel plate containing 1 to 0.8% and further adding 0.01 to 0.5% of one or more rare earth elements. Layer them together and pass them between the rolls for 30 minutes.
% or more to obtain a laminated press-welded plate, and the obtained laminated press-welded plate is further rolled if necessary, and at that time, intermediate annealing at 250 to 550 °C is performed before or during this rolling, and then annealing at 600 to 1300 °C A method for producing a high Al-containing ferritic stainless steel sheet, which comprises performing a diffusion treatment under conditions in which the Al layer is alloyed without melting at a temperature within a range. 4. C:≦0.03%, Cr:≦30%, Ti:0.0
An Al plate having a thickness corresponding to the amount of Al to be contained on at least one side of a stainless steel plate containing 1 to 0.8% and further adding 0.01 to 0.5% of one or more rare earth elements. Layer them together and pass them between the rolls for 30 minutes.
% or more to obtain a laminated press-welded plate, and if necessary, the obtained laminated press-welded plate is further rolled and formed into the desired shape, and the processed plate is subjected to intermediate annealing at 250 to 550°C, and then subjected to intermediate annealing at 600 to 1300 A method for producing a high-Al-containing ferritic stainless steel sheet formed body, which comprises performing a diffusion treatment at a temperature in the range of °C under conditions in which the Al layer is alloyed without melting.