JPH09310157A - Austenitic stainless hot rolled steel sheet excellent in deep drawability and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the deep drawability of an austenitic stainless hot rolled steel sheet by providing a steel sheet with a texture in which the accumulating degree in the crystal plane parallel to the sheet face is regulated to specified value. SOLUTION: This austenitic stainless hot rolled steel sheet is the one having a texture in which the accumulating degree in the [111] plane parallel to the steel sheet is regulated to >=1.2. The steel sheet has a compsn. contg., by weight, 0.005 to 0.1% C, 0.05 to 1% Si, 0.05 to 2% Mn, <=0.02% P, <=0.03% S, <=0.005% Al, 15 to 25% Cr, 5 to 15% Ni, 0.005 to 0.3% N, <=0.01% O, and the balance substantial Fe. Furthermore, one or more kinds selected from 0.05 to 5% Cu, 0.05 to 5% Co, 0.05 to 5% Mo, 0.05 to 5% W, 0.01 to 0.5% Ti, 0.01 to 0.5% Nb, 0.01 to 0.5% V, 0.01 to 0.5% Zr, 0.0003 to 0.01% B and 0.0003 to 0.01% Ca are preferably incorporated therein. The steel stock is subjected to heating and rough rolling, and finish rolling is executed so as to regulate the temp. in the final pass to >=1050 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-rolled austenitic stainless steel sheet having excellent deep drawability even when hot-rolled, and a method for producing the same.

[0002]

2. Description of the Related Art Austenitic stainless steel sheets are widely used for bathtubs, pots, dishes, sinks, etc. because of their excellent corrosion resistance. In such applications, it is necessary that the press formability such as bending property, overhang property, and deep drawing property is good, but austenitic stainless steel is excellent in bendability and overhang property, There is a problem that the deep drawability is not always excellent. Nevertheless, there is no known technique for improving the deep drawability of austenitic stainless steel itself. In other words, the conventional technology for improving the press formability of austenitic stainless steel is as follows:
Suppressing the occurrence of ears after molding as disclosed in JP-A-54-072713 and JP-A-58-224113, which are focused on improving bendability and overhanging property. It was only what was focused on doing.

[0003]

It is known that the texture of the deep drawing of a metal plate is affected by the texture. For example, the metallurgical society of Japan, 32 (1968) 9,742-745, describes the drawing of an Al plate. The effect of texture on workability has been reported. Estimated from the contents of this report, it can be considered that even in austenitic stainless steel sheets, the {111} texture parallel to the sheet surface is effective for improving deep drawability. However, in austenitic stainless steel sheet,
No industrially feasible method for developing the {111} texture has been known so far, and no results of investigating the deep drawing workability of such an austenitic stainless steel sheet are found.

Accordingly, an object of the present invention is to provide a hot-rolled austenitic stainless steel sheet having excellent deep drawability in view of the problems of the above-mentioned known art. Another object of the present invention is to provide a manufacturing method for industrially manufacturing an austenitic stainless hot rolled steel sheet having excellent deep drawability.

[0005]

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have found that, as described above, even in austenitic stainless steel sheets, the {111} texture is effective for improving the deep drawability. Therefore, various studies were made on a method of developing {111} texture. as a result,
Appropriate control of hot rolling conditions, especially when the temperature of the final pass (hot rolling end temperature) in hot rolling is significantly higher than the conventional temperature (about 900 to 1000 ° C), It was discovered that it is possible to form a texture in which the degree of accumulation of {111} parallel to the plate surface is significantly increased.

FIG. 1 shows that for SUS304 having a P content of 0.03 wt%, the rolling reduction in the final pass of the final rolling is 15% and the strain rate is 15.
{111} parallel to the surface of the hot rolled sheet rolled at 0 / sec
This is the result of investigating the effect of hot rolling finishing temperature on the degree of texture accumulation. From Figure 1, the hot rolling finishing temperature is 1050 ℃
It can be seen that the above-mentioned high temperature promotes the development of {111} texture parallel to the plate surface. The inventors also:
A method for increasing the degree of accumulation of {111} texture parallel to the plate surface of the hot rolled SUS304 sheet was examined. FIG.
Is parallel to the plate surface of hot-rolled sheet hot-rolled with hot-rolling finishing temperature of 1060 ℃ for SUS304 with P content of 0.03wt% {1
11] It is the result of investigating the effects of the hot rolling finish rolling reduction and strain rate on the degree of integration of the texture. From Fig. 2, the reduction rate of the final pass of hot rolling finish rolling is set to 20% or more and the strain rate is
It can be seen that the development of {111} texture parallel to the plate surface is remarkably promoted at 180 / sec or more. Furthermore, the inventors also examined the effect of the amount of P on the degree of accumulation of {111} texture parallel to the plate surface of the hot rolled SUS304 plate. Figure 3 shows the {111} aggregate parallel to the sheet surface of the hot rolled sheet obtained by hot rolling SUS304 at a hot rolling finishing temperature of 1060 ° C, a final rolling final pass rolling reduction of 15% and a strain rate of 150 / sec. It shows the effect of the amount of P on the degree of accumulation of tissue. FIG.
From the results, it is recognized that the accumulation of {111} texture parallel to the plate surface is remarkably increased when the P content is 0.02 wt% or less.

As described above, the finish hot rolling temperature is high,
It was found that by increasing the reduction rate and strain rate in the final pass of finish rolling, and by decreasing the P amount, the integration degree of {111} parallel to the plate surface can be increased. In this way, {11
1} The mechanism of the development of the texture is not always clear, but when hot-rolled under the above conditions, the texture of any orientation recovers or recrystallizes during or immediately after hot rolling. As a result, there is no phenomenon in cold rolling such as preferentially recrystallizing {200} where strain is likely to accumulate and eroding {111} texture where strain is less likely to accumulate. And then {11
1} It is considered that the texture develops.

FIG. 4 shows the relationship between the limiting drawing ratio and the degree of accumulation of {111} texture parallel to the plate surface for the hot rolled SUS304 sheet.
It was confirmed that the limit drawing ratio is significantly improved by controlling the degree of texture accumulation to 1.2 or more. Further, the above experimental results are obtained by using a hot rolled sheet of SUS304 as hot-rolled, but if it is manufactured according to the method of the present invention, it is almost recrystallized even after hot rolling, and recovered. Has been completed. Therefore, even if further annealing is performed after hot rolling, the texture does not change significantly, so annealing after hot rolling is not necessary. It is also possible to further anneal after hot rolling for the purpose of further softening.

The present invention has been completed based on the above findings, and its gist structure is as follows. 1) An austenitic stainless hot-rolled steel sheet having excellent deep drawability, which has a texture in which the degree of {111} parallel to the plate surface is 1.2 or more.

2) C: 0.005 to 0.1 wt%, Si: 0.05 to 1.
0 wt%, Mn: 0.05 to 2.0 wt%, P: 0.02 wt% or less, S:
0.03 wt% or less, Al: 0.005 wt% or less, Cr: 15-25 wt%,
Ni: 5-15 wt%, N: 0.005-0.3 wt%, O: 0.01 wt%
Austenitic stainless steel hot rolled with excellent deep drawability, characterized by containing the following, the balance being Fe and unavoidable impurities, and having a texture in which the degree of accumulation of {111} parallel to the plate surface is 1.2 or more. steel sheet.

3) C: 0.005 to 0.1 wt%, Si: 0.05 to 1.
0 wt%, Mn: 0.05 to 2.0 wt%, P: 0.02 wt% or less, S:
0.03 wt% or less, Al: 0.005 wt% or less, Cr: 15-25 wt%,
Ni: 5-15 wt%, N: 0.005-0.3 wt%, O: 0.01 wt%
Includes the following, and Cu: 0.05-5.0 wt% and Co: 0.05-
5.0 wt% group, Mo: 0.05-5.0 wt% and W: 0.05-5.
0 wt% group, Ti: 0.01-0.5 wt%, Nb: 0.01-0.5 wt
%, V: 0.01 to 0.5 wt% and Zr: 0.01 to 0.5 wt% group, B: 0.0003 to 0.01 wt% and Ca: 0.0003 to 0.01 wt%
Characterized by having a texture in which one or more selected from among the above are contained, the balance is Fe and inevitable impurities, and the degree of accumulation of {111} parallel to the plate surface is 1.2 or more. Austenitic stainless hot rolled steel sheet with excellent deep drawability.

4) The austenitic stainless steel according to any one of 1) to 3) above, wherein the steel material is heated, rough-rolled, and then finish-rolled at a final pass temperature of 1050 ° C. or higher. Method of manufacturing hot rolled steel sheet.

5) The final pass of finish rolling was performed at a strain rate of 18
The method for producing an austenitic stainless hot rolled steel sheet according to the above 4), wherein the rolling reduction is 0 / sec or more and the rolling reduction is 20% or more.

6) The method for producing an austenitic stainless hot rolled steel sheet according to the above 4) or 5), wherein a lubricant is used in the final pass of finish rolling.

7) Manufacture of an austenitic stainless hot-rolled steel sheet according to any one of 4) to 6) above, in which a sheet bar obtained by rough rolling is joined with a preceding sheet bar and continuously finish-rolled. Method.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. In the austenitic stainless hot rolled steel sheet according to the present invention, the accumulation degree of {111} parallel to the sheet surface is 1.2 or more. This is because, as shown in FIG.
1} If the degree of integration of the texture is 1.2 or more, good characteristics with a limiting drawing ratio of 2.2 or more can be obtained. Therefore, in the present invention, the integration degree of {111} parallel to the plate surface is 1.
It is 2 or more, preferably 1.4 or more, and more preferably 1.6 or more.

C: 0.005 to 0.1 wt% C is a strong austenitizing element and is added in an amount of 0.005 wt% or more. However, if it is added in excess of 0.1 wt%, blowholes are likely to occur during welding. Therefore, 0.005-0.1 wt
The range is%.

Si: 0.05 to 1.0 wt% Si is added as a deoxidizing agent in an amount of 0.05 wt% or more during melting.
However, if the added amount exceeds 1.0 wt%, descaling during hot rolling becomes difficult. Therefore, 0.05-1.0 wt%
Range.

Mn: 0.05 to 2.0 wt% Mn needs to be added in an amount of 0.05 wt% or more in order to stabilize austenite, fix S, and improve hot workability. However, when the amount of Mn exceeds 2.0 wt%, descaling during hot rolling becomes difficult. Therefore, 0.
The range is from 05 to 2.0 wt%.

P: 0.02 wt% or less P is limited to 0.02 wt% or less as shown in FIG. 3, so that the degree of integration of {111} parallel to the plate surface becomes large, and the limit drawing ratio is increased. Grows larger. Therefore, 0.02wt%
Below, preferably 0.015 wt% or less.

S: 0.03 wt% or less S is an element that lowers hot workability and lowers corrosion resistance. The content of S is 0.
Since up to 03 wt% is acceptable, it should be 0.03 wt% or less.

Al: 0.005 wt% or less Al is added as a deoxidizing agent as needed during melting.
However, if the amount exceeds 0.5 wt%, descaling during hot rolling becomes difficult. Therefore, the upper limit is 0.5 wt%
And

Cr: 15 to 25 wt% Cr is an element for improving corrosion resistance and oxidation resistance.
It is necessary to add 15 wt% or more. However, the amount
If it exceeds 25 wt%, the steel is apt to become brittle. Therefore, 15
The range is up to 25 wt%.

Ni: 5 to 15 wt% Ni is an element that stabilizes austenite and improves toughness and corrosion resistance. It is necessary to add 5 wt% or more. However, even if the amount exceeds 15 wt%,
These effects saturate. Therefore, the range is 5 to 15 wt%.

N: 0.005 to 0.3 wt% N is an element that stabilizes austenite and improves corrosion resistance, and must be added in an amount of 0.005 wt% or more. However, if the addition amount exceeds 0.3 wt%, blowholes tend to occur during welding. Therefore, 0.005
~ 0.3 wt%.

O: 0.01 wt% O is an element that deteriorates the workability of steel, and it is desirable to reduce it, but its content is allowed up to 0.01 wt%. The upper limit is preferably 0.007 wt%.

Cu: 0.05 to 5.0 wt%, Co: 0.05 to 5.0 wt% Cu and Co are elements that stabilize austenite and improve corrosion resistance, and both are added in an amount of 0.05 wt% or more. However, even if the added amount exceeds 5.0 wt%, the effect is saturated. Therefore, 0.05-
The range is 5.0 wt%.

Mo: 0.05-5.0 wt%, W: 0.05-5.0 wt% Mo and W are both elements that improve corrosion resistance.
More than 05wt% is added. However, the amount of these additives is 5.
If it exceeds 0 wt%, it becomes brittle. Therefore, the range of all elements is 0.1 to 5.0 wt%.

Ti: 0.01-0.5 wt%, Nb: 0.01-0.5 wt%
%, V: 0.01-0.5 wt%, Zr: 0.01-0.5 wt% All of Ti, Nb, V, and Zr are useful for suppressing the formation of Cr carbonitride during welding and for suppressing sensitization. Element is added at 0.01 wt% or more. However, if the added amount exceeds 0.5% by weight, large inclusions are formed and the toughness is remarkably deteriorated. Therefore, 0.01 to 0.5 wt%
Range.

B: 0.0003 to 0.01 wt% B is added in an amount of 0.0003 wt% or more to prevent brittleness in secondary processing. However, if the amount exceeds 0.01% by weight, the workability decreases. Therefore, the range is 0.0003 to 0.01 wt%.

Ca: 0.0003 to 0.01 wt% Ca is an element useful in combination with Al ₂ O ₃ to reduce the strength of inclusions, increase ductility, and improve workability.
The effect is exhibited by adding 0003 wt% or more. However, if the amount exceeds 0.01 wt%, the corrosion resistance decreases. Therefore, 0.
The range is 0003 to 0.01 wt%.

Next, manufacturing conditions will be described. The heating temperature for hot rolling is preferably in the range of 1150 to 1250 ° C.
Following the heating, hot rolling including rough rolling and finish rolling by multipass rolling of 4 to 8 passes is performed. At this time, it is necessary to consider the final pass of the finish rolling as follows. -Temperature of final pass of hot rolling: As shown in Fig. 1, the degree of integration of {111} parallel to the plate surface is increased by setting the temperature of the final pass to 1050 ° C or higher, and the limiting drawing ratio is increased. . Therefore, the temperature is 1050 ° C or higher, preferably 1060 ° C or higher.

Strain rate and reduction rate of the final pass of hot rolling: As shown in FIG. 2, by setting the strain rate and the reduction rate of the final pass of hot rolling to 180 / sec or more and 20% or more, respectively, The degree of integration of {111} parallel to the plate surface is increased, and the limiting aperture ratio is increased. Therefore, the strain rate and reduction rate of the final pass should be 180 / sec or more and 20% or more, respectively.

Use of a lubricant in the final pass of hot rolling and continuous rolling: The sheet bar obtained by rough rolling is joined and finish rolling is continuously performed in the rolling in the longitudinal direction of the coil. This is effective in uniformly increasing the strain rate and the rolling reduction in the pass and ensuring a uniform and excellent deep drawability in the coil length direction. Also, the use of a lubricant is effective in making the amount of strain uniform in the thickness direction. The use of these lubricants and the means of continuous rolling can be obtained by adopting either one of them, but it is desirable to use them in combination because the combined use of both means will provide further effects. Here, in continuous rolling, a sheet bar obtained by rough rolling is joined with a preceding sheet bar, and finish rolling is continuously performed. Also, the method of lubrication rolling is
It may be performed by spraying a low-melting glass-based lubricant on the steel sheet before rolling.

The hot-rolled sheet produced by the above method can be used as it is, but in general, the final product is obtained by further descaling. The descaling method is as follows: mechanical preliminary descaling such as shot blasting and bending, and then 75 to 90 ° C. and 15 to 30 ° C.
% Sulfuric acid for 20-120 seconds, then 50-70 ° C
2 to 1 to 5% hydrofluoric acid and 5 to 20% nitric acid mixed acid
It may be performed by a method such as immersing for 0 to 120 seconds.

[0036]

EXAMPLE An austenitic stainless steel having the composition shown in Table 1 was melted by a usual converter method, and a slab having a thickness of 200 mm was produced by a continuous casting process. This slab is soaked in a slab heating furnace at 1150 to 1250 ° C. for 1 to 2 hours, then 1100 to
Rough rolling was performed at 1150 ° C. with a total reduction of 85%, and then final-pass rolling of 7 passes was performed under the conditions shown in Table 2 to obtain hot-rolled sheets of various sheet thicknesses. Further, these hot-rolled sheets were divided, one of them was left as it was, and the other was further annealed at 1150 ° C. for 30 seconds in a continuous annealing furnace. The as-hot-rolled material and hot-rolled annealed material produced by the above method were mechanically prescaled by shot blasting, and then subjected to 80 ° C., 24
% Sulfuric acid for 30 seconds and further immersed in a mixed acid of 3% hydrofluoric acid and 12% nitric acid at 60 ° C. for 30 seconds for descaling to obtain a test material.

With respect to each of the obtained test materials, the degree of accumulation of the {111} texture parallel to the plate surface and the limiting drawing ratio were investigated.
Here, the degree of accumulation of {111} texture parallel to the plate surface is
The surface parallel to the rolled surface ground to 1/4 of the plate thickness was polished with # 1000 emery paper, and the processed structure was removed by etching with aqua regia, followed by the inverse method (Translated by Gentaro Matsumura: Curity X-ray diffraction) The intensity ratio with a random sample was measured according to the summary (1986, pages 290 to 293).
The limiting drawing ratio was determined by the ratio of the diameter of the steel plate to the diameter of the punch, which is the limit that can be drawn with a 33 mmφ cylindrical punch when graphite grease is applied to the steel plate and the wrinkle suppressing force is set to 1 ton.

The test results obtained are also shown in Table 2. No. 1,2,4,6,8,10,12 ~ 15,17,18,20, which corresponds to the present invention example
22,24,26,28 to 33, both the as-hot-rolled material and the hot-rolled and annealed material have a degree of accumulation of {111} parallel to the plate surface of 1.2 or more and a critical drawing ratio of 2.2 or more, and draw formability. Is good. On the other hand, the finishing temperature of hot rolling is less than 1050 ℃, No. 3,5,7,
For 9,11,16,19,21,23,25,27, both the as-hot-rolled material and the hot-rolled and annealed material have an accumulation degree of {111} parallel to the plate surface of less than 1.2 and a limiting drawing ratio of less than 2.2. Yes, draw formability is insufficient.
Further, among the examples of the present invention, No. 13 having a reduction rate of 20% or more and a strain rate of 180 / sec was compared with No. 12 having a reduction rate of 15% and a strain rate of 150 / sec. , Parallel to the plate surface {11
Both the integration degree and the limiting aperture ratio of 1} show better values. Furthermore, among the examples of the present invention, N having a P content of 0.01 wt%
Compared with No. 12 in which the amount of P is 0.03 wt%, o. 17 has a higher degree of integration of {111} parallel to the plate surface and a better limiting drawing ratio. And, in the examples of the present invention, No. 2 and 14 which were subjected to continuous rolling and lubrication were respectively {111} integration degree parallel to the plate surface, as compared with No. 1 and 13 which were not subjected to continuous rolling and lubrication, The critical draw ratio was good, and stable texture and deep drawability were obtained in the length direction.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

As described above, according to the present invention, a texture parallel to the plate surface and having a high degree of {111} integration can be obtained,
It becomes possible to manufacture an austenitic stainless hot rolled steel sheet having excellent deep drawability. According to the method of the present invention, it is not necessary to perform cold rolling and subsequent annealing, and can be easily carried out industrially. Therefore, an austenitic stainless hot-rolled steel sheet for deep drawing can be manufactured at low cost. It will be possible. Therefore, it is possible to easily and inexpensively manufacture molded articles such as bathtubs, pots, pipes, tableware, sinks, and the like.

[Brief description of drawings]

[Fig. 1] Parallel to the plate surface of hot rolled SUS304 sheet {11
1] It is a figure which shows the influence of the hot rolling finishing temperature which affects the degree of integration of a texture.

[Fig. 2] Parallel to the plate surface of the hot rolled SUS304 sheet {11
1] It is a figure which shows the influence of the hot rolling finish rolling reduction and the strain rate which affect the degree of integration of a texture.

[Fig. 3] Parallel to the plate surface of a hot rolled SUS304 plate {11
1] It is a figure which shows the influence of P amount which affects the accumulation degree of a texture.

[Fig. 4] Influence on the limiting drawing ratio of SUS304 parallel to the plate surface {1
11] It is a figure which shows the influence of the accumulation degree of a texture.

Claims (7)

[Claims] 1. A hot rolled austenitic stainless steel sheet having excellent deep drawability, which has a texture in which the degree of accumulation of {111} parallel to the sheet surface is 1.2 or more. 2. C: 0.005-0.1 wt%, Si: 0.05-1.0 wt
%, Mn: 0.05 to 2.0 wt%, P: 0.02 wt% or less, S: 0.03
wt% or less, Al: 0.005 wt% or less, Cr: 15 to 25 wt%, Ni:
Aggregate containing 5 to 15 wt%, N: 0.005 to 0.3 wt%, O: 0.01 wt% or less, the balance being Fe and unavoidable impurities, and having an accumulation degree of {111} parallel to the plate surface of 1.2 or more. Austenitic stainless steel hot rolled steel sheet having excellent deep drawability characterized by having a structure. 3. C: 0.005-0.1 wt%, Si: 0.05-1.0 wt
%, Mn: 0.05 to 2.0 wt%, P: 0.02 wt% or less, S: 0.03
wt% or less, Al: 0.005 wt% or less, Cr: 15 to 25 wt%, Ni:
5 to 15 wt%, N: 0.005 to 0.3 wt%, O: 0.01 wt% or less, Cu: 0.05 to 5.0 wt%, Co: 0.05 to 5.0 wt%
%, Mo: 0.05-5.0 wt%, W: 0.05-5.0 wt%, Ti: 0.
01-0.5 wt%, Nb: 0.01-0.5 wt%, V: 0.01-0.5 wt%
%, Zr: 0.01 to 0.5 wt%, B: 0.0003 to 0.01 wt% and
Ca: contains any one or more selected from 0.0003 to 0.01 wt%, the balance consisting of Fe and unavoidable impurities, and the accumulation degree of {111} parallel to the plate surface is 1.2 or more. An austenitic stainless hot-rolled steel sheet having an excellent deep drawability characterized by having a texture. 4. The austenitic stainless steel heat according to any one of claims 1 to 3, characterized in that a steel material is heated, rough-rolled, and then finish-rolled with a final pass temperature of 1050 ° C or higher. Manufacturing method of rolled steel sheet. 5. The final pass of finish rolling is set at a strain rate of 180 / se.
The method for producing an austenitic stainless steel hot-rolled steel sheet according to claim 4, wherein the rolling reduction is c or more and the rolling reduction is 20% or more. 6. The method for producing an austenitic stainless hot rolled steel sheet according to claim 4, wherein a lubricant is used in the final pass of finish rolling. 7. A sheet bar obtained by rough rolling is joined to a preceding sheet bar and continuously finish-rolled.
7. The method for manufacturing an austenitic stainless hot rolled steel sheet according to any one of 6 above.