JP2008063597A - HIGH Ni-Cr-CONTAINING AUSTENITIC STAINLESS STEEL WIRE ROD - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high Ni-Cr-containing austenitic stainless steel wire rod having conflicting characteristics of the reduction in Ni and the lowering of strength in high Ni-containing steel kinds such as SUS310S, and in which breakage is hard to be generated upon rope manufacturing. <P>SOLUTION: The high Ni-Cr-containing austenitic stainless steel wire rod has a composition comprising, by mass, 0.01 to 0.05% C, 0.1 to 1.0% Si, 1.0 to 2.5% Mn, 19.0 to 20.0% Ni, 24.0 to 25.0% Cr, 0.1 to 1.0% Cu and 0.02 to 0.08% N, and the balance Fe with inevitable impurities, and whose breakage index upon rope manufacturing satisfies inequality (A): 0.328(C+N)-0.0028Ni+0.0415Cr≤1.0. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high Ni, Cr containing austenitic stainless steel wire.

  High Ni-containing steel grades such as SUS310S have a large cost increase due to soaring Ni raw materials, and therefore it is desired to reduce raw material costs within the standard range (reduction in Ni).

  However, since Ni saving leads to high strength, there has been a problem that breakage is likely to occur during steelmaking.

  In addition, the high Cr content steel type is easy to precipitate carbide during heat treatment, easily breakage due to carbide during steelmaking, and deteriorated corrosion resistance, it was necessary to adjust the component to suppress the precipitation of carbide. .

  Therefore, it is necessary to improve breakage by a method that does not increase the cost in accordance with Ni saving for reducing the raw material cost.

  Various proposals have heretofore been made for high Ni, Cr-containing austenitic stainless steels. For example, Japanese Patent Laid-Open No. 2005-23357 (the following Patent Document 1) describes Ni: 8 to 30%, Cr: 15 to 30 Stainless steel excellent in welding workability and containing 20% is described.

  However, this Patent Document 1 improves welding workability by defining a relational expression between the ferrite structure ratio of weld metal and Cu, and has not been studied for breakage during steelmaking. .

As described above, a steel wire having high Ni-containing steel grades such as SUS310S, which has contradictory characteristics of Ni saving and low strength, and is less likely to break during steel forming processing has not been realized.
Japanese Unexamined Patent Publication No. 2005-23357

  Accordingly, the present invention solves the problems of the prior art as described above, and has high Ni-containing steel grades such as SUS310S, which have contradictory characteristics of Ni saving and low strength, and is less likely to break during steelmaking. It is an object to provide a Ni, Cr-containing austenitic stainless steel wire.

In order to solve the above-mentioned problems, the present invention has been made as a result of intensive studies on a component system that satisfies both Ni saving and low strength, and the gist of the present invention is as described in the claims. The contents are as follows.
(1) In mass%,
C; 0.001 to 0.05%,
Si: 0.1 to 1.0%,
Mn: 1.0-2.5%
Ni; 19.0 to 20.0%,
Cr: 24.0 to 25.0%,
Cu; 0.01 to 1.0%,
N; containing 0.02 to 0.08%, consisting of the balance Fe and inevitable impurities,
A high Ni, Cr-containing austenitic stainless steel wire characterized by a breakage index at the time of steelmaking satisfying the following formula (A).

0.328 (C + N) -0.0028Ni + 0.0415Cr≤1.0 ... (A)
(2) The high Ni, Cr-containing austenitic stainless steel wire according to (1), further containing B; 0.001 to 0.01% by mass.
(3) The high Ni, Cr-containing austenitic stainless steel wire according to (1) or (2), wherein the metal structure is a stepped structure or a mixed structure.

  According to the present invention, in a high Ni content steel grade such as SUS310S, by devising the component range of C, Cr, etc., there is a contradictory characteristic of Ni saving and low strength, and breakage occurs during steelmaking processing. It is possible to provide an austenitic stainless steel wire containing a high Ni, Cr content that is difficult to achieve, and has remarkable industrially useful effects.

  The best mode for carrying out the present invention will be described in detail below.

  First, the technical idea of the present invention will be described.

  Due to soaring Ni raw materials, high Ni-containing steel types such as austenitic stainless steel, especially SUS310S, have a large cost of raw material costs, and it is desired to reduce raw material costs by reducing Ni within the standard range.

  However, Ni-saving leads to high strength, and breakage occurs at the time of steelmaking at the customer, so simple Ni-saving is not generally accepted.

  Therefore, breakage must be improved in accordance with Ni saving.

  As a method of improving breakability, 1) component adjustment and 2) high temperature and long time for heat treatment are conceivable, but 2) cannot be adopted because it will surely increase the cost due to high temperature and long time for heat treatment conditions.

  Therefore, the present inventors decided to improve breakability by adjusting the amount of element with a small cost increase by 1) component adjustment.

  On the other hand, with high Cr steel grades, carbides are likely to precipitate during cooling from high temperatures, and problems with corrosion resistance are likely to occur. Therefore, it is necessary to solve the problem, but the cost of the heat treatment that can be rapidly cooled is large, so the cost increases. It is necessary to adopt a component adjustment method with a small increase.

  As a component adjustment method with a low cost increase, in addition to lowering the strength by reducing C, it has been found that C is restricted to 0.01 to 0.05% in order to exhibit the effect of suppressing carbide precipitation during heat treatment. .

  In order to reduce the strength, Cr was reduced to further reduce costs. The degree of solid solution strengthening of Cr is generally small in SUS304 and is not effective, but a high alloy such as the present invention has found that the effect of Cr solid solution strengthening is very large and was used for strength reduction.

That is, the present invention is mass%,
C; 0.001 to 0.05%,
Si: 0.1 to 1.0%,
Mn: 1.0-2.5%
Ni; 19.0 to 20.0%,
Cr: 24.0 to 25.0%,
Cu; 0.01 to 1.0%,
N; containing 0.02 to 0.08%, consisting of the balance Fe and inevitable impurities,
The breakage index at the time of steelmaking satisfies the following formula (A).

0.328 (C + N) -0.0028Ni + 0.0415Cr≤1.0 ... (A)
In the formula (A), C, N, Ni, and Cr represent mass% of each component.

  The reason for limitation of each component is demonstrated below.

  C: Although C is harmful to the corrosion resistance of stainless steel, it is effective for both strength reduction and carbide precipitation suppression. In addition, the preferable range of C is 0.001 to 0.03%.

  Si: Si is added in an amount of 0.1% or more as a deoxidizing element for stainless steel. However, excessive addition deteriorates hot workability and increases the frequency of occurrence of surface defects, so it is added at 1.0% or less. In addition, the preferable range of Si is 0.3 to 0.8%.

  Mn: Mn is a γ-stabilizing element and can be added as a substitute for Ni and has a deoxidizing effect. Therefore, 1.0% or more is added. % Or less. In addition, the preferable range of Mn is 1.0 to 1.5%.

  Ni: Ni is a basic component of stainless steel together with Cr. In the present invention, Ni is added in the range of 19.0 to 20.0% in order to reduce alloy costs. In addition, the preferable range of Ni is 19.0 to 19.5%.

  Cr: Cr is a basic component of stainless steel and is added from the viewpoint of corrosion resistance. However, the present inventors have found that a high Ni steel grade has a large degree of solid solution strengthening of Cr, and Cr is 24.0-25. By reducing it to the range of 0.0%, the strength is reduced and the precipitation of carbides is suppressed. In addition, the preferable range of Cr is 24.0 to 24.5%.

  Cu: Since Cu improves the corrosion resistance of stainless steel, it is added at 0.1% or more. However, even if added over 1.0, the effect is saturated, so the range of addition is 0.01-1.0%. In addition, the preferable range of Cu is 0.01 to 0.5%.

  N: If the content of N is large, the steel structure becomes hard and the hot workability deteriorates, so the content is made 0.08% or less. Moreover, since making the minimum of N less than 0.02% increases melting cost, it is made 0.02% or more.

  Furthermore, it is preferable to contain B; 0.001 to 0.01% by mass% as a selective element. B is added in order to improve hot workability in an austenitic high alloy. If it is 0.001% or less, the effect is poor, and if it is 0.01% or more, the B compound precipitates at the grain boundary and is detrimental to hot workability. In addition, the preferable range of B is 0.003 to 0.008%.

  Further, Ni can be saved if the breakage index shown in the above formula (A) satisfies ≦ 1.0. For example, cost performance can be improved within the component specification of TYPE310.

  In the present invention, components other than those described above are not specified, but the following components may be added.

  Mo: Mo is an important additive element for ensuring corrosion resistance, and an effect is seen with addition of 0.01% or more. However, since it is an expensive element, the upper limit is preferably 4%.

  S: Since S deteriorates hot workability, it is desirable to reduce it as much as possible, and it is preferable to make the component range 0.010% or less.

P: P is a harmful element from the viewpoint of corrosion resistance and hot workability. In particular, in order to deteriorate ductility immediately after casting, it is desirable to reduce it as much as possible from the viewpoint of preventing cracks on the surface of the slab. It is preferable to set it to 040% or less.
The balance other than the above components consists of iron and inevitable impurities.

  Table 1 shows the breakage index and metal structure calculated by the formula (A) for the wires made of the alloys shown in Invention Examples A to L and Comparative Examples 1 to 11 as examples of the present invention.

  In Table 1, as for the metal structure, a case where the structure after heat treatment is a stepped structure or a mixed structure specified in JIS G 0571 is marked with ◯, and a case where it is a grooved structure is marked with ×.

  It was confirmed that the A to L steels according to the method of the present invention show good characteristics both in the breakage index, in the presence or absence of breakage during steelmaking and in the metal structure.

  On the other hand, in Comparative Steels 1 to 11, C or Cr in the steel is out of the scope of the present invention, so the breakage index exceeds 1.0, and there is breakage during steelmaking. The metal structure was also x.

  The effects of the present invention have been clarified by the above examples.

Claims (3)

% By mass
C; 0.001 to 0.05%,
Si: 0.1 to 1.0%,
Mn: 1.0-2.5%
Ni; 19.0 to 20.0%,
Cr: 24.0 to 25.0%,
Cu; 0.01 to 1.0%,
N; containing 0.02 to 0.08%, consisting of the balance Fe and inevitable impurities,
A high Ni, Cr-containing austenitic stainless steel wire characterized by a breakage index at the time of steelmaking satisfying the following formula (A).
0.328 (C + N) -0.0028Ni + 0.0415Cr≤1.0 ... (A) Furthermore, in mass%,
B: 0.001-0.01% is contained, The high Ni and Cr containing austenitic stainless steel wire rod of Claim 1 characterized by the above-mentioned. 3. The high Ni, Cr-containing austenitic stainless steel wire according to claim 1, wherein the metal structure is a stepped structure or a mixed structure.