JPH073405A - Stainless steel for gasket and production thereof - Google Patents

Abstract

PURPOSE:To produce an inexpensive stainless steel for gasket, excellent in setting resistance (spring characteristics) and stress corrosion cracking resistance. CONSTITUTION:The stainless steel for gasket has a composition consisting of, by weight, <=0.05% C, 1.0-5.0% Si, <=2.0% Mn, 15.0-22.0% Cr, 5.0-9.0% Ni, 0.1-0.4% N, one or >=2 kinds among 0.03-0.30% V, 0.03-0.30% (Nb+Ta), and 0.03-0.30% Ti, and the balance essentially Fe. Further, a material, after component regulation into the above composition, is cold-rolled at >=20% draft and aged at 300-600 deg.C for >=30sec, by which the stainless steel for gasket can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to stainless steel for gaskets and a method for manufacturing the same.

[0002]

2. Description of the Related Art Gaskets for automobiles, for example, cylinder head gaskets mounted on the mating surfaces of a cylinder block and a cylinder head of an engine, and a cylinder mounted between a cylinder head and a head cover. As the head cover gasket, the gasket mounted on the mating surface of the manifold and the cylinder head, and other gaskets, those mainly made of asbestos have been conventionally used.

However, in recent years, the harmful effect of asbestos on the environment has become a problem, so that a metal gasket made of stainless steel has come to be used as a substitute for such a gasket made mainly of asbestos. Is coming.

As the stainless steel for the metal gasket, SUS301 series (17Cr-7Ni series) has been mainly used, but in recent years, as the performance of automobiles has increased, the load on the gasket, for example, heat load or The tightening load is increasing, and it is difficult to say that the conventional SUS301-based materials have sufficient performance, especially sagging resistance (spring characteristics) and corrosion resistance, causing deterioration of sealability and stress corrosion cracking. Fear has arisen.

In the case of a metal gasket, a bead portion (spring acting portion) is formed on a stainless steel strip so as to perform a sealing action at the same portion, but this spring acting portion is increased due to an increase in tightening load or the like. Causes permanent deformation, which deteriorates the sealing property and causes cracks at places where stress is concentrated.

In order to deal with this, it is conceivable to use a SUS310-based (25Cr-20Ni-based) material as the metal gasket, but this material has high Ni and high Cr.
There is a problem that the price is high because of the content.

[0007]

The invention of the present application has been made as a background of such circumstances. One aspect of the present invention relates to stainless steel, the gist of which is C: ≤0.05%, Si: 1.0 to 5.0%, M by weight.
n: ≦ 2.0%, Cr: 15.0 to 22.0%, Ni:
5.0-9.0%, N: 0.1-0.4%, and V, N
Any one or more of b + Ta and Ti is V: 0.03 to 0.30%, Nb + Ta: 0.03 to
0.30%, Ti: contained in the range of 0.03 to 0.30%, and the balance consists essentially of Fe (claim 1).

Another invention of the present application relates to a manufacturing method thereof, the gist of which is C: ≦ 0.05, S on a weight basis.
i: 1.0 to 5.0%, Mn: ≤ 2.0%, Cr: 1
5.0 to 22.0%, Ni: 5.0 to 9.0%, N:
0.1 to 0.4% and any one of V, Nb + Ta, and Ti
V or 0.02 to 0.30 respectively
%, Nb + Ta: 0.03 to 0.30%, Ti: 0.0
After cold-rolling the material containing 3 to 0.30% in the range and adjusting the composition to the composition consisting essentially of Fe at a rolling reduction of 20% or more, the material is heated in the temperature range of 300 to 600 ° C. for 30 minutes.
Aging treatment is performed for more than a second (claim 2).

[0009]

[Operation and effect of the invention] The invention of claim 1 is an inexpensive SUS.
In addition to increasing the Si content in 301 series materials, a certain amount of N is positively added and a certain amount of V, Nb + T is added.
Crystal grains are refined by precipitation of carbonitrides by adding a, Ti, etc., and the present invention effectively enhances stress corrosion cracking resistance and fatigue resistance of stainless steel for gaskets. You can Therefore, according to the present invention, an inexpensive material can be used to cope with severe usage conditions in a gasket.

Next, the reasons for limiting each component in the present invention will be described in detail. [Reason for limitation] C: ≤0.05% C solid-dissolves in the base layer to strengthen the matrix, while forming carbonitrides to contribute to the refinement of crystal grains, but if it exceeds 0.05% 0.0 for impairing corrosion resistance and stress corrosion cracking resistance
5% or less.

Si: 1.0 to 5.0% Si improves stress corrosion cracking resistance and settling resistance (spring characteristics), but for that purpose, it is necessary to contain 1.0% or more. However, the effect is saturated at 5.0%, and addition of more than that deteriorates hot workability and cold workability, so the upper limit is made 5.0%.

Mn: ≦ 2.0% Mn is added as a deoxidizer. However, if it exceeds 2%, the cold workability is impaired.

Cr: 15.0 to 22.0% Cr needs to be added in an amount of 15% or more in order to secure corrosion resistance and heat resistance. However, the effect is saturated at 22%, and if it is added more than this, delta ferrite appears and hinders workability, so the content is made 22% or less.

Ni: 5.0 to 9.0% Ni is an austenite stabilizing element and must be added in an amount of 5% or more to ensure corrosion resistance and heat resistance. However, 9%
Therefore, the effect is saturated, and since Ni is an expensive element, its addition amount is suppressed to 9% or less.

N: 0.1 to 0.4% As described above, N reacts with V, Nb + Ta, Ti, etc. to precipitate a nitride, which contributes to grain refinement. In order to obtain the effect, 0.1% or more is positively contained. However, 0.
If it exceeds 4%, bubbles are generated at the time of manufacturing a steel ingot and the like to cause blowholes, so the content is made 0.4% or less.

V, Nb + Ta, Ti: 0.03 each
~ 0.30% These elements contribute to improve strength and heat resistance by refining crystal grains by forming carbonitrides. The lower limit of each is 0.03%. On the other hand, the effect is saturated at 0.30%, and if more is added, cold workability is deteriorated due to the formation of inclusions, so the content is made 0.30% or less.

A second aspect of the present invention relates to a method for producing stainless steel for gaskets, which comprises subjecting the material having the above composition to cold working at a rolling reduction of 20% or more and further subjecting it to heat treatment (aging treatment). By applying it, it is possible to effectively improve the settling resistance required for the gasket.

When cold working and further aging treatment are carried out in accordance with the present invention, the carbonitrides are preferentially precipitated at the portions where strain is generated by cold working, and the deformation resistance is improved.

[0019]

EXAMPLES In order to further clarify the characteristics of the present invention, examples thereof will be described in detail below. Raw materials having the composition shown in Table 1 were melted in an arc furnace, and then decarburized and refined by blowing argon and oxygen in a decarburization and refining furnace to produce a stainless steel ingot of about 1 ton.

[0020]

[Table 1]

Next, this was decomposed and rolled into a size of about 150 × 300 mm square, and then hot rolled into a plate material having a plate thickness of 3.0 mm. Furthermore, this is cold rolled to a plate thickness of 0.4 mm,
Subsequently, solution heat treatment (ST) was performed at 1000 ° C. It is subsequently cold-rolled to a thickness of 0.2 mm and then 4
Heat treatment (aging treatment) was performed under the conditions of 00 ° C. × 3 minutes.

When a tensile test and a spring limit value measurement were performed on the obtained sample, the results shown in Table 2 were obtained. In addition, in the same test, the measurement was also performed for those that were not subjected to heat treatment (aging treatment) for comparison. The results are also shown in Table 2.

[0023]

[Table 2]

From the results of this table, in the case of the steel of the present invention, SUS
It can be seen that the mechanical properties are improved and the Kb value is effectively increased in comparison with the 301 material.

For the Kb value, the operation of elastically bending and deforming a flat plate by applying a load, then removing the load and returning the flat plate to its original shape is repeatedly performed while gradually changing the load, and finally the permanent deformation occurs. It shows the limit stress value that remains, and its measuring method is described in JIS H 3130.
(Beryllium copper, phosphor bronze, and nickel silver plates and strips for springs)
Stipulated in.

Next, gaskets were made of stainless steel having the composition shown in Table 1 (all of which were aged),
Using this, an engine durability test (bench test) was performed for 200 hours. The results are shown in Table 3.

[0027]

[Table 3]

As can be seen from these results, the steel of the present invention has better stress corrosion cracking resistance than the comparative steel (SUS301).

Although the embodiment of the present invention has been described in detail above, this is merely an example, and the present invention can be carried out in a mode in which various modifications are made based on the knowledge of those skilled in the art without departing from the spirit of the invention. .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazukuni Takada 248 Kano, Higashiosaka-shi, Osaka Japan Gasket Co., Ltd.

Claims (2)

[Claims] 1. C: ≦ 0.05% Si: 1.0 to 5.0 on a weight basis.
% Mn: ≤ 2.0% Cr: 15.0-2
2.0% Ni: 5.0 to 9.0% N: 0.1 to 0.4% and any one or more of V, Nb + Ta, and Ti respectively V: 0.03 to 0.30 % Nb + Ta: 0.03 to 0.30% Ti: 0.03 to 0.30%, and the balance stainless steel for gaskets consisting essentially of Fe. 2. C: ≦ 0.05% Si: 1.0 to 5.0 on a weight basis.
% Mn: ≤ 2.0% Cr: 15.0-2
2.0% Ni: 5.0 to 9.0% N: 0.1 to 0.4% and any one or more of V, Nb + Ta, and Ti respectively V: 0.03 to 0.30 % Nb + Ta: 0.03 to 0.30% Ti: 0.03 to 0.30%, with the balance being a material adjusted to a composition consisting essentially of Fe, cold rolled at a reduction rate of 20% or more. A method for producing a stainless steel for gasket, which comprises subjecting to rolling and then aging treatment in a temperature range of 300 to 600 ° C. for 30 seconds or more.