JPS5827339B2 - Heat-resistant steel with excellent hot workability and oxidation resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-resistant steel having excellent oxidation resistance, strength, and hot workability at high temperatures.

Conventionally, Inco has been used as a material with high oxidation resistance and high temperature strength.
ne 1601. , SUS 310 S, etc.
These are used in reactors, afterburners, etc. as materials for preventing automobile exhaust gas pollution, but they are extremely expensive because they contain a large amount of Ni.

On the other hand, Al5I 302B is an austenitic alloy with Si added to improve oxidation resistance.

There is Al5I 314.

Although these Si-added austenitic steels exhibit excellent oxidation resistance due to continuous heating, they have the disadvantage that scale easily peels off in oxidation resistance tests that involve repeated high-temperature heating and cooling.

In addition, it is already known that adding yttrium to austenitic stainless steel improves oxidation resistance, but the present inventors have developed a composite of yttrium and a rare earth element of the lanthanide group (hereinafter referred to as La-Ce). Through the addition of C, we have successfully invented an austenitic stainless steel that has excellent hot workability and high-temperature strength, and exhibits excellent scale exfoliation resistance even when subjected to repeated heating and cooling.

That is, the steel of the present invention contains, by weight, 0.15% or less carbon, 0.5-5.0% silicon, 0.02-2.0% manganese, 8-35% nickel, and 2% chromium-12. In addition, yttrium and rare earth elements of the lanthanide group (La-Ce)
) in a combination of 0.02 to 0.3% (however, both alone are 0.15% or less), and the remainder consists essentially of iron.

The present invention will be explained in detail below.

The reasons for limiting the ingredients in the present invention are as follows.

C is an element necessary to increase high-temperature strength, and has a content of 0.15%.
If it is more than that, the workability will be poor, and C will be difficult to form a solid solution in solution treatment, which will impair the corrosion resistance.

Cr is necessary to improve high-temperature oxidation resistance, but 27
If it is more than 12%, there is a problem in processability, and if it is less than 12%, oxidation resistance deteriorates.

Mn is required at 0.02% or more to obtain a deoxidizing effect, and like Cr, it is an austenite-forming element, and N
It is an element that should be increased in order to lower the amount of i, but too much Mn deteriorates the oxidation resistance, so it is set to 2.0% or less.

Si is required in an amount of 0.5% or more in order to obtain high-temperature oxidation resistance, but if it exceeds 5%, hot workability deteriorates, so it should not be added.
．． 5 to 5.0%.

If Ni is less than 8%, austenite becomes unstable and the corrosion resistance is poor, so the lower limit is set to 8%, but if the amount added is too large, the price of the alloy becomes high, so it is set at 8 to 35%.

Y and La-Ce are contained in combination to improve oxidation resistance, and it is necessary to add 0.02% or more. By adding them in combination, hot workability can be improved even in steel containing 5% Si. Although an excellent alloy can be made, if the combined addition amount exceeds 0.3%, hot workability will be impaired.

Y and La-Ce elements alone are limited to 0.15% or less.

If it exceeds 0.15%, hot workability deteriorates.

Next, embodiments of the present invention will be shown and their characteristics will be explained.

Table 1 shows the chemical composition of the steel of the present invention compared to that of conventional heat-resistant steel (SUS).
3108. Al5T 302B, Al5I 31
4) and steel with single addition of Y or La-Ce, Al+La-C
It is shown together with comparative materials of e-added steel and Al + Y-added steel, and shows their hot workability.

Figure 1 shows some examples of materials shown in Table 1 above.
In a repeated oxidation test in which heating in the atmosphere at ℃ for 30 minutes followed by air cooling for 10 minutes was repeated 400 times, SUS 3108. Al
5I 302B and Al5I 314 are used as comparison materials, and the test results are shown for the present invention steels A, B, C, D, and E, steels with single addition of Y or La-Ce, steels with addition of Al+La-Ce, and steels with addition of Al+Y. be.

As is clear from this, the oxidation resistance of the steel of the present invention to which Y and La-Ce are added in combination is significantly improved compared to the conventional steel and the steel with the addition of only Al5I.
Although 302B has considerably lower peeling resistance than SUS 3108, the peeling resistance is further improved by adding Y or La-Ce alone.

On the other hand, the steel to which Y and La-Ce are added in combination according to the present invention has improved peeling resistance, as shown in FIG. 1, compared to steel to which only one addition is made.

Figure 2 compares the oxidation resistance when TIG welding steels A and C of the present invention with Al5I 302B and SUS 3108. The plate material including the welded part was heated in the atmosphere at 1100°C for 30 minutes, then air cooled for 10 minutes at 400°C. This shows the results of a repeated oxidation test, which was repeated several times, and shows that the oxidation resistance of the welded part is equivalent to that of the base metal.

In addition, the steel of the present invention (F) also has 13
Sufficient hot workability was obtained at 00°C.

[Brief explanation of drawings]

In the accompanying drawings, FIG. 1 shows the results of a repeated atmospheric oxidation test of the steel shown in the example, and FIG. 2 shows the results of a repeated atmospheric oxidation test of the plate material shown in the example including the welded part.

Claims (1)

[Claims] 1 Carbon 0.15% or less, silicon 0.5-5.0% by weight
%, manganese 0.02-2.0%, nickel 8-35%
, contains 12-27% of chromium, and further contains 0.02-0.3% of yttrium and lanthanide group rare earth elements.
A heat-resistant steel having excellent hot workability and oxidation resistance, characterized in that it contains 0.15% or less of both alone, and the remainder consists essentially of iron.