JP3212131B2 - Fe-Cr alloy with excellent carburization resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Fe--Cr alloy having excellent workability and excellent carburization resistance.

[0002]

2. Description of the Related Art Generally, Fe-Cr alloys are known as materials having excellent corrosion resistance. Improvements in physical properties of Fe-Cr alloys, including improvements in corrosion resistance, workability and oxidation resistance, are exemplified below. Various proposals have been made.

[0003] Japanese Patent Publication No. 63-58904 discloses a ferritic stainless steel having a Cr content of 11.0 to 16.0% by weight. Suggests steel.

[0004] Japanese Patent Publication No. 2-1902 discloses an Fe-Cr alloy having a Cr content of more than 20.0% by weight and not more than 25% by weight, particularly high temperature resistance during welding in which Mo, Mn and Nb are respectively contained in specific amounts. A corrosion-resistant ferritic stainless steel with excellent crackability and weld toughness is proposed.

JP-A-3-2355 discloses that the Cr content is 1
A ferritic stainless steel having a cold workability, toughness, and corrosion resistance in which a specific amount of Nb is contained in a ratio of 6.0 to 25.0% by weight of Fe-Cr alloy, particularly in the ratio of the total amount of C and N. Suggests steel.

[0006]

Generally, Fe-Cr alloys use relatively large amounts of Cr because corrosion resistance is first emphasized. As a result, workability has to be sacrificed as a result.

[0007] When Fe-Cr alloys are used as piping materials in hydrocarbon (for example, naphtha) cracking equipment in petroleum plants and the like, carburization resistance is required. Was insufficient, and further improvement was demanded.

An object of the present invention is to provide an Fe—Cr alloy having excellent workability and carburization resistance.

[0009]

The inventor of the present invention has conducted intensive studies to achieve the above object, and found that impurities such as C, N, P, O, S, etc., which existed in the conventional Fe-Cr alloy, were removed. It has been found that when the purity is reduced to high purity, the workability is remarkably improved and the carburization resistance is improved, and when a specific amount of Sn, As, Sb is contained, the carburization resistance is further improved. Was completed.

That is, according to the present invention, the Cr content is 5 to 60.
% By weight, the total amount of C, N, O, P and S is 100 pp
m and contains at least one selected from Sn, As and Sb, and the content satisfies the following formula (1).
In addition, there is provided an Fe—Cr alloy excellent in carburization resistance , the balance being Fe and inevitable impurities, and the above object is achieved. 0.01% by weight ≦ Sn + 3As + 3Sb ≦ 1.0% by weight (1)

[0011]

The factors affecting carburization resistance will now be described with reference to the drawings.

FIG. 1 shows the relationship between C and C for a Fe-30% Cr-0.5% Sn alloy having a constant C content of 16 ppm.
The relationship between the total amount of N, O, P, and S and the amount of carbon adsorbed by a high-temperature heating test in CO / CH ₄ gas is shown.
When the total amount of N, O, P and S is 100 ppm or less, it is clear that the adsorption amount is extremely low.

FIG. 2 shows Fe-Cr-0.3% Sn-0.
The relationship between the Cr content and the amount of carbon adsorbed by a high-temperature heating test in CO gas for a 1% As alloy is shown for the cases where the total amount of C, N, O, P and S is 400 ppm and 81 ppm. From this figure, it can be seen that the amount of carbon absorption decreases as the Cr content increases, but when the total amount of C, N, O, P and S is 81 ppm, the degree of reduction in the amount of carbon absorption is significantly larger than when 400 ppm, and 5% Cr content
It is clear that the tendency is particularly remarkable when it is above.

FIG. 3 is a graph showing Sn-Fe alloy containing 32 ppm of C, N, O, P and S in total.
This graph shows the relationship between + 3As + 3Sb (% by weight) and the amount of infiltrated carbon at 200 μm, 500 μm, and 1000 μm from the alloy surface by a high-temperature heating test in CO / CH ₄ gas. From this figure, it is clear that when the value of Sn + 3As + 3Sb becomes 0.01% by weight or more, the amount of ingress carbon decreases drastically, and elements such as Sn, As, and Sb inhibit the ingress of carbon in the surface layer of the alloy. It can be seen that the function is performed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the configuration of the present invention will be described in detail, but more preferred embodiments of the present invention and advantages based thereon will become apparent.

Cr: 5 to 60% by weight, preferably 10 to
It contains 40% by weight. Cr is an element necessary for realizing the carburization resistance of the alloy of the present invention, and also imparts corrosion resistance. If the content is within the above range, C, N, O, P, S
Combined with the condition that the total amount is 100 ppm or less, the carburization resistance is remarkably excellent, and the corrosion resistance is also excellent. However, an excessive content exceeding 60% by weight is not preferable because it makes the production of the alloy of the present invention difficult.

C, N, O, P, S: The total amount of these elements is 100 ppm or less. By using such an extremely small amount, workability is significantly improved and carburization resistance is also significantly improved. .

Sn, As, Sb: These elements are important elements for improving carburization resistance. These elements exert a deterrent effect on the surface layer when carbon enters the alloy. The alloy of the present invention contains one or more of these elements, and the amount thereof is adjusted to satisfy the following formula. 0.01% by weight ≦ Sn + 3As + 3Sb ≦ 1.0% by weight Preferably, 0.05% by weight ≦ Sn + 3As + 3Sb ≦ 0.5% by weight. When the content satisfies this condition, the above-mentioned function acts and contributes to the improvement of carburization resistance. However, when the value of Sn + 3As + 3Sb exceeds 1.0% by weight due to the excessive element content, surface defects occur, The productivity of the alloy decreases.

Further, the contents of Sn, As, and Sb are preferably within the following ranges from the viewpoint of hot workability and the like. Sn: 0.05 to 0.5% by weight As: 0.02 to 0.1% by weight Sb: 0.02 to 0.1% by weight

The alloy of the above conditions are satisfied invention, processability and carburization resistance is significantly improved, excellent in course corrosion resistance.

In order to produce the Fe—Cr alloy of the present invention, as raw materials, ultrahigh-purity electrolytic iron, electrolytic Cr, and high-purity electrolytic S
n, reduced As, and reduced Sb are used. The main impurity of each raw material is oxygen.
The Fe-Cr alloy of the present invention can be produced by melting and casting under an ultra-high vacuum exceeding ^-5 torr.

[0022]

The present invention will be specifically described below with reference to examples.

100 kg of a test material having a component range shown in Table 1
It was produced in a high frequency induction heating ultra-high vacuum melting furnace. After subjecting these test materials to forging, cutting, and hot rolling, they were subjected to annealing and cold rolling to produce a steel sheet having a thickness of 1.0 ^tmm .

[0024]

[Table 1]

[0025] 1 from these samples ^t mm × 20 × 100m
m test pieces were prepared, and (1) 50% C
o + N ₂ bal, 500 ° C. × 100 hours heat treatment test in atmosphere, and (2) 800 ° C. in 100% Co atmosphere
A heat treatment test was performed for × 500 hours, and for (1), the amount of infiltrated carbon at a depth of 200 μm from the alloy plate surface was measured,
Regarding (2), the total amount of carbon absorbed in the alloy was measured, and the results are shown in Table 2.

[0026] From the results in Table 2, it is clear that in the composition range of the alloy of the present invention, the penetration of carbon into the alloy is suppressed as compared with the composition range of the comparative alloy. From these results, it is clear that the alloy of the present invention is an alloy having excellent carburization resistance.

[0027]

Since the alloy of the present invention is an Fe-Cr alloy having excellent workability and excellent resistance to carbonization, it can be suitably used in a carburizing environment such as a piping material of a petrochemical plant such as a naphtha cracking device.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the total amount of C, N, O, P and S and the amount of carbon absorbed.

FIG. 2 is a graph showing a relationship between a Cr content and a carbon absorption amount.

FIG. 3 is a graph showing the relationship between the value of Sn + 3As + 3Sb and the amount of invading carbon.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasushi Kato 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Inside the Technical Research Headquarters, Kawasaki Steel Works (72) Inventor Mitsuyuki Fujisawa Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba No. 1 Kawasaki Steel Corp. Technical Research Division (56) References JP-A-50-66445 (JP, A) JP-A-48-34018 (JP, A) JP-A-63-57747 (JP, A) 58-61258 (JP, A) JP-A-49-62316 (JP, A) JP-A-49-62315 (JP, A) JP-A-49-62317 (JP, A) (58) Fields investigated (Int) .Cl. ⁷ , DB name) C22C 38/00 302 C22C 27/06 C22C 38/60

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein the Cr content is 5 to 60% by weight,
N, O, is not less 100ppm or less the total amount of P and S, moreover Sn, the content containing at least one selected from As and Sb is less than the following formula (1), the remainder
An Fe —Cr alloy having excellent carburization resistance, which is Fe and inevitable impurities . 0.01% by weight ≦ Sn + 3As + 3Sb ≦ 1.0% by weight (1)