Steel material and steel product using the same

Patent metadata

Field	Value
Publication number	US-12104231-B2
Application number	US-202217751230-A
Country	US
Kind code	B2
Filing date	May 23, 2022
Priority date	May 24, 2021
Publication date	Oct 1, 2024
Grant date	Oct 1, 2024

Abstract

The present invention relates to a steel material including, in mass %: 0.310≤C≤0.410; 0.001≤Si≤0.35; 0.45≤V≤0.70; Cr≤6.00; 6.25≤Mn+Cr; Mn/Cr≤0.155; Cu+Ni≤0.84; 0.002≤P≤0.030; 0.0003≤S≤0.0060; P+5S≤0.040; 2.03<Mo<2.40; 0.001≤Al≤0.050; and 0.003≤N≤0.050, with the balance being Fe and unavoidable impurities.

First claim

What is claimed is:

1. A steel material comprising, in mass %:
0.310≤C≤0.410;
0.001≤Si≤0.35;
0.6<V≤0.70;
Cr≤6.00;
6.25≤Mn+Cr;
Mn/Cr≤0.155;
Cu+Ni≤0.84;
0.002≤P≤0.030;
0.0003≤S≤0.0060;
0.0035≤P+5S≤0.040;
2.10≤Mo≤2.39;
0.001≤Al≤0.050; and
0.013≤N≤0.040,
with the balance being Fe and unavoidable impurities,
wherein the steel has an impact value of 30 J/cm 2 or more, and
wherein the steel has simultaneously a fracture toughness of >50 Mpa·√m and an S reduction in hardness of ≤2.1 HRC.

2. The steel material according to claim 1 , comprising the Cr and Mn in ranges of, in mass %,
5.58≤Cr≤6.00 and
0.60≤Mn≤0.86.

3. The steel material according to claim 1 , further comprising, in mass %, at least one element selected from the group consisting of
0.30<W≤2.00 and
0.30<Co≤1.00.

4. The steel material according to claim 1 , further comprising, in mass %,
0.0002<B≤0.0080.

5. The steel material according to claim 1 , further comprising, in mass %, at least one element selected from the group consisting of
0.004<Nb≤0.100,
0.004<Ta≤0.100,
0.004<Ti≤0.100, and
0.004<Zr≤0.100.

6. The steel material according to claim 1 , further comprising, in mass %, at least one element selected from the group consisting of
0.0005<Ca≤0.0500,
0.03<Se≤0.50,
0.005<Te≤0.100,
0.01<Bi≤0.50, and
0.03<Pb≤0.50.

7. The steel material according to claim 1 , wherein the steel material has the impact value of 30 J/cm 2 or more when a square bar of 12 mm×12 mm×55 mm prepared from the steel material is thermally refined to a hardness of 45.5 HRC to 46.5 HRC by the following heat treatment in a vacuum furnace, an impact test specimen is prepared from the square bar, and an impact test is conducted at 15° C. to 35° C.,
in the heat treatment, the square bar is held at 1,250° C. for 0.5 H; then cooled from 1,250° C. to 1,000° C. at 2° C./min to 10° C./min, cooled from 1,000° C. to 600° C. at 2° C./min, and cooled from 600° C. to 150° C. at 2° C./min to 10° C./min; then heated to Ac3 temperature+25° C.; held at Ac3 temperature+25° C. for 1 H; then cooled from Ac3 temperature+25° C. to 620° C. at 15° C./H, and cooled from 620° C. to 150° C. at 30° C./H to 60° C./H; subsequently held at 1,030° C. for 1 H; then cooled from 1,030° C. to 600° C. at 60° C./min to 100° C./min, cooled from 600° C. to 450° C. at 45° C./min to 100° C./min, cooled from 450° C. to 250° C. at 30° C./min to 100° C./min, and cooled from 250° C. to 150° C. at 5° C./min to 30° C./min; and subsequently, a cycle consisting of heating to a temperature range of 580° C. to 630° C. and cooling to 100° C. or less is applied one or more times.

8. A steel product formed of the steel material according to claim 7 .

9. The steel material according to claim 1 , wherein the steel material comprises no carbides having a maximum length of more than 0.3 μm, or
if the steel material comprises carbides having a maximum length of more than 0.3 μm,
carbides forming a dashed-line-form discontinuous string at intervals of 50 μm or less has the maximum length of more than 0.3 μm and less than 0.6 μm, or
a length of a dashed-line-form discontinuous string at intervals of 50 μm or less is less than 300 μm when the dashed-line-form discontinuous string is formed of carbides having a maximum length of 0.6 μm or more.

10. The steel material according to claim 1 , wherein the steel has a hardness of 46.5 HRC or more after quenching.

Assignees

• Daido Steel Co Ltd

Inventors

• Kawano Masamichi

Classifications

• C21D8/02

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• C21D8/00

  Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) · CPC title

• C21D8/06

  during manufacturing of rods or wires · CPC title

• C22C38/22

  with molybdenum or tungsten · CPC title

• C22C38/20

  with copper · CPC title