Low alloy high speed tool steel having constant toughness

• US 20040187972A1
• Filed: 03/23/2004
• Published: 09/30/2004
• Est. Priority Date: 03/24/2003
• Status: Abandoned Application

• Current Assignee: Daido Steel Company Limited
• Original Assignee: Daido Steel Company Limited
• Inventors: Ozaki, Kozo
• Application Number:
  US10/806,440
• Publication Number:
  US 20040187972A1
• Time in Patent Office: Days
• US Class Current: 148/333
• CPC Class Codes: C21D 1/18 Hardening C21D1/02 takes precedence; Quenching with or without subsequent tempering quenching devices C21D1/62
• CPC Class Codes: C21D 6/002 containing Cr C21D6/004 takes precedence
• CPC Class Codes: C22C 38/001 containing N
• CPC Class Codes: C22C 38/002 containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• CPC Class Codes: C22C 38/02 containing silicon
• CPC Class Codes: C22C 38/04 containing manganese
• CPC Class Codes: C22C 38/06 containing aluminium
• CPC Class Codes: C22C 38/20 with copper
• CPC Class Codes: C22C 38/22 with molybdenum or tungsten
• CPC Class Codes: C22C 38/24 with vanadium
• CPC Class Codes: C22C 38/26 with niobium or tantalum
• CPC Class Codes: C22C 38/30 with cobalt
• CPC Class Codes: C22C 38/32 with boron
• CPC Class Codes: C22C 38/42 with copper
• CPC Class Codes: C22C 38/44 with molybdenum or tungsten
• CPC Class Codes: C22C 38/46 with vanadium
• CPC Class Codes: C22C 38/48 with niobium or tantalum
• CPC Class Codes: C22C 38/52 with cobalt
• CPC Class Codes: C22C 38/54 with boron

Abstract

Disclosed is an improved low alloy high speed tool steel, which exhibits constant toughness with small dispersion of the properties after heat treatment and regardless of the size of the products. The steel consists essentially of, by weight %, C: 0.50-0.75%, Si: 0.02-2.00%, Mn: 0.1-3.0%, P: up to 0.050%, S: up to 0.010%, Cr: 5.0-6.0%, W: 0.5-2.0%, V: 0.70-1.25%, Al: up to 0.1%, 0: up to 0.01% and N: up to 0.04% and the balance of Fe. In the steel [Mo+0.5W](Mo-eq.) is 2.5-5.0%, [Mo-eq.]/V is 2-4. In the annealed state the steel contains carbides of [MC+M₆C]-type and/or M₂₃C₆(M₇C₃)-type, and after quenching from a temperature of 1100-1200° C., it contains substantially no remainig carbide or, even contains, almost all the carbides are of MC-type.

Claims

1. A low alloyed high speed tool steel, which consists essentially of, by weight %, C:

0.50-0.75%, Si;

0.02-2.00%, Mn;

0.1-3.0%, P;

up to 0.050%, S;

up to 0.010%, Cr;

5.0-6.0%, W;

0.5-2.0%, V;

0.70-1.25%, Al;

up to 0.1%, 0;

up to 0.01% and N;

up to 0.04% and the balance of Fe, provided that [Mo+0.5W](Mo-eq.) is 2.5-5.0%, that Mo-eq./V is 2-4, and that it contains carbides of, in the annealed state, [MC+M₆C]-type and/or M₂₃C₆(M₇C₃) -type, and after quenching from a temperature of 1100-1200°

C., substantially no remaining carbide or, even contained, almost all the carbides being of MC-type.

2. The low alloy high speed tool steel according to claim 1, wherein Si-content is 0.2-0.8%.

3. The low alloy high speed tool steel according to claim 1, wherein the steel further contains at least one of the group consisting of Ni:

up to 2.0%, Cu;

up to 1.0% and Co;

up to 3.0%.

4. The low alloy high speed tool steel according to claim 1, wherein the steel further contains B:

up to 0.01%.

5. The low alloy high speed tool steel according to claim 1, wherein the steel further contains Nb:

up to 0.1%, and wherein Mo-eq./(V+5Nb) is 2-4.

6. The low alloy high speed tool steel according to claim 1, wherein the steel further contains at least one of the group consisting of Ni:

up to 2.0%, Cu;

up to 1.0% and Co;

up to 3.0%, and B;

up to 0.01%.

7. The low alloy high speed tool steel according to claim 1, wherein the steel further contains at least one of the group consisting of Ni:

up to 2.0%, Cu;

up to 1.0% and Co;

up to 3.0%, and Nb;

up to 0.1%, and wherein Mo-eq./(V+5Nb) is 2-4.

8. The low alloy high speed tool steel according to claim 1, wherein the steel further contains B:

up to 0.01% and Nb;

up to 0.1%, and wherein Mo-eq./(V+5Nb) is 2-4.

9. The low alloy high speed tool steel according to claim 1, wherein the steel further contains at least one of the group consisting of Ni:

up to 2.0%, Cu;

up to 1.0% and Co;

up to 3.0%, B;

up to 0.01%, and Nb;

up to 0.1%, and wherein Mo-eq./(V+5Nb) is 2-4.