High Strength, High Toughness Steel Alloy
A high strength, high toughness steel alloy is disclosed. The alloy has the following weight percent composition. Element C 0.30-0.55 Mn 0.6-1.75 Si 0.9-2.8 Cr 0.6-2.5 Ni 2.70-7.0 Mo + ½ W 0.25-1.3 Cu 0.30-1.25 Co 0.01 max. V + (5/9) × Nb 0.10-1.0 Ti 0.01 max. Al 0.015 max. Ca 0.005 max. The alloy further includes a grain refining element selected from the group consisting of 0.0001-0.01% Mg, 0.001-0.025% Y, and a combination thereof. The balance of the alloy is iron and usual impurities. Also disclosed is a hardened and tempered steel article having very high strength and fracture toughness and formed from the alloy set forth above. The alloy article according to this aspect of the invention is further characterized by being tempered at a temperature of about 500° F. to 600° F.
1 . A high strength, high toughness steel alloy having good temper resistance, said alloy comprising, in weight percent, about:
C
0.30-0.55
Mn
0.6-1.75
Si
0.9-2.8
Cr
0.6-2.5
Ni
2.70-7.0
Mo + ½ W
0.25-1.3
Cu
0.3-1.25
Co
0.01 max.
V + (5/9) × Nb
0.1-1.0
Ti
0.01 max.
Al
0.015 max.
Ca
0.005 max.
a grain-refining element selected from the group consisting of 0.0001-0.01% Mg, 0.001-0.025% Y, and a combination thereof; and
the balance being iron and usual impurities wherein phosphorus is restricted to about 0.01% max. and sulfur is restricted to not more than about 0.001% max., and wherein
2≦(% Si+% Cu)/(% V+( 5/9)×% Nb)≦34.
2 . The alloy as set forth in claim 1 wherein the alloy contains at least about 0.002% yttrium.
3 . The alloy as set forth in claim 2 wherein the alloy contains not more than about 0.020% yttrium.
4 . The alloy as set forth in claim 1 wherein the alloy contains not more than about 0.006% magnesium.
5 . The alloy as set forth in claim 1 wherein the alloy contains not more than about 0.002% calcium.
6 . The alloy as set forth in claim 1 wherein the alloy contains at least about 0.35% carbon.
7 . The alloy as set forth in claim 1 wherein the alloy contains at least about 0.7% manganese.
8 . The alloy as set forth in claim 7 wherein the alloy contains not more than about 1.5% manganese.
9 . The alloy as set forth in claim 1 wherein the alloy contains at least about 1.2% silicon.
10 . The alloy as set forth in claim 9 wherein the alloy contains not more than about 2.7% silicon.
11 . The alloy as set forth in claim 1 wherein the alloy contains at least about 0.7% chromium.
12 . The alloy as set forth in claim 11 wherein the alloy contains not more than about 2.0% chromium.
13 . The alloy as set forth in claim 1 wherein the alloy contains not more than about 5.0% nickel.
14 . The alloy as set forth in claim 1 wherein Mo+½ W is at least about 0.4%.
15 . The alloy as set forth in claim 14 wherein Mo+½ W is not more than about 1.1%.
16 . The alloy as set forth in claim 1 wherein V+( 5/9)×Nb is at least about 0.25%.
17 . The alloy as set forth in claim 1 wherein
14.5≦(% Si+% Cu)/(% V+( 5/9) ×% Nb)≦34.
18 . A high strength, high toughness steel alloy having good temper resistance, said alloy comprising, in weight percent, about:
C
0.35-0.50
Mn
0.7-1.5
Si
1.2-2.7
Cr
0.7-2.0
Ni
2.75-5.0
Mo + ½ W
0.4-1.1
Cu
0.35-1.2
Co
0.01 max.
V + (5/9) × Nb
0.25-1.0
Ti
0.01 max.
Al
0.01 max.
Ca
0.002 max.
a grain-refining element selected from the group consisting of 0.0001-0.006% Mg, 0.002-0.020% Y, and a combination thereof; and
the balance being iron and usual impurities wherein phosphorus is restricted to about 0.01% max. and sulfur is restricted to not more than about 0.001% max., and wherein
14.5≦(% Si+% Cu)/(% V+( 5/9)×% Nb)≦34.
19 . A high strength, high toughness steel alloy having good temper resistance, said alloy comprising, in weight percent, about:
C
0.33-0.50
Mn
0.8-1.3
Si
1.0-2.70
Cr
1.5-1.8
Ni
3.0-5.0
Mo + ½ W
0.25-0.90
Cu
0.3-1.25
Co
0.01 max.
V + (5/9) × Nb
0.1-0.40
Ti
0.01 max.
Al
0.015 max.
Ca
0.001 max.
a grain-refining element selected from the group consisting of 0.0001-0.008% Mg, 0.002-0.025% Y, and a combination thereof; and
the balance being iron and usual impurities wherein phosphorus is restricted to about 0.01% max. and sulfur is restricted to not more than about 0.001% max., and wherein
14.5≦(% Si+% Cu)/(% V+( 5/9)×% Nb)≦34.
20 . The alloy as set forth in claim 19 wherein the alloy contains not more than about 0.45% carbon.
21 . The alloy as set forth in claim 19 wherein the alloy contains at least about 0.40% carbon.
22 . The alloy as set forth in claim 19 wherein the alloy contains not more than about 4.5% nickel.
23 . The alloy as set forth in claim 19 wherein the alloy contains at least about 4.0% nickel.
24 . The alloy as set forth in claim 19 wherein the alloy contains not more than about 1.2% copper.
25 . The alloy as set forth in claim 19 wherein the alloy contains not more than about 0.006% magnesium.
26 . The alloy as set forth in claim 19 wherein the alloy contains not more than about 0.020% yttrium.
27 . A high strength, high toughness steel alloy having good temper resistance, said alloy comprising, in weight percent, about:
C
0.33-0.45
Mn
0.8-1.3
Si
1.0-2.70
Cr
1.5-1.8
Ni
3.0-4.5
Mo + ½ W
0.25-0.90
Cu
0.35-1.25
Co
0.01 max.
V + (5/9) × Nb
0.10-0.40
Ti
0.01 max.
Al
0.015 max.
Ca
0.001 max.
a grain-refining element selected from the group consisting of 0.0001-0.006% Mg, 0.002-0.025% Y, and a combination thereof; and
the balance being iron and usual impurities wherein phosphorus is restricted to about 0.01% max. and sulfur is restricted to not more than about 0.001% max., and wherein
14.5≦(% Si+% Cu)/(% V+( 5/9)×% Nb)≦34.
28 . A high strength, high toughness steel alloy having good temper resistance, said alloy comprising, in weight percent, about:
C
0.40-0.50
Mn
0.8-1.3
Si
1.5-2.70
Cr
1.5-1.8
Ni
4.0-5.0
Mo + ½ W
0.25-0.90
Cu
0.3-1.2
Co
0.01 max.
V + (5/9) × Nb
0.10-0.40
Ti
0.01 max.
Al
0.015 max.
Ca
0.001 max.
a grain-refining element selected from the group consisting of 0.0001-0.008% Mg, 0.002-0.020% Y, and a combination thereof; and
the balance being iron and usual impurities wherein phosphorus is restricted to about 0.01% max. and sulfur is restricted to not more than about 0.001% max., and wherein
14.5≦(% Si+% Cu)/(% V+( 5/9)×% Nb)≦34.
29 . A hardened and tempered article made from a high strength, high toughness steel alloy as set forth in any of claims 1 , 18 , 19 , 27 , and 28 wherein the article is tempered at a temperature of about 500° F. to 600° F.
30 . The hardened and tempered article as set forth in claim 29 which provides a room temperature tensile strength of at least about 295 ksi and a Charpy V-notch impact toughness of at least about 15 ft-lbs.