Scope – This specification covers carbon, alloy and stainless steel nuts intended for use in high-pressure and/or high-temperature service. Unless otherwise specified, heavy hex nuts (ANSI B 18.2.2) shall be used. Nuts up to and including 1 inch nominal size shall be UNC Series Class 2B fit. Nuts over 1 inch nominal size shall be either UNC Series Class 2B fit or 8 UN Series Class 2B fit.
Grades
|
2 |
Medium Carbon Steel |
2H |
Medium Carbon Steel Quenched & Tempered |
2HM |
Medium Carbon Steel Quenched & Tempered |
4 |
Carbon Molybdenum Quenched & Tempered |
7 |
Alloy Steel Quenched & Tempered |
7M |
Alloy Steel Quenched & Tempered |
8 |
AISI 304 Stainless Steel |
8M |
AISI 316 Stainless Steel |
Mechanical Properties
|
Specification |
Marking |
Nom. Size, In. |
Tempering
Temp. °F |
Proof Load Stress, ksi |
Hardness |
Min |
Max |
A194 Grd 2 |
2 |
1/4 – 4 |
1000 |
150 |
B159 |
B352 |
A194 Grd 2H |
2H |
1/4 – 4 |
1000 |
175 |
C24 |
C38 |
A194 Grd 2HM |
2HM |
1/4 – 4 |
1000 |
150 |
B159 |
B237 |
A194 Grd 4 |
4 |
1/4 – 4 |
1100 |
175 |
C24 |
C38 |
A194 Grd 7 |
7 |
1/4 – 4 |
1100 |
175 |
C24 |
C38 |
A194 Grd 7M |
7M |
1/4 – 4 |
1100 |
150 |
B159 |
B237 |
A194 Grd 8 |
8 |
1/4 – 4 |
– |
80 |
B126 |
B300 |
A194 Grd 8M |
8M |
1/4 – 4 |
– |
80 |
B126 |
B300 |
Chemical
Properties
|
Element |
2, 2H, 2HM |
4 |
7 , 7M (4140) |
8 (304) |
8M (316) |
Carbon |
0.40 min |
0.40 – 0.50 |
0.37 – 0.49 |
0.08 max |
0.08 max |
Manganese |
1.00 max |
0.70 – 0.90 |
0.65 – 1.10 |
2.00 max |
2.00 max |
Phosphorus, max |
0.040 |
0.035 |
0.035 |
0.045 |
0.045 |
Sulfur, max |
0.050 |
0.040 |
0.040 |
0.030 |
0.030 |
Silicon |
0.40 max |
0.15 – 0.35 |
0.15 – 0.35 |
1.00 max |
1.00 max |
Chromium |
|
|
0.75 – 1.20 |
18.0 – 20.0 |
16.0 – 18.0 |
Nickel |
|
|
|
8.0 – 11.0 |
10.0 – 14.0 |
Molybdenum |
|
0.20 – 0.30 |
0.15 – 0.25 |
|
2.00 – 3.00 |
Recommended Mating Materials
|
Bolt Grade |
Nuts Spec/Grade |
Washers Spec/Grade |
B7 |
A194 Grade 2H |
F436 |
B8 Class 1 |
A194 Grade 8 |
SS304 |
B8M Class 1 |
A194 Grade 8M |
SS316 |
B8 Class 2 |
A194 Grade 8 |
SS304 |
B8M Class 2 |
A194 Grade 8M |
SS316 |