Material Selection for Steel Fasteners
The below table shows the application of various grades of steel fasteners for different range of temperatures.
Material: Bolt/ Nut |
Temperature Range |
A320B8/Gr 8 |
(-100°C) – (-200°C) |
A320L7/Gr 4 |
(-46°C) – (-100°C) |
A320L7/Gr 4 |
0°C – (-45°C) |
A307 |
0°C – 300°C |
A193 B7 /Gr 2H |
300°C – 400°C |
A193 B16 /Gr 4 |
400°C – 550°C |
A193 B8 /Gr 8 |
550°C – 650°C |
A193 B8M /Gr 8M |
550°C – 650°C |
High Temperature High Tension Alloy Bolt Material
ASTM A193 B7 (Cr-Mo) Chemical & Mechanical Properties
This material is considered as the most suitable for bolts to be used at temperature below 450 °C, with a minimum effect on its structural strength during application at a high temperature. The material has the following chemical properties and physical characteristics.
ASTM A193 B7 (Cr-Mo) |
Chemical Properties |
Range (%) |
Carbon (C) |
0.37 – 0.49 |
Manganese (Mn) |
0.65 – 1.10 |
Phosphorus (P) |
0.035 max |
Sulfur (S) |
0.04 max |
Silicon (Si) |
0.15 – 0.35 |
Chromium (Cr) |
0.75 – 1.20 |
Molybdenum (Mo) |
0.15 – 0.25 |
ASTM A193 B7 (Cr-Mo) |
Mechanical Properties |
2-1/2″ and under |
over 2-1/2″ to 4.0″ |
over 4.0″ to 7.0″ |
Min Tempering Temperature (F) |
1100 (593C) |
1100 (593C) |
1100 (593C) |
Min Tensile Strength (ksi) |
125 (860MPa) |
115 (795MPa) |
100 (690MPa) |
Min Yield Strength (ksi) |
105 (105MPa) |
95 (655MPa) |
75 (515MPa) |
Elongation in 4D (min %) |
16 |
16 |
18 |
Reduction of Area (min %) |
50 |
50 |
50 |
Max Hardness |
321HB (35HRC) |
321HB (35HRC) |
277HB (29HRC) |
ASTM A1193 B7M (Cr- Mo ) Chemical & Mechanical Properties
ASTM A193 B7M (Cr- Mo ) |
Chemical Properties |
Range (%) |
Carbon (C) |
0.37 – 0.49 |
Manganese (Mn) |
0.65 – 1.10 |
Phosphorus (P) |
0.035 max |
Sulfur (S) |
0.04 max |
Silicon (Si) |
0.15 – 0.35 |
Chromium (Cr) |
0.75 – 1.20 |
Molybdenum (Mo) |
0.15 – 0.25 |
ASTM A193 B7M (Cr- Mo ) |
Mechanical Properties |
4.0″ and under |
over 4.0″ to 7.0″ |
Min Tempering Temperature (F) |
1150 (620C) |
1150 (620C) |
(final heat treatment shall be |
done after all machining and |
forming operations, including |
thread rolling and any type |
of cutting) |
Min Tensile Strength (ksi) |
100 (690MPa) |
100 (690MPa) |
Min Yield Strength (ksi) |
80 (550MPa) |
75 (515MPa) |
Elongation in 4D (min %) |
18 |
18 |
Reduction of Area (min %) |
50 |
50 |
Max Hardness |
235HB (99HRB) |
277HB (29HRC) |
ASTM A193 B16 (Cr-Mo-V) Chemical & Mechanical Properties
This material is considered as the most suitable for bolts to be used at temperature below 450°C, even at a high temperature range, the material has superior physical characteristics compared to ASTM A193 B7. The chemical properties and physical characteristics are as follows;
ASTM A193 B16 (Cr-Mo-V) |
Chemical Properties |
Range (%) |
Carbon (C) |
0.36 – 0.47 |
Manganese (Mn) |
0.45 – 0.70 |
Phosphorus (P) |
0.035 Max |
Sulfur (S) |
0.04 Max |
Silicon (Si) |
0.15 – 0.35 |
Chromium (Cr) |
0.80 – 1.15 |
Molybdenum (Mo) |
0.50 – 0.65 |
Aluminum (Al) |
0.015 Max |
Vanadium (V) |
0.25 – 0.35 |
ASTM A193 B16 (Cr-Mo-V) |
Mechanical Properties |
2-1/2″ and under |
over 2-1/2″ to 4.0″ |
over 4.0″ to 7.0″ |
Min Tempering Temperature (F) |
1200 (650C) |
1200 (650C) |
1200 (650C) |
Min Tensile Strength (ksi) |
125 (860MPa) |
110 (760MPa) |
100 (690MPa) |
Min Yield Strength (ksi) |
105 (105MPa) |
95 (655MPa) |
85 (586MPa) |
Elongation in 4D (min %) |
18 |
17 |
16 |
Reduction of Area (min %) |
50 |
45 |
45 |
Max Hardness |
321HB (35HRC) |
302HB (33HRC) |
277HB (29HRC) |
ASTM A193 B8 Class1, 1A and 2 (AISI 304) Chemical & Mechanical Properties
ASTM A193 B8 Class1, 1A and 2 (AISI 304) |
Chemical Properties |
Range (%) |
Carbon (C) |
0.08 Max |
Manganese (Mn) |
2.00 Max |
Phosphorus (P) |
0.045 Max |
Sulfur (S) |
0.030 Max |
Silicon (Si) |
1.00 Max |
Chromium (Cr) |
18.00 – 20.00 |
Nickel (Ni) |
8.00 -11.00 |
Molybdenum (Mo) |
– |
ASTM A193 B8M Class1, 1A and 2 (AISI 316) Chemical & Mechanical Properties
ASTM A193 B8M Class1, 1A and 2 (AISI 316) |
Chemical Properties |
Range (%) |
Carbon (C) |
0.08 Max |
Manganese (Mn) |
2.00 Max |
Phosphorus (P) |
0.045 Max |
Sulfur (S) |
0.030 Max |
Silicon (Si) |
1.00 Max |
Chromium (Cr) |
16.00 – 18.00 |
Nickel (Ni) |
10.00 -14.00 |
Molybdenum (Mo) |
2.00 – 3.00 |
Mechanical Properties |
Class 1: B8, B8M |
Class 1A: B8A, B8MA |
All diameters |
All diameters |
Heat Treatment |
Carbide Solution Treated |
Carbide Solution Treated |
in the finished condition |
Min Tensile Strength (ksi) |
75 (515MPa) |
75 (515MPa) |
Min Yield Strength (ksi) |
30 (205MPa) |
30 (205MPa) |
Elongation in 4D (min %) |
30 |
30 |
Reduction of Area (min %) |
50 |
50 |
Max Hardness |
223HB (96HRB) |
192HB (90HRC) |
3/4″ and smaller |
241HB (100HRB) |
|
B8 Class 2 |
Mechanical Properties |
3/4″ and under |
over 3/4″ to 1.0″ included |
over 3/4″ to 1.0″ included |
over 1-1/4″ to 1-1/2″ included |
Heat Treatment |
Carbide Solution Treated |
Carbide Solution Treated |
Carbide Solution Treated |
Carbide Solution Treated |
and Strain Hardened |
and Strain Hardened |
and Strain Hardened |
and Strain Hardened |
Min Tensile Strength (ksi) |
125 (860MPa) |
115 (795MPa) |
105 (725MPa) |
100 (690MPa) |
Min Yield Strength (ksi) |
100 (690MPa) |
80 (550MPa) |
65 (450MPa) |
50 (345MPa) |
Elongation in 4D (min %) |
12 |
15 |
20 |
28 |
Reduction of Area (min %) |
35 |
35 |
35 |
45 |
Max Hardness |
321HB (35HRC) |
321HB (35HRC) |
321HB (35HRC) |
321HB (35HRC) |
|
|
|
|
|
|
B8M Class 2 |
Mechanical Properties |
3/4″ and under |
over 3/4″ to 1.0″ included |
over 3/4″ to 1.0″ included |
over 1-1/4″ to 1-1/2″ included |
Heat Treatment |
Carbide Solution Treated |
Carbide Solution Treated |
Carbide Solution Treated |
Carbide Solution Treated |
and Strain Hardened |
and Strain Hardened |
and Strain Hardened |
and Strain Hardened |
Min Tensile Strength (ksi) |
110 (760MPa) |
100 (690MPa) |
95 (655MPa) |
90 (620MPa) |
Min Yield Strength (ksi) |
95 (655MPa) |
80 (550MPa) |
65 (450MPa) |
50 (345MPa) |
Elongation in 4D (min %) |
15 |
20 |
25 |
30 |
Reduction of Area (min %) |
45 |
45 |
45 |
45 |
Max Hardness |
321HB (35HRC) |
321HB (35HRC) |
321HB (35HRC) |
321HB (35HRC) |
Low-Temperature Alloy Steel Bolt Material
ASTM A320-L7, L7M (Cr-Mo) Chemical & Mechanical Properties
This material is considered as the most suitable for bolts to be used at temperature 0-(-100 °C). The chemical properties and physical characteristics are as follows:
Chemical Properties |
Range (%) |
Carbon (C) |
0.38 – 0.48 |
Manganese (Mn) |
0.75 – 1.00 |
Phosphorus (P) |
0.035 max |
Sulfur (S) |
0.04 max |
Silicon (Si) |
0.15 – 0.35 |
Chromium (Cr) |
0.80 – 1.10 |
Molybdenum (Mo) |
0.15 – 0.25 |
Mechanical Properties |
L7 |
L7M |
2-1/2″ and under |
Min Tempering Temperature (F) |
1100 (593C) |
1150 (620C) |
Min Tensile Strength (ksi) |
125 (860MPa) |
100 (690MPa) |
Min Yield Strength (ksi) |
105 (725MPa) |
80 (550MPa) |
Elongation in 4D (min %) |
16 |
18 |
Reduction of Area (min %) |
50 |
50 |
Max Hardness |
277 – 321HB |
235HB or 99HRB |
|
for referecence |
|
Minimum Impact Value ft-lb (J) |
20 (27) |
|
(Average of three specimen) |
Minimum Impact Value ft-lb (J) |
15 (20) |
|
(Specimen of a set) |
ASTM A320 B8 (18Cr-8Ni) Chemical & Mechanical Properties
This material is considered as the most suitable for bolts and nuts to be used at temperatures (-)100-(-)200 °C. The chemical properties are as follows:
Chemical Properties |
B8 |
B8M |
Range (%) |
Range (%) |
Carbon (C) |
0.08 max |
0.08 max |
Manganese (Mn) |
2.00 max |
2.00 max |
Phosphorus (P) |
0.045 max |
0.045 max |
Sulfur (S) |
0.30 max |
0.30 max |
Silicon (Si) |
1.00 max |
1.00 max |
Chromium (Cr) |
18.00 – 20.00 |
16.00 – 18.00 |
Nickel (Ni) |
8.00 – 10.50 |
10.00 – 14.00 |
Molybdenum (Mo) |
|
2.00 – 3.00 |
Nut Material
ASTM A194
This is the material for bolts made from ASTM A-193 B7, considered to be used with suitable heat treatment. The chemical properties and physical properties are as follows:
Chemical Properties |
2H/2HM |
4 |
7/7M |
8/8A |
8M/8MA |
Range (%) |
Range (%) |
Range (%) |
Range (%) |
Range (%) |
Carbon (C) |
0.40 min |
0.04 – 0.05 |
0.37 – 0.49 |
0.08 |
0.08 |
Manganese (Mn) |
1 |
0.70 – 0.90 |
0.65 – 1.10 |
2 |
2 |
Phosphorus (P) |
0.04 |
0.035 |
0.035 |
0.045 |
0.045 |
Sulfur (S) |
0.05 |
0.04 |
0.04 |
0.03 |
0.03 |
Silicon (Si) |
0.4 |
0.15 – 0.35 |
0.15 – 0.35 |
1 |
1 |
Chromium (Cr) |
|
|
0.75 – 1.20 |
18.0 – 20.0 |
16.0 – 18.0 |
Nickel (Ni) |
|
|
|
8.0 – 11.0 |
10.0 – 14.0 |
Molybdenum (Mo) |
|
0.20 – 0.30 |
0.15 – 0.25 |
|
|
|
Hardness Requirement |
Mechanical Properties |
Brinell |
Rockwell-C Scale |
Rockwell-B Scale |
2H (To 1-1/2″ incl) |
248 – 327 |
24 – 35 |
|
2H (Over 1-1/2″) |
212 – 327 |
35 max |
95 min |
2HM/7M |
159 – 235 |
|
84 – 99 |
4 and 7 |
248 – 327 |
24 – 35 |
|
8/8M |
126 – 300 |
|
60 – 105 |
8A/8MA |
126 – 192 |
|
60 – 90 |
ASTM A307
This material is suitable in structural application where nominal strength along with weldability is required.
Chemical Properties |
Range (%) |
Carbon (C) |
0.29 |
Manganese (Mn) |
1.2 |
Phosphorus (P) |
0.04 |
Sulfur (S) |
|
Gr. A |
0.15 |
Gr. B |
0.05 |
Mechanical Properties |
Gr. A |
Gr. B |
Min Tempering Temperature (F) |
|
|
Min Tensile Strength (ksi) |
60 (415) |
60 – 100 |
Min Yield Strength (ksi) |
|
|
Elongation in 4D (min %) |
18 |
18 |
Reduction of Area (min %) |
|
|
Max Hardness |
121 – 241HB |
121 – 212HB |