SPECIFICATION LIBRARY
ASTM A194
ASTM A194 Specification Overview
ASTM A194 is a standard specification for carbon and alloy steel nuts for bolts used in high-pressure or high-temperature service, or both. This document outlines the specific requirements for various grades within the standard, focusing on their chemical and mechanical properties.
|
Grade |
Material Type |
Typical Application |
|
2H |
Carbon steel, quenched and tempered |
High-pressure, high-temperature environments |
|
2HM |
Carbon steel, quenched and tempered, 100% hardness tested |
Similar to 2H but with mandatory hardness testing |
|
7 |
Alloy steel, tempered and quenched |
Low-temperature environments |
|
8 (Class 1) |
Austenitic stainless steel (304) |
General-purpose corrosion-resistant environments |
|
8 (Class 2) |
Austenitic stainless steel (304), strain-hardened |
Higher strength version of Grade 8 |
|
8M (Class 1) |
Austenitic stainless steel (316) |
Corrosive environments, superior to Grade 8 in corrosion resistance |
|
8M (Class 2) |
Austenitic stainless steel (316), strain-hardened |
Higher strength and corrosion resistance than Grade 8M Class 1 |
|
B6 |
Martensitic stainless steel (410) |
High-strength, good heat resistance, moderate corrosion resistance |
This table encapsulates the primary attributes and applications of each ASTM A194 grade, aiding in the selection of the appropriate grade for specific environmental and mechanical requirements.
Chemical Composition
The chemical composition for each grade specifies the alloying elements and their permissible limits:
|
Grade |
Carbon (C) |
Manganese (Mn) |
Phosphorus (P) |
Sulfur (S) |
Silicon (Si) |
Chromium (Cr) |
Molybdenum (Mo) |
Nickel (Ni) |
|
2H, 2HM |
0.40 max |
1.00 max |
0.04 max |
0.05 max |
0.40 max |
- |
- |
- |
|
7 |
0.37-0.49 |
0.65-1.10 |
0.035 max |
0.040 max |
0.15-0.35 |
1.00-1.50 |
0.40-0.65 |
- |
|
8 Class 1 |
0.08 max |
2.00 max |
0.045 max |
0.030 max |
1.00 max |
18.0-20.0 |
- |
8.0-11.0 |
|
8 Class 2 |
0.08 max |
2.00 max |
0.045 max |
0.030 max |
1.00 max |
18.0-20.0 |
- |
8.0-11.0 |
|
8M Class 1 |
0.08 max |
2.00 max |
0.045 max |
0.030 max |
1.00 max |
16.0-18.0 |
2.00-3.00 |
10.0-14.0 |
|
8M Class 2 |
0.08 max |
2.00 max |
0.045 max |
0.030 max |
1.00 max |
16.0-18.0 |
2.00-3.00 |
10.0-14.0 |
|
B6 |
0.08-0.15 |
1.00 max |
0.040 max |
0.030 max |
- |
11.5-13.5 |
- |
- |
Mechanical Properties
The mechanical properties vary among the grades to meet the demands of different high-pressure and high-temperature applications:
|
Grade |
Tensile Strength (ksi) |
Yield Strength (ksi) |
Elongation (%) |
Hardness (Brinell) |
|
2H |
175 min |
150 min |
16 min |
212 max |
|
2HM |
175 min |
150 min |
16 min |
212 max |
|
7 |
100 min |
80 min |
16 min |
235-321 |
|
8 Class 1 |
80 min |
- |
- |
321 max |
|
8 Class 2 |
150 min |
130 min |
15 min |
321-352 |
|
8M Class 1 |
75 min |
- |
- |
321 max |
|
8M Class 2 |
90 min |
80 min |
- |
321-352 |
|
B6 |
110 min |
85 min |
15 min |
179-217 |
Applications of ASTM A194 Grades
Grade 2H and 2HM: These grades are commonly used in oil and gas, power generation, and petrochemical industries, especially for flanged joints, valves, and fittings subjected to high temperatures and pressures.
Grade 7: Suited for environments where temperatures may reach up to 450°C, making it ideal for use in high-temperature steam services and other thermal applications.
Grade 8 and 8M (Class 1 and 2): Known for their exceptional corrosion resistance, these grades are typically employed in marine, chemical processing, and desalination plants, where exposure to corrosive elements is a concern.
Grade B6: Made from martensitic stainless steel, this grade is often used in applications requiring good resistance to heat and moderately corrosive environments, such as in power plants and in the manufacturing of certain chemicals.
The ASTM A194 standard provides detailed specifications for various grades of nuts, each designed to meet specific requirements of high-pressure and high-temperature service environments. The grades 2H, 2HM, 7, 8, 8M, and B6 each have unique chemical and mechanical properties, ensuring that the right material can be selected for the right application, optimizing performance and safety in industrial settings.
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