SPECIFICATION LIBRARY
ASTM A193
ASTM A193 encompasses a broad range of high-strength alloy steel and stainless steel materials used for bolts, screws, studs, and other externally threaded fasteners in high-temperature or high-pressure environments. This standard is pivotal in sectors like petrochemical, oil and gas, power plants, and structural engineering, where reliability and performance under extreme conditions are paramount.
Overview of ASTM A193 Standard
The ASTM A193 standard specifies the mechanical properties, chemical composition, and testing requirements for fasteners. These materials are selected for their ability to withstand harsh environments, including elevated temperatures and pressures, without compromising integrity.
Detailed Analysis of Selected ASTM A193 Grades
B7: Comprising chromium-molybdenum steel, grade B7 is renowned for its high strength and is often used in the manufacture of bolting for flanges and pressure vessels.
B16: A chromium-molybdenum-vanadium alloy, B16 is known for its enhanced strength at higher temperatures, making it ideal for high-pressure and high-temperature applications.
B7M: Similar to B7 but with controlled hardness requirements, B7M is used in applications where resistance to stress corrosion cracking is essential.
B8: Made of 304 stainless steel, B8 grade fasteners are used in environments requiring corrosion resistance and moderate strength at high temperatures.
B8M: With 316 stainless steel construction, B8M fasteners offer superior corrosion resistance, especially in chloride-containing environments, compared to B8.
B6: Fabricated from 410 stainless steel, B6 is utilized where high strength and moderate corrosion resistance are required.
Chemical Composition of Selected ASTM A193 Grades
The chemical composition of these grades varies to meet different mechanical and environmental demands:
ASTM A193: The Backbone of Industrial Fastening
|
Grade |
Carbon |
Manganese |
Phosphorus |
Sulfur |
Silicon |
Chromium |
Nickel |
Molybdenum |
|
B7 |
0.38-0.48% |
0.75-1.00% |
Max 0.035% |
Max 0.040% |
0.15-0.35% |
0.80-1.10% |
- |
0.15-0.25% |
|
B16 |
0.36-0.47% |
0.45-0.70% |
Max 0.035% |
Max 0.040% |
0.15-0.35% |
0.80-1.15% |
- |
0.50-0.65% |
|
B7M |
0.38-0.48% |
0.75-1.00% |
Max 0.035% |
Max 0.040% |
0.15-0.35% |
0.80-1.10% |
- |
0.15-0.25% |
|
B8 |
Max 0.08% |
Max 2.00% |
Max 0.045% |
Max 0.030% |
Max 1.00% |
18.0-20.0% |
8.0-11.0% |
- |
|
B8M |
Max 0.08% |
Max 2.00% |
Max 0.045% |
Max 0.030% |
Max 1.00% |
16.0-18.0% |
10.0-14.0% |
2.00-3.00% |
|
B6 |
0.15-0.20% |
Max 1.00% |
Max 0.040% |
Max 0.030% |
Max 1.00% |
11.5-13.5% |
- |
- |
Mechanical Properties of Selected ASTM A193 Grades
|
Grade |
Diameter |
Tensile Strength |
Yield Strength |
Elongation |
Hardness |
|
B7 |
up to 2-1/2" |
125 ksi min |
105 ksi min |
16% min |
321 max HB |
|
2-1/2" - 4" |
115 ksi min |
95 ksi min |
16% min |
321 max HB |
|
|
B16 |
up to 2-1/2" |
130 ksi min |
115 ksi min |
18% min |
321-352 HB |
|
2-1/2" - 4" |
120 ksi min |
100 ksi min |
17% min |
321-352 HB |
|
|
B7M |
up to 4" |
100 ksi min |
80 ksi min |
18% min |
235 max HB |
|
B8 Class 1 |
up to 4" |
75 ksi min |
30 ksi min |
30% min |
223 max HB |
|
B8 Class 2 |
up to 3/4" |
125 ksi min |
100 ksi min |
12% min |
321 max HB |
|
3/4" - 1" |
115 ksi min |
80 ksi min |
15% min |
321 max HB |
|
|
1" - 1-1/4" |
105 ksi min |
65 ksi min |
20% min |
321 max HB |
|
|
1-1/4" - 1-1/2" |
100 ksi min |
50 ksi min |
28% min |
321 max HB |
|
|
B8M Class 1 |
up to 4" |
75 ksi min |
30 ksi min |
30% min |
223 max HB |
|
B8M Class 2 |
up to 3/4" |
110 ksi min |
95 ksi min |
15% min |
321 max HB |
|
3/4" - 1" |
100 ksi min |
80 ksi min |
20% min |
321 max HB |
|
|
1" - 1-1/4" |
95 ksi min |
65 ksi min |
25% min |
321 max HB |
|
|
1-1/4" - 1-1/2" |
90 ksi min |
50 ksi min |
30% min |
321 max HB |
|
|
B6 |
up to 4" |
110 ksi min |
85 ksi min |
15% min |
217-248 HB |
Manufacturing Process and Heat Treatment
ASTM A193 fasteners are typically produced through various processes like forging, rolling, and machining, followed by heat treatment (quenching and tempering) to achieve the desired mechanical properties. The specific heat treatment process depends on the grade and the properties required.
Applications and Design Considerations
Each ASTM A193 grade is designed for specific applications, considering factors like temperature, pressure, and corrosive environment. For example, B7 is widely used in the petrochemical industry for flanged joints, while B8 and B8M are preferred in marine and acidic environments.
Real-world applications of ASTM A193 grades illustrate their performance and reliability. For instance, grade B7 fasteners are commonly used in high-temperature steam lines, while B8M fasteners are chosen for their superior corrosion resistance in chemical processing plants.
Quality Assurance and Compliance Testing
Adherence to ASTM A193 standards is ensured through rigorous testing, including tensile testing, hardness testing, and impact testing. These procedures guarantee that the fasteners meet the specified mechanical and chemical requirements.
Recommended Hardware
|
ASTM A193 Grade |
Recommended Nuts |
Recommended Washers |
|
B7 |
ASTM A194 Grade 2H |
ASTM F436 |
|
B16 |
ASTM A194 Grade 7 |
ASTM F436 |
|
B7M |
ASTM A194 Grade 2HM |
ASTM F436 |
|
B8 |
ASTM A194 Grade 8 |
304SS / 316SS |
|
B8M |
ASTM A194 Grade 8M |
316SS |
|
B6 |
ASTM A194 Grade 6 |
316SS / 410SS |
ASTM A194 Grade 2H, 2HM: These are carbon or alloy steel nuts, quenched and tempered, recommended for use with ASTM A193 Grade B7 fasteners.
ASTM A194 Grade 7: Specifically chosen for high-temperature service, these grades are compatible with B16 fasteners, providing the necessary mechanical properties and temperature resistance.
ASTM A194 Grade 8 and 8M: Made of austenitic stainless steel, these nuts are used with B8 and B8M fasteners, respectively, offering excellent corrosion resistance and strength at high temperatures.
ASTM A194 Grade 6: This grade is suitable for use with ASTM A193 Grade B6 fasteners and is made of martensitic stainless steel, offering good mechanical properties and resistance to high temperatures.
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