ASTM A193 Grade B8MA Specification for high tensile bolts, screws, stud bolts, anchor bolts, threaded rods and other externally threaded fasteners, made from 316 stainless steel.
ASTM A193 Grade B8MA is a standard material specification for corrosion resistant 316 stainless steel fasteners such as bolts, screws, studs, threaded rods and other externally threaded parts, for use in high tensile, high temperature and special purpose applications such as pressure piping & pressure vessels bolting. Grade B8MA is a carbide solution treated 316 stainless steel and similar to Grade B8M except the latter is carbide solution treated after head forming and the former is a carbide solution treated in finished condition. Grade B8MA is classified under tensile class 1A having a minimum tensile requirement of 75 ksi, yield 30 ksi and maximum hardness limit of 190 HWB or 90 HRB. This specification covers requirements for chemical composition, mechanical properties, hardness, heat-treatment and recommended nuts-washers for Grade B8MA Fasteners.
The “B8M” designation refers to Type 316 stainless steel, which contains molybdenum (Mo) for improved resistance to pitting and crevice corrosion. The “A” suffix indicates that the material has been strain-hardened to enhance mechanical properties.
| Grade | A193 B8MA Class 1A |
|---|---|
| USA UNS | S31600 |
| Other Names | |
| Corresponding Standard | ASTM A193/A193M-2019 Alloy-steel and stainless steel bolting for high temperature or high pressure service and other special purpose applications |
| Classification | Austenitic Stainless Steel |
| Properties | Strength Corrosion Resistance Low-Temperature Toughness Forgability Weldability |
A193 B8MA Class 1A Chemical Element Composition Content (%)
| Component | C | Si | Mn | P | S | Cr | Ni | Mo |
|---|---|---|---|---|---|---|---|---|
| Minimum Value | – | – | – | – | – | 16 | 10 | 2 |
| Maximum Value | 0.08 | 1 | 2 | 0.045 | 0.03 | 18 | 14 | 3 |
A193 B8MA Class 1A Mechanical Properties
| Heat Treatment or Condition | Tensile Strength σb Mpa |
Yield Point σs Mpa |
Elongation or Extension Rate δ % |
Reduction of Area ψ % |
Hardness HBW |
|---|---|---|---|---|---|
| Carbide Solution Treatment in Finished Condition | ≥515 | ≥205 | ≥30 | ≥50 | ≤192 |
Equivalent grade of A193 B8MA
| China | Taiwan, China | Japan | South Korea | United States | International Organization for Standardization | Germany | France | European Standard | Sweden | United Kingdom | |||||
| GB | ISC | CNS | JIS | KS | ASTM | UNS | ISO | Numerical Grade | DIN EN/DIN | W-Nr. | NF EN/NF | EN | Numerical Grade | SS | BS EN/BS |
| 06Cr17Ni12Mo2 | S31608 | 316 | SUS 316 | STS 316 | 316 | S31600 | X5CrNiMo 17-12-2 | 4401-316-00-I | X5CrNiMo 17-12-2 (X5CrNiMo 18-10) X5CrNiMo 17-13-3 (X5CrNiMo 18-12) |
1.4401 1.4401 1.4436 1.4436 |
Z6CND 17-11 Z6CND 17-12 |
X5CrNiMo 17-12-2 X3CrNiMo 17-13-3 |
1.4401 1.4436 |
2347 2343 |
316S16 316S31 |
Recommended Nuts & Washers for A193 B8MA Stud bolt
| Nut Specification | Washer Specification |
|---|---|
| ASTM A194 Grade 8MA | ASTM A240 TP316 |
Available Forms & Specifications
Stud Bolts, Hex Bolts, Nuts, and Washers
hread Types: UNC / UNF / 8UN / Metric
Diameter Range: ¼” to 2½” (M6 to M64)
Coatings (Optional): PTFE Xylan
FAQ – ASTM A193 B8MA Class 1A Stud Bolts
1. What is ASTM A193 B8MA Class 1A?
ASTM A193 B8MA Class 1A refers to strain-hardened Type 316 stainless steel stud bolts with improved corrosion resistance and mechanical properties. The “A” denotes that the material is strain-hardened to increase strength, while Class 1A specifies that the material undergoes a controlled process to maintain its mechanical properties.
2. What are the key features of B8MA Class 1A stud bolts?
High Strength – Strain-hardened for superior mechanical properties
Excellent Corrosion Resistance – Resistant to chloride pitting, crevice corrosion, and oxidation
High-Temperature Resistance – Suitable for applications up to 1100°F (593°C)
Reliable Performance – Ensures durability in harsh industrial environments
3. What are the typical applications of ASTM A193 B8MA Class 1A stud bolts?
Marine & Offshore – Seawater-resistant fasteners for ships, offshore rigs, and subsea equipment
Chemical Processing Plants – Used in acidic and corrosive environments
Petrochemical & Oil Refineries – Ideal for piping systems, reactors, and valves
Power Plants & Boilers – High-strength studs for turbines, heat exchangers, and pressure vessels
Pharmaceutical & Food Industry – Non-reactive stainless steel for sanitary conditions
4. What are the available sizes and thread types for B8MA Class 1A stud bolts?
Diameter Range: ¼” to 2½” (M6 to M64)
Thread Types: UNC / UNF / 8UN / Metric
Length: Custom lengths available
5. What is the difference between B8MA Class 1A compare to B8M?
| Property | B8M | B8MA Class 1A |
|---|---|---|
| Strength | Standard | Higher (Strain-Hardened) |
| Corrosion Resistance | Excellent | Excellent |
| Temperature Resistance | High | High |
| Hardness | Lower | Higher |
