ASTM A193 Specification: Bolting for High Temperature/Pressure Service
The ASTM A193 specification is the standard for high-performance bolting materials, covering alloy and stainless steel bolts, studs, and other fasteners intended for use in pressure vessels, valves, flanges and fittings. These materials are specifically engineered for service conditions involving high temperatures, high pressures, or other special purpose applications where standard fasteners are inadequate.
ASTM A193 bolts are available in a variety of different grades and are mostly classified as either ferritic including B7, B7M, B16 and austenitic stainless steels namely B8, B8M, B8T, B5. The choice of material that includes the design, the conditions of service and mechanical properties are important. An example of this is grade A193 B7 (high-strength bolting) is the most popular, whereas A193 B8 (Type 304 Stainless Steel) is usually used because of its bright corrosion resistance in high temperature. Manufacturing processes may include either hot-wrought rolling or forging, and subsequent controlled cooling and the appropriate heat treatment (e.g. quenching and tempering of ferritic steels, solution treating of carbide alloys).
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ASTM A193 Bolt & Fasteners Suppliers, Manufacturers & Exporter
Jade Alloys is a specialized supplier, manufacturer and exporter of high quality ASTM A193 fasteners, and offers critical bolting solutions that are used in high-temperature and high-pressure industrial service. We have an extensive selection in compliance with the strict ASTM A193 Specification that encompasses alloy and stainless steel bolting metals that can be used in pressure vessels, flanges, and fittings. All the major ASTM A193 grades such as B7, B7M, B16, B8 and B8M are available and we have guaranteed ourselves to match the varying application needs depending on the strength, temperature durability and corrosion resistance. We can provide competitive price structures of ASTM bolts, A193, all over the world by ensuring high quality control and utilizing efficient production processes, thereby guaranteeing your project the high quality and certified ASTM bolts in a quick and cost-effective manner.
ASTM A193 Bolt Products
ASTM A193 Bolting Grades
The ASTM A193 specification encompasses numerous grades, each with unique chemical, strength, and testing requirements tailored for specific high-pressure and high-temperature applications. Understanding these differences is crucial for proper fastener selection, as summarized below. For complete, detailed information, check out ASTM standards.
| B7 |  |
Hex bolts, screws, stud bolts, double ended studs, full thread rods, full threaded studs |
| B7M |  |
Hex bolts, screws, stud bolts, double ended studs, Stud for foundation, wind energy bolts, Fasteners for wind turbines |
| B16 |  |
Hex bolts, screws, stud bolts, double ended studs, Stud for foundation, wind energy bolts, Fasteners for wind turbines |
| B8 |  |
Hex bolts, screws, stud bolts, double ended studs, Stud for foundation, wind energy bolts, Fasteners for wind turbines |
| B8M |  |
Hex bolts, screws, stud bolts, double ended studs, Stud for foundation, wind energy bolts, Fasteners for wind turbines |
| B8T |  |
Hex bolts, screws, stud bolts, double ended studs, Stud for foundation, wind energy bolts, Fasteners for wind turbines |
ASTM A193 Grade B7 Bolts and Studs
The most common and widely known grade of ASTM A193 bolting is grade B7 which is mainly used in the industry when connecting the flanges of pipes and in construction. These threaded studs and bolts are made of Chromium-Molybdenum alloy steel and are subject to the quenching and tempering (heat treatment) to meet desired high-strength mechanical properties. Although most of them are supplied in a simple, bare metal, most are coated (e.g., hot-dip galvanized, PTFE, or Xylan) to provide greater corrosion resistance, although users should be aware that any coating can reduce the maximum high-temperature service capability of the fastener.
ASTM A193 Grade B8 Bolts
ASTM A193 Grade B8 bolts and threaded studs are manufactured using AISI 304 stainless steel, which is the most commonly used stainless grade in the fasteners industry. The material is an austenitic stainless steel and such an alloy needs carbide solution treatment (or solution annealing) which is a treatment which includes heating then being quenched in water as fast as possible to achieve optimum inherent corrosion resistance. These clips are provided as Class 1 following this treatment. Grade B8 Class 2 bolts are subject to an extra strain hardening treatment after the solution treatment to achieve greater strength and less galling potential. These higher-strength Class 2 bolts are specially indicated as B8SH with the symbol of the grade underlined.
ASTM A193 Grade B8M fasteners
ASTM A193 Grade B8M Class 1 fasteners are similar to Grade B8 fasteners, but made of AISI 316 stainless steel instead of being made of AISI 304. The 316 stainless molybdenum gives it better corrosion protection than 304. Fasteners in Grade B8M, Class 1 must be treated using carbide solution and Class 2 is further subjected where strain hardening process enhances strength and minimizes the possibility of galling. Class 2 fasteners have a mark of B8MSH with the symbol of the grade underlined.
ASTM A193 Grade B7M bolts
ASTM A193 Grade B7M bolts and studs have the same chemical makeup as Grade B7 that is a quenched and tempered, medium-carbon alloy steel. Grade B7M fasteners are however manufactured to reduce the strength levels, and need to be subjected to 100% hardness tests on each fastener in the lot. Such bolts are better resistant to chloride, sulfide, and hydrogen stress corrosion cracking (SCC), and are frequently used in sour-gas service.
ASTM A193 Grade B16 bolts
ASTM A193 Grade B16 bolts and threaded studs are made out of a chromium-molybdenum-vanadium alloy steel. Although their strength needs are similar to Grade B7, the inclusion of vanadium and application of higher tempering temperature enable Grade B16 fasteners to sustain their structure and strength at high operating temperatures. These are usually applied in the power generation and petrochemical sectors to boilers, turbines and other high temperature pressurized equipment. Grade B16 does not have an inherent corrosion resistance unlike the stainless steel grades in the A193 specification, unless it is coated.
ASTM A193 Material for Grades
| Grade / Tensile Class | Material |
| A193 B7 | Chromium Molybdenum Alloy Steel, Quenched & Tempered |
| A193 B8 | AISI 304 Stainless Steel |
| A193 B8C | AISI 347 Stainless Steel |
| B8C Class 1 | AISI 347 Stainless Steel, Carbide Solution Treated |
| B8C Class 2 | AISI 347 Stainless Steel, Carbide Solution Treated & Strain Hardened |
| A193 B8T | AISI 321 Stainless Steel, Carbide Solution Tested |
| A193 B8M | AISI 316 Stainless Steel |
| B8T Class 1 | AISI 321 Stainless Steel, Carbide Solution Tested |
| B8T Class 2 | AISI 321 Stainless Steel, Carbide Solution Tested & Strain Hardened |
| A193 B16 | Chromium Molybdenum Vanadium Alloy Steel, Quenched & Tempered |
Mechanical Properties of ASTM A193 Bolts
| Grade | Size | Tensile ksi, min | Yield, ksi, min | Elong, %, min | RA % min |
|---|---|---|---|---|---|
| B7 | Up to 2-1/2 | 125 | 105 | 16 | 50 |
| 2-5/8 – 4 | 115 | 95 | 16 | 50 | |
| 4-1/8 – 7 | 100 | 75 | 18 | 50 | |
| B8 Class 1 | All | 75 | 30 | 30 | 50 |
| B8M Class 1 | All | 75 | 30 | 30 | 50 |
| B8 Class 2 | Up to 3/4 | 125 | 100 | 12 | 35 |
| 7/8 – 1 | 115 | 80 | 15 | 35 | |
| 1-1/8 – 1-1/4 | 105 | 65 | 20 | 35 | |
| 1-3/8 – 1-1/2 | 100 | 50 | 28 | 45 | |
| B8M Class 2 | Up to 3/4 | 110 | 95 | 15 | 45 |
| 7/8 – 1 | 100 | 80 | 20 | 45 | |
| 1-1/8 – 1-1/4 | 95 | 65 | 25 | 45 | |
| 1-3/8 – 1-1/2 | 90 | 50 | 30 | 45 |
ASTM A193 Material Chemical Composition
| Element | B7 (AISI 4140) | B8 (AISI 304) | B8M (AISI 316) |
|---|---|---|---|
| Carbon | 0.37 – 0.49% | 0.08% max | 0.08% max |
| Manganese | 0.65 – 1.10% | 2.00% max | 2.00% max |
| Phosphorus, max | 0.035% | 0.045% | 0.045% |
| Sulfur, max | 0.040% | 0.030% | 0.030% |
| Silicon | 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 | 0.15 – 0.25% | 2.00 – 3.00% |
ASTM A193 Fasteners Heat Treatment
To be heat treated, both ASTM A193 B7 and B7M fasteners should be quenched in a liquid media and then tempered. In the case of B7M fasteners, the last heat treatment, many times the tempering stage, although it is also indicated as required, should occur in any case once all the machining and forming is done including thread rolling and any cutting. Hardness testing, nondestructive inspection or ultrasonic tensioning may be performed on a surface prepared.
Unless otherwise specified, Grade B7 material may be heat-treated using furnace heating, induction heating, or electrical resistance methods.
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Request a QuoteFrequently Asked Questions About ASTM A193
The ASTM A193 specification is the international standard for high-performance bolting materials, specifically covering alloy steel and stainless steel studs and bolts. Its primary use is in demanding service conditions involving high temperatures or high pressures. Approved since 1936, this standard is heavily utilized across critical industrial sectors, most notably in petroleum and chemical construction applications, where joint integrity is essential.
ASTM A193 bolts are manufactured from various alloy and stainless steels, depending on the required grade. For example, Grade B6 bolts and rods are made from AISI 410 stainless steel which is quenched and tempered to enhance its strength. Since this is a stainless steel grade, it is frequently chosen for highly corrosive environments combined with elevated ambient temperatures.
The key difference lies in their intended application: ASTM A325 is the standard for heavy hex structural bolts primarily used in building construction, designed for shear strength. Because of this structural application, A325 bolts must always have a forged head and are manufactured in diameters from 1/2″ through 1-1/2”. In contrast, ASTM A193 covers bolts and studs designed specifically for high-pressure, high-temperature service (such as in power generation and chemical plants). A193 fasteners are commonly found securing pressure vessels, pipe flanges, and valve assemblies.
