ASTM · ASTM A193 M / ASME SA193 M

ASTM A193 / ASME SA 193 Specification: High-Temperature Fasteners

Technical Overview of the ASTM/ASME A/SA 193 Standard

The ASTM/ASME A/SA 193 specification establishes strict requirements for alloy and stainless steel fasteners designed for use in high-pressure and high-temperature equipment (flanged joints, valves, pressure vessels). According to this standard, the fastener category includes studs, bolts, screws, rods, and wire. Initial bar stock must be hot-rolled, with the option for subsequent calibration (cold drawing) or centerless grinding. Austenitic steel grades must undergo mandatory heat treatment in the form of solution annealing or a combination of annealing and strain hardening.

EV Group China recommends selecting a specific steel grade based on design loads, operating environment conditions, temperature range, and required mechanical properties.

Note 1: The standard includes the 15 most common steel grades. Other alloys may be added to the specification as needed.

Note 2: For fasteners made of carbon or alloy steels intended for moderate temperatures, the requirements of specification A 354 should be used.

Note 3: For low-temperature operating conditions, refer to specification A 320 / A 320M.

Matching nuts for these fasteners are regulated by specification A 194 / A 194M. Additional technical requirements S1–S10 apply exclusively upon special request when placing an order.

The specification uses both the imperial system (inch-pound) and the metric system (SI). These systems are independent; mixing values from different systems is not permitted, as this leads to non-compliance with the standards.

Production Technology

Steel for EV Group China fasteners is manufactured using open-hearth, basic-oxygen, or electric-arc furnace melting, as well as the vacuum induction melting (VIM) method. Secondary refining and vacuum degassing of the melt are permitted. Basic-oxygen melting is limited to steels with a chromium content of up to 6%.

Heat Treatment Requirements

Ferritic steels undergo heat treatment to achieve optimal high-temperature properties. After hot deformation (rolling or forging), the workpieces are cooled to below the critical temperature. To stabilize the structure, the products are reheated for grain refinement followed by quenching. Grade B16 undergoes heat treatment in the temperature range of 925–954°C (1700–1750°F) followed by oil quenching. The tempering temperature regime is determined for each steel grade according to tabular values.

Chemical Composition of ASTM A193 / A193M Steel Grades

Mechanical Properties

For austenitic steels, the class is determined by the heat treatment method. Classes 1 and 1D undergo solution annealing. Class 1A is processed after final machining for maximum corrosion resistance. Class 2 undergoes strain hardening.

For bar stock with a diameter exceeding 90 mm (3 1/2 inches), an increase in carbon content up to 0.50% is permitted for grades B7 and B7M.

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