ASTM A193/A193M
ASTM A193/A193M fasteners are designed for bolted joints exposed to elevated temperatures, high pressures, and demanding service conditions. Rather than being a single material grade, ASTM A193/A193M covers a range of alloy steel and stainless steel grades, allowing the fastener material and mechanical properties to be selected according to the requirements of the application. Common grades include B7 and B7M for alloy steel applications, B8 and B8M for stainless steel applications, and B16 for elevated-temperature service.
Our ASTM A193/A193M fasteners include stud bolts, threaded rods, heavy hex bolts, and socket screws, available in different dimensions and configurations to suit various bolted-joint designs. The dimensional requirements, material chemistry, and mechanical property requirements that are important when selecting A193/A193M fasteners, helping engineers and purchasers compare grades and choose the appropriate fastener for their service conditions.
Specification:
| Item | Specification |
|---|---|
| Standard | ASTM A193/A193M |
| Product Type | Stud Bolts, Heavy Hex Bolts,Socket Screw,Threaded Rod |
| Dimension Standard | ASME B18.31.2, ASME B 18.2.1,ASME B 18.3, ASME B 18.31.3 |
| Thread | UNC,UNF,8UN |
| Thread Standard | ASME B1.1 |
| Thread Class | 1A,2A,3A |
| Material | Alloy Steel,Stainless Steel |
| Steel Property Class | A193 B7, A193 B7M,A193 B16, |
| Stainless Steel Class | A193 B8, A193 B8M |
| Surface Treatment | Black Oxidation, Zinc Plated, HDG, Bright Finish,Passivation |
| Inspection | Dimension,Thread,Mechanical Proeprty,Coating |
Dimension Standard:
ASTM A193/A193M specifies the material, chemical composition, and mechanical property requirements for high-temperature and high-pressure bolting, while the dimensional requirements depend on the type of fastener being supplied. Selecting the appropriate dimensional standard helps ensure that the fastener has the correct diameter, length, head dimensions, thread configuration, and other features required for installation and assembly.
For different A193/A193M fastener types, the applicable dimensional standards may include ASME B18.31.3 for stud bolts, ASME B18.31.2 for threaded rods, ASME B18.2.1 for heavy hex bolts, and ASME B18.3 for socket screws. These standards provide the dimensional framework for the corresponding fastener configurations, while the ASTM A193/A193M grade determines the required material and mechanical performance.
Chemical Composition:
The chemical composition of an ASTM A193/A193M fastener is closely related to its material grade and the service conditions for which it is selected. Instead of treating all A193 fasteners as the same material, the grade identifies a specific alloy or stainless steel chemistry with different characteristics. For example, A193 B7 fasteners are manufactured from chromium-molybdenum alloy steel commonly associated with AISI 4140/4142, while B8 fasteners are based on AISI 304 stainless steel and B8M fasteners on AISI 316 stainless steel. The addition of elements such as chromium, nickel, and molybdenum gives these materials different combinations of strength, corrosion resistance, and high-temperature performance.
The chemical composition table below provides the specified limits for the principal elements in each grade, allowing engineers and purchasers to verify the material requirements against mill test reports (MTRs) and select the appropriate grade for their application.
| Class | Carbon | Manganese | Phosphorus | Sulfur | Silicon | Chromium | Molybdenum | Nickel |
| B7 | 0.37-0.49 | 0.65-1.1 | ≤0.035 | ≤0.04 | 0.15-0.35 | 0.75-1.2 | 0.15-0.25 | - |
| B7M | 0.37-0.49 | 0.65-1.1 | ≤0.035 | ≤0.04 | 0.15-0.35 | 0.75-1.2 | 0.15-0.25 | - |
| B16 | 0.36-0.47 | 0.45-0.7 | ≤0.035 | ≤0.04 | 0.15-0.35 | 0.8-1.15 | 0.5-0.65 | - |
| B8 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 18-20% | - | 8-11% |
| B8M | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 16-18% | 2-3% | 10-14% |
Mechanical Proeprty:
A193 B7 Stud Bolts
A193 B7 stud bolts are chromium-molybdenum alloy steel fasteners known for their high tensile and yield strength. They are commonly supplied in quenched-and-tempered condition and provide the strength and hardness required for demanding bolted joints, particularly in pressure equipment and high-temperature service.
A193 B8 Stud Bolts
A193 B8 stud bolts are austenitic stainless steel fasteners commonly manufactured from AISI 304 stainless steel. Their mechanical performance is characterized by good tensile strength, ductility, and toughness, with the specified properties depending on the product size and material condition.
A193 B8M Stud Bolts
A193 B8M stud bolts are austenitic stainless steel fasteners commonly manufactured from AISI 316 stainless steel. Their mechanical properties provide a balance of strength and ductility, while the molybdenum-containing alloy composition also contributes to the material’s resistance to localized corrosion and chloride-containing environments.
A193 B16 Stud Bolts
A193 B16 stud bolts are chromium-molybdenum-vanadium alloy steel fasteners developed for high-strength applications and elevated-temperature service. Compared with conventional carbon or alloy steel bolting, the specified alloy composition and heat treatment provide the strength, hardness, and temperature capability required for demanding applications.
The table below summarizes the specified mechanical property requirements for A193 B7, B8, B8M, and B16, including tensile strength, yield or proof strength, elongation, reduction of area, and hardness.
| Class | Diameter | Tensile Strength(ksi) | Yield Strength 0.2% offset(ksi) | Elongation in 4 D（%） | Reduction of Area(%) | Hardness |
| B7 | ≤2-1/2” | ≥125 | ≥105 | ≥16 | ≥50 | ≤321 HB or 35HRC |
| 2-1/2“-4” | ≥115 | ≥95 | ≥16 | ≥50 | ≤321 HB or 35HRC | |
| 4“-7” | ≥100 | ≥75 | ≥18 | ≥50 | ≤321 HB or 35HRC | |
| B7M | ≤4” | ≥100 | ≥80 | ≥18 | ≥50 | ≤235 HB or 99HRB |
| 4“-7” | ≥100 | ≥75 | ≥18 | ≥50 | ≤235 HB or 99HRB | |
| B16 | ≤2-1/2” | ≥125 | ≥105 | ≥18 | ≥50 | ≤321 HB or 35HRC |
| 2-1/2“-4” | ≥110 | ≥95 | ≥17 | ≥45 | ≤321 HB or 35HRC | |
| 4“-7” | ≥100 | ≥85 | ≥16 | ≥45 | ≤321 HB or 35HRC | |
| B8(Class1) | ≥75 | ≥30 | ≥30 | ≥50 | ≤223 HB or 96HRB | |
| B8M(Class1) | ≥75 | ≥30 | ≥30 | ≥50 | ≤223 HB or 96HRB | |
| M8(Class2) | 3/4"-1" | ≥115 | ≥80 | ≥15 | ≥35 | ≤321 HB or 35HRC |
| 1"-1-1/4" | ≥105 | ≥65 | ≥20 | ≥35 | ≤321 HB or 35HRC | |
| 1-1/4"-1-1/2" | ≥100 | ≥50 | ≥28 | ≥45 | ≤321 HB or 35HRC | |
| B8M(Class2) | 3/4"-1" | ≥100 | ≥80 | ≥20 | ≥45 | ≤321 HB or 35HRC |
| 1"-1-1/4" | ≥95 | ≥65 | ≥25 | ≥45 | ≤321 HB or 35HRC | |
| 1-1/4"-1-1/2" | ≥90 | ≥50 | ≥30 | ≥45 | ≤321 HB or 35HRC |