ASME A193 B7 threaded rod is a high-end alloy steel bolt used in high-temperature and high-pressure environments. A193-B7 studs are often used in conjunction with A194-2H hexagonal heavy-duty nuts. They are commonly used in industries such as petrochemicals, boilers and pressure vessels, and pipe flanges, and conform to the ASTM A193 standard.
B7 and B7M refer to two different mechanical properties and chemical composition requirements for studs. B7M has stricter hardness requirements and lower mechanical strength compared to B7. They have excellent heat resistance and pressure resistance. This material allows B7 studs to maintain good stability even when subjected to high temperature and high pressure environments for extended periods.
B7M studs use the same material, but their hardness and strength are adjusted to meet the needs of different applications. It needs to be determined based on the specific work environment and requirements. If the project requires higher tensile strength and impact toughness, please select model B7; while when the project has special requirements for hardness and resistance to stress corrosion cracking, B7M studs will be a more suitable choice.
Materials
A193-B7 is made of chromium-molybdenum alloy steel (Cr-Mo steel), corresponding to US steel grades 4140 and 4142. Its performance is comparable to or even slightly superior to the commonly used 42CrMo material in China. The Mo (molybdenum) and Mn (manganese) content in B7 is slightly higher than that of ordinary 42CrMo steel, giving it better high-temperature strength, fatigue resistance, and tempering stability.
| Item | Material grade | Tensile strength(MPa) | Yield strength (MPa) | Elongation (%) | Hardness |
|---|---|---|---|---|---|
| A193-B7 | Chromium-molybdenum alloy steel(4140/42CrMo) | ≥ 861 | ≥ 724 | ≥ 16 | ≤ HRC 35 (≈ HB 235) |
| A193-B7M | Improved B7, with higher ductility | ≥ 689 | ≥ 551 | ≥ 18 | ≤ HRC 35 |
Characteristic
- High strength: excellent tensile and yield properties, can withstand high-pressure connection environment.
- High temperature resistance: suitable for high temperature working conditions below 450℃.
- Good toughness: maintain stable mechanical properties under impact load and thermal stress.
- Strong heat treatability: obtain uniform organization and properties through tempering treatment.
Heat Treatment Process
A193-B7 is usually Quenched & Tempered to ensure a balance between strength and toughness. The standard process is: Annealing → Tempering (Quenching + Tempering)
Surface Treatment
Native, blackened, galvanized, hot-dip zinc plated, nickel plated, cadmium plated, Dacromet, PTFE, fluoropolymer coated, Xylan 1424 coated and more.
Teflon Coated A193-B7 Threaded Studs
American Standard all-thread studs are required by ASME B 18.31.2 for procurement of American Standard Unified Inch Thread – Alloy Steel Bolt Material for High Temperature Use (SA 193, SA 453).
| Standard | Material Type & Grade | Normal Size (in.) | Length | Screw Thread | Mechanical Requirement | |||||
| σb (MPa) | σ0.2 (MPa) | δ4 (%) | ψ (%) | Hardness | ||||||
| ASME/ANSI B 16.5 ASME/ANSI B 18.2.1 ASME/ANSI B 1.1 | A 193 | B7 | ≤2.5 | According to order | UNC, 8UN Accuracy of thread Grade 2A | ≥860 | ≥725 | 16 | 50 | ≤HB321 |
| B7M | ≤2.5 | ≥690 | ≥550 | 18 | ≤HB235 | |||||
| B16 | ≤2.5 | ≥860 | ≥725 | ≤HB321 | ||||||
| B8/B8M/B8C/B8T (CL. 1) | All diameters | ≥515 | ≥205 | 30 | 50 | ≤HB223 | ||||
| B8/B8C/B8T (CL. 2) | ≤0.75 | ≥860 | ≥690 | 12 | 35 | ≤HB321 | ||||
| ＞0.75~1 | ≥795 | ≥550 | 15 | |||||||
| ＞1~1.25 | ≥725 | ≥450 | 20 | |||||||
| ＞1.25~1.5 | ≥690 | ≥345 | 28 | 45 | ||||||
| B8M (CL. 2) | ≤0.75 | ≥760 | ≥655 | 15 | 45 | |||||
| ＞0.75~1 | ≥690 | ≥550 | 20 | |||||||
| ＞1~1.25 | ≥655 | ≥450 | 25 | |||||||
| ＞1.25~1.5 | ≥620 | ≥345 | 30 | |||||||
| A 453 | 660 B | All diameters | ≥895 | ≥585 | 15 | 18 | HB248~341 | |||
A193-B7 Stud Features PTFE (Teflon®) Coating
- Excellent corrosion resistance: resistant to salt spray, acid and alkali and chemical media corrosion.
- Anti-seize performance: prevent threads from galling under high temperature and pressure.
- Low coefficient of friction: stable installation torque and controllable preload.
- Various colors available: blue, green, silver gray, etc. for easy identification of specifications or applications.
Teflon A193-B7 studs are the preferred solution for corrosion-resistant applications such as offshore platforms, petrochemical pipelines, marine equipment, and nuclear power plants.
American Standard A193-B7 Full Thread Stud Size Specifications
American Standard all-thread studs (Stud Bolt) implementation standards are:
ASME B18.31.2 – “Continuous Thread Studs for General Applications”
Commonly used matching thread standards:
Unified National Thread (UN) – UNC / UNF
| Size | 1/4 | 5/16 | 3/8 | 7/16 | 1/2 | 9/16 | 5/8 | 3/4 | 7/8 | 1 | 1-1/8 | 1-1/4 | 1-3/8 | 1-1/2 | 1-5/8 | 1-3/4 | 1-7/8 | 2 | 2-1/4 | 2-1/2 | 2-3/4 | 3 | 3-1/4 | 3-1/2 | 3-3/4 | 4 | ||||
| d | 0.25 | 0.3125 | 0.375 | 0.4375 | 0.5 | 0.5625 | 0.625 | 0.75 | 0.875 | 1 | 1.125 | 1.25 | 1.375 | 1.5 | 1.625 | 1.75 | 1.875 | 2 | 2.25 | 2.5 | 2.75 | 3 | 3.25 | 3.5 | 3.75 | 4 | ||||
| d | 0.25 | 0.3125 | 0.375 | 0.4375 | 0.5 | 0.5625 | 0.625 | 0.75 | 0.875 | 1 | 1.125 | 1.25 | 1.375 | 1.5 | 1.625 | 1.75 | 1.875 | 2 | 2.25 | 2.5 | 2.75 | 3 | 3.25 | 3.5 | 3.75 | 4 | ||||
| PP | UNC | 20 | 18 | 16 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 7 | 6 | 6 | – | 5 | – | 4-1/2 | 4-1/2 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | |||
| UNF | 28 | 24 | 24 | 20 | 20 | 18 | 18 | 16 | 14 | 12 | 12 | 12 | 12 | 12 | – | – | – | – | – | – | – | – | – | – | – | – | ||||
| 8UN | – | – | – | – | – | – | – | – | – | – | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | ||||
| u | Max | UNC | 0.1 | 0.111 | 0.125 | 0.143 | 0.154 | 0.167 | 0.182 | 0.2 | 0.222 | 0.25 | 0.286 | 0.286 | 0.333 | 0.333 | – | 0.4 | – | 0.444 | 0.444 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | ||
| UNF | 0.071 | 0.083 | 0.083 | 0.1 | 0.1 | 0.111 | 0.111 | 0.125 | 0.143 | 0.167 | 0.167 | 0.167 | 0.167 | 0.167 | – | – | – | – | – | – | – | – | – | – | – | – | ||||
| 8UN | – | – | – | – | – | – | – | – | – | – | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | ||||
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