| Customization: | Available |
|---|---|
| Material: | Stainless,Carbon,Alloy |
| Type: | Hexagon Head |
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There are several grades within the A193 specification. Each grade possesses unique chemical requirements, strength requirements, testing requirements, and applications. This website summarizes the similarities and differences between many of the grades. For more specific information, please refer to the actual ASTM A193 specification which can be purchased directly from ASTM International.
| Bolt Grade | Nuts | Washers |
|---|---|---|
| B7 | A194 Grade 2H | F436 |
| B8 Class 1 | A194 Grade 8 | SS304 |
| B8M Class 1 | A194 Grade 8M | SS316 |
| B8 Class 2 | A194 Grade 8 | SS304 |
| B8M Class 2 | A194 Grade 8M | SS316 |
| Element | 2, 2H, and 2HM | 4 | 7 and 7M (AISI 4140) | 8 (AISI 304) | 8M (AISI 316) |
|---|---|---|---|---|---|
| Carbon | 0.40% min | 0.40 - 0.50% | 0.37 - 0.49% | 0.08% max | 0.08% max |
| Manganese | 1.00% max | 0.70 - 0.90% | 0.65 - 1.10% | 2.00% max | 2.00% max |
| Phosphorus, max | 0.040% | 0.035% | 0.035% | 0.045% | 0.045% |
| Sulfur, max | 0.050% | 0.040% | 0.040% | 0.030% | 0.030% |
| Silicon | 0.40% max | 0.15 - 0.35% | 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 | 0.20 - 0.30% | 0.15 - 0.25% | 2.00 - 3.00% |
ASTM A193 Grade B7 bolts and threaded studs are manufactured from a chromium-molybdenum steel and are quenched and tempered (heat treated) to develop the desired mechanical properties (strength). Grade B7 is the most common grade of A193 bolts used in construction. B7 threaded studs and short, headed bolts are readily available in the marketplace. Grade B7 bolts are commonly used in pipe flange connections. These bolts are typically bought and sold in a plain, bare metal finish but are often hot-dip galvanized, zinc plated, Xylan coated, PTFE coated, or otherwise coated for corrosion resistance. Note that coated bolts may not be able to withstand the high temperatures that uncoated B7 bolts can be subjected to.
| Grade | Size | Tensile ksi, min | Yield, ksi, min | Elong, %, min | RA % min | HBW | HRC |
|---|---|---|---|---|---|---|---|
| B7 | Up to 2-1/2 | 125 | 105 | 16 | 50 | 321 max | 35 max |
| 2-5/8 - 4 | 115 | 95 | 16 | 50 | |||
| 4-1/8 - 7 | 100 | 75 | 18 | 50 |
ASTM A193 Grade B8 Class 1 bolts and threaded studs are manufactured from AISI 304 stainless steel. Type 304 is the most common grade of stainless steel used in the fastener industry. Fasteners manufactured using this austenitic stainless steel require carbide solution treatment on bars to be threaded or after the heading operation for bolts with forged heads. Carbide solution treatment, also referred to as solution annealing, is a process in which fasteners or stainless bars are heated and then water-quenched to assure maximum corrosion resistance. A193 Grade B8 Class 2 bolts are strain hardened after carbide solution treatment to achieve increased strength characteristics and reduce the potential for galling. Class 2 bolts are marked "B8SH" with the grade symbol underlined.
| Grade | Size | Tensile ksi, min | Yield, ksi, min | Elong, %, min | RA % min | HBW | HRC |
|---|---|---|---|---|---|---|---|
| B8 Class 1 | All | 75 | 30 | 30 | 50 | 223 max | 96 max |
| B8 Class 2 | Up to 3/4 | 125 | 100 | 12 | 35 | 321 max | 35 max |
| 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 |
ASTM A193 Grade B8M Class 1 fasteners are similar to Grade B8 but instead are manufactured from AISI 316 stainless steel as opposed to AISI 304 stainless steel. Type 316 stainless offers superior corrosion resistance to type 304 stainless due to the added molybdenum. Grade B8M Class 1 fasteners require carbide solution treatment, while Class 2 fasteners require an additional strain hardening operation which increases the strength and reduces the susceptibility to galling. Class 2 fasteners are marked "B8MSH" with the grade symbol underlined.
| Grade | Size | Tensile ksi, min | Yield, ksi, min | Elong, %, min | RA % min | HBW | HRC |
|---|---|---|---|---|---|---|---|
| B8M Class 1 | All | 75 | 30 | 30 | 50 | 223 max | 96 max |
| B8M Class 2 | Up to 3/4 | 110 | 95 | 15 | 45 | 321 max | 35 max |
| 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 Grade B7M bolts and studs are identical in chemistry to Grade B7 (quenched and tempered medium carbon alloy steel), but have lower strength requirements and require 100% hardness testing of all fasteners manufactured in the lot. Grade B7M bolts resist chloride, sulfide, and hydrogen stress corrosion cracking (SCC) and are frequently used in sour gas service.
| Grade | Diameter | Tensile ksi, min | Yield, ksi, min | Elong, %, min | RA % min | HBW | HRC |
|---|---|---|---|---|---|---|---|
| B7 | Up to 4 | 100 | 80 | 18 | 50 | 235 max | - |
| Over 4 - 7 | 100 | 75 | 18 | 50 |
Grade variations of the A193 specification which are rarely used and therefore not addressed on this site include: B6X, B8A, B8C, B8CA, B8MA, B8M2, B8M3, B8P, B8PA, B8N, B8NA, B8MN, B8MNA, B8MLCuN, B8MLCuNA, B8r, B8RA, B8S, B8SA, B8LN, B8LNA, B8MLN, B8MLNA, B8CLN, B8CLNA, B8T, and B8TA.
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