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| Customization: | Available |
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| Material: | ASTM A193 Grade B7 (AISI 4140/4142) |
| Type: | Hexagon Head |
| Shipping Cost: | Contact the supplier about freight and estimated delivery time. |
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| Item | Specification |
|---|---|
| Product Name | ASTM A193 Grade B7 Heavy Hex Bolt |
| Dimension Standard | ASME B18.2.1 |
| Material Grade | ASTM A193 B7 (Chromium-Molybdenum Alloy Steel, AISI 4140/4142) |
| Surface Finish | Blue White Zinc Plated |
| Certificate | EN 10204 3.1 MTC (Chemical Composition, Mechanical Properties, Hardness) |
| Size Range | 1-3/4" to 4-7/8" |
| Matching Nut | ASTM A194 Grade 2H Heavy Hex Nut |
What is ASTM A193 Grade B7
A193 B7 is the workhorse grade for high-temperature and high-pressure bolting, specified in the vast majority of carbon steel piping classes across all ASME pressure classes from 150 to 2500
.B7 bolts are manufactured from AISI 4140 or 4142 chromium-molybdenum steel, quenched and tempered at a minimum of 593°C to develop the required combination of strength and toughness
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Chemical Composition
| Element | Composition (%) |
|---|---|
| Carbon (C) | 0.38 - 0.48 |
| Manganese (Mn) | 0.75 - 1.00 |
| Phosphorus (P) max | 0.035 |
| Sulfur (S) max | 0.040 |
| Silicon (Si) | 0.15 - 0.35 |
| Chromium (Cr) | 0.80 - 1.10 |
| Molybdenum (Mo) | 0.15 - 0.25 |
Mechanical Properties
| Diameter Range | Yield Strength (min) | Tensile Strength (min) | Hardness |
|---|---|---|---|
| Up to 2-1/2" | 105 ksi (724 MPa) | 125 ksi (862 MPa) | 235-331 HB |
| Over 2-1/2" to 4" | 95 ksi (655 MPa) | 115 ksi (793 MPa) | 235-331 HB |
| Over 4" to 7" | 75 ksi (517 MPa) | 100 ksi (690 MPa) | 235-331 HB |
Temperature Limits
| Condition | Temperature |
|---|---|
| Maximum continuous service | 450°C (840°F) |
| Minimum without impact test | -29°C (-20°F) |
Above 450°C, B7 loses yield strength rapidly due to tempering effects. For temperatures above 450°C, use A193 B16. For temperatures below -29°C, use A320 L7
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Your size range 1-3/4" to 4-7/8" corresponds to ASME B18.2.1 heavy hex bolt dimensions. Below is the reference dimension table for the relevant sizes:
| Nominal Size | Width Across Flats (in) | Head Height (in) |
|---|---|---|
| 1-3/4" | 2.750 | 1.094 |
| 2" | 3.125 | 1.219 |
| 2-1/4" | 3.500 | 1.375 |
| 2-1/2" | 3.875 | 1.531 |
| 2-3/4" | 4.125 | 1.688 |
| 3" | 4.625 | 1.812 |
| 3-1/4" | 4.875 | 1.938 |
| 3-1/2" | 5.250 | 2.062 |
| 3-3/4" | 5.625 | 2.188 |
| 4" | 6.000 | 2.312 |
Note: Full dimension table available as PDF attachment or referenced directly from ASME B18.2.1
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Blue White Zinc Plated
This is an electrodeposited zinc coating per ASTM B633 for corrosion protection
The coating is applied with pre- and post-coating treatment to reduce the risk of hydrogen embrittlement
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Important Note on Zinc Plating and High Strength Steel
ASTM B633 states that high strength steels having a tensile strength greater than 1700 MPa (247 ksi) should not be zinc electroplated due to hydrogen embrittlement risk
A193 B7 bolts typically have tensile strength below 125 ksi (862 MPa), well below this threshold. However, if your application requires NACE MR0175 compliance, zinc plating is generally not recommended because NACE service requires a maximum hardness of 22 HRC, and the plating process may introduce hydrogen
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Certificate Content
EN 10204 3.1 is an inspection certificate issued by the manufacturer's authorized representative, based on specific inspection of the actual delivered product . It must include:
Chemical composition: Heat number level chemical analysis
Mechanical properties: Tensile strength, yield strength, elongation, reduction of area
Hardness test: Actual hardness values of finished bolts
Heat number traceability: Complete traceability from heat number to finished product
Heat treatment condition
Purpose of Certificate
Large buyers need the 3.1 certificate for incoming inspection and project audits. Without a 3.1 certificate, the buyer cannot prove material compliance to the end user or EPC . For bolting in pressure piping, 3.1 is the industry standard certificate type
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Flange Connection
Heavy hex bolts are the standard fastener for ASME B16.5 and B16.47 flanged joints. The heavy hex head provides a larger bearing surface than standard hex bolts, distributing the clamping load more evenly across the flange face and reducing the risk of flange face damage
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Matching Recommendation
| Bolt Grade | Matching Nut | Service |
|---|---|---|
| A193 B7 | A194 2H | General high-temp (up to 450°C) |
| A193 B7M | A194 2HM | Sour service (NACE MR0175) |
For NACE MR0175 / H2S service, B7M with hardness max 22 HRC and 2HM nuts are required
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Not for NACE Service: Standard A193 B7 has a hardness range of 235-331 HB (approximately 22-35 HRC). NACE MR0175 requires maximum 22 HRC for carbon and low-alloy steels in sour service.For H2S environments, specify B7M with 2HM nuts.
Temperature Limit: B7 is suitable for continuous service up to 450°C. For higher temperatures, use B16.
Certificate Type: EN 10204 3.1 certificate must be based on the actual shipped batch. Do not use test data from other batches.
Shanghai G&T Industrial Co., Ltd., located in Jing'an District, Shanghai, offers OEM/ ODM services for fasteners. With over 20 years of experience in the production and export of high-quality standard fasteners, non-standard parts, which are widely used in various fields such as high-speed rail, ships, nuclear power, new energy, mechanical equipment, petrochemicals, aerospace, etc.
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