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Hex Head Bolt China Manufacturer
QS Fastener: Hex Head Bolt China Manufacturer
Name: Hex Head Bolt China Manufacturer
Standard: ASME
Material: SA193 B7
Size: 5/16 to 4 inch
Thread: 8 UN
Length: 30 to 1000 mm
Grade: 10.9
Price: USD 2.25 - 6.99/ Kg
MOQ: 10kg
Customization: yes
Delivery time: 7-30 Day
Application: Oil Pipeline, Machinery, Chemical Industry, Building
Standard: ASME
Material: SA193 B7
Size: 5/16 to 4 inch
Thread: 8 UN
Length: 30 to 1000 mm
Grade: 10.9
Price: USD 2.25 - 6.99/ Kg
MOQ: 10kg
Customization: yes
Delivery time: 7-30 Day
Application: Oil Pipeline, Machinery, Chemical Industry, Building
Quantity
As a senior fastener engineer, I can confirm that this Hex Head Bolt from a leading China Manufacturer is engineered for mission-critical bolting applications. It is manufactured from SA193 B7 chromium-molybdenum alloy steel, strictly in accordance with ASME B18.2.1, and is available in diameters from 5/16” to 4” (with full M6–M60 customization) and lengths from 30 to 1,000 mm. The 8 UN precision thread profile ensures consistent engagement and load transfer, making it the preferred choice for high-integrity joints in oil pipelines, chemical plants, heavy machinery, and structural steelwork.
Material & Heat Treatment
The alloy is subjected to a controlled quenching (850–900°C) and high-temperature tempering (600–650°C) cycle, producing a fine tempered sorbite microstructure with a Rockwell hardness of HRC 32–39. This delivers a minimum tensile strength of 861 MPa and yield strength of 723 MPa, meeting Grade 10.9 per ISO 898-1. An additional aging treatment at 300–400°C for 4–6 hours promotes Cr₂₃C₆ carbide precipitation at grain boundaries, ensuring that tensile strength retention remains ≥90% even at 450°C – a critical factor for high-temperature flange sealing. Vacuum degassing tightly controls carbon (0.38–0.48%), chromium (1.0–1.5%), and molybdenum (0.15–0.25%), while limiting sulfur and phosphorus to avoid temper embrittlement.
The alloy is subjected to a controlled quenching (850–900°C) and high-temperature tempering (600–650°C) cycle, producing a fine tempered sorbite microstructure with a Rockwell hardness of HRC 32–39. This delivers a minimum tensile strength of 861 MPa and yield strength of 723 MPa, meeting Grade 10.9 per ISO 898-1. An additional aging treatment at 300–400°C for 4–6 hours promotes Cr₂₃C₆ carbide precipitation at grain boundaries, ensuring that tensile strength retention remains ≥90% even at 450°C – a critical factor for high-temperature flange sealing. Vacuum degassing tightly controls carbon (0.38–0.48%), chromium (1.0–1.5%), and molybdenum (0.15–0.25%), while limiting sulfur and phosphorus to avoid temper embrittlement.
Mechanical Performance & Quality Assurance
Per ASTM F606, M20 test specimens achieve a fracture load ≥120 kN with elongation ≥12%, and yield point scatter is maintained within ±3% using the 0.2% offset method (DIN EN ISO 6892-1). The black oxide coating (Fe₃O₄, 8–12 μm thick) provides consistent lubrication, stabilizing the torque coefficient between 0.12–0.16 (DIN 946), so preload deviation stays ≤±10% – significantly reducing leakage risks in high-pressure flange connections. Wedge load testing shows no cracking at 120% proof load, confirming compliance with ASME B18.2.1. Charpy V-notch impact energy at -20°C exceeds 45 J (EN ISO 148-1), guaranteeing ductile behavior and brittle fracture resistance even in low-temperature environments.
Per ASTM F606, M20 test specimens achieve a fracture load ≥120 kN with elongation ≥12%, and yield point scatter is maintained within ±3% using the 0.2% offset method (DIN EN ISO 6892-1). The black oxide coating (Fe₃O₄, 8–12 μm thick) provides consistent lubrication, stabilizing the torque coefficient between 0.12–0.16 (DIN 946), so preload deviation stays ≤±10% – significantly reducing leakage risks in high-pressure flange connections. Wedge load testing shows no cracking at 120% proof load, confirming compliance with ASME B18.2.1. Charpy V-notch impact energy at -20°C exceeds 45 J (EN ISO 148-1), guaranteeing ductile behavior and brittle fracture resistance even in low-temperature environments.
Sourcing & Supply
This China Manufacturer offers flexible customization, competitive pricing at USD 2.25–6.99/kg, a low MOQ of 10 kg, and lead times of 7–30 days – delivering a reliable, cost-effective solution for heavy-duty bolting requirements worldwide.
This China Manufacturer offers flexible customization, competitive pricing at USD 2.25–6.99/kg, a low MOQ of 10 kg, and lead times of 7–30 days – delivering a reliable, cost-effective solution for heavy-duty bolting requirements worldwide.
FAQ
Q1: What is the maximum operating temperature for this black oxide coated Hex Head Bolt?
The bolt maintains ≥90% of its tensile strength up to 450°C, thanks to the aging strengthening process and Cr₂₃C₆ carbide precipitation. For short-term peaks, it can withstand up to 500°C, but sustained exposure above 450°C is not recommended without additional surface protection.
The bolt maintains ≥90% of its tensile strength up to 450°C, thanks to the aging strengthening process and Cr₂₃C₆ carbide precipitation. For short-term peaks, it can withstand up to 500°C, but sustained exposure above 450°C is not recommended without additional surface protection.
Q2: Can this Hex Head Bolt be customized to non-standard lengths or diameters beyond the listed range?
Yes. Although the standard offering covers 5/16” to 4” and M6 to M60, the China Manufacturer supports full-size customization, including special lengths, reduced shanks, or modified thread run-out, subject to engineering review and minimum order quantity.
Yes. Although the standard offering covers 5/16” to 4” and M6 to M60, the China Manufacturer supports full-size customization, including special lengths, reduced shanks, or modified thread run-out, subject to engineering review and minimum order quantity.
Q3: How does the black oxide coating affect torque-tension relationship during installation?
The black oxide layer (8–12 μm thick) provides a stable friction coefficient, yielding a torque coefficient of 0.12–0.16 per DIN 946. This ensures preload scatter within ±10%, allowing more accurate hydraulic or manual torqueing without the need for additional lubricants in most cases.
The black oxide layer (8–12 μm thick) provides a stable friction coefficient, yielding a torque coefficient of 0.12–0.16 per DIN 946. This ensures preload scatter within ±10%, allowing more accurate hydraulic or manual torqueing without the need for additional lubricants in most cases.
Q4: What quality documentation is provided with shipments from this China Manufacturer?
Each lot is accompanied by a material test certificate (EN 10204 Type 3.1 or 3.2), dimensional inspection reports, hardness and tensile test records, and a wedge load test certificate – all traceable to heat numbers and compliant with ASME, ASTM, and ISO standards.
Each lot is accompanied by a material test certificate (EN 10204 Type 3.1 or 3.2), dimensional inspection reports, hardness and tensile test records, and a wedge load test certificate – all traceable to heat numbers and compliant with ASME, ASTM, and ISO standards.
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