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Black Oxide Alloy Steel Hex Head Bolts

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Introduction

Black oxide alloy steel hex head bolts are hexagon bolts made from alloy steel such as 40Cr or 42CrMo, heat treated to property class 10.9 or 12.9, and finished with a black oxide conversion coating plus oil. The coating adds almost no thickness, so the thread fit does not change, and the dark finish reduces glare. Corrosion resistance depends on the oil film, so the finish is chosen for indoor or lightly protected use.

Shanghai Soverchannel Industrial Co., Ltd. produces alloy steel hex bolts in M6 to M30 from its Nantong Jinzhai Hardware plant, with black oxide, phosphate and Dacromet finishes and heat-treatment records kept for each batch.

Specification

Specification

StandardDIN 931, DIN 933, ISO 4014, ISO 4017
MaterialAlloy steel, for example 40Cr or 42CrMo
Property class10.9 or 12.9
Surface finishBlack oxide with oil
ThreadMetric coarse or fine, tolerance 6g
Size rangeM6 to M30
Length20 mm to 300 mm
Coating thicknessNegligible, no change to thread fit
Use environmentIndoor, dry or oiled assemblies
NoteAdd oil or wax for extra protection during storage

Advantages

Applications

Machinery Assembly

Frames, gearbox housings, motor mounts and guards where a full thread gives maximum engagement.

Equipment Maintenance

Replacement bolts for pumps, conveyors and crushers, ordered by standard number and class.

Steel Framing

Brackets, base plates and light structural connections.

Automotive Chassis

Cross-members, subframe brackets and suspension mounts where class 8.8 is specified.

Agricultural Machinery

Implement frames and hitch assemblies exposed to dirt and vibration.

Core Features

  1. Hex head: standard wrench sizes allow fast tightening with common tools.
  2. Quenched and tempered core: delivers the 800 MPa tensile level required for class 8.8.
  3. Rolled thread: improves fatigue performance compared with cut threads.
  4. Gauge-checked threads: go and no-go gauges confirm fit before packing.

Frequently Asked Questions

What is the difference between DIN 933 and DIN 931?
DIN 933 is fully threaded, while DIN 931 has a plain shank section. Use DIN 933 for short grips or tapped holes, and DIN 931 when the unthreaded shank should carry shear load.
Is DIN 933 the same as ISO 4017?
Dimensions are very close and the two are used interchangeably in most orders. State both numbers on the purchase order and the drawing to avoid confusion at inspection.
Can I get class 8.8 bolts with a hot-dip galvanized finish?
Yes. Class 8.8 is generally accepted for hot-dip galvanizing. Nuts must then be tapped oversize so the thread still assembles.
What documents can be supplied with an order?
Material certificates, mechanical test reports and coating thickness records can be provided for each batch when requested at the quotation stage.
Why Global B2B Buyers Choose Our Fasteners

EN 10204 3.1 MTC

Every batch comes with full traceability, including material certificates, tensile strength, and hardness test reports to ensure smooth project acceptance.

500+ Tons/Month Capacity

Direct supply from our Nantong Jinzhai Hardware plant. Standard sizes (M8-M24) are kept in stock for 3-7 days rapid dispatch.

100% Thread Gauge Check

Strict go/no-go gauge inspection after thread rolling guarantees perfect 6g tolerance fit, eliminating the risk of stripped threads.

OEM/ODM Flexibility

Support custom lengths, special head shapes, fine threads, and head marking (Logo/Grade) with fast CAD drawing confirmation.

Export Standard Packaging Pallet

Export-Standard Packaging & Logistics

We understand the harsh conditions of international shipping. Our packaging is designed to prevent rust, damage, and customs delays.

  • ISPM 15 Fumigation-Free Wooden Pallets: Meets global customs quarantine requirements for hassle-free clearance.
  • Heavy-Duty Cartons + Inner PE Liner: Double protection against high humidity and salt spray during ocean freight.
  • Customized Shipping Marks: Clear, durable labels with your company info, item number, and quantity for easy warehouse counting.
  • Transparent Packing Data: We provide exact CBM, GW, and carton dimensions in the quotation to help you calculate shipping costs accurately.
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About Us
Shanghai Soverchannel Industrial Co., Ltd.
Shanghai Soverchannel Industrial Co., Ltd. is a manufacturer integrating R&D, production, and sales, focusing on providing high-precision non-standard and standard fastening solutions for customers. China Black Oxide Alloy Steel Hex Head Bolts ManufacturersOEM/ODM Black Oxide Alloy Steel Hex Head Bolts Manufacturers and China Black Oxide Alloy Steel Hex Head Bolts Manufacturers. The company has been deeply engaged in the automotive fastener industry for many years. It owns its own manufacturing plant, Nantong Jinzhai Hardware Co., Ltd., and has accumulated solid technical strength and rigorous quality control experience.

Our main products cover various high-quality bolts, nuts, steel processing parts, welding components, and customized special-shaped parts. China Black Oxide Alloy Steel Hex Head Bolts Manufacturers. Relying on advanced production equipment and a full-process inspection system, we are not only capable of mass-producing high-standard parts but also excel in customizing non-standard bolts and complex special-shaped components according to specific customer requirements. Over the years, we have always adhered to technology-driven development and earned trust through quality, becoming a reliable partner for numerous customers in the automotive and industrial fields.
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