Introduction

Grade 8.8 Bolts are high tensile steel fasteners manufactured for structural and machinery applications. They provide stable load-bearing performance and prevent loosening or failure under heavy stress and vibration.

Technical Parameters

Strength Grade:	8.8
Tensile Strength:	≥ 800 MPa
Yield Strength:	≥ 640 MPa
Material:	Carbon or alloy steel
Hardness:	22–32 HRC
Standard:	ISO, DIN, ASTM, GB
Size Range:	M6 – M36
Surface Finish:	Black oxide, zinc plated, HDG

Key Features

Heat Treated Carbon Steel

Quenched and tempered steel structure provides controlled hardness and reduces risk of brittle fracture under stress and vibration.

6g Precision Thread Fit

Manufactured to 6g tolerance for smooth engagement with nuts, reducing installation issues and improving assembly efficiency.

Hydrogen Embrittlement Control

Post-plating baking process reduces internal stress and helps prevent delayed cracking in high-strength applications.

Customization Services

Head Style:	Hex head, Socket head, Flange head, Countersunk head
Size:	Diameter and length (custom range)
Thread:	Coarse thread, Fine thread
Material:	Carbon steel, Alloy steel
Surface Treatment:	Zinc plated, Hot-dip galvanized, Black oxide
Marking:	Logo stamping available
Packaging:	Bulk packaging, Carton packaging, OEM labeling

Applications

Automotive:

Engines, chassis, and suspension systems.

Wind Energy:

Connecting turbine blades and towers.

Heavy Machinery: Excavators, cranes, and bulldozers.

Steel Construction: Bridges, warehouses, and skyscraper skeletons.

Railway:

Track laying and locomotive assembly.

Quality Control

Quality Inspection Includes:

Raw material spectrometer testing.

Dimensional inspection during production.

Hardness testing after heat treatment.

Tensile strength testing according to ISO 898-1.

Final visual and surface inspection before packaging.

FAQ

Q: What is the main structural advantage of Grade 8.8 bolts?

A: They provide a balance between tensile strength and ductility, reducing risk of brittle failure under dynamic loads.

Q: Can Grade 8.8 bolts be used in load-bearing steel structures?

A: Yes, they are widely used in steel frames, bridges, and machinery where controlled load distribution is required.

Q: How is the strength of Grade 8.8 bolts achieved?

A: Through quenching and tempering heat treatment, which adjusts hardness and improves mechanical stability.

Q: Can they be used with standard nuts and washers?

A: Yes, they are designed for full compatibility with standard metric fastening systems.

Q: What is your production capacity?

A: Capacity is structured for continuous mass production with flexible scheduling for bulk orders.

Q: What shipping methods are available?

A: Sea freight is the main option for bulk orders, with palletized export packaging for safe transportation.

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Grade 8.8 Bolts