Materials And Standards For Class 8.8 Bolts

Standards for Class 8.8 bolts do not specify a fixed material grade. They only define the allowable range of chemical composition. Any material whose chemical composition and mechanical properties after heat treatment meet standard requirements can be used to manufacture Class 8.8 high-strength bolts. In practical material selection, commonly used wire rod grades in the industry are taken as references for Class 8.8 bolt material selection.

To satisfy all performance indicators of Class 8.8 bolts, raw materials must undergo quenching and tempering heat treatment to achieve the following mechanical properties:

The nominal tensile strength of the bolt material reaches 800 MPa;

The yield-to-tensile ratio of the bolt material is 0.8;

The nominal yield strength of the bolt material reaches 800 × 0.8 = 640 MPa;

Class 8.8 hex head bolts can adopt wire rods such as 1035ACR (for M10 and below), 1040ACR (for M12 and above), CH38F, 1045ACR, 1039, 10B21, 10B33 and 10B38;

Class 8.8 socket head cap screws can adopt CH38F, 1039, 10B21 (for M10‑M12), 10B33 (for M14), 10B38 (for M12‑M24), 1035ACR (for M10 and below), 1040ACR (for M12 and above) and other wire rods;

Reference for wire rod selection of various carbon steel fasteners: Class 4.8 hex head bolts: 1008K, 1010, 1015K; Class 6.8 hex head bolts: 1032, 1035, 1040, CH38F, 1039; Class 8.8 hex head bolts: 1035ACR (for M10 and below), 1040ACR (for M12 and above), CH38F, 1045ACR, 1039, 10B21, 10B33, 10B38; Class 8.8 socket head cap screws: CH38F, 1039, 10B21 (for M10‑M12), 10B33 (for M14), 10B38 (for M12‑M24), 1035ACR (for M10 and below), 1040ACR (for M12 and above); Class 10.9 hex head bolts: 1045ACR, 10B38; Class 8 and higher nuts: 1015 (M＜16), CH38F (M≥16); Class 10 nuts: CH38F, 1039, 10B21, 10B33; Class 12 nuts: 1039, 10B21, 10B33, 10B38; Carriage bolts: 1008, 1010, 1015; Hex flange bolts: CH38F, 1039, 10B21, 10B33, 10B38; Hex wood screws: 1008K, 1010; Self-tapping screws, drywall screws, drill screws and plywood screws: 1018, 1022, CH22A.

A full understanding of material characteristics and performance standards for Class 8.8 bolts helps select raw materials properly to meet the application requirements of various engineering projects.