What types of screws typically require only quenching heat treatment

Screws that require high hardness and wear resistance while having moderate requirements for core toughness usually only need to undergo quenching heat treatment. These screws mainly include high-strength structural screws (such as 8.8-grade and above medium-carbon steel/alloy steel bolts), spring-type screws (such as 60-90 steel spring screws), and special-shaped fasteners like E-type bolts. Here is a detailed analysis:

High-strength structural screws: For example, bolts made of medium-carbon steel (such as 45# steel) or alloy steel (such as 40Cr, 35CrMo, 42CrMo) with a grade of 8.8 and above are commonly used in structural connections that bear high loads. These screws can obtain high-hardness martensite structures through quenching, significantly improving surface wear resistance and tensile strength. Meanwhile, core toughness is balanced through quenching and tempering (quenching + high-temperature tempering) to prevent brittle fracture.

Spring-type screws: Spring screws made of 60 steel, 70 steel, and high-carbon steels (80 steel, 90 steel) need to ensure high elastic limits, yield limits, and fatigue limits. Medium-temperature tempering (420-520℃) after quenching can form tempered troostite structures, combining high strength with good elasticity.

Special-shaped fasteners such as E-type bolts: E-type bolts (U-bolts or horseshoe-shaped bolts) are commonly used for fixing pipes, cables, etc. Quenching can significantly improve their wear resistance and tensile strength. By controlling the heating temperature (800-900℃), holding time, and quenching medium (water, oil, or salt bath), the hardening effect can be optimized. Subsequent tempering treatment reduces brittleness and stabilizes the structure.

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