Fasteners are a universal component used for mechanical connection and fixation. The heat treatment process for fasteners is divided into two processes: heating and cooling. Reasonable control of each process can achieve the desired heat treatment quality.

(1) For bolts, studs, screws, nuts, and non-standard parts with ML35 (32, 40) as the main components, due to the issue of material hardenability, quenching media with faster cooling speed should be selected during the heat treatment process to meet the requirements of hardness, metallographic structure, and mechanical properties of the parts during quenching.

① When the product specifications are M4~M16, 3%~5% KR6480 polymer water-based quenching agent can be selected. If 35 and 35S steel is selected, it can be relaxed to M18~M20.

② When the product specification is M10~M24, 8%~10% KR7280 water-soluble quenching agent can be selected.

③ When the product specification is greater than M24, 10% to 15% KR7280 water-based quenching agent can be selected.

④ When the product is mainly made of 45 steel, KR6480 or KR7280 can be selected based on the size of the product.

(2) The quenching medium used for bolts, studs, screws, nuts, and non-standard shaped parts mainly composed of 35CrMo, 40Cr, 20MnTiB, etc. is as follows.

① The products are mainly made of 35CrMo and 40Cr, and can choose KR118 fast quenching oil or 5%~10% KR6480 polymer water-soluble quenching agent.

② The main products are 20MnTiB and 35VB, and quenching agents such as KR7280 or KR6480 can be selected.

(3) Shallow carburized self tapping screws, pins, etc., mainly made of low-carbon steel materials such as 10, 15, 20, 20Cr, 1018, 1022, 10B21, etc., can use quenching agents such as KR6480 or KR118.

(4) Spring washers, retaining rings, etc. mainly made of 65Mn, 60Si2Mn, 70 steel, etc., can use KR118 rapid quenching oil.

(5) There are many types of products with a large size span, and KR1188 or KR6480 can be selected, which can meet the quenching and carburizing quenching quality of all alloy steels and carbon steels of a certain size.