Correct Selection of Quenching Medium in Heat Treatment of Fasteners

July 20, 2023

Fasteners are a general-purpose component used for mechanical connection and fixation. It has the characteristics of rich types, complex shapes and sizes, and various materials.
Fasteners are widely used in many industries such as machinery, automobiles, aviation, aerospace, construction, transportation, communications, electronic appliances, etc. Each industry has various requirements for fasteners, including different comprehensive mechanical properties . The comprehensive mechanical properties of fasteners are mainly determined by the selected materials and heat treatment quality, so it is imperative to strictly and reasonably select materials and improve the level and quality of heat treatment.

Heat treatment is divided into two processes of heating and cooling, and the ideal heat treatment quality can be obtained by scientifically controlling the two processes respectively. Reasonable selection and scientific use of quenching medium is the essence of controlling the cooling process. The following is the company's long-term service experience in the fastener heat treatment industry to share with you.

1. Bolts, studs, screws, nuts and special-shaped non-standard parts, mainly ML35 (32, 40), etc., due to the problem of material hardenability, such parts should use a quenching medium with a faster cooling rate during heat treatment , so as to meet the requirements of the hardness, metallographic and mechanical properties of parts quenched. I. The product size is M4-Ml 6, you can choose 3-5% KR6480 polymer water-soluble quenching agent, if you choose 35#, 35A, 35S can be relaxed to M18--M20. II. The product size is M10~M24, you can choose 8~10% KR7280 water-soluble quenching agent. III. If the product size is larger than M24, 10~15% KR7280 water-soluble quenching agent can be selected. IV, the main product is 45#, you can choose KR6480 or KR7280 according to the size of your product. 2. 35CrMo, 40Cr, 20MnTiB, 35VB and other bolts, studs, screws, nuts and special-shaped non-standard parts I. If your products are mainly 35CrMo and 40Cr, you can choose KR118 rapid quenching oil or 5-10% KR6480 polymer water-soluble quenching agent. Ⅱ. If your products are mainly 20MnTiB and 35VB, you can choose KR7280 or KR6480. Three, low carbon steel 10#, 15#, 20#, 20Cr, 1018, 1022, 10B21 and other materials can choose KR6480 or KRll8 for shallow carburized self-tapping screws and pins 4. KRl18 rapid quenching oil can be used for spring washers and retaining rings mainly made of 65Mn, 60Si2Mn, and 70. 5. There are many types of products, and KR118 or KR6480 can be selected for large size spans (which can meet the quenching and carburizing quenching of all alloy steels and carbon steels of a certain size). The internal quality of the workpiece depends on the quality of heat treatment. Quenching medium plays a decisive role in heat treatment, but it is the smallest piece of heat treatment production cost. As long as you pay a little attention to quenching medium and choose professional and reliable products, you can enjoy professional consultation and after-sales service. To the unexpected effect, and greatly reduce the overall production cost.

How much role does post-weld heat treatment of steel structure bolts play?

Steel structure bolts | During the welding process, due to the unevenness of heating and cooling, as well as the restraint or external restraint of the member itself, welding stress will always be generated in the member after the welding work is completed. The existence of welding stress in the component will reduce the actual bearing capacity of the welded joint area, produce plastic deformation, and even lead to the destruction of the component in severe cases. ??Post-weld hydrogen elimination treatment refers to the low-temperature heat treatment performed after the welding is completed and the weld has not been cooled below 100°C. The general specification is to heat to 200~350°C and keep warm for 2-6 hours. The main function of post-weld hydrogen elimination treatment is to accelerate the escape of hydrogen in the weld seam and the heat-affected zone, and it is extremely effective in preventing welding cracks in low-alloy steel welding. ?? Stress relief heat treatment is to make the welded workpiece in high temperature state, its yield strength decreased, to achieve the purpose of relaxing welding stress. There are two commonly used methods: one is the overall high temperature tempering, that is, put the weldment as a whole into the heating furnace, slowly heat it to a certain temperature, then keep it warm for a period of time, and finally cool it in the air or in the furnace. In this way, 80%-90% of welding stress can be eliminated. Another method is local high-temperature tempering, that is, only heating the weld seam and its surrounding area, and then cooling slowly to reduce the peak value of welding stress, so that the stress distribution is relatively gentle, and the purpose of partially eliminating welding stress is achieved.

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