Grade 8 nuts need heat treatment? First of all, it is necessary to distinguish between DIN934 and ISO4032. ISO4032 is revised on the standard of DIN934. The nut thickness of the standard is increased, and the specified nut holding load increases with the increase of the specification. For example, the grade 8 nut is increased from 840mpa to 920mpa
The mechanical properties
The mechanical properties of nuts are also different. DIN934 is required according to din267-4, while ISO4032 is in accordance with DIN ISO 898-2
Now there are DIN934 true grade 8 and false grade 8 on the market, and the key is according to which mechanical performance requirements.
The main difference is material and heat treatment.
For example, the ordinary DIN934 below grade 8 is Q195. If grade 8 is required, 35K steel must be selected and heat treatment must be carried out.
So what is the main difference between true 8 and false 8 in the production process?
Grade 8 is made of 35K steel with heat treatment. The false grade 8 is also made of 35K steel, but no heat treatment is carried out. A false grade 8 can not guarantee the mechanical property and safety performance. Therefore, the price of Grade 8 nuts without heat treatment will be more than 10% cheaper. And most of the finished products will crack.
How to select the true grade 8 nut
First of all, look at the Marking on the nut. Generally, the marking below grade 8 is s | 8 | while the marking of true grade 8 is S8, in which S stands for steel.
If you want to ensure that S8 type is true grade 8 nut, it is necessary to carry out laboratory testing of mechanical properties, to see whether its load and hardness meet the requirements.
The heat treatment
The heat treatment of nut means that the nut is heated, insulated, and cooled in a certain medium, and its performance is controlled by changing the surface or internal structure of the metal material.
Heat treatment is one of the important processes in mechanical manufacturing. Compared with other processing technologies, heat treatment generally does not change the shape and chemical composition of the bending workpiece but improves the performance of the workpiece by modifying the internal microstructure or chemical composition of the workpiece surface. Its characteristic is to improve the internal quality of the workpiece, which is generally not visible to the naked eye.
In order to make the metal nut have the required mechanical properties, physical properties, and chemical properties, in addition to the reasonable selection of materials and various forming processes, heat treatment is essential. Steel is the most widely used material in the mechanical industry. The microstructure of steel is complex and can be controlled by heat treatment.
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