Frequently asked questions about high-strength screws!

With the development and progress, the industry has higher and higher requirements for high-strength screws. At present, the development prospects of high-strength screws are good, but there are still some problems in domestic high-strength screws. It is understood that there are the following main problems.

1.?1. Make sure the load and wedge load are not up to standard. Proof load and wedge load are the key A items to evaluate the mechanical properties of products under tensile load. Especially important for high-strength high-strength screws. The proof load is used to evaluate the resistance of a product to plastic deformation under a specified tensile load. If the index does not meet the requirements, plastic deformation may occur due to the preload and working load, thereby reducing the preload and loosening the connection. The wedge load test is an evaluation of the tensile strength of the bolt product and the connection strength of the head rod. This index does not meet the standards. Under the action of large loads, especially impact loads, or when the supporting surface is subjected to local loads, it will break or turn around, resulting in connection failure and even safety accidents.

2. The hardness is unqualified. Hardness is also an important indicator for evaluating the mechanical properties of high-strength titanium screws. The materials used in each performance class vary. When selecting high-strength screws, the mechanical performance level is an important basis. When installing and using, the working load and installation torque should be determined according to the performance level. For specific materials, the hardness should be controlled at a reasonable level, high hardness can reduce the fatigue resistance of the product. In order to improve the strength of the product, some enterprises control the hardness at a higher level, resulting in some products exceeding the standard.

3. The decarburization layer exceeds the standard, and the decarburization layer is also a class A project. Due to decarburization, the surface hardness and strength of the parts are greatly reduced, which seriously affects the surface contact strength and fatigue life of high-strength screws, especially the damage of threaded parts. The main The reason is decarbonization of raw materials, decarbonization of material transformation and decarbonization of product heat treatment.

4. The size is too bad. High-strength screw is a general-purpose component, which requires high interchangeability, and its size difference will directly affect its interchangeability, and even affect its connection strength, loosening resistance or service life. The main reason for the unqualified size is improper process control. In order to save materials, the control part size is close to the lower limit, the equipment is not adjusted in time during the production process, and the out-of-tolerance mold is used. Qualified approval; the third is that the dosage cannot be regularly measured and verified, and even a gauge that exceeds the wear limit is used.