Screw heat treatment, we are also called screws hardened. Screws have iron and stainless steel screws. Iron generally requires a little harder hardness. All need to be hardened. However, stainless steel screws rarely need to be hardened. Because of its hardness, it can be hard enough. The following describes iron heat treatment methods.
First, heat treatment: According to the object and purpose can choose different heat treatment.
Quenched and tempered steel: high temperature tempering after quenching (500-650°C)
Spring steel: Tempered after tempering (420-520°C)
Carburizing steel: quenched after carburizing and then tempered at low temperature (150-250°C)
After the low-carbon and medium-carbon (alloy) steels are quenched into martensite, the general rule is that the strength decreases with increasing tempering temperature, while the plasticity and toughness increase. However, due to the different carbon content in the low and medium carbon steels, the tempering temperature has different effects on them. Therefore, in order to obtain good overall mechanical performance, the following approaches can be taken:
(1) Select low-carbon (alloy) steel and perform quenching at a low temperature below 250°C to obtain low-carbon martensite. In order to improve the surface wear resistance of such steels, only the carbon content of each surface layer is increased, that is, surface carburizing, generally referred to as carburizing structural steel.
(2) Carbon steel with high carbon content is used, quenched and then tempered at a high temperature (500-650°C) (so-called quenching and tempering treatment) so that it can maintain sufficient strength under high plasticity conditions. This kind of steel is quenched and tempered steel. If you want to get high strength, you would rather reduce the plasticity and
Toughness can be tempered at low temperatures for a low-carbon, gold-containing quenching and tempering, and so-called "ultra-high-strength steels" are obtained.
(3) Steels with carbon content between medium and high carbon (such as 60, 70 steel) and some high carbon steels (such as 80, 90 steel), if used to make springs, in order to ensure high elasticity Limits, yield limits, and fatigue limits are tempered after tempering.
Second, the work process:
(A), quenched and tempered steel:
1. Preheating treatment: normalizing -> annealing (pearlite steel) -> high temperature tempering (martensite steel)
(1) The purpose of normalizing is to refine grains, reduce the degree of banding in the structure, and adjust the hardness to facilitate machining. After normalizing, the steel has equiaxed fine grains.
2. Quenching: The steel body is heated to about 850°C for quenching. The quenching medium can be selected according to the size of the steel and the hardenability of the steel. Generally, water or oil or even air quenching can be selected. The steel in the quenched state has low plasticity and large internal stress.
3, tempering:
(1) In order to make steels with high plasticity, toughness, and appropriate strength, steels are tempered at high temperatures around 400-500°C. Steels that are more sensitive to temper brittleness must be rapidly cooled after tempering to suppress tempering. The occurrence of brittleness.
(2) If the part is required to have a particularly high strength, tempering is performed at about 200°C to obtain a medium-tempered tempered martensite structure.
(b) Spring steel:
1. Quenching: Oil quenching at 830-870°C.
2. Tempering: Tempering around 420-520°C to obtain tempered troostite.
(III) Carburizing steel:
1. Carburizing: A kind of chemical heat treatment refers to infiltrating C elements into the surface of steel parts in a certain medium with a certain chemical element at a certain temperature. Preheating (850°C) Carburizing (890°C) Diffusion (840°C)
2. Quenching: carbon and low-alloy carburizing steels, generally using direct quenching or once quenching.
3. Tempering: Tempering at low temperature to eliminate internal stress and improve the strength and toughness of the carburized layer. The tempering temperature of our dental screw production is about 360°C, and the self-drilling screws (wallboard nails) are tempered at about 200°C, and then cooled to 34-35°C and 39-40°C, respectively.
Screws are hardened, screws are heat-treated, and general screw SMEs do not have the heat treatment plant of the company. Usually need to send to the professional screw and hard factory to do. Therefore, our company producing screws attaches great importance to the choice of heat treatment plant. To choose a reasonable price, the screw after heat treatment is of high quality