24 July 2021 Precision Alloys
4j50 Precision Alloy Steel Bar
4J50 precision alloy steel, iron nickel fixed expansion alloy is obtained by adjusting the nickel content in a given temperature range with the expansion coefficient of different soft glass and ceramic match a series of fixed-expansion alloy its expansion coefficient and Curie point with the nickel content Increase and increase. The group of gold is widely used in the vacuum industry sealing structure materials.
Organizational structure
1,4J50 Phase transition temperature:
2,4J50 Time - Temperature - Tissue Transition Curve:
3,4J50 alloy structure: the group of gold are stable austenitic tissue.
4,4J50 Grain size: The grain size of the alloy deep-drawn zone should not be less than 7, the grain size of less than 7 must not exceed 10% of the area. When the average grain size of the strip less than 0.13 mm in thickness is estimated, the number of grains along the thickness of the strip shall not be less than eight.
Process performance
1,4J50 Formability: The alloy is very cold and hot. Hot processing temperature should not be too high, heating time should not be too long, should avoid heating in a sulfur-containing atmosphere. When the tape cold strain rate greater than 75%, will cause plastic anisotropy after annealing. Cold strain rate of 10% to 15%, heated to 950 ~ 1050 ℃ (during the brazing process) significant grain growth, resulting in reduced plasticity of the alloy, the thin section may also lose the metal vacuum tightness . Therefore, the final product strain rate should be controlled at about 60% [2,5].
2,4J50 Welding performance: The alloy has good welding performance, brazing and spot welding. The alloy should be pre-oxidized before sealing with soft glass and other materials.
3,4J50 parts heat treatment process: heat treatment can be divided into: stress relief annealing, intermediate annealing and pre-oxidation treatment.
(1), stress relief annealing: In order to eliminate the residual stress in the machined parts to be stress relief annealing: 430 ~ 540 ℃, heat 1 ~ 2h, furnace cooling or air cooling.
(2), intermediate annealing: In order to eliminate the alloy in the cold-rolled, cold drawn, cold stamping process caused by the hardening phenomenon in order to facilitate the continued processing. Workpieces to be in a vacuum or protective atmosphere, heated to 700 ~ 800 ℃, holding 30 ~ 60min, and then furnace cooling, air cooling or water quenching.
(3), pre-oxidation treatment: The combination of gold for the sealing material used, before the seal should be pre-oxidation treatment. The alloy surface to generate a layer of uniform thickness, dense oxide film. The parts were heated in saturated wet hydrogen at 1100 ° C for 30 min and then oxidized in air at about 800 ° C for 5-10 min. Weight gain of 0.1 ~ 0.3mg / cm2 is appropriate.
The group of gold can not be hardened with heat treatment.
4,4J50 Surface treatment: Before heat treatment, welding or glass sealing, the metal surface dirt and grease must be removed. Serious oxide layer can be used when sandblasting or immersion in the molten alkali, and then pickling. Slight oxide scale with 25% hydrochloric acid solution at 70 ℃ pickling.
5,4J50 Machining and Grinding Properties: This alloy is similar in machinability to austenitic stainless steel. When processing high-speed steel or carbide cutting tools, low-speed machining, cutting coolant can be used. Grinding performance is good.