Valve quenching-tempering chromium-silicon alloy spring steel wire (YB/T5105-1993)
Quenching and tempering is one of the most commonly used surface hardening methods for valve springs. Quenching is achieved by rapidly cooling the steel from austenitic area (high temperature zone) to martensite transformation area (relatively low temperature zone). As the quenching temperature approaches martensite transformation temperature, the steel material will shrink and harden abruptly, and then enter the temperature range called tempering. The main purpose of tempering is to eliminate or reduce the structural residual stress, to refine the metal grains. Chromium-silicon alloy spring steel wire is a kind of steel belonging to metal material, which is widely used in valve manufacturing industry.
YB/T5105-1993 has strict requirements on chromium-silicon alloy spring steel wire used in valve manufacturing industry. The raw materials used are smelted in electric furnace, static furnace, oxygen converter, vacuum furnace or other equipment, and then joined in the process of descending and forming. After decarburization and incremental sizing, it is further processed into products of various sizes by galvanized drawing, in order to meet the requirements of valve industry for physical tensile strength, elongation and using radius of steel wire and other performance indicators.
The production process of chromium-silicon alloy spring steel wire mainly includes steel making, hot rolling, cold drawing and heat treatment. Generally, the melting process will be adjusted according to the chemical composition of the steel. The smelting temperature of chromium-silicon alloy spring steel wire is generally 1550 ~ 1700℃. After the steel material is heated to the required temperature, it is heated to a higher temperature for annualizing or normalizing. The purpose of annualizing is to reduce the size deviation of steel material, refine the crystal grain, improve its cutting process and mechanical properties, and improve its impact toughness. After the hot rolling, cold drawing process and heat treatment, it will reach the requirements of YB/T5105-1993.
The quenching and tempering processes of chromium-silicon alloy spring steel wire mainly include quenching annealing and tempering annealing. Quenching is the process of cooling the steel quickly from high temperature to low temperature. This process can improve the strength, hardness and wear resistance of steel, but at the same time, the steel material may be softened and the workload of subsequent heat treatment is increased. Therefore, it is necessary to carry out tempering afterward.
The tempering process of chromium-silicon alloy spring steel wire is generally carried out at the temperature range of 340℃~700℃ for a period of time. According to different materials, the tempering temperature, tempering time and tempering process are different. Through the tempering process, the materials tensile strength, yield strength, flexural strength, hardness, fatigue strength and other properties can be enhanced, and its conductivity, electrical properties, toughness and wear resistance can also be improved.
In order to ensure high quality of chromium-silicon alloy spring steel wire and meet the technical requirements of YB/T5105-1993, strict control should be done in the whole quenching and tempering repair process, such as quenching process control, control of tempering temperature, control of tempering time, control of tempering atmosphere, control of tempering speed, etc. In addition, strict inspection should be done in the whole production process and the quality of products should meet the requirements of relevant standards, so as to ensure the good performance of products and meet the requirements of customers for production and manufacture of valve springs.
