Specialised analysis of spring steel wire heat treatment technology-Hongfeng New Material

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Specialised analysis of spring steel wire heat treatment technology

Dec 09,2024

In order to improve the performance of spring steel wire, people nowadays come up with a variety of ways is to achieve a certain effect. In this article, we discuss the different forming methods of spring steel wire heat treatment.
Root forming method of spring steel wire manufacturing can be divided into cold forming and hot forming (also known as strengthening after forming and forming after strengthening) two categories.
1. Cold forming spring steel heat treatment
For small springs, such as wire diameter of less than 8 mm below the coil spring or spring steel strip, etc., can be strengthened in the heat treatment or cold deformation strengthening after forming, that is, with cold drawn wire cold roll forming. Cold-drawn steel wire has high strength, which is the use of cold-drawn deformation of steel to produce work hardening and obtain. Cold-drawn spring steel wire according to its strengthening process can be divided into three kinds of cases.
(1) lead bath isothermal quenching cold drawn steel wire. To be the coil first cold drawn to a certain size, in the heating to Ac3 +80 ~ 100 austenitising, isothermal quenching in a lead bath in 450 ~ 550 has been obtained fine lamellar pearlitic organisation and then many times cold-drawn to the required diameter. By adjusting the amount of carbon in the steel and cold-drawn type variable (type variable up to 85 ~ 90%), in order to the high strength and a certain degree of plasticity of the spring steel wire. This lead quenching and drawing treatment is actually a kind of deformation heat treatment, that is, the pearlitic body want to change after deformation, can make the steel wire strength of 3000MPa or so.
(2) cold-drawn steel wire. This steel wire is mainly through the deformation of cold-drawn and strengthened, but with the lead quenching cold-drawn steel wire is different, it is in the middle of the cold-drawn process to join a about 680 degrees of intermediate spheroidal annealing to improve the plasticity of the steel wire to continue to cold-drawn to the required final size, the strength of its strength is lower than that of the lead quenching cold-drawn steel wire strength. Spring steel wire 丨 Shandong spring steel wire 丨 galvanized spring steel wire 丨 steel wire manufacturer 丨 grand steel wire rod products Co.
(3) quenched and tempered steel wire: this steel wire is cold-drawn to the final size, and then quenched and tempered at medium temperatures to strengthen the final cold roll forming. The disadvantage of this strengthening process is more complex, and lead quenching and cold-drawn steel wire strength than low.
By the above three methods of strengthening the steel wire in the cold roll forming must be added a low-temperature tempering process, the tempering temperature of 250 ~ 300, tempering time of 1 hour. The purpose of low-temperature tempering is to eliminate stress, stabilise the size, and improve the elastic limit. In practice, the steel wire has been found to have been strengthened in the cold roll-forming elastic limit is often not high, this is because the cold roll-forming will be easy to move for the wrong number of increase, and because of the Bausch & Lomb effect caused by the beginning of the plastic resistance to reduce. Therefore, in the cold roll forming must be carried out after a low-temperature tempering, has caused more changes in the process, improve the elastic limit.
2. Heat treatment of hot formed spring
Hot forming springs is generally a combination of quenching and hot forming, that is, the heating temperature is slightly higher than the quenching temperature, hot roll forming after heating, and then use the residual heat quenching, and finally 350 ~ 450 degrees of medium temperature tempering, so as to obtain the tempered quartzite organisation. This is a deformation heat treatment process, can effectively improve the elastic limit and fatigue life. General automotive large leaf springs are used in this way. Neutral coil springs can also be formed under cold, and then quenched and tempered.
In order to give full play to the performance potential of spring steel, in the spring heat treatment should be noted that the following three elements
(1) spring steel is mostly silicon-manganese steel, silicon has the role of promoting decarburisation, manganese has the role of promoting grain growth. Surface decarburisation and grain growth military just fatigue strength greatly reduced, so the heating temperature, heating time and heating medium should pay attention to the choice and control. Such as the use of salt furnace rapid heating and heating under the condition of protective atmosphere. After quenching should be tempered as soon as possible to prevent delayed fracture.
(2) tempering temperature is generally 350 ~ 450 degrees. If the steel surface condition is good (such as by grinding), should be selected with a low-limit temperature tempering; Conversely, the upper limit of the temperature can be tempered to improve the toughness of steel, reduce the sensitivity of surface defects.
(3) spring steel with high silicon content, steel is easy to produce graphite in the process of retreat, to which attention must be paid. General steel into the factory required to test the graphite content.

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