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Do you know the spring wire standard?

Date of release:2019-04-18 00:00:00 Author: Click:

The current national and industry recommended standards of carbon spring steel wire are divided into two types:




1. Cold-drawn spring steel wire




One is cold deformation steel wire, also known as cold drawn spring steel wire. The cold-drawn carbon spring steel wire is firstly treated with lead quenching to obtain sostenite structure, and then the surface is phosphorized and drawn to the finished size with a large surface reduction rate. The steel wire structure is fibrous, with high tensile strength and elastic limit, and good bending and torsion performance. Cold drawn spring steel wire is the most widely used spring steel wire with high dimensional precision, clean surface, no oxidation and decarbonization defects, stable fatigue life.




2, oil quenching and tempering steel wire




Another type of carbon spring steel wire is martensite steel wire, also known as oil quenching and tempering steel wire. Carbon steel wire through quenching and tempering treatment, can obtain good comprehensive mechanical properties, when the steel wire specification is smaller (≤2.0mm), the oil quenching and tempering steel wire of the strength indicators of the bisochronic treatment after cold drawn steel wire is lower. When the steel wire specification is larger (≥6.0mm) sostenitized steel wire is unlikely to use a large surface reduction rate to obtain the required strength index, and oil quenched and tempered steel wire as long as completely quenched can obtain higher performance than cold drawn steel wire. Under the same tensile strength, martensite steel wire has higher elastic limit than cold deformation steel wire. The microstructure of cold-drawn steel wire is fibrous and anisotropic, and the microstructure of oil-quenched and tempered steel wire is uniform tempered martensite, which is almost isotropic. At the same time, the anti-relaxation property of oil-quenched and tempered steel wire is better than that of cold-drawn steel wire, and the service temperature (150 ~ 190℃) is also higher than that of cold-drawn steel wire (≤120℃). Large specification oil quenching, tempering steel wire has a tendency to replace cold drawn steel wire.




Carbon steel wire




The application range and process characteristics of various types of carbon spring steel wire are introduced according to the standards below.




(1) YB/ t5220-93 carbon spring steel wire for non-mechanical spring




The standard is applicable to carbon spring steel wire for non-mechanical springs such as sofa cushion spring, seat cushion, backrest tension spring, clamp spring, etc. Steel wire is divided into A1, A2, A3 according to different tensile strength requirements. A9 nine groups, each group steel wire regardless of size according to a range of strength supply, tensile strength deviation ≤200Mpa. The A1, A2 and A3 groups are used to make lower stress springs. A3, A4 and A5 are used to make general stress springs. The A7, A8 and A9 are used to make higher stress springs. Mattress springs are generally selected in A3 and A4 groups.




The steel wire of A1-A3 group is generally made of 45 ~ 70 steel, 65Mn or 70 steel of A3 ~ A6 group, 70 or T8MnA (82B) steel wire of A7 ~ A9 group. Because the steel wire supplied according to this standard is basically used to make static spring, the fatigue life requirements are relatively loose, steel wire can be used to control rolling control cold cold strip directly drawn finished products. Steel wire pre-forming heat treatment can also be used to replace the lead bath treatment. At the same time, converter steel is allowed to be used as raw material.




(2) GB/ t4357-89 carbon spring steel wire




This standard is the universal standard of cold drawn carbon spring steel wire, which is mainly used to make static spring working under various stress states. Steel wire can be supplied in three grades according to the working stress state of spring: class B for low stress spring, class C for medium stress spring, and class D for high stress spring. Finished steel wire test tensile strength, torsion, winding and bending four properties.




This standard steel wire is mainly used to make static mechanical spring, the vibration frequency of its service period is higher than that of non-mechanical spring, there are certain requirements on fatigue life, and the finished product also increases the assessment of torsional performance. Therefore, the wire rod should be smelted by electric furnace or electric furnace + out-of-furnace refining method, and the wire rod in P≤0.030%, S≤0.020%, etc. If free ferrite is contained in the microstructure of finished steel wire, the fatigue life of the spring will be reduced. In general, 5% ~ 1.5% free ferrite is stored in the cold-cut strip controlled by rolling control, so it is not suitable to use wire rod to produce finished steel wire directly. In principle, the steel wire supplied according to this standard should be treated with lead bath to eliminate free ferritic tissue before forming, and the finished steel wire microstructure should be fibrotic sostenite tissue.




(3) GB/ t4358-1995 carbon spring steel wire for important USES




The steel wire supplied according to this standard is mainly used to make dynamic springs operating under various stress conditions. According to the working stress state of the spring, the steel wire can be supplied in three groups: group E is suitable for the dynamic spring with medium stress, group F is suitable for the dynamic spring with high stress, and group G is suitable for the dynamic spring with high fatigue life. Finished steel wire test tensile strength, torsion, winding, bending and decarbonization five performance indicators.




Because the steel wire supplied according to this standard is used to make dynamic spring under medium and high stress conditions, the finished steel wire must take into account the fatigue limit and the fatigue life of the spring in addition to maintaining high elastic limit and good toughness index. Therefore, the purity of steel, nonmetal inclusion and gas content, ferrite content and surface decarbonization degree have higher requirements. Steel wire wire rod must be smelted by electric furnace + off-furnace refining method, which has higher requirements on the chemical composition of wire rod: P≤0.025%, S≤0.020%, Cr ≤0.10%, Ni≤0.15% (0.12%), Cu≤0.20%. In actual production, in order to improve fatigue life, Mn is usually controlled at the high limit. Group E chooses 70 or 70Mn (72B), group F chooses T8MnA or T9RtA, and group G chooses 65Mn (Mn can be adjusted to 0.9-1.2%) or 67B. The purpose of reducing the content of P and S in steel, increasing the content of Mn and refining outside furnace is to reduce the content of non-metal inclusion in steel, improve the form of inclusion and reduce the content of gas, and improve the fatigue limit and fatigue life. If there is free ferrite in the microstructure of steel wire, the fatigue life will be greatly reduced. Steel wire supplied according to this standard must be treated with lead quenching before forming.




Group G steel wire is used to make valve spring working in the state of severe vibration, which has high requirements on fatigue life. Therefore, 65Mn wire rod with better toughness is selected. Although the tensile strength has decreased somewhat, the fatigue life is more guaranteed. Steel wire surface decarburization, formation of ferrite organization seriously affect the fatigue performance, the standard of group G wire increases the decarburization layer inspection, provisions shall not be greater than 1.0% total decarburization layer depth d, but for large size wire (Φ > 4.0 mm) by the ratio of surface restriction, decarburization layer from hot rolled wire rod is difficult to eliminate, standard supplementary provisions: "the consent of the buyer can supply the decarburization layer, and no more than 1.5% diameter d wire".




(4) gjb1497-92 specification for carbon spring steel wire for special purpose




On certain occasions, spring has beyond the conventional requirements of spring, spring, such as gun is easy to carry and use, the spring of the space is very small, stretch to is enough big, must choose high tensile strength and toughness is better to make the spring steel wire, the special use carbon spring steel wire is adapt to the needs of the standard.




The standard provides that steel wire can be supplied in groups a, b and c. Group c is suitable for high stress spring, group b is suitable for high stress spring, and group a is suitable for super high stress spring. T9A, T10A and T8MnA are recommended for steel wire. In fact, the tensile strength of steel wire increases with the increase of carbon content, and the torsion performance (toughness index) decreases with the increase of carbon content. Considering comprehensively, the three steel wire companies in dalian of liaoning special steel group choose T9A steel wire with rare earth to produce group a, b and c steel wire. The finished steel wire is examined for six performance indexes: tensile strength, torsion, torsional fracture, winding, tensile strength uniformity and dimensional uniformity. The mechanical properties of common specifications are shown in table 6.




It should be pointed out that the ultra-high tensile strength of steel wire is obtained at the expense of part of plasticity and fatigue life, which is only suitable for making springs with simple shape and low fatigue life requirements.




(5) YB/ t5103-93 oil quench-tempered carbon spring steel wire




The oil quenched and tempered steel wire is first produced to the finished size, and then the oil quenched and tempered steel wire is processed to the tempered martensite for delivery. The uniformity of structure is an important index to determine the performance of oil-quenched and tempered steel wire. Due to the limited hardenability of carbon spring steel wire, the core of steel wire with too large specifications cannot be completely transformed into martensite after quenching and tempering, so the standard stipulates that the supply diameter of oil-quenched and tempered carbon spring steel wire is less than 12.0mm.




Compared with cold-drawn carbon spring steel wire, the tensile strength and elastic limit of oil-quenched and tempered steel wire with diameter ≤2.0mm are lower than that of cold-drawn steel wire. But large size wire (6.0 mm) Φ acuity sorbite after processing, can't use large ratio of surface drawing for high tensile strength, and as long as oil quenching tempering steel wire completely hardening, can obtain higher tensile strength than cold-drawn steel wire. Even under the same tensile strength condition, the elastic limit of oil-quenched and tempered steel wire is higher than that of cold-drawn steel wire.




The anisotropy of cold-drawn spring steel wire is obvious, while the oil quenched and tempered steel wire is almost homogeneous. The fatigue life and stress relaxation performance of oil-quenched and tempered steel wire are much better than that of cold-drawn steel wire, with higher working temperature (150 ~ 170℃) and better creep resistance. In addition, the oil quenching and tempering steel wire straight degree is good, the steel wire spring straight after the opening roll, almost no bending, winding spring forming performance is better. Therefore, oil quenched and tempered carbon spring steel wire almost replaced the cold drawn carbon spring steel wire in industrial developed countries.




(6) YB/ t5102-93 valve oil quenched and tempered carbon spring steel wire




The relationship between YB/ t5102-93 and YB/ t5103-93 is equivalent to that between GB/ t4358-1995 and GB/ t4357-89. The former is used to make dynamic springs, while the latter is a universal standard and is mainly used to make static springs. Since dynamic oil quenching and tempering spring requires more strict uniformity of structure and limited hardenability of carbon steel, YB/T5102 provides smaller supply specifications (diameter ≤6.0mm).




Valve oil quenching and tempering carbon steel wire use range and quality control requirements are basically the same as GB/ t4358-1995 G group, here will not be repeated.




Alloy steel wire




Our three kinds of alloy spring steel wire, alloy spring steel wire, oil quenching tempering silicon-manganese spring wire, valve oil quenching tempering chromium silicon alloy spring steel wire, alloy spring from the developed countries use current situation, the proportion of oil quenching tempering steel wire is more and more big, the Japanese industrial standard (JIS) regulation, alloy spring steel wire all at oil quenching tempering state. [3]




(1) GB/ t5218-1999 alloy spring steel wire




The standard will be the original gb5218-85 "silicon manganese spring steel wire", gb5219-85 "chromium vanadium spring steel wire" and gb5221-85 "chromium silicon spring steel wire" three standards into a standard.




The standard is suitable for making alloy spring steel wire for high and medium stress spring. The steel wire winding spring can only be used after quenching and tempering after forming.




The standard lists 60Si2MnA, 50CrVA and 55CrSiA steel Numbers, and also stipulates that other steel wires can be supplied according to the requirements of the buyer.




Steel wire is generally delivered in cold drawn state, finished product diameter ≤5.0mm tensile strength b≤1035Mpa, diameter >5.0mm steel wire HB≤302, equivalent to light tensile state. Cuhk specifications (Ф > 8.0) in the finished cold drawn surface reduction rate is less than 25%, small wires (Ф 5.0) or less degressive rate less than 30%. The delivery wire in annealed state is too soft, which is easy to produce dead bending. When winding the spring, the spring often has bad shape and uneven pitch. It is difficult to form rough spring when the steel wire is too hard and the spring rebound when winding. Therefore, the direct winding spring of steel wire to the light state of supply the most suitable. For steel wire repurchase and cold processing (such as flattening, rolling into shaped section, etc.), it is recommended to choose annealed delivery steel wire.




In order to ensure the performance of winding spring, the finished steel wire is wound test. The diameter ≤5.0mm steel wire is wound 6 times on the mandle-rod which is equivalent to 1 ~ 2 times of the diameter of steel wire, and shall not be broken or broken.




Decarbonization and surface defects seriously reduce the fatigue life of springs, which must be strictly controlled. Especially 60Si2MnA and 55CrSi, which contain high silicon content, are easy to decarbonize when annealing. Low temperature and long time annealing process are recommended for spheroidization annealing of wire rod and recrystallization annealing of semi-finished products. As mentioned before, high fatigue life requirements of the spring, must choose polished steel wire, but need to distinguish between annealing or cold pull polished. When the 50CrV soft steel wire is polished, the grinding chips are easy to adhere to the surface of the steel wire and form irregular small white spots. Therefore, cold pull polishing process is adopted as far as possible to reduce the surface "white spots".




Under the condition of surface quality assurance, the inclusion content becomes the most important factor affecting the fatigue life, so the standard stipulates that non-metallic inclusions and graphite carbon test can be added when required by the buyer.




(2) YB/ t5104-93 oil quenching-tempering silicomanganese alloy spring steel wire




After the use of oil quenching and tempering alloy spring steel wire spring, do not need to conduct quenching and tempering treatment, as long as the cold drawn carbon spring steel wire for stress relief treatment can be used, popular, the diameter of 14.0mm alloy spring more and more use of these two standards.




YB/ t5104-93 is available in 3 categories, class A for static springs with medium load, class B for dynamic springs with medium load and medium fatigue life, and class C for dynamic springs with high stress, such as automobile suspension springs.




(3) YB/ t5105-93 "valve oil quenching - tempering chromium silicon alloy spring steel wire".




YB/ t5105-93 is suitable for valve springs in engines subjected to severe dynamic loads.


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