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Vacuum hardened spring steel wire

Application of Vacuum Hardening Spring Steel Wire

Springs and elastic components are basic parts with a large quantity and a wide range, and can be said to be ubiquitous. As a control element in power machinery, electrical appliances, instruments, and weapons, it is also a very critical part. Its basic function is to use the elasticity of the material and the structural characteristics of the spring to convert mechanical work or kinetic energy into deformation energy, or convert deformation energy into kinetic energy or mechanical work, in order to achieve buffering or vibration reduction. , control motion or reset, energy storage or measurement purposes. Therefore, springs are widely used in various mechanical equipment, instruments, military products, electrical appliances, furniture, home appliances, and even stationery and toys.

There are many kinds of spring materials, and the most used in production is the spring special steel classified as spring steel. Such as carbon spring steel, low-alloy spring steel and high-strength spring steel, etc., followed by spring materials with special properties, such as stainless acid-resistant spring steel, heat-resistant spring steel and alloys (nickel-based, titanium-based and cobalt-based alloys, Copper-based alloy with high elasticity and high conductivity). Non-metallic elastic materials include rubber, plastic, ceramics and fluids.

To obtain the desired properties, spring steel must have a higher carbon content. The carbon content of carbon spring steel is between 0.6-0.9%. Due to the poor hardenability of carbon spring steel, it is only used to manufacture springs with a cross-sectional size of no more than 10-15mm. For springs with larger cross-sectional dimensions, alloy spring steel must be used.

Cold-drawn spring steel wire, especially in fine gauge, can achieve high comprehensive mechanical properties. This kind of steel wire does not achieve the required mechanical properties by cold deformation, but by martensitic transformation strengthening. As long as the steel has sufficient hardenability, both thick and thin steel wires can obtain relatively uniform and fine martensite and good mechanical properties. This type of steel wire has no internal stress, excellent straightness, good cold winding, and uniform and stable quality. The limit is extremely high, and the fatigue resistance is good, which replaces the production process of vacuum hardening and tempering after winding with annealing material, and greatly improves productivity and product quality. It also makes large-diameter vacuum hardening-tempering steel wires and steel rods easy to manufacture.

Spring steel wire vacuum heat treatment

Vacuum hardening-tempering steel wire is divided into two categories, one is ordinary quality vacuum hardening-tempering steel wire, which is used to manufacture important mechanical springs, and the other is specially used to manufacture valve springs or other valve spring steel wires that require high fatigue performance. The main difference is that the latter has high metallurgical quality, less harmful impurities (P, S, O, etc.), higher surface quality, and smaller fluctuation range of mechanical properties.

Vacuum hardening and tempering is a common vacuum heat treatment process for steel. Generally, the final vacuum heat treatment of springs is as follows: 1. Springs or elastic elements that have been cold-formed from strengthened wires and strips do not require high-temperature quenching but only require stress-relief annealing. 2. Springs wound from thermoformed or annealed materials must be hardened, vacuum tempered or austempered.

Low alloy spring steel wire in vacuum annealed state

Such spring materials of steel wire include silicon-manganese spring steel wire such as 60Si2MnA (GB/T5218), chrome-silicon spring steel wire (GB5221), chrome-vanadium spring steel wire (GB5218) and chrome-vanadium spring steel wire for valves (YB/T5136). In addition, there are 65Si2MnWA and 70Si3MnA. Silicon-manganese spring steel wire has five delivery states: cold drawn (L), vacuum annealed (T), normalized (h), high temperature tempered (Gh) and silver bright (Zy), and the wire diameter ranges from Φ1.0 to Φ12. .0. Chromium vanadium or chrome silicon spring steel wire only has two types: cold drawn (L) and vacuum annealed (T), and the wire diameter ranges from Φ0.8 to Φ12.0. There are four types of chromium vanadium spring steel wire for valves: cold drawn (L), vacuum annealed (T), cold drawn + silver bright (L+Zy), vacuum annealed + silver bright (T+y), wire diameter range Φ0.5 ~Φ12.0.

This type of steel wire is soft or semi-hard, and must be vacuum hardened-tempered to achieve the required mechanical properties after cold winding into a spring. The quality of the spring is not only closely related to the quality of the steel wire raw material, but also depends to a large extent on the process level of vacuum heat treatment. In particular, those compressor valve springs made of steel wires with specifications <Φ1.0 are large in quantity and small in size. They are easily deformed during vacuum heat treatment production, the quenching quality cannot meet the requirements, the surface is oxidized, and the corrosion is serious. It is made of vacuum hardened-tempered steel wire.

Grinding or polishing the thicker annealed or vacuum hardened-tempered steel wire to improve the surface quality, reduce surface defects, and improve the fatigue life of the spring. Supplied as coils or as straight rods to length, it is often used to manufacture very important springs. For example, the valve springs of cars, the pressure regulating springs of fuel injection nozzles and the circlips of drill bits in the petroleum industry, etc., these springs must be hardened and tempered before they can be used. During vacuum heat treatment, its surface quality should be protected, and collisions should not cause scratches or oxidative decarburization. For example, the above important springs are made of polished or polished vacuum hardened steel wire. Then its vacuum heat treatment is simple, and the inner quality can be guaranteed.