Classification of spring steel

1、 Classification by chemical composition
According to GB / T 13304 standard, spring steel is divided into non alloy spring steel (carbon spring steel) and alloy spring steel according to its chemical composition.

Carbon spring steel
The carbon content (mass fraction) of carbon spring steel is generally 0.62% ~ 0.90%. According to its manganese content, it can be divided into general manganese content (mass fraction) (0.50% ~ 0.80%), such as 65, 70, 85 and higher manganese content (mass fraction) (0.90 ~ 1.20%), such as 65Mn.

Alloy spring steel
Alloy spring steel is a kind of steel which can improve the mechanical properties, hardenability and other properties of the steel by adding one or several alloy elements on the basis of carbon steel, so as to meet the requirements of manufacturing various kinds of spring.

The basic composition series of alloy spring steel include silicon manganese spring steel, silicon chromium spring steel, chromium manganese spring steel, chromium vanadium spring steel, tungsten chromium vanadium spring steel, etc. On the basis of these series, some brands have added molybdenum, vanadium or boron to improve their properties in some aspects.
In addition, some brands are selected from other steel categories, such as high-quality carbon structural steel, carbon tool steel, high-speed tool steel and stainless steel.

2、 Classification according to production and processing methods
1. Hot rolled (forged) steel includes hot rolled round steel, square steel, flat steel and steel plate, and forged round steel and square steel.
2. Cold drawn (rolled) steel includes steel wire, steel strip and cold drawn material (cold drawn round steel).
3、 Classification according to steel delivery status
1. Hot rolled (forged) steel
A. The steel delivered in hot rolled (forged) state is hot formed into spring, and then quenched and tempered.
B. The steel delivered in annealed condition is cold formed into spring, then quenched and tempered.
All of the above shall meet the requirements of the corresponding delivery state hardness.

2. Cold drawn (rolled) steel
A. Steel wire
① After the steel wire is made into spring, it only needs to be tempered at low temperature to eliminate the stress.
② After the steel wire is cold drawn to the required size, it is subjected to continuous heating, continuous oil quenching and lead tempering. After the steel wire is made into spring, only the bottom temperature fire is needed to eliminate the stress.
③ Cold drawn steel wire (i.e. steel wire without quenching and tempering treatment)
a. Delivery in cold drawn condition.
b. Delivery in annealed, normalized or tempered condition.
The steel wire delivered in the above two states shall be quenched and tempered after being made into spring.
B. Steel strip
① After being delivered in cold rolling condition, the spring should be tempered at low temperature to relieve stress.
② After being delivered in quenched and tempered condition, the spring shall be tempered at low temperature to remove the stress.
③ After being delivered in annealed condition, the spring shall be quenched and tempered
C. Cold drawn steel
The steel delivered in annealed condition is cold formed into spring, then quenched and tempered.

4、 Other classification methods
In addition to the above, there are other classification methods, such as:
According to the different delivery conditions, it can be divided into delivery by chemical composition (mechanical properties) and delivery by hardenability.
According to the working conditions of spring, it can be divided into static load bearing spring steel, impact load bearing spring steel, high (low) temperature resistant spring steel and corrosion-resistant spring steel.