Spring wire (PP) is a high-strength metal alloy product. It is used in the production of compression, torsion, tension springs; different types of hooks, axes, pins, strings for piano and other parts with spring characteristics.
Features and requirements
The most popular diameter is 6-8 millimeters. For the manufacture of spring wire used wire rod of steel. Technical requirements are established in accordance with GOST 14963-78 or GOST 9389-75. Sometimes deviations from the norm to the requirements of the spring wire are allowed. For example, at the request of the customer, the amount of manganese in the composition can vary, but only if chromium and nickel were not used in the manufacture.
In order to avoid partial or complete destruction of finished products, GOST prescribes the ideal surface of the wire web without any defects.
During operation, the load will be created in places that are not resistant to flaws. Therefore, all raw materials, before the manufacture of springs, are tested.
The strength of the spring web depends on the size of the diameter, the strength of the small diameter is much higher. For example, a cross-sectional size of 0.2-1 millimeters is almost twice as strong as a wire with a cross-section of 8 millimeters. The form of release of the finished spring wire can be in the form of coils, coils (permissible weight 80-120 kilograms) and bays (500-800 kilograms).
According to the established GOST rules, the wire is created by pulling or dragging the initial blanks through holes located in order to reduce the diameter of the cross section. To increase the tensile strength at the end, thermal hardening is carried out. When drawing on the last outlet of the machine, a special form for calibration, a die, is installed. It is installed in the case when the material must be made already calibrated and not have defects on the surface.
The main properties of raw materials for the manufacture of wire is the elasticity and fluidity of the material. The increase in elasticity is achieved by quenching the alloy in oil, the temperature of which can be 820-870 C.
Next is the tempering of the wire at a temperature of 400-480 C. The hardness of the canvas is 35-45 units (from 1300 to 1600 kilograms per 1 square millimeter of the plane). To increase such technical properties as load suppression, carbon or high alloy steel is used. Typically, manufacturers make it from alloy grades - 50KhFA, 50KhGFA, 55KhGR, 55S2, 60S2, 60S2A, 60S2N2A, 65G, 70SZA, U12A, 70G.
The chemical composition of the steel wire is divided into carbon and alloy. The former are classified as low carbon with a carbon content of up to 0.25%, medium carbon with a carbon content of 0.25 to 0.6% and high carbon with a carbon content of 0.6 to 2.0%. A separate variety is stainless steel or corrosion resistant. Such characteristics are achieved by adding nickel (9-12%) and chromium (13-27%) to the composition of the alloying components. Depending on the starting material, the final result may be dark or light, soft or hard.
It is impossible not to note such a variety as a steel wire with memory - titanium and neodymium in the composition give it unusual properties.
If the product is straightened and after a while heated over a fire, the wire will return to its original shape. According to the mechanical properties, the spring wire is divided into:
- classes - 1, 2, 2A and 3;
- stamps - A, B, C;
- resistance to goods - highly loaded and heavily loaded;
- application for loads - compression, bending, tension and torsion;
- section diameter - round and oval, square and rectangular, hexagonal and trapezoidal shapes are also possible;
- type of stiffness - stiffness is variable and stiffness is constant.
According to the manufacturing accuracy, the wire can be of increased accuracy - it is used in the production and assembly of complex mechanisms, normal accuracy - it is used in the manufacture and assembly of less complex mechanisms.
Where is it used?
The production of springs can be cold and hot. For cold winding, special spring-coiling machines and machines are used. The wire must be made of carbon steel, because the final part will not be hardened. In Russia, the cold method is used more often, since it is not so expensive and expensive.
Cold winding equipment is equipped with two main shafts, one adjusts the tension, the second sets the direction of the turn.
- The spring wire is prepared for work, checked for defects.
- The wire cloth is threaded through the bracket in the caliper, and the end is fixed with a clip on the frame.
- The upper shaft is adjustable tension.
- The winding roller is turned on (its speed depends on the diameter of the wire).
- The canvas is trimmed when the desired number of turns is reached.
- The last stage is the mechanical and heat treatment of the finished part.
Using the hot method, it is possible to manufacture parts only with a cross-section diameter of 1 cm or more. During winding, fast and uniform heating occurs. The process is as follows.
- The wire cloth, heated red-hot, is pushed through the clamp and the ends are fixed with clamps.
- The upper roller sets the tension.
- The rotation speed is regulated (also everything depends on the diameter), the machine turns on.
- After the workpiece is removed.
- Next is thermal hardening - cooling in an oil solution.
- Machining the finished part and applying an anti-corrosion compound.
During the hot winding method, cutting the spring into parts is not provided if the desired size has already been achieved, that is, the winding takes place over the full length of the web. After that, it is cut into pieces of the desired length. In this method, the last heat treatment is needed to relieve internal stress on the part. It is recommended to work with an oil solution, and not with water, so that cracks do not go on the steel during hardening.
What the spring wire looks like, see below.