Materials Forming

Wires with different cross-sectional shapes and sizes of various metals and alloys can be produced by drawing. The drawing size is accurate, the surface is smooth, the drawing equipment and mold are simple, and it is easy to manufacture. According to the temperature of the metal during the drawing process, drawing below the recrystallization temperature is considered cold drawing, drawing above the recrystallization temperature is considered hot drawing, and drawing above room temperature but below the recrystallization temperature is considered warm drawing. Cold drawing is the most commonly used drawing method in wire and wire production. During hot drawing, the metal wire should be heated before entering the mold hole, mainly used for drawing high melting point metal wires such as tungsten and molybdenum. During the warm drawing process, the metal wire needs to be heated to the specified temperature through a heater before entering the mold hole for drawing. Mainly used for drawing difficult to deform alloy wires such as zinc wire, high-speed steel wire, and bearing steel wire.

According to the number of molds that the wires pass through simultaneously during the drawing process, drawing through only one mold is considered as single pass drawing, and drawing through multiple (2-25) molds in sequence is considered as multi pass continuous drawing. Single pass wire drawing has slow speed, low productivity, and low labor productivity, and is commonly used for drawing large diameter, low plasticity, and irregular wire. Multi pass drawing has the characteristics of fast wire speed, high mechanization and automation, high productivity and labor productivity, and is the main method of wire production. It is divided into non sliding continuous drawing and sliding continuous drawing. According to the state of the lubricant used for drawing, liquid lubricant is used for wet drawing, and solid lubricant is used for dry drawing. According to the cross-sectional shape of the drawn metal wire, there are circular wire drawing and irregular wire drawing. According to the pulling force acting on the wire drawing, there are positive pulling force and reverse pulling force. There is also special drawing, such as roller die drawing. The cross-sectional shape of drawn metal wire can be divided into circular wire drawing and irregular wire drawing.

Extrusion, especially cold extrusion, has the characteristics of high material utilization, improved material structure and mechanical properties, simple operation, and high productivity. It can produce important long rods, deep holes, thin walls, and special-shaped cross-sections with low cutting volume.Processing technology. Extrusion is mainly used for forming metals, but it can also be used for forming non-metals such as plastics, rubber, graphite and clay blanks. According to the blank temperature, extrusion can be divided into three types: hot extrusion, cold extrusion and warm extrusion. Extrusion when the metal blank is higher than the recrystalline temperature (see plastic deformation) is hot extrusion; extrusion at room temperature is cold extrusion; extrusion above room temperature but not exceeding the recrystalline temperature is warm extrusion. According to the plastic flow direction of the blank, extrusion can be divided into: positive extrusion with the same flow direction as the pressure direction, reverse extrusion with the opposite flow direction and pressure direction, and composite extrusion with the positive and negative flow of the blank. Pressure hot extrusion is widely used in the production of pipes and profiles of non-ferrous metals such as aluminum and copper, and belongs to the metallurgical industry.

The hot extrusion of steel is not only used for the production of special pipes and profiles, but also for the production of solid and drilled (through-hole or non-through-hole) carbon steel and alloy steel parts that are difficult to form by cold extrusion or warm extrusion, such as rods, barrels, containers, etc, with thicker heads. The dimensional accuracy and surface finish of hot-extruded parts are better than that of hot-die forgings, but the mating parts usually still need to be finished or cut. Cold extrusion was originally only used to produce lead, zinc, tin, aluminum, copper and other pipes and profiles, as well as toothpaste hoses (lead coated with tin on the outside), dry battery boxes (zinc), bullet shells (copper) and other parts. In the middle of the 20th century, cold extrusion technology began to be used for carbon structural steel and alloy structural steel parts, such as rods and rod-shaped parts of various cross-sectional shapes, piston pins, wrench sleeves, spur gears, etc, and later used to squeeze some high-carbon steel, rolling bearing steel and stainless steel parts.

Cold extrusion has high precision and a smooth surface, and can be used directly as a part without cutting or other finishing. Cold extrusion is easy to operate and is suitable for small parts produced in large quantities (the diameter of steel extruded parts usually does not exceed 100 mm). Warm extrusion is an intermediate process between cold extrusion and hot extrusion. Under appropriate circumstances, temperature extrusion can realize the advantages of both. However, warm extrusion requires heating the blank and preheating the mold. High temperature lubrication is not ideal and the mold life is short, so it has not been widely used.

The advantage of rolling is that it can destroy the casting tissue of the ingot, refine the grain of the plate, and eliminate tissue defects, so that the plate tissue is dense and the mechanical properties are improved. This improvement is mainly reflected in the rolling direction, so that the sheet is no longer isotropic to a certain extent; the air bubbles, cracks and pores formed during the casting process can also be suppressed under the action of high temperature and high pressure. The disadvantage is that after hot rolling, the non-metallic inclusions inside the sheet are pressed into thin sheets, and the phenomenon of stratification (interlayer) occurs. Layering greatly reduces the tensile properties of the sheet over the entire thickness range, and as the weld shrinks, there is a possibility of inter-layer tearing. The local strain caused by weld shrinkage often reaches several times the strain at the yield point, which is much greater than the strain caused by the load; the residual stress caused by uneven cooling.

Residual stress is the stress of internal self-equilibrium without external force. Hot-rolled plates of various cross-sections have this residual stress. Generally, the larger the cross-sectional size of the plate, the greater the residual stress. Although the residual stress is self-balancing, it still has a certain impact on the performance of the vehicle under the action of external forces.For example, it may adversely affect deformation, stability, and fatigue resistance. At the same time, the thickness and side width of the hot-rolled plate are not well controlled. We are familiar with thermal expansion and cold contraction. Even if the length and thickness are up to standard at the beginning, there will still be a certain negative difference after cooling. The wider the side width of this negative difference, the thicker the thickness, and the more obvious the performance. Therefore, for large plates, the edge width, thickness, length, angle and edge of the plate cannot be too precise.

The forging method is characterized in that the forging method includes the steps of forging and drawing holes, inserting a wax bar, molding and heat treatment, the forging and drawing process is to draw a solid rod into a seamless hollow tube; the process of inserting a wax bar is to insert a wax bar corresponding to the inner diameter of the hollow tube into the interior of the hollow tube; and the molding process is to place the hollow tube with the wax bar between the upper mold and the lower mold, and set up the mold cavities of the upper and lower molds, respectively. There are corresponding concave and convex shapes. After pressing the upper and lower molds together, a reinforcement can be formed on the periphery of the pipe; the thermochemical process is formed by molding. Forged pipe fittings are highly shock-absorbing and can withstand high pressure. It consists of forging and drawing holes, inserting wax strips, molding and heating. Reinforcing bars are formed in the cross-section, and finally the wax strip is melted and thermized out to form the molded fittings. By the forging method described above, concave reinforcing bars are formed on the surface of the tubing, which can improve the vibration-damping properties of the tubing and at the same time strengthen the tubing. The compression performance can also improve its aesthetics and variability, thereby solving the problem of poor vibration damping and compression performance of the existing solid fittings. Commonly used forging methods include free forging, die forging and tire film forging.

1. Free forging: Free forging is the use of impact or pressure to deform the metal between the upper and lower iron. To obtain the desired shape and size of the forgings. In heavy machinery, free forging is a method of producing large forgings and forming oversized forgings.

2. Die forging: Under the action of pressure or impact, the metal billet is deformed in the mold cavity of the forging die, so as to obtain the forging process method. The method of production of forgings accurate size, small machining allowance, complex structure, high productivity.

3. Tire die forging: Tire die forging is a use of tire molds in the free forging equipment to produce drop-forged parts of the process method. Usually, the free forging method is used to manufacture blanks, and then formed in the tire mold.

Compared to cast and forged parts, stamped parts are thin, uniform, light and strong. Stamping can produce workpieces with ribs, ribs, fluctuations or flanges that are difficult to manufacture by other methods to increase their stiffness. Due to the use of precision molds, the accuracy of the workpieces can reach micron level with high repeatability and consistent specifications, and holes and bosses can be punched out. Cold stamped parts are usually no longer machined or require only a small amount of machining. The precision and surface condition of hot stamped parts are lower than that of cold stamped parts, but still better than cast and forged parts, with less processing. Compared with other machining and plastic processing methods, stamping has many unique advantages in technology and economy.

The main performance is as follows:

(1) stamping high productivity, easy to operate, easy to realize mechanization and automation. This is because stamping depends on the die and stamping equipment to complete the processing. The stroke of an ordinary press can reach dozens of times per minute, and high-speed pressure can reach hundreds or even thousands of times per minute. It may take a punch.

(2) in the stamping process, because the mold to ensure the size and shape of the stamped parts precision, generally will not damage the surface quality of the stamped parts, mold life is generally longer, stable stamping quality, interchangeability, with "exactly the same" characteristics. Characteristics.

(3) Stamping can process parts with large size range and complex shape, such as second hand of clock, longitudinal beam of automobile, cover, etc. Together with the cold deformation and hardening effect of materials in the process of stamping, the strength and rigidity of stamping are very high.

(4) Stamping generally does not produce chips and debris, consumes less material, does not require other heating equipment, is a material-saving, energy-saving processing methods, stamping parts at low cost.

Rotary forging is characterized by pulse loading and multi-directional forging, which is conducive to the uniform deformation and plasticity of the metal. Therefore, the process is not only suitable for general metal bars, but also for high alloys with high strength and low plasticity, especially for billets and forging of refractory metals such as tungsten, molybdenum, niobium and their alloys. Spin forging is characterized by high forging quality, high dimensional accuracy, high production efficiency and high degree of automation. Spin forging has a wide range of forging size, but the equipment structure is complex and specialized.

Spin forging is widely used in the production of step shafts for various machines such as automobiles, machine tools, locomotives, etc, including right-angle steps and shafts with taper;

It is characterized by pulse loading and multi-directional forging, with a high striking frequency of 180 to 1700 times per minute. As a result of multi-hammer forging, the metal is deformed under the action of three-way compressive stress, which is favorable to the improvement of metal plasticity. Spin forging is not only suitable for general metal materials with good plasticity, but also for high strength, low plasticity materials, especially widely used in forging high-temperature refractory powder sintered materials with less plasticity and drawing tungsten, molybdenum, tantalum, rare materials. Metals such as niobium, zirconium and hafnium, as well as very low strength coated materials, such as aluminum tubes coated with aluminum-nickel powder.