Said bolts, nuts, we can start from the most commonly used production of small and medium-sized cold heading materials and processes. Cold heading steel is generally low- and medium-carbon high-quality carbon structural steel and high-quality alloy structural steel used for cold heading to manufacture various mechanical standard parts and fasteners. Due to the high cleanliness of the steel required by the cold heading process, the content of Si and Al in the steel must be strictly controlled, and the controlled rolling and controlled cooling processes are adopted to avoid martensite, bainite and weiss body structure. The steel has a fine grain and carbide spheroidized structure to improve the plasticity and cold upset properties of the steel. Said material gap, imported cold-rolled steel and domestic 35# medium carbon steel composition is similar, but its metallographic structure is very small and uniform, white small granular pro-eutectoid ferrite is very evenly distributed on the substrate, no net The presence of tissue. The grain size is only 1-2μm, which is about 1/10 of the domestic medium carbon steel. And has a good strong plasticity. Domestic research suggests that the imported materials may not be completely austenitized during heat treatment, but only heated to the two-phase region of austenite and ferrite for heat preservation and then cooled to room temperature. The microstructure after heat treatment is fine and carburized. Compared with normal austenitized cementite, the body is smaller in size, thinner in thickness and more evenly distributed, showing a special "two-phase structure" of imported steel wire. It is essentially a complete pearlite structure with only a small amount of small pieces (about 5 μm in size) of pro-eutectoid ferrite. The determination of the cold heading process is based on the plasticity of the part material (the allowable upsetting rate) combined with the shape of the part structure, dimensional accuracy, and consideration to avoid various defects. The ultimate deformation degree in cold heading is the limit upsetting rate when the surface of the material begins to crack during the upsetting process. The limit upsetting rate is the parameter obtained by softening the material after a certain diameter and a certain height through softening. . The material properties have a great influence on the upset shape that can be achieved. Some materials can be upset to meet the requirements, some are not, and cracking is the biggest problem. If you have the same ingredients, your grain may not meet the requirements at all. When the material properties are completely in compliance with cold and cold extrusion conditions, what remains is the design process and the properties of the mold. In the end, the process design is still an accurate understanding of the boundary constraints. To be precise to the understanding of the stress state at each point, the most important is the stress of the corners and the flow properties of the material. If you can't understand these things, the material will crack and your craft design will fail. Even if you can swear, you can blame others for no use. You can only ask experts to do it because you can't handle this problem. In the academic world, the extrusion method in which the flow direction of the gold chips is parallel to the axis of the punch is collectively referred to as an axial extrusion method. There are also radial extrusion and squeezing methods. 1. Positive extrusion, that is, the flow direction of the metal is consistent with the direction of the convex transverse movement. Positive extrusion is divided into two types: solid part extrusion and hollow part extrusion. The positive extrusion process can produce solid and hollow parts of various shapes, such as screws, mandrels, tubes and cartridges. 2. Back-squeezing, the flow direction of the gold shavings is opposite to the moving direction of the punch. 3. Co-extrusion, the flow direction of a part of the metal of the blank is the same as the direction of movement of the punch, and the flow direction of the other part of the gold is opposite to the direction of movement of the punch. 4. Reduced-diameter extrusion, a metamorphic positive extrusion method with a small degree of deformation, the blank section is only slightly reduced. There are more ways to produce nuts. There are sorting extrusion methods suitable for the production of large and medium nuts. The process includes: cutting, ball pressing, initial forming, punching, fine punching, etc. This is also the production of cold extrusion. Typical production process for nuts. Starting from the cutting off, each step has its detailed calculation process, and of course the correction of empirical data. When a large automatic cold heading machine is used for cutting, flattening, playing, softening and annealing, and then being formed by press-sequencing, the efficiency of such combined production is doubled. In terms of producing nuts by cold extrusion, the world has been gradually reforming the processing technology. The core problem is to improve production efficiency, improve material utilization, and reduce losses. The final direction is a one-step molding method, which uses a round bar to extrude its shape and internal thread at a time. This is the most complicated process for producing nuts. The core problem is the problem of interlayer flow of materials, that is, when the material is squeezed. The internal damage of the material caused by the lattice stretching and displacement of the material caused by the interlayer flow caused by the inner hole after the inner hole has been bitten into the mandrel thread and other series of problems. Concerned about surprises Tags: cold heading materials and production processes for counting bolts and nuts Previous: What are the common faults of electric hammer? Electric hammer repair method Daquan Next: Bolt loosening problem is increasing fasteners anti-loose way out Night Light,Led Bulb Light,Colorful Night Light,Led Cabinet Light NINGBO ZHENGUO INTELLINGENT LIGHTING CO.,LTD , https://www.zguolight.com
The axial extrusion method can be further subdivided into: 
