Screw is an important material, which is not only manifested in its wide application in many fields, but also in its function of connecting and fixing and its indispensable role. However, the screws on the market can be classified according to the differences in materials and uses, which makes it necessary for us to master certain professional knowledge and discriminating ability before actually purchasing. Here is the information about several aspects of screw material listed by Xiaobian for everyone. Including the brief introduction of screw material, other properties of screw material and so on.
1. Brief introduction of screw materials
At present, there are three standard parts in the market: carbon steel, stainless steel and copper.
(1) carbon steel. We distinguish low carbon steel, medium carbon steel, high carbon steel and alloy steel by carbon content in carbon steel materials. ?
1. C% of low carbon steel ≤ .25%? It is usually called A3 steel in China. Foreign countries are basically called 18, 115, 118, 122, etc. Mainly used for 4.8-grade bolts, 4-grade nuts, small screws and other products without hardness requirements. (Note: The drill tail nail is mainly made of 122 material. )
2, medium carbon steel .25%, .45%. At present, it is basically not used in the market.
3. Alloy steel: alloy elements are added to plain carbon steel to improve some special properties of steel, such as 35, 4 Cr-Mo, SCM435 and 1B38. Fangsheng screw mainly uses SCM435 Cr-Mo alloy steel, and its main components are C, Si, Mn, P, S, Cr and Mo.
(2) stainless steel. Performance grades: 45, 5, 6, 7, 8
Mainly austenite (18%Cr, 8%Ni) has good heat resistance, corrosion resistance and weldability. A1，A2，A4? Martensite and 13%Cr have poor corrosion resistance, high strength and good wear resistance. C1, C2, C4 ferritic stainless steel. 18%Cr has better upsetting property and stronger corrosion resistance than martensite. At present, the imported materials on the market are mainly Japanese products. According to the level, it is mainly divided into SUS32, SUS34 and SUS316.
(3) copper. Commonly used materials are brass … zinc-copper alloy. H62, H65 and H68 copper are mainly used as standard parts in the market.
2. Other properties of screw materials
1. The above materials are non-magnetic in normal state. 34M is slightly magnetic after cold working (about 1.6u-2.u); The magnetism of 34HC is (about 1.1u-1.6u); The magnetism of 316 material is less than 1.1u after cold working.
2. All materials have good ductility and are easy to be cold-formed, and the tensile strength and yield strength can meet the requirements. (Ts? Tensile strength? min? 7N/mm,? Ys? Yield strength? min? 45N/mm)
(2) the relationship between the main chemical components and the properties of stainless steel.
1. Carbon? C can increase hardness and strength, but too high a content will reduce its ductility and corrosion resistance
2. Chromium? Cr can increase corrosion resistance, oxidation resistance, grain refinement, strength, hardness and wear resistance? 3. Nickel? Ni can increase high temperature strength and corrosion resistance, and decrease the rate of cold work hardening? 4. molybdenum? Mo? Increased strength, excellent corrosion resistance to oxides and seawater? 5. copper? Cu? Conducive to cold forming and reducing magnetism
3. Common quality problems of screws
1. The head of the screw is deformed and the head is crooked. The possible reasons are poor installation of the first punch of the screw die and improper adjustment of the machine.
2. The head of the screw is not round. The reason is that the screw die is not properly selected or the one-punch forming is not full enough.
3. The screw has burrs or burrs. The reason is that the first punch forming is not good, mainly because the gap between the punch and the die hole is too large or the punch is too short.
4. The screw head is cracked, and the screw head is cracked. The reason may be that there is something wrong with the quality of the screw wire itself, so before starting the screw wire, the quality department must check it and spot it with medicine. Especially stainless steel screw wires, it is necessary to find out which one is stainless steel 21 and which one is stainless steel 34. It may also be due to the wrong use of a die (such as a die with a hexagonal head for the pan head) and the failure of the viscosity of the lubricating oil. For the problem of screw head, please read the article written by manager Zhu above-detection of high-strength screw fracture or head crack. In this article, some problems encountered in the screw head and how to detect them are clearly introduced.
Of course, the common quality reasons of screws are more than the above, which is only part of it. There are other quality problems. Manager Zhu will talk about them then. The quality reasons of the above screws are for reference.
above, we have presented a detailed and professional system about the material of the screw through the introduction of the screw material, other properties of the screw material and other information. We know that the three materials of carbon steel, stainless steel and copper have a great relationship with its functional parameters, and even have a decisive role to some extent. I believe that in the future, you can reduce unnecessary troubles in the process of actually purchasing screws and screen out the products that are most suitable for you.
that's all about screw materials, I hope it can help you! ?