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Selection of manufacturing materials for different types of standard parts

by:Fortuna     2021-05-08
The selection of raw materials for different screw types is very important in the manufacturing process. Most of the fastener materials are steel. Our commonly used material standard parts are: ISO (international) GB (China) DIN (Germany) AISI/SAE (United States) JIS (Japan).
Materials for external threads such as bolts
For some low-carbon steel fasteners such as ISOClass4.8SAEGrade1-2 or ISOClass4.8SAEGrade1-2 without mechanical performance requirements, Q235ASAE1015DINC15 is sufficient, no heat treatment is required at all, and they are made directly by cold working, and fasteners with higher grades such as ISOClass6. For 8SAEGrade3-4, steel with a carbon content of more than 0.2%, such as C1020C1022Ml20ML35, etc., does not require any heat treatment, and the cold working strength can fully meet the requirements. In fact, the higher the carbon content, the more difficult it is to cold form, and there is no need to use the 6.8 grade screw for overkill. Special circumstances are a different matter.
The most commonly used screws are ISOClass8.8SAEGrade5. Generally, medium carbon steel is used. ML35SAE1035DIN35JISSWRCH35K is heat treated (quenched + tempered), or SAE514040Cr, etc. can also be used. The increase in alloying elements has a great effect on the hardenability of heat treatment. Help, so you can choose to use alloy steel for screws with large specifications, so that the use of medium carbon steel will not lead to the existence of the phenomenon of impermeability in the central part that we often say.
ISOClass9.810.9SAEGrade8 needs to use low to medium alloy steel material, after heat treatment (quenching + tempering), the alloy material has a good combination of material mechanical properties, the commonly used material is 40Cr35CrMoSAE5140SCM435SAE4135SAE4137JISSCr440(H)DIN41Cr4 Etc. In fact, 45# can also achieve the required mechanical properties, but it is slightly inferior to alloy steel in terms of comprehensive mechanical properties.
ISOClass12.9SATMA574 is a high-strength bolt with high requirements for mechanical properties. It needs to be heat-treated (quenched + tempered) with medium carbon alloy steel, such as SCM43535CrMoSAE4137SAE4135DIN34CrMo4. If the surface treatment of this kind of high-strength bolt is to be pickled During this process, hydrogen embrittlement will occur, so there must be a process of removing hydrogen (especially for fasteners with sharp corners), or it will die miserably.
Materials for internal threads such as nuts
C1010Q235A or C15 is generally used for those without mechanical performance requirements or ISOClass5-6SAEGrade3-4. No heat treatment is required, and cold working is sufficient. ISOClass8, SAEGrade5, generally use Ml35SAE1035DINC35, small size nuts do not need to be heated to achieve the required mechanical properties, large size nuts must be heat treated (quenching + tempering), this point GB3098.2 said very clearly.
ISOClass10, SAEGrade8 generally use medium carbon steel to meet its strength requirements after heat treatment. Medium carbon steel such as SAE1035. One thing you must pay attention to is that nuts and bolts are different. Their stress is mainly compression rather than extension. Therefore, the strength of the nut is not only related to the material, but also related to many factors, including accuracy, thread pitch, and inner chamfer of the nut. , Nut thickness, etc.
Materials for Flat Washers
Flat washers without mechanical performance requirements are generally made of corner materials, such as Q235A. When the hardness is required but not high, thicker plates can be used to calender to achieve the required hardness.
Washers for anti-loosening such as spring pads are generally made of 65Mn70# or S50CMS70CM, and they must be heat treated (quenched + tempered).
Rivets and pins
Rivets and pins generally use the same materials as bolts, but some rivets should not be too hard, and some even require HRB60 or less. Generally, the normalized material hardness is HRB70-80, so some rivets must be annealed to meet the performance requirements.
The self-tapping nails generally use C1018C1020C1022 and other materials, but some domestic manufacturers use 18#15#20# to save costs and cut corners. Some manufacturers use Q235A, and then the surface carburizing treatment is completed. The self-tapping nails are made like this The resilience of its heart is not up to the requirements and it is easy to break.
I don't know much about stainless steel fasteners. It seems that SUS304 is very commonly used.
Other special requirements for materials
If the company wants to make fasteners for welding, arc welding and gas welding generally have no requirements for materials. If the customer uses spot welding, he should use low-carbon steel obediently. If the strength must be increased, some low-carbon materials with higher Mn elements can be used. This is just a very simple example, many of which can only be noticed in actual production.
When the customer specifies to use a certain grade of material, and the company does not have this material for a while, or this material is not easy to purchase in the market, you can understand the purpose of the customer’s fasteners, which is in line with the mechanical properties. Upon request, a written application can be submitted to request replacement materials. Some purchasing customers are not very professional in fasteners, and the choice of materials is not always the best. As a manufacturer specializing in the production of fasteners, we can give customers better suggestions to achieve both benefits.
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