Commonly used material standard parts

Now 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

Some low-carbon steel fasteners such as ISO Class 4.8 SAE Grade 1-2 that do not have mechanical performance requirements are sufficient to use Q235A SAE 1015 DIN C15. No heat treatment is required at all, and they are directly cold-worked, and the grade is slightly higher. Fasteners such as: ISO Class 6.8 SAE Grade 3-4 use steel with a carbon content of 0.2% or more, such as C1020 C1022 Ml20 ML35, etc. This type of screw 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 ISO Class 8.8 SAE Grade 5. Medium carbon steel is generally used. ML35 SAE 1035 DIN 35 JIS SWRCH35K is heat-treated (quenched + tempered), and SAE5140 40Cr, etc. can also be used. The alloy elements are increased. It is of great help to the hardenability of heat treatment, 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. (Guide: Basic knowledge on the use of standard parts)

ISO Class 9.8 10.9 SAE Grade 8 is to use low to medium alloy steel material, after heat treatment (quenching + tempering), the alloy material has a good combination of mechanical properties of the material, the commonly used material is 40Cr 35CrMSAE5140 SCM435 SAE4135 SAE4137 JIS SCr440(H) DIN 41Cr4, 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.

ISO Class12.9 SATM A574 is a high-strength bolt with high requirements for mechanical properties. Medium-carbon alloy steel must be heat treated (quenched + tempered), such as SCM435 35CrMo SAE 4137 SAE4135 DIN 34CrMo4. If the surface treatment of the strength bolts undergoes the pickling process, hydrogen embrittlement will occur, so the process of hydrogen removal must be done (especially the fasteners with sharp corners), otherwise it will die miserably.

Nuts and other internal thread materials that do not have mechanical performance requirements or ISO Class 5-6 SAE Grade 3-4 generally use C1010 Q235A or C15. No heat treatment is required, but cold working is sufficient. ISO Class 8, SAE Grade 5, generally use Ml35 SAE1035 DIN C35, small size nuts do not need heat to achieve the required mechanical properties, large size nuts must be heat treated (quenching + tempering), this is GB3098.2 That is very clear.

ISO Class 10 and SAE Grade 8 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...

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. Spring washers and other anti-loose washers are generally made of 65Mn 70# or S 50CMS 70CM, and they must be heat treated (quenched + tempered)

Rivets and pins

Rivets and pins generally use the same materials as bolts, but some rivets cannot be too high in hardness, and some even require HRB60 or less. Generally, the normalized material hardness is HRB70-80, so some rivets need to be annealed to meet the performance requirements.

Self-tapping nails generally use materials such as C1018, C1020, C1022, 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 toughness of the attacking nail's heart is not up to the requirement, 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 a 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 learn about the purpose of the customer’s fasteners. 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.

Of course, the materials used for fasteners should pay attention to more than these. For example, the material must pass the aging period before use (I wrote an article about this in the past), and the rusty surface material is used to make some full-threaded fasteners. Fasteners or fasteners that need to be ground on the surface, the center of the material and the shrinkage cavity should not be used to make polishing head screws...

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