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Understanding of die steel

    Understanding of die steel
    1. Subject: Basic understanding of die steel, especially plastic steel

    2. Introduction:

    1. The types of steel are extremely diverse and many, among which there are three types of steel for molds:

    Index tendency

    a. Plastic mold steel: high polish

    b. Hot work tool steel: high strength, high temperature resistance

    c. Cold work tool steel: high pressure resistance and wear resistance-‘high speed tool steel’ is a branch

    2. Common brand marks:

    a. JIS-Japanese Industrial Standards

    b. ASTM-American Society for Testing and Materials specifications

    c. AISI-American Iron and Steel Institute Specification

    d. DIN——German National Standard

    e. GB/YB——Chinese Standard

    3. Usage practice: attach the catalog of typical manufacturers’ products

    1. P20, the most commonly used plastic steel

    2. PDS5, similar to P20, but more difficult to process than P20, the disadvantage is that it is easy to harden at higher temperature

    3. PDS1, not equal to S45C, not for cavity use, used in mold base to reduce cost

    4. If durability is required, the mold base material is S50C or S55C. The common domestic method to overcome difficulties is S45C forging, which has higher hardness and better wear resistance than S50C. Note: Someone once said that S45C forging is better than S50C. Sex, in fact, the S50C may be suspected of being a fake product

    5. When the hardness of the cavity steel is higher than P20, NAK80 can be selected for durability

    6. Choice tendency:

    a. Plastic steel: It is used in plastic injection molding, and then distinguishes the requirements of mirror polishing, corrosion resistance, etc.

    b. Cold-worked steel: used in standard parts of guide column sleeves, and also used in precision metal molds or wear-resistant plastic molds or cold stamping dies

    c. Hot work steel: aluminum or zinc alloy die casting mold

    7. Many plastic steels are pre-hardened to avoid heat treatment deformation

    8. Composition tendency of various steel materials: medium carbon: 0.3-0.8% C content

    a. Plastic steel: medium carbon or low carbon, a small amount of nickel-chromium (1-10%) or a medium amount close to SUS420 stainless steel chromium (>10%), corrosion resistance

    b. Hot work steel: medium C, small amount of Cr

    c. Cold work steel: high C Note: high speed steel: high C, a small amount of tungsten, molybdenum, vanadium (even cobalt). Adding a small amount of chromium can increase the strength.

    9. Decomposition of major categories:

    a. Cold work steel: This type of steel is used at room temperature. Due to the high hardness and wear resistance requirements, the carbon content is high carbon steel (C>0.8%), and even a small amount of tungsten, molybdenum, and vanadium elements are added to help improve Wear resistance, in addition, high hardness must prevent brittleness, so chromium (about 4-12%) is added to improve toughness and strength, and manganese is often supplemented

    b. Hot work steel: The main requirement of this type of steel is the use environment at a higher temperature of about 500-850℃, so the high temperature resistant tungsten, molybdenum, vanadium elements are equivalent to cold work steel, because its wear resistance is not the main requirement. The carbon content is only medium carbon steel (0.3-0.8%), and its influence on toughness is reduced, so the chromium content is slightly reduced (about 3-5.2%)

    c. Plastic steel: Abrasion resistance of the mold cavity surface is the main requirement, so it belongs to low carbon steel (C<0.3%) to reduce its oxidation tendency, and medium chromium or a small amount of nickel chromium is added to improve its corrosion resistance.

    S136———Suitable for molds with acidic materials, high output, and mirror surface requirements.

    S136-SUP—–suitable for molds with acidic materials, high output, and mirror surface requirements. Compared with S136, this material has higher acid resistance and more uniform texture.

    8407———Suitable for molds with acidic materials, high output, and low appearance requirements. The toughness of the material is better after hardening, and it is often used for alloy die-casting molds. Plastic materials contain high glass This material is often used for fiber molds.

    H13———-The performance is equivalent to 8407, but the toughness is slightly worse after hardening, so heavy alloy (such as copper alloy) molds are generally not recommended.

    S136H——–Applicable to molds with acidic materials and certain appearance requirements, but average output.

    Almost all of the above are anti-corrosion materials, especially the choice between S136 and S136H has been difficult for many people to decide. In this case, because S136 needs to be hardened, it can be finished. For molds with low yields, if you choose The manufacturing cost is about 15%-20% higher than the pre-hardened S136H.

    NAK80——-This is an excellent non-corrosive material, the pre-hardened hardness reaches about 40HRC, the cutting performance and polishing performance are very good, and it can even reach the mirror surface requirements, but it will be very fast in the production process It is corroded by acidic substances and the edges are hazy. However, NAK80 is a good choice for POM materials that are not very corrosive and have no appearance requirements.

    718H———Non-corrosive materials commonly used in Europe and the United States, the pre-hardness is generally above 32HRC, and the cutting performance and polishing performance are very good. It is commonly used in the cavity of softer plastic molds such as ABS, PP, etc. on.

    738H———non-corrosive material, the pre-hardness is generally above 32HRC, the cutting performance and polishing performance are general, and it is commonly used in the interior of softer plastic molds such as ABS, PP, and it is not recommended. The part of the appearance of the molded product. The materials mentioned above can basically be attributed to the 2344 and P20 material families except NAK80. You should try your best to consider the material characteristics, production requirements, and mold costs when selecting. It can be used as a reference for the late XDJM.

    2343 and 2344-are hot work tool steels. I personally think that these two are similar. 2343 is used less, and 2344 is used more.

    2767———Mostly used in hardware molds, 2764 is not clear about it

    2083———The price is low, can be quenched for acidic plastics, has good polishing performance, and 2083H can also be used without quenching.

    For high-priced models. Use S136 when you want a mirror.

    2083 for low-cost models,

    Use NAK80 or 718H without acid.

    Use 718 and S136 for quenching above HRC58 degrees,

    8407 is more than a hundred;

    NAK80 is mostly used in Datong, Japan;

    2344,2083, etc. Multi-purpose Long Kee. We generally use 2343ESU as the core, which has good wear resistance, toughness and hardenability.

    In addition to the above features, 2344 is more conducive to cooling.

    Compare him and what is the difference between 8407?

    The strength and hardness of 2767 are better, but it is not good for welding and processing. Compared with 2343, 2764 is slightly softer. I think it is used in places where it is broken. In addition, 2083 and 9986 are used to make long-axis cores. For the same model, the steel with H refers to the pre-hardened steel; the steel without H is not pre-hardened, and it is softer, and the steel without H is often heat treated.

    718H is the most used on ordinary plastic molds, 738 is a bit worse than 718.

    NAK80—— has good polishing performance and is often used for molds or transparent materials to be polished. Japanese customers often require NAK80. This material has been hardened, reaching more than HRC40.

    SKD11—— can be heat treated to above HRC60 degrees, commonly used as plug molds, stamping molds, knife molds, etc.

    DF2 is similar to SKD11—but many profiteers often use domestically produced materials.

    SKD61-a hot work die steel, can be used for die casting molds, often heat treated to about HRC50, with good toughness. It is also commonly used as small inserts for plastic molds.

    H13——–is an American grade, which is the same material as SKD61.

    NAK55 is similar to NAK80, but I haven’t used it.

    635—— Make bakelite mold.

    236——A kind of stainless steel, designated by the customer, for PBT+30%GF.

    S136—–It is a material with good corrosion resistance and good polishability. It is commonly used and emits corrosive gases and corrosive materials. It is also commonly used for transparent materials.

    S136H—-It is the hard material of S136, I don’t need to say the purpose

    1. For plastic molds made of materials such as PC, PBT+GF, PA, etc., it is economical to use SKD61 material for heat treatment to HRC48-52 degrees.

    2. For PC transparent materials, or hard molds that require polishing on the mold surface, or emit corrosive gas, S136 heat treatment is a good choice.

    3. For thermosetting plastic molds such as bakelite molds, SKD61 or 8407 heat treatment can be used. However, white steel inserts or black steel inserts are additionally mounted at the pouring point. Wugang has the best wear resistance, but it cannot be processed by traditional machining methods, and can only be processed by special processing such as wire cutting and EDM.

    4. For the hardware to be embedded in the mold