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< >Mold steel classification
>The United States divides mold steel into three major categories according to mold service conditions. The American Metal Society Tool Steel Committee lists three categories: cold work mold steel, hot work mold steel and plastic mold steel. Category. Among them, cold work mold steel is divided into subcategories, hot work die steel subcategory, and plastic mold steel subcategory. The selection of materials for each subcategory depends on three main factors
>◆ Size and shape complexity,
>◆ The material being processed,
>◆ Durability requirements or design life .
>
>◆ The group is oil-quenched cold-work die steel (commonly known as oil steel, there is a steel type, the carbon content is,
>◆ The group is air-quenched alloy cold-work die steel, there is a steel type , the carbon content ranges from.
>◆ The group is high carbon and high chromium cold work die steel, there is a steel type, the carbon content is.
>◆ The group is impact resistant tool steel, there is a steel type, Carbon content.
>For cold work molds, there are also high-speed steel (group and ultra-high-speed steel (group, cobalt-based cemented carbide and steel-bonded carbide (group, group, powder steel and engineering ceramics) Tungsten tool steel (group, special-purpose tool steel (group. For molds that are mainly wear-resistant, the hardness is higher than R. For molds that require high impact resistance and toughness, the hardness is lower than R. Mainly use the most common quenched and tempered steel, spring steel, hot work mold or base steel. For large stamping dies, such as automotive exterior stamping parts, cast iron is mainly used. For simple ones or with a small number of lifespans, zinc-based alloys or polymer composites are used.
>The use of high-speed steel and ultra-high-speed steel in cold work dies Applications are growing rapidly. The main reason is that it has a high compressive strength/hardness ratio. And the hardness can be selected between R.
>Powder mold steel has excellent wear resistance life, hardness is not high R, and has many applications.
>Carbon tool steel still has a certain application range in punches or soft material stamping dies with a life of 10,000 pieces.
>
>Hot-work molds work under high temperature conditions, requiring materials with heat strength and thermal wear resistance. In order to ensure the service life of the mold, the mold must Cooling, alternating hot and cold molds will cause cracks, that is, thermal fatigue cracks, so the materials are required to have crack resistance and thermal fatigue resistance.
>Select materials according to the main series arranged by thermal strength
> Low alloy quenched and tempered die steel (,, medium chromium hot work die steel, tungsten hot work die steel).
>Non-standard hot work die steel such as hot upsetting forging dies are of the age hardening type. There are problems that cannot be used during use. When the thermal wear resistance is met, you can choose,.
>When the mold is required to be mainly hot work wear resistance, you can choose,, powder steel. High temperature wear resistance of steel-bonded carbide cobalt-based carbide The resistance is very high, but its thermal fatigue resistance (that is, hot and cold fatigue crack resistance) is very poor. Mainly, it is divided into five categories.
>◆ Carburized plastic mold steel,,,,,. This type of steel has very low carbon content. It is mainly produced by the early American extrusion molding method and requires It has good cold plasticity and high extrusion performance. Surface carburizing and quenching after molding improves the surface hardness and has a long service life. The ultra-low carbon in the core can minimize the deformation during quenching.
>◆Quenched and tempered plastic mold, .At present, plastic molds are used in a large amount and have become the main body. Most of them are used in the pre-hardened state.
>◆ Medium carbon alloy tool steel is used for thermosetting plastic molds. Steel grades include, and, and, and also have applications. The characteristics of this type are
>It is basically a secondary hardened gold steel with good thermal strength.
>Contains high chromium and is highly corrosive to the atmosphere.
>Excellent hardenability, suitable for large modules.
>◆Stainless steel is used for plastic molds with high corrosion resistance requirements. The main steel grades are,,,.
>◆Aging steel is aged to obtain high performance. There are two types, one is low carbon aging steel and the other is maraging steel. The latter is a carbon-free, high-purity, high-strength, high-toughness material used in the aerospace industry. It is used in plastic molds that require high mechanical properties, dimensional accuracy, smooth finish and corrosion resistance.
>Selection of plastic mold steel
>For thin-walled plastic boxes, when the production batch is less than 10,000 pieces, the pre-hardened state (B~) is used, and it is used when it is highly corrosive.
> Ordinary plastic molds with long service life can be used when the hardness of R plastic parts is not too large after carburizing and quenching. Used when the corrosiveness is strong.
> Used for non-high temperature thermosetting molds. It is used after carburizing and quenching. It is highly corrosive.
>High-temperature thermosetting plastic molds are made of and or carburized steel. These have higher chromium content and have good tempering resistance and high-temperature oxidation resistance.
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