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Die and Mold Materials

                      We have already noticed that a die or mold has different movable and stationary parts
                      (clamping elements, springs, pins, bolts, bushings, support pillars, etc.) generally made from
                      different engineering materials, from plastics to cemented carbides.

                      However, key die or mold parts that act on specific requirements of the die and mold industry
                      usually are from particular materials, which should be emphasized.

                      Tool Steels
           Die and Mold Materials
                      Tool steels relate to a type of steels that, as indicated in its name, is intended first of all for
                      making tools for cutting and forming metals and other materials. There are many national and
                      international standards for specified tool steels. Moreover, in order to answer to the particular
                      requirements of industry, steel manufacturers produce different steels in accordance with their
                      own specification. These steels often have no standard designation and are identified by their
                      trade names. In this guide we use the standards of the American Iron and Steel Institute (AISI)
                      and the Society of Automotive Engineers (SAE). The parallel designation in conformity
                      with other acting standards is sometimes given in the text; and the information section at the
                      end of this guide contains a cross-reference table with comparative designation of tool steels
                      in keeping with the different national standards.

                       Die and mold makers deal with steel in wide ranges of hardness, from low (HB 200 and less)
                       to high (HRC 63).

                      In line with the main field of application there are six general and two special-purpose classes
                      of tool steels, from which the following are the most popular in the die and mold industry:

                    • Cold-work tool steels including A series (air-hardening medium-alloy),
                      D series (high-carbon high-chromium) and O series (oil hardening)
                    • Hot-work H series
                    • Water hardening W series
                    • Plastic mold P series
                    • Shock resistant S series
                    • Special-purpose L series (low-alloy)

                      In die and mold design, the main properties of tool steels are strength, wear resistance,
                      corrosion resistance, etc. However, while for a die and tool maker dealing with the material,
                      which has already been specified by designers, more important properties are: hardness,
                      machinability, polishability and dimensional stability.

                      The steel manufacturers supply steels in different delivery conditions: annealed, pre-hardened
                      and hardened. Consequently, in die and mold making process, hardness of tool steel
                      (even the same grade) can vary within a wide range from HB 200 and less (soft steel)
                      to HRC 63 (hard steel). Normally, high stock removal rate characterizes rough machining of
                      a soft material while closed allowances are usual for finish cuts when material hardness is high.
                      The term “pre-hardened steel” is not well-defined. It means that steel is hardened and tempered
                      to relatively not high hardness but different steel producers use different limits for its
                      specification. Generally, it is less than HRC 45, however, in technical literature and references the
                      steels with that hardness often relate to hard steel. The term and its hardness limit are allied
                      to cutting tool development and their ability to cut material. Therefore, steels can be divided
                      into the following conditional groups depending on their hardness:

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