Kyocera - Основной каталог 2010-2011 ENG

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                Heat Treatment and Hardness Expression

                  Heat Treatment

                 One of the ways to determine the hardness of steel is the heat treatment and it is classified to 3 types.

                                                         Heat Treatment

                             Quenching (Tempering)                        Normalizing  Annealing

                Temperature                                                 Quenching After heating to over 727°C, cool rapidly          Quenching makes steel hard because it cools down red-hot
                                                                          (Tempering) down to 550°C in water or oil.                     steel very rapidly in water or oil, but it may promote internal
                                                                                                                                         stress. In order to remove such internal stress, tempering is
                               727°C  Rapidly  Very Slowly                                                                               used.
                             600°C                                                                                                       (After cooled down once, reheat it to 200°C~600°C)

                                                          Rather Rapidly  Normalizing After heating to over 727°C, cool down rapidly to  It miniaturizes the crystals. (Steel is also composed of small
                                               Slowly                                    600°C and then to normal temperature.           cells.) It is used to improve the mechanical character or
                                                                                                                                         machinability.
                             550°C    Slowly

                                                           Time           Annealing After heating to over 727°C, cool down very          It miniaturizes the crystals like the process of normalizing, but
                             Heat Treatment Method                                       slowly to 600°C, then to normal temperature.    the crystal size is bigger than that of normalizing.
                                                                                                                                         It targets machinability improvement and distortion correction.

                             Hardness Value

                             Hardness                                     Reference Standard            Example                                        Explanation of Example

                Brinell Hardness                            JIS Z 2243 1992                       250HB                                  Hardness Value : 250, Hardness Symbol : HB
                                                                                                  200~250HB                              When the hardness has the range
                Vickers Hardness                            JIS Z 2244 1998                       640HV                                  Hardness Value : 640, Hardness Symbol : HV
                Rockwell Hardness                           JIS Z 2245 1992                       60HRC                                  Hardness Value : 60, Hardness Symbol : HRC
                Shore Hardness                              JIS Z 2246 1992                       50HS                                   Hardness Value : 50, Hardness Symbol : HS

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