A METHOD FOR PRODUCING A HIGH STRENGTH STEEL PIECEA method for producing a high strength steel piece having desired mechanical properties, obtainable by a reference heat treatment comprising a first reference treatment and a final reference treatment comprising at least an overaging, The method comprising a step of heat treating on an equipment comprising at least an overaging means for which it is possible to set at least one operating point, the final treatment comprising an overaging for which it is possible to calculate two final treatment parameters OAP1 and OAP2 depending on an operating point of the overaging means. A minimum OAP1 min and a maximum OAP2 max final treatment parameters are determined in order to obtain the desired properties, at least one operating points of the overaging section means is determined such that OAP1 ≥ OAP1 min and OAP2 ≤ OAP2 max. The piece is heat treated accordingly. The parameters are with T(t) the temperature at time t Formula (I)A method for producing a high strength steel piece having desired mechanical properties, the piece being made of a steel for which it is known that it is possible to obtain said desired mechanical properties by a reference heat treatment comprising a first reference treatment conferring to the steel piece a defined structure and a final reference treatment comprising at least an overaging, said method for producing a high strength steel piece comprising a step of heat treating the piece on an equipment comprising at least overaging means in order to obtain desired mechanical properties for the piece, the step of heat treating comprising at least a final treatment made on the steel piece having the same structure than the defined structure resulting from said first reference treatment, the final treatment comprising at least an overaging step made on said overaging means for which it is possible to set at least one operating point, for which it is possible to calculate two final treatment parameters OAP1 and OAP2 depending on said at least one operating point of the overaging means, characterized in that it comprises the steps of:- determining a minimum first final treatment parameter OAPI min and a maximum second final treatment parameter OAP2max respectively, in order to obtain the desired mechanical properties,- determining at least the at least one operating points of the overaging section means such that the first final treatment parameter OAP1 and the second final treatment parameter OAP2 resulting from operating points fulfill:OAP1≥ OAP1 minandOAP2≤ OAP2 max- and heat treating the piece on the equipment running according to the determined operating points,- wherein, if T(t) is the temperature in °C of the steel piece at the time t, t0 the time of the beginning of the final treatment and tf the time of the end of the final treatment: the corresponding first overaging parameter OAP1 is : wherein Q = activation energy of the diffusion of carbon and R = ideal gas constant, and the second overaging parameter OAP2 is:T0 being the temperature at time t0. 2 - The method according to claim 1 characterized in that the desired mechanical properties are minimum values for at least a traction property such as the yield strength and/or the tensile strength and for at least a ductility property such as the total elongation and/or the uniform elongation and/or the hole expansion ratio and/or the bending properties.3 - The method according to claim 1 or 2, characterized in that the first reference treatment comprise an annealing at a temperature higher than the Ac1 transformation point of the steel in order to obtain before quenching a structure containing at least 50% of austenite and a quenching down to a temperature QT lower than the Ms transformation point of the steel in order to obtain a structure comprising just after quenching at least martensite and austenite and the overaging is made at a temperature not less than the quenching temperature QT and lower than the Ac1 transformation point of the steel. 4 - The method according to claim 3, characterized in that the annealing is made at a temperature higher than Ac3 in order to obtain before quenching a structure fully austenitic.5 - The method according to claim 3 or 4, characterized in that the quenching temperature QT is such that the structure resulting from the final treatment contains at least 10% of austenite.6 - The method according to any one of claims 1 to 5, characterized in that the final treatment comprises further to the overaging step, a hot dip coating step, for example a galvanizing or a galvannealing step.7 - The method according to claims 1 to 6, characterized in that the steel piece is a steel sheet produced on a continuous line and the overaging means is an overaging section of a continuous annealing line, in that the before entering in the overaging section, the sheet is annealed and quenched according to the first reference treatment.8 - The method according to any claim from 1 to 6, characterized in that the steel piece is the hot formed piece and the overaging means is a furnace in which the piece is maintained and in that, just before entering in the furnace, the structure of the hot formed piece is the same as the structure of the piece after the first reference treatment 9 - The method according to any claim from 1 to 8, characterized in that to determine the minimum first final treatment parameter and maximum second final treatment parameter, a plurality of experiments are performed with overaging consisting in a heating from the temperature QT up to a holding temperature Th at a heating speed of more than 10°C/s, a holding step at the holding temperature Th for a plurality of durations tm and a cooling down to the room temperature at a cooling speed higher than 10°C/s but not too high so as not to form fresh martensite in the structure.10 - The method according to claim 7 characterized in that, to determine the minimum first fin...
고강도 강 피스를 제조하기 위한 방법제 1 기준 처리 및 최종 기준 처리를 포함하는 기준 열 처리에 의해 획득가능한, 원하는 기계적 특성들을 가지는 고강도 강 피스를 제조하기 위한 방법은 적어도 과시효를 포함한다. 방법은, 적어도 하나의 작동점을 설정할 수 있는 적어도 과시효 수단을 구비하는 장비에서 열 처리하는 단계를 포함하고, 최종 처리는 과시효 수단의 작동점에 따라 2 개의 최종 처리 파라미터들 (OAP1, OAP2) 을 산출할 수 있는 과시효를 포함한다. 최소 OAP1min 및 최대 OAP2max 최종 처리 파라미터들은 원하는 특성들을 획득하기 위해서 결정되고, OAP1 ≥ OAP1min 이고 OAP2 ≤ OAP2max 이도록 과시효 섹션 수단의 적어도 하나의 작동점들이 결정된다. 그에 맞춰, 피스는 열 처리된다. 파라미터들은 시간 (t) 에서 온도 T(t) 와 수학식 (Ⅰ) 을 이용한다.원하는 기계적 특성들을 가지는 고강도 강 피스를 제조하기 위한 방법으로서, 상기 피스는, 상기 강 피스에 규정된 조직을 부여하는 제 1 기준 처리, 및 적어도 과시효를 포함하는 최종 기준 처리를 포함하는 기준 열 처리에 의해 상기 원하는 기계적 특성들을 획득할 수 있는 것으로 알려진 강으로 만들어지고,상기 고강도 강 피스를 제조하기 위한 방법은, 상기 피스를 위한 원하는 기계적 특성들을 획득하도록 적어도 과시효 수단을 포함하는 장비에서 상기 피스를 열 처리하는 단계를 포함하고,상기 열 처리하는 단계는 상기 제 1 기준 처리에서 유발되는 규정된 조직 이외에도 동일한 조직을 가지는 강 피스에서 수행되는 적어도 최종 처리를 포함하고,상기 최종 처리는, 적어도 하나의 작동점을 설정할 수 있고 상기 과시효 수단의 상기 적어도 하나의 작동점에 따라 2 개의 최종 처리 파라미터들 (OAP1, OAP2) 을 산출할 수 있는, 상기 과시효 수단에서 수행된 적어도 과시효 단계를 포함하고, 상기 방법은: - 원하는 기계적 특성들을 획득하도록 최소 제 1 최종 처리 파라미터 (OAP1min) 및 최대 제 2 최종 처리 파라미터 (OAP2max) 를 각각 결정하는 단계,- 작동점들로부터 기인한 제 1 최종 처리 파라미터 (OAP1) 및 제 2 최종 처리 파라미터 (OAP2) 가:OAP1 ≥ OAP1min 그리고OAP2 ≤ OAP2max 를 만족시키도록 과시효 섹션 수단의 적어도 하나의 작동점들을 적어도 결정하는 단계, - 결정된 상기 작동점들에 따라 가동하는 장비에서 상기 피스를 열 처리하는 단계를 포함하고,- T(t) 가 시간 (t) 에서 상기 강 피스의 온도 (단위: ℃) 이고, t0 이 최종 처리 개시 시간이고 tf 가 최종 처리 종료 시간이라면:대응하는 제 1 과시효 파라미터 (OAP1) 는:여기에서, Q = 탄소 확산 활성화 에너지이고 R = 이상 가스 상수이고, 제 2 과시효 파라미터 (OAP2) 는: T0 은 시간 (t0) 에서 온도인 것을 특징으로 하는, 원하는 기계적 특성들을 가지는 고강도 강 피스를 제조하기 위한 방법.