钢的组织控制与设计(一)

CONTROL AND DESIGN OF MICROSTRUCTURE IN STEELS(Ⅰ)

以H13热作模具钢和高强度钢为例,分别重点讨论钢的组织控制和设计。对H13钢,应消除原生碳化物和偏析,改善二次碳化物分布,使成分均匀化,缩小钢块纵、横向性能差,可将现国产H13钢的使用寿命显著提高。对兼具高强度(Rm>2000MPa)和韧性钢的组织,拟设计为:低温回火马氏体组织,含高密度位错的细条马氏体,包有残余奥氏体薄膜,并分布弥散的碳化物(避免渗碳体的形成);钢含低的碳量,并含有一定量的Si,Al和Mn,Ni,Mo等合金元素及Nb等碳化物形成元素;适当应用Q-P处理、双相区退火、贝氏体或马氏体等温处理等。文章分两期发表。

Taking H13 mold steel and high strength steel as examples respectively, control and design of microstructure in steels are emphasized. For H13 steel, to diminish the primary carbides and segregation, to improve the distribution of secondary carbides and to homogenize the solute concentrations are required in order to decrease the directional difference in mechanical properties in a steel bar, in turn to prolong significantly the life of mold. For steel with combination of strength and toughness, the designed microstrueture would be low temperature tempered martensite, i.e., fine lath martensite with high density of dislocation, coated with thin film of austenite and distributed with fine carbides （formation of eementite should be prevented if possible）, containing low content of carbon, certain amount of alloying elements Si, A1 and Mn, Ni, Mo as well as carbide forming element Nb etc. Q＆P process, intereritieal annealing and isothermal holding for production of bainite or martensite may be used if in need. The article is issued in two parts.