Study Of High Strength And High Toughness Homogenizing Cr-Ni-Mo–V Series Steels

Currently, one common problem of the ultra-high pressure vessel steels is the high strength and low toughness of those manufacturing material. With the ultra-high vessel widely used in all kinds of fields,the ultra-high pressure vessel steels require not only a good match of strength and toughness, but also the uniformity of mechanical performance.At the same time,because the ultra-high pressure industry in China started lately and its starting point was low,most of steels which were used in china to ultra-high pressure vessels depend on coping some steels of abroad,whose mechanical properties were worse than foreign. Considering the fact that the lack of the ultra-high pressure vessel steels of domestic independent R & D and mechanical properties,in order to break through “bottleneck” problem badly to prevent the progress of domestic ultra-high pressure fields,combined with the actual demand of a certain domestic design institute,I assume the R&D task of high strength and high toughness homogenizing Gr-Ni-Mo-V series steels used to ultra-high pressure vessels.Though analyzing the role of various alloying elements in steel and its strengthened mechanism in the process of heat treatment,it is concluded the alloy composition design method of the new ultra-high pressure vessel Cr- Ni- Mo – V steel, completed the smell of experimental steels, under the cooperation of Shenyang yin jie special alloy forging factory completed the forged work of test steel later.Considering the higher alloy content characteristic in the ultra-high pressure vessel Cr- Ni- Mo – V steels,drawing lessons from existed research on the heat treatment process of ultra-high pressure vessel steels, developed the heat treatment process of hardening,quenching and normalizing for the ultra-high pressure vessel steels,completed the heat treatment work of test steel. Through the test, statistics and analysis of mechanical properties of test steels, achieved a new ultra-high pressure vessel steel which can meet the requirements of this subject,filled the gap of domestic ultra-high pressure industry.Analyzed the affection of quenching temperature on microstructure and mechanical properties of the new ultra-high pressure vessel Cr- Ni- Mo – V steel, it is concluded thatthe quenching temperature on the influence of the strengthening mechanism of alloy steelsimultaneously,analyzed the affection of tempering temperature on microstructure and mechanical properties of the new ultra-high pressure vessel Cr- Ni- Mo – V steel,it is obtained that the tempering temperature on the influence of the strengthening mechanism of alloy steel.Through thermal expansion experiment completed the test obtained the curves of the thermal linear expansions versus the temperature under different cooling speed,and its continuous cooling transformation( CCT) curves were measured。Researched the effects of austenizing temperature and austenitizing time on the grain size and micro hardness of the new test steel, giving theoretical supports for formulating suitable heat treatment process in the actual production.