任毅
,
刘文月
,
张帅
,
王爽
,
高红
上海金属
海底管线用钢要求具有较大的均匀塑性变形延伸率、较低的屈强比等,该管线钢的高强度与高塑性匹配主要来源于双相组织的作用.针对海底管线用钢的组织和塑性变形能力进行了研究.结果表明,海底管线用钢的母材组织由铁素体、贝氏体及少量MA岛构成,其组织形貌与控轧控冷工艺密切相关.细化的双相组织具有良好的塑性指标和较低的屈强比,保证了管线钢具有良好的强塑性匹配.
关键词:
管线钢
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组织
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屈强比
,
延伸率
Seok-Hwan Ahn
,
Insup Lee
材料科学技术（英文）
Plasma radical nitriding was performed to harden the surface of SCM440 steel for 1-10 h at temperature range of 450-550℃. This process involved the use of NH3 gas instead of N2 gas employed for the well-established plasma nitriding method. No compound layer was formed during this process except the experiment carried out at 500℃ for 10 h. The main phase produced in the diffusion zone was identified to be γ′-Fe4(N, C). A diffusion depth increased with increasing treatment temperature and time (up to about 250 μm). The surface hardness of radical nitrided layer was about two times higher than that of the untreated surface. The tensile test was carried out to estimate the mechanical properties of surface-hardened SCM440 steel prepared at various plasma radical nitriding treatment time and temperature. The influence of radical nitriding treatment on the tensile strength of the specimen was found to be insignificant. The highest value of the ultimate tensile strength was obtained in the experiment carried out at 500℃ for 1 h. However, the elongation was greatly affected by the radical nitriding processing parameters. The maximum value of elongation, which is equal to about 18.1%, was also obtained under the condition of 500℃ for 1 h.
关键词:
Plasma radical nitriding
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null
,
null
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null
Yu CHEN
材料科学技术（英文）
strength of 775 MPa, high elongation of 29% and low ductile-brittle transmission temperature less than -80℃ has been developed in laboratory based on the common silicon and manganese chemical composition. The experimental results showed that the microstructures were featured with ultra fine grain size less than 5 μm, appropriate retained austenite volume fraction around 11.8% and purified ferrite grain, which may result in well balanced mechanical properties for the steel.
关键词:
Ultra fine grain
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null
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null
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null
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