超高强韧油井管合金设计与高强韧机制

 为了揭示1 000 MPa级低碳加铌钒钛微合金钢的高强韧机制,研究了S1(w(C)=0.09%)与S2(w(C)=0.17%)两种合金成分的油井管钢成分-工艺-组织-性能关系。试验表明,两种成分试验钢经水淬后的组织分别为板条贝氏体加少量马氏体和马氏体加少量贝氏体的复相组织。两种成分钢经过450~600 ℃、30 min的中温回火后,组织中均出现碳化物析出,且S1试验钢回火后的屈服强度基本不变,抗拉强度下降了约70 MPa,S2试验钢回火后的屈服强度与抗拉强度迅速升高170 MPa左右。溶度积公式的计算结果表明,两种钢的水淬组织中铌、钛元素析出彻底且析出物的体积分数都很小,因此回火铁素体基体中的VC析出强化对S1试验钢回火后屈服强度保持不变以及S2试验钢回火后屈服、抗拉强度提高起到重要作用。     

Investigation of separation phenomenon in high-toughness X70 thick-walled linepipe steel

Separation is a commonly observed phenomenon during drop weight tear testing in high-toughness linepipe steels. Severe separation is harmful because it may cause fracturing or bursting of pipes. In this study,a quantitative measurement of separation was proposed,and using this new method,a relationship between the separation and microstructure was determined and discussed. The microstructures observed using optical and scanning electron microscopy revealed that the separation was related to the mixed ferritic and bainitic microstructures,or rather,it was related to the carbon enrichment in bainite.     

Assessment of the austemperability of high-silicon cast steels through Jominy hardenability tests

The austemperability of seven high silicon cast steels with different alloy contents was characteri sed. The maximum round bar diameter that can be fully austempered changed from about 10?mm for an unalloyed steel to more than 70?mm for a low-alloy steel. The austemperability was calculated by applying a procedure based on a standard Jominy test and the characterisation of the microstructure along the Jominy sample. The method, which was validated experimentally, creates a relatively simple procedure to measure austemperability. Processing factors such as the ability of the salt bath to extract heat and the austempering temperature are accounted for the method. The metallographic study revealed the influence of microsegregation on hardenability, which is particularly important for cast steels.     

热处理工艺对高C-Cr高强耐磨钢组织和性能的影响

设计了一种高C-Cr高强耐磨钢,测试了末端淬透性,研究了不同热处理工艺对微观组织演变和性能的影响,测试了力学性能和耐磨损性能,利用SEM和TEM表征了微观组织。试验结果表明,随距离淬火端距离的增大,试验钢的硬度呈现单调递减的趋势,0~2.5 cm为硬度平缓降低阶段,布氏硬度在63~65HRC的区间。马氏体淬火+回火处理后,试验钢基体组织主要为马氏体板条,板条尺寸大小不一。经贝氏体等温淬火处理后,贝氏体板条相互平行,板条尺寸平均。贝氏体板条间存在薄膜状的残留奥氏体,贝氏体板条内部存在长度为100~150 nm的碳化物析出相,析出相与贝氏体板条呈60°取向排列。磨损过程中,达到800转时,马氏体基体试验钢失重168 mg,贝氏体基体失重192 mg,增加了14.28%,马氏体基体的耐磨损性能更高。而贝氏体基体的力学性能却明显高于马氏体基体,屈服强度达到1 955 MPa,抗拉强度达到了2 485 MPa,伸长率仍然达到了7%。     

不同锰铬含量对贝氏体钢组织转变的影响

文章利用全自动相变仪对不同锰铬含量的贝氏体钢组织转变进行了试验研究,对比分析了不同锰铬元素含量对贝氏体钢过冷奥氏体相变点的影响,并研究了不同转变温度对贝氏体钢组织转变的影响,试验结果表明贝氏体钢组织转变的最佳温度为330℃,为贝氏体钢生产工艺开发提供了理论依据。     

Q-I-Q-T工艺对60Si2CrVA钢断裂韧性的影响

研究60Si2CrVA弹簧钢经淬火-等温-淬火-回火(Q-I-Q-T)热处理后复相组织含量与断裂韧性间的关系。结果表明,在实验的等温温度范围内,随着等温温度的升高,残余奥氏体和贝氏体含量逐渐增大,60Si2CrVA钢强度降低,断裂韧性逐渐增加,在300℃等温时,断裂韧性达到最大值66.37 MPa.m1/2。稳定的残留奥氏体与过渡形态贝氏体量增加是提高断裂韧性的主要原因。