高性能钢铁材料在实体膨胀管领域的应用前景

实体膨胀管技术作为一项先进的钻井技术,其技术优势在套损修复、固井、完井等领域逐渐显露出来。管材的设计研发是实体膨胀管3大关键技术之一,也是制约膨胀管应用的主要技术瓶颈。介绍了实体膨胀管的技术原理,综述了国内外实体膨胀管管材的研发现状,重点分析了实体膨胀管管材所需的力学性能。在此基础之上,着重介绍了现有的双相钢、TRIP-assisted钢以及高锰奥氏体TWIP/TRIP钢3种高塑性高强度钢铁材料的力学性能特点、材料设计原理及热处理工艺,对它们作为实体膨胀管管材使用的可行性进行了讨论。     

780MPa级热镀锌用TRIP钢退火工艺及组织演变

研究了热镀锌用高强TRIP钢的退火工艺对性能的影响和组织演变规律.结果表明:实验用钢可获得780.00MPa以上的抗拉强度和24.00%以上的断后延伸率;两相区加热温度和贝氏体保温时间对钢的力学性能具有显著影响,两相区加热温度为850℃,贝氏体保温时间为30s时,实验用钢能获得最佳的综合力学性能;在贝氏体中温相变后,仍有部分亚稳奥氏体(碳含量较低)在后续冷却过程中发生马氏体相变,从而导致钢退火后的微观组织由铁素体、贝氏体、残余奥氏体和马氏体组成.     

Effect of strain-induced martensitic phase transformation on the formability of nitrogen-alloyed metastable austenitic stainless steels

Strain-induced martensitic phase transformation and its influence on the formability of newly developed nitrogen-alloyed metastable austenitic stainless steels were systematically investigated. Yield strength for the asreceived steels bearing lownickel content was around 300 MPa and their elongation ratios varied from 55. 2% to61. 7%. Erichsen numbers of these samples differed from 13. 82 to 14. 57 mm. Although its Cu content was lower than that of other samples,steel D2 exhibited better plasticity and formability,which was attributed to γ→α'martensitic phase transformation. EBSD,XRD,and magnetism tests showed that increases in deformation ratio gradually increased the α' martensite phase of a sample,thereby contributing to its strain and inducing the optimal transformation-induced plasticity effect. An M_(d30/50) temperature of around 20 ℃,which is close to the deformation temperature,provided the austenite with adequate stability and gradually transformed it into martensite,thereby endowing lean ASS with better formability.     

残余奥氏体中的碳元素在TRIP钢变形前后的分布

利用TEM和EPMA对TRIP钢中残余奥氏体形貌以及碳元素的分配进行了研究,发现TRIP钢中的残余奥氏体以多种形态分布,且碳在残余奥氏体中的浓度显著高于其他两相中的浓度,此时残余奥氏体可以通过EPMA中的贫硅区表示;变形之后的残余奥氏体将会发生相变,通过TEM发现残余奥氏体在受到应力作用而发生相变之后转变为细小的立方马氏体,且由于碳原子来不及扩散,马氏体中的含碳量和奥氏体中的含碳量基本相同。     

Effects of Solution Treatment and Test Temperature on Tensile Properties of High Mn Austenitic Steels

Tensile properties of high Mn austenitic Fe‐26.5Mn‐3.6Al‐2.2Si‐0.38C‐0.005B (HM1) and Fe‐18.9Mn‐0.62C‐0.02Ti‐0.005B (HM2, in mass%) steels after different solution treatments have been investigated. The results show that the solution treatment has a significant influence on microstructure and mechanical properties of the investigated steels. By appropriate solution treatment the product of tensile strength (R_m) and total elongation (A₅₀) of the hot rolled steel can be improved from ? 40000‐50000 MPa% to ? 55000‐65000 MPa% depending on the steel chemical composition. A solution treatment with a very high temperature, e.g. at 1100 °C for the Fe‐18.9Mn‐0.62C‐0.02Ti‐0.005B steel, results in a significant increase in the ?‐martensite fraction during quenching. This deteriorates the ductility of the steel. A solution treatment at low temperature in the austenitic range, e.g. at 700 °C for the Fe‐18.9Mn‐0.62C‐0.02Ti‐0.005B steel, results in a decrease in the grain size of the steel. This suppresses the ?‐martensite transformation during cooling. EBSD measurements revealed the mechanisms contributing to the overall plasticity of the investigated steels on the microscale. The plasticity of the 26.5Mn‐3.6Al‐2.2Si‐0.38C‐0.005B steel is produced mainly by TWIP mechanism under the examined experimental conditions, whereas for the Fe‐18.9Mn‐0.62C‐0.02Ti‐0.005B steel TWIP and TRIP mechanisms occur with different degrees depending on the test temperature of the tensile test.     

TRIP钢在分段冷却过程中的相变行为

 建立了热轧低碳Si Mn系TRIP钢相变动力学模型。将该模型用于模拟热轧TRIP钢分段冷却过程中显微组织的演变,并定量分析了热变形和冷却速率对热变形奥氏体相变行为的影响。结果表明,预测值与实测值符合较好;降低终轧温度、提高终轧变形量,延长两相区缓冷时间都能促进铁素体相变,从而有利于提高残余奥氏体中的碳含量。     

Relative Influences of Aluminium and Silicon on the Kinetics of Bainite Formation from Intercritical Austenite

Bainite formation from intercritical austenite is of great practical importance for the production of TRIP‐assisted steels. Silicon and aluminium play important roles during this transformation by delaying carbide precipitation, thus favouring the carbon enrichment of untransformed austenite, which makes its stabilisation down to room temperature possible. Previous studies have shown a strong dependence of bainite formation kinetics on both chemical composition and transformation temperature. In the present work, the effect of silicon and aluminium contents on bainite formation kinetics is investigated experimentally using dilatometry combined with microscopical observations. The experimental results are analysed by comparison with thermodynamic parameters, such as the activation energy G¹ for nucleation of bainite and the carbon content C_to corresponding to the T_o‐curve. It is shown that the faster transformation kinetics induced by the substitution of silicon by aluminium can be ascribed (i) to a higher driving force for nucleation, (ii) to a higher carbon content C_to at the To‐curve and (iii) to the precipitation of carbide in austenite in steels with a low Al content.     

临界区退火处理对0.15C-1.5Mn-1.5Al冷轧TRIP钢相变和力学性能的影响

利用热膨胀仪、热处理实验、拉伸实验和X衍射实验研究了不同临界退火温度对0.15C-1.5Mn-1.5Al TRIP钢相变、残余奥氏体特征和力学性能的影响.结果表明:不同临界退火温度下的热膨胀曲线具有相同的变化过程,两相区奥氏体含量随临界退火温度的升高而上升,而其碳含量则下降;临界退火温度影响试样的残余奥氏体特征和力学性能,820℃退火处理时残余奥氏体的体积分数为14%,碳的质量分数为1.36%;力学性能也是820℃退火时最佳,强塑积可达25400 MPa·%,且变形过程中具有高的瞬时加工硬化指数(n值).     

New Steel Solutions for the Worldwide Car Industry

Steel development as a scientific process requires both metallurgical background and state‐of‐the‐art analysis and testing technology. In the future, we expect much shorter development periods owing to the increased use of computer simulation. Successful developments are the result of consistent team work, both in the steel companies and in the cooperation with automobile producers. Customer involvement at an early stage permits to speed up the development by simultaneous engineering. The success of a material in the market depends more and more on its comprehensive definition by relevant parameters. Scientific technical services form a part of marketing. Modern high‐strength steels are enjoying success and are finding ever more application in new cars.     

等温淬火温度对超细贝氏体钢组织及耐磨性的影响

设计了一种0.7C的低合金超细贝氏体钢,并通过膨胀仪、二体磨损实验、光学显微镜、扫描电镜、X射线衍射、激光扫描共聚焦显微镜及能谱仪,研究了不同等温淬火温度对超细贝氏体钢的贝氏体相变动力学、微观组织以及干滑动摩擦耐磨性的影响,揭示超细贝氏体钢在二体磨损条件下的耐磨性能和磨损机理.研究结果表明,不同等温温度下的超细贝氏体钢都由片层状贝氏体铁素体和薄膜状以及块状的残留奥氏体组成;随着等温温度的升高,超细贝氏体的相变速率提高,相变孕育期及相变完成时间缩短,但贝氏体铁素体板条厚度增加,残留奥氏体含量增加,硬度值有所降低;超细贝氏体钢磨损面形貌以平直的犁沟为主,主要的磨损机理为显微切削;不同等温温度下所获得的超细贝氏体的耐磨性能都优于回火马氏体,且随着等温温度的降低,耐磨性能提高.其中在250℃等温所获得的超细贝氏体钢具有最优的耐磨性能,其相对耐磨性为回火马氏体的1.28倍.这主要与超细贝氏体钢中贝氏体铁素体板条的细化及磨损过程中残留奥氏体的形变诱导马氏体相变（TRIP）效应有关.     

热处理对TRIP 590钢微观组织及力学性能的影响

采用Gleeble3800热模拟机对TRIP钢拉伸试样进行不同工艺条件的快速热处理模拟实验,并采用金相分析、显微硬度测试等方法对试样进行组织观察和性能测试,目的是通过适宜的热处理工艺促使材料微观组织中出现适量的残余奥氏体组织,增强该材料在变形过程的相变诱导塑性(TRIP)效应,强化材料结果表明:在两相区内,TRIP钢中的残余奥氏体含量随着退火温度和退火时间的增加而增大,以25℃/s缓慢加热到700℃,再以150℃/s的速率快速加热到820℃保温120s后淬火处理,处理后的试样,残余奥氏体体积分数达到13％,显微硬度最高,达到262HV.