共查询到20条相似文献,搜索用时 46 毫秒
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摘要:以热轧耐低温H型钢为研究对象,采用光学显微镜、扫描电镜、透射电镜分析和力学性能测试等手段,研究了完全淬火和亚温淬火对试验钢微观组织和力学性能的演变规律。结果表明,试验型钢经780℃亚温淬火+600℃回火处理后,形成回火索氏体+铁素体的网状组织;试验型钢900℃淬火+600℃回火处理后,转变得到具有马氏体位向的回火索氏体,碳化物分布更加细小均匀,位错密度下降。2种热处理工艺制备H型钢综合力学性能优良,屈服强度均达到500MPa以上,900℃淬火+600℃回火处理后钢的屈服强度和抗拉强度更高。-40℃低温冲击韧性比热轧状态下出现大幅度提高,随着淬火温度升高冲击功更加稳定。 相似文献
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低屈强比钢板要求双相组织,生产控制难度大。通过发挥预矫直机的大压下量预矫作用,优化Mulpic水冷参数,改善了钢板板形及性能;优化回火温度及时间,控制组织内软硬相比例,确保了钢板各项性能及屈强比。济钢采用在线淬火+离线回火的工艺生产的油罐钢屈强比在0.90以下,一次性能合格率90%以上。 相似文献
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在实验室条件下对热轧X120管线钢进行两种不同工艺淬火,研究了回火温度对不同淬火态试验钢组织力学性能的影响。试验结果表明:直接快冷工艺下,显微组织以板条铁素体+马氏体为主;缓冷+直接快冷工艺下以粒状贝氏体+板条铁素体+马氏体为主。随回火温度升高,两种试验钢强度均出现起伏,在400~500℃范围内回火后,冲击功和伸长率均得到改善;采用直接快冷工艺在350℃和600℃回火后出现断口分离现象,从而导致力学性能波动,而缓冷+快冷工艺在回火过程中力学性能稳定性较好。因此,采用缓冷+快冷工艺+(450~500℃)回火,其力学性能达到X120级管线钢性能要求。 相似文献
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利用扫描电镜(SEM)、透射电镜(TEM)和力学性能检验等试验方法,研究了系列回火温度对TMCP处理的屈服强度550 MPa级抗震建筑用钢微观组织、第二相析出及力学性能的影响。结果表明,随着回火温度的提高,试验钢屈服强度和抗拉强度变化趋势一致,屈强比呈明显的上升趋势。分析认为:回火前后力学性能的变化主要与回火后更多弥散的尺寸在25 nm以下的新的细小粒子析出以及M/A岛的分解和发生位错亚结构回复软化有关,试验钢450℃回火后钢板具有最佳综合力学性能:抗拉强度为703 MPa,屈服强度为588 MPa,伸长率为17.5%,-20℃冲击吸收能量为240 J,屈强比0.84满足建筑用钢要求。 相似文献
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在高强度钢板中,超低碳烘烤硬化钢板(简称BH钢板)是新型优质汽车用薄板.在生产BH钢板时,需要有效地控制屈服强度,以保证较好的深冲性能.采用四方图识别了影响屈服强度的关键因素,包括化学成分、热轧参数、冷轧参数等;基于大量的生产过程历史数据,分别用回归分析、神经元网络、决策树三种不同方法进行分析,建立各关键输入变量(KIV)对屈服强度(KOV)影响的多变量模型.以神经元网络模型为例,进行了模型评价.以该模型为基础,在已知某些KIV取值的情况下,能够较为准确地预测BH钢成品的屈服强度,合格率提高7个百分点,取得了较好的经济效益. 相似文献
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The bond behavior of reinforcing bars in concrete is a critical issue in the design of reinforced concrete structures. This study focuses on the bond strength of fiber reinforced polymer (FRP) rebars in normal strength concrete. Four different types of rebars were tested using the pullout method: aramid FRP (AFRP); carbon FRP (CFRP); glass FRP (GFRP), and steel. This involved a total of 151 specimens containing 6, 8, 10, 16, and 19?mm rebars embedded in a 203?mm concrete cube. The test embedment lengths were five, seven, and nine times the rebar diameter (db). For each rebar, the test results include the bond stress–slip response and the mode of failure. The test results showed that the bond strength of an FRP rebar is, on average, 40–100% the bond strength on a steel rebar for pullout failure mode. Based on this research, a proposal for the average bond strength of straight FRP rebars in normal strength concrete is made, which verifies an existing bond strength relationship (GFRP) and extends its application to AFRP and CFRP. It is an expression that is a function of the rebar diameter, and the concrete compressive strength. 相似文献
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Filaments, films, tubes, membranes, and shells are considered as a general class of low-dimensional objects, the thickness of which is much smaller than their length and possible displacements. The strength of such materials almost achieved the theoretical limit, and their bearing capacity is restricted by macroscopic elastic (or viscoelastic) loss of stability rather than fracture. The generality of the phenomena of the loss of bearing capacity in low-dimensional objects and elastic (or viscoelastic) instability and its modes (wrinkles and focuses in twisting of a wire and a ribbon and in buckling, corrugation, curvature condensation of tubes and shells and plastic folds in flicking) is analyzed. 相似文献
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This paper evaluates the shear strength, Vc, of intermediate length (2.5 < a∕d < 6) simply supported concrete beams subjected to four-point monotonic loading and reinforced with deformed, glass fiber-reinforced polymer (GFRP) reinforcement bars. Six different overreinforced GFRP designs, ρ > ρb, were tested with three replicate beams per design. All samples failed as a result of diagonal-tension shear. Measured shear strengths at failure are compared with theoretical predictions calculated according to traditional steel-reinforced concrete procedures and recently published expressions intended for beams reinforced with GFRP. Recommendations are made regarding the adequacy of shear strength prediction equations for GFRP-reinforced members. The study concludes that shear capacity is significantly overestimated by the “Building Code Requirements for Structural Concrete and Commentary” (ACI 318-99) expression for, Vc, as a result of the large crack widths, small compression block, and reduced dowel action in GFRP-reinforced flexural members. Shear strength was found to be independent of the amount of longitudinal GFRP reinforcement. A simplified empirical equation for predicting the ultimate shear strength of concrete beams reinforced with GFRP is endorsed. 相似文献