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摘要:为掌握形变对共析钢连续冷却过程中珠光体相变的影响,研究了共析钢在720~920℃温度范围内进行形变后,在连续冷却过程中奥氏体向珠光体相变的规律,建立了相变时的过冷度和珠光体片层间距的相互关系,并预测了试验钢的力学性能。结果表明:形变储存能促进共析钢在50℃/s高冷速下发生珠光体相变,形成片层间距为129~187 nm的超细片层珠光体,抗拉强度达到近1000MPa,且随着形变温度提高,形变储存能减小,珠光体相变温度降低,珠光体片层间距减小,屈服强度和抗拉强度提高。 相似文献
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为了优化82B钢的成分和热轧冷却工艺,以提高82B盘条的强度,测定了80钢和82B钢的等温转变温度对相变时间、珠光体片层间距的影响以及Cr元素对82B相变温度的影响,分析了Cr合金化和相变控制对82B盘条的微观组织和抗拉强度的影响。对于82B,当温度在595~615℃相变速度最快,其转变时间为10~15s,在590~625℃可得到理想的0.10~0.20μm的珠光体片层间距;通过添加0.18%~0.24%Cr和控制热轧冷却速度,可以控制82B钢的相变温度区间和相变速度,得到均匀细片状的珠光体组织;将Φ12.5mm 82B盘条的主要成分调整为0.78%~0.84%C、0.15%~0.35%Si、0.78%~0.88%Mn和0.18%~0.24%Cr;在热轧控冷过程中,弱化水冷,强化风冷,控制82B盘条的吐丝温度为840~880℃,目标值860℃,增大82B盘条在风冷线上的冷速,提高了盘条的强度。 相似文献
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通过热模拟机 Gleeble- 15 0 0对控制冷却过程的模拟 ,研究了相变区冷速对 6 0 Si2 Mn A弹簧钢的组织结构、珠光体量、珠光体片层间距和平均晶粒尺寸的影响 ,结果表明 ,冷速 v≤ 5℃ / s时 ,组织为珠光体 +铁素体 ;v>5℃ / s时 ,有马氏体产生 ;v=3℃ / s时珠光体量达到 85 % ;珠光体片层间距在 v=9~ 11℃ / s时达到较小值 0 .118~ 0 .133μm;在 v=7℃ / s时 ,平均晶粒尺寸达到较小值 2 6 .1μm。综合考虑 ,终轧温度 95 0℃ ,吐丝温度在 870~ 930℃范围内 ,相转变时冷却速度控制在 5℃ / s,产品性能得到明显改善 相似文献
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利用Thermecmastor-Z型热模拟试验机,结合金相显微镜(OM)、扫描电镜(SEM)、维氏硬度计等,系统研究了奥氏体区变形对50CrV4钢连续冷却相变和等温相变规律的影响。建立了试验钢动态CCT曲线。研究结果表明,奥氏体变形能促进连续冷却转变过程中铁素体-珠光体、贝氏体转变,但亦可提高奥氏体的机械稳定性,进而抑制马氏体转变,Ms点由331.6℃(奥氏体未变形)降低至291℃(950℃下变形50%+890℃下变形50%,变形速率均为5s-1,变形后冷速为20℃/s)。当轧后冷速小于0.5℃/s时,试验钢中可获得铁素体+珠光体组织。此外,在研究不同变形量对试验钢等温相变规律影响时发现,650℃等温时,试验钢中发生铁素体-珠光体相变。随着变形量的增加(由30%增加至50%),其等温相变动力学加快(相变完成时间由197.6s减小至136.5s),铁素体体晶粒尺寸、珠光体片层间距减小,硬度增加。 相似文献
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用膨胀法结合显微组织观察及硬度测量方法,得到了U75V钢轨钢动态CCT曲线。结果表明:当冷却速度为0.05~3℃/s时的U75V钢轨钢的显微组织为珠光体组织,而且随着冷却速度的加快珠光体片层间距逐渐减小;冷却速度为5℃/s时主要的显微组织为珠光体组织,但出现少量马氏体组织;当冷却速度为15~50℃/s时的显微组织为马氏体和残余奥氏体组织。随着冷却速度的增大,硬度呈增加趋势。高铁用U75V钢轨钢奥氏体向珠光体开始转变温度不超过700℃,相变结束温度不低于500℃,当冷却速度为2~3℃/s时珠光体片层间距最为细小。 相似文献
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通过热膨胀试验测定了82B试验钢的临界转变温度并绘制静态CCT曲线;研究了冷却制度对82B盘条金相组织的影响。结果表明:冷却相变时大的过冷度,可以减小片层间距,提高索氏体化率,得到强度和伸长率更好的盘条。因此须增加相变前的冷速(不低于8℃/s),控制相变过程中温度的稳定(560~640℃),控制相变后冷速不进入马氏体转变区间。经过工艺调整,盘条的索氏体化率从88%提高到90%以上,珠光体片间距控制在150 nm以下。 相似文献
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高碳帘线钢72A连续冷却转变(CCT)的特性 总被引:3,自引:1,他引:2
采用热膨胀法,通过THERMECMASTOR-Z热模拟实验机测试了高碳帘线钢72A(%:0.72C、0.53Mn、0.22Si)的连续冷却转变(CCT)曲线,并分析了开始冷却温度(840~930℃)和冷却速度(0.8~22℃/s)对钢组织的影响。结果表明,相同开始冷却温度条件下,冷却速度越快,相变时间越短;相同冷速条件下,随着开始冷却温度的升高,到达相变开始转变温度的时间和到达转变终了温度的时间会延后;提高开始冷却温度,珠光体的百分含量增加,珠光体片层间距减少,有利于提高线材力学性能。 相似文献
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本文为获得具有良好综合性能的U74钢轨,探讨了生产超细珠光体组织重轨的优化热轧及轧后冷却工艺制度,研究了热轧及轧后冷却工艺参数对奥氏体及珠光体组织的影响规律,其结果为:变形温度控制在850~900℃,变形程度控制在50%珠光体片层间距最小,随冷却速度增加而减小;变形温度在850~900℃球团最小并随变形程度,冷却速度增大而减小,通过多道次热轧变形工艺模拟试验测定获得超细珠光体组织的最佳变形工艺为850℃终轧,5~10℃/s冷却工艺。按优化热轧工艺轧制试样的性能达到:σb=1100~1150MPa,σs=750MPa,σs=12—15%,Ψ=37~42%,珠光体片层S为900(?),σ_bσ_s分别比现场轧态轨高150~200MPa,σ_5高3~5%,片层S要小1~1.5倍,并接近热处理钢轨的性能。 相似文献
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试验0.5~0.7Cr铲斗刀板型钢(/%:0.22~0.30C,0.25~0.45Si,0.95~1.20Mn,0.006~0.009P,0.008~0.010S,0.5~0.7Cr,0.015~0.065Nb,0~0.040Ti)由50kg真空感应炉熔炼,热轧成16mm厚板,终轧温度850~900℃,空冷。通过光学显微镜、扫描、透射电镜和力学性能测试研究了Nb-Ti含量(0.015Nb,0.035Nb-0.010Ti,0.065Nb-0.040Ti)对热轧态铲斗刀板钢组织和力学性能的影响。结果表明,试验钢组织为F+P,随Nb-Ti含量增加,钢板的晶粒细化,珠光体片层间距降低,(Nb,Ti)C和(Nb,Ti)(C,N)析出物增多,强度增加,0.065Nb-0.040Ti钢板的力学性能为屈服强度632MPa,抗拉强度916MPa,延伸率17.7%,KAV40 J,HB硬度值234。 相似文献
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The microsturctural transformation of austenite grain, pearlite interlamellar spacing, and lamellar cement ite thickness of spring steel 60Si2MnA for railway were studied in the hot-rolled and reheated states. Furthermore, the effect of microstructural characterization on its final mechanical properties was discussed. The results showed that as far as 60Si2MnA, the pearlite interlamellar spacing determined the hardness, whereas, the austenite grain determined the toughness. Compared with microstructure and mechanical properties in the hot rolled state, after reheating treatment at 950 ℃, its average grain sizes are apparently fine and the pearlite interlamellar spacing and lamellar cementite thickness coarsen to some extent, but both hardness and impact toughness increase to HRC 48 and 8.5 J, respectively. In the course of making spring, the optimum reheating austenitizing temperature for the 60Si2MnA steel is 950 ℃. 相似文献
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分析研究了 Mn含量0.78%-0.92%对0.20%碳冷镦钢Φ20 mm热轧盘条组织和力学性能的影响。盘条热轧的终轧温度为880℃,缓冷。结果表明,Mn含量由0.78%增加至0.92%时,盘条抗拉强度由485 MPa升高至508 MPa,增加了 23 MPa,伸长率由31%降至28%,下降了3个百分点,断面收缩率由58%降52%,下降6个百分点;HRB硬度值增加4.5;试验钢组织中铁素体晶粒尺寸由28μm降低至18 μm,珠光体比例由23%增加至26%;且珠光体片层间距有所减小,淬透性能提高。 相似文献
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SUN Yan-Kun 《钢铁研究学报(英文版)》2009,16(5):61-61
The ultra-fast cooling technology of large-section bars GCr15 bearing steel was researched connected with industry practice, the microstructure in different cooling patters were researched by optical microscopy、transmission electron microscopy and energy spectrometer, it was concluded that: the large-section bars of GCr15 bearing steel passed the zone of secondary carbide precipitation quickly through the ultra-fast cooling technology(UFC) the instantaneous cooling rate of which was about 200℃/s, the finishing cooling temperature was higher than Ms, the lamellar spacing of pearlite was thinner and thinner and the micro-hardness was bigger and bigger along with the reduction of re-reddening temperature,the precipitation of network carbide was restrained when re-reddening temperature was 690℃, and fine laminated pearlite was obtained through transformation of pseudopearlition which induced the reduction of the diamond of pearlite grain and refinement of the lamellar spacing of pearlite, ideal microstructures promoting spheroidizing annealing were obtained. 相似文献
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51CrV4钢因具有良好的热处理性能与力学性能,广泛用作为高等级弹簧钢。为改善现有锯片钢的不足,根据51CrV4特有的化学成分,创新性地将其用于制造金刚石焊接锯片基体。通过研究动态CCT曲线,卷取温度对显微组织与第二相析出物的影响,淬火与回火工艺对碳化物尺寸、晶粒尺寸、力学性能的影响,评估了51CrV4钢用于制造金刚石焊接锯片基体的可行性。结果表明:卷取温度升高,先共析铁素体尺寸与珠光体片层间距变大,10 nm粒径以下的(V,Cr)C析出物在MC相析出物中所占的比例减少;淬火温度由800提高到900 ℃时,奥氏体晶粒尺寸先缓慢变化,随后快速长大,固溶的碳化物质量分数增多,回火后锯片硬度增强,而回火温度由450提高到550 ℃时,马氏体板条界片层状渗碳体逐步球化,强度明显下降,塑性小幅提高;设定合适的卷取温度控制热轧态中第二相碳化物的尺寸,并在850~900 ℃淬火、约450 ℃回火是生产高硬度、高韧性51CrV4金刚石焊接锯片的关键工艺。 相似文献
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采用中高碳成分添加低密度元素Si、Al进行轻量化的设计思路设计了试验钢的化学成分,试验钢采用50 kg真空感应炉冶炼。利用金相显微镜、SEM扫描电镜和力学性能检测设备对试制后的Φ6 mm盘条进行了显微组织观察、珠光体片层间距的测量和屈服强度、抗拉强度、延伸率的检验。结果表明:盘条在600℃等温2 h后的金相显微组织为铁素体+珠光体的混合组织,珠光体的片层间距为(126±5) nm,屈服强度大于1 183 MPa、抗拉强度大于1 425 MPa、延伸率大于10%,其力学性能满足电缆用铠装钢的技术要求。 相似文献
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Clean high carbon heavy rail steel was prepared by the process of vacuum induction furnace smelting, forging and rolling. Mechanisms of RE on the impact toughness and fracture toughness for clean high carbon steel were investigated. In addition, the appropriate range of RE content for clean high carbon steel was determined. Both the austenite grain size and pearlite lamellar spacing decreased due to small amount of RE, consequently the impact toughness and fracture toughness were improved evidently. When the RE content exceeded a critical value, the pearlite lamellar spacing was increased, because RE was segregated on the austenite grain boundaries, damaged the orientation relationship of pearlite transformation, caused the disorder growth and morphology degenerating of pearlite. With the increasing of RE content, both the impact toughness and fracture toughness of clean high carbon steel were gradually increased at first and then decreased. It was found that when the RE content was between 00081% and 00088%, both the impact toughness and fracture toughness of clean high carbon heavy rail steel were the best. The maximum ballistic work was 212 J (20 ℃) and 122 J (-20 ℃), respectively. The maximum plane-strain fracture toughness was 4567 MPa·m1/2 (20 ℃) and 3704 MPa·m1/2 (-20 ℃), respectively. 相似文献
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The microstructural evolutions and mechanical properties of vanadium microalloyed steel (30MSV6) during precipitation hardening were studied. The effects of aging temperature and cooling rate on mechanical strength (yield strength and ultimate tensile strength) were similar. Increasing aging temperature or cooling rate firstly increased the mechanical strength of specimens up to their maximum values, which then decreased with further increase in aging temperature or cooling rate. Microstructural evolutions revealed that cooling rate had significant effects on the pearlite interlamellar spacing and size of pre-eutectoid ferrite. Unlike the effect of austenitizing temperature, the pearlite interlamellar spacing and pre-eutectoid ferrite size were decreased by increasing the cooling rate from austenitizing temperature. According to the microstructural evolutions and mechanical properties, the optimal heat treatment process of microalloyed steel 30MSV6 was austenitizing at 950 ℃ for 1 h, air cooling (3. 8 ℃/s) and aging at 600 ℃ for 1. 5 h. This optimal heat treatment process resulted in a good combination of elongation and yield strength. 相似文献