Development of Nb-V-Ti Hot-Rolled High Strength Steel With Fine Ferrite and Precipitation Strengthening

A hot-rolled steel with high yield strength of 700 MPa, good elongation of about 20% and low ductile-brittle transition temperature (DBTT) lower than-70℃ has been developed in laboratory. The results show that adopting finishing rolling temperature of around 800 ℃ is rational, and coiling temperature is between 400 and 500℃. The strength of developed 700 MPa hot-rolled high strength steel is derived from the cumulative contribution of fine grain size, dislocation hardening and precipitation hardening. The fine grain strengthening and precipitation hardening are the dominant factors responsible for such high strength, and good elongation and toughness are predominantly due to fine grain ferrite.     

Mn-Mo-Nb-B低碳微合金钢的应变诱导析出

采用热模拟及透射电子显微镜结合纳米束能谱技术,研究了Mn-Mo-Nb-B系多元微合金钢奥氏体变形后等温过程中(松弛)的析出行为。实验结果表明:经变形后,在850℃和900℃保温过程中,Mn-Mo-Nb-B多元微合金钢析出颗粒尺寸在各个阶段均小于相同工艺下Nb-Ti钢中析出相的尺寸。统计结果显示,析出颗粒的尺寸均复合正态分布,并且峰位尺寸接近平均尺寸。析出相中Nb/Ti比随着松弛时间而增大。松弛阶段后期,Mo进入(Ti,Nb)(C,N)的晶格当中,其含量随着时间的延长而增加。     

CSP热轧低碳钢的强化机制研究

研究了CSP热轧低碳SPHC钢的微观组织、第二相粒子的析出及其对强度的影响,对马钢CSP生产的SPHC钢和常规热轧工艺的SPHC钢进行了屈服强度比较.结果表明,马钢SPHC钢的实测值比计算值高42MPa,常规工艺生产的SPHC钢实测值与计算值比较接近.对马钢SPHC钢进行透射电镜观察,观察到其中存在纳米级的、亚微米级的和微米级的3种尺寸级别的第二相粒子,马钢SPHC钢沉淀强化的强度增量为40 MPa.     

工程机械用TQ960E微合金化低碳高强度钢的开发

研究了工程机械用TQ960E微合金化低碳高强度钢的化学成分设计、钢质纯净度提升、热处理工艺试验、析出物分析等,结果表明,TQ960E钢12 mm热轧板(/%:0. 18C,0.23Si,1.50Mn,0.010P,0.003S,0.06Ti,0.002B,0.006 3N,0.001 30)最佳淬火温度860～900℃,回火温度300～350℃,工业化试制出的钢板屈服强度≥1000 MPa,抗拉强度≥1 100 MPa,延伸率≥10%,-40℃ 冲击功≥34 J,满足国内工程机械用超高强钢的标准及应用要求。     

CSP生产的微钛低碳高强度钢中的纳米级析出物

对CSP生产的低碳微钛高强度钢进行了化学相分析和高分辨率透射电镜的观察.发现钢中纳米级M3C型颗粒的数量要比MC型颗粒多2个数量级,其中＜18 nm的M3C有0.024%,而＜18 nm的MC只有0.000 9%.高分辨率电镜观察的结果表明,纳米级析出物主要有3类,第1类主要含Ti、Fe、C、O、N,第2类含Fe、C、O,第3类只含Fe、O.     

薄板坯连铸连轧低碳微合金高强度钢的力学性能与组织控制

利用薄板坯连铸连轧工艺和控轧与控冷工艺,生产了低碳微合金高强度钢.利用光学显微镜、扫描电子显微镜(SEM)和透射电子显微镜(TEM)分析了该钢的微观组织结构.该钢主要由精细的针状铁素体、粒状贝氏体和多边形铁素体组成.铁素体和贝氏体组织中存在由位错形成的胞状亚结构,这有利于品粒细化.薄板坯连铸连轧工艺生产的低碳微合金高强度钢具有良好的综合力学性能.其屈服强度达到了600 MPa级,伸长率大于20%.     

High Strength High Carbon Low Alloy Pearlite-Ferrite-Tempered Martensite Steels

High strength multiphase steels have been developed consisting of combination of pearlite, tempered martensite and small amount of ferrite, by suitable heat treatment of a high carbon low alloy rail steel (0.7 % C). The desired microstructure has been obtained by holding fully homogenized steel in pearlitic range for small durations followed by water quenching and subsequent tempering at 773 K for 18 h. Variation in mechanical properties has been studied with the change in volume fraction of different phases. Yield strength, ultimate tensile strength and elongation are observed to be in the range of 500–1,000 MPa, 900–1,185 MPa and up to 16.8 %, respectively. Continuous and discontinuous yielding along with substantial work hardening has been explained as a function of tempered martensite content.     

含钒低合金高强钢的沉淀析出行为

介绍了含钒低合金高强钢沉淀析出的形成,分析了碳氮化钒的一般析出、相间析出和纤维状析出的典型形貌、析出模型等,给出了最新的研究现状,探讨了含钒低合金高强钢的应用前景。     

Dynamic and Static Recrystallization Behavior of Low Carbon High Niobium Microalloyed Steel

 The recrystallization behavior of a low carbon high Nb microalloyed steel was investigated using Continuous and interrupted hot compression tests. The results showed that the onset of dynamic recrystallization (DRX) could be detected from inflection in the plot of the strain hardening rate θ against stress σ regardless of whether the stress peak appears or not. According to Zener-Hollomon parameter the activity energy of DRX (Qdef) was obtained, and a new modified expression calculating Qdef was proposed in consideration of the chemical composition of experimental steel. Applying the 2% offset method the static softening fraction was determined. The graphic representation of the softening fraction vs. interrupt time gave the information of the non-static recrystallization temperature (about 1000℃)and the relationship of precipitation-time-temperature. Static recrystallization kinetics follow Avrami’s law in high deformation temperature, and different values of the exponent n were given to illustrate the different effects of Nb element on static recrystallization at different deformation temperature.     

Effect of Cooling Patterns on Microstructure and Mechanical Properties of Hot-Rolled Nb Microalloyed Multiphase Steel Plates

 The effect of the run-out table cooling patterns on the microstructure and mechanical properties of Nb microalloyed steel plates was investigated by hot rolling experiment. The results showed that the mixed microstructure containing ferrite, bainite and significant amounts of retained austenite can be obtained through three kinds of cooling patterns on the run-out table under the same hot rolling condition. Three kinds of cooling patterns possess different austenite transformation kinetics, which leads to variations in microconstituent characteristics. The yield strength increases, the tensile strength decreases and the total elongation tends to increase as the cooling patterns Ⅰ, Ⅱ and Ⅲ were applied respectively. The yield strength, the total elongation and the product of tensile strength and ductility reach the maximum values (547 MPa, 37.2% and 28384 MPa·%, respectively) for the steel plate processed by cooling pattern Ⅲ.     

铜沉淀在低合金高强度钢中的特性

1　简介低合金高强度 ( HSL A)钢 ,如海洋结构用钢HSL A- 1 0 0 ,要求强度、韧性与焊接性等综合性能。为达到这些性能 ,需在低碳钢中添加几种合金元素 ,加铜就是为了通过时效硬化来提高强度。几种参考文献中均讨论过时效期间铜沉淀的特性及强化机理。在时效初始阶段形成粘着性微细体心立方沉淀物。随着时效时间的延长 ,体心立方相转化成非粘着性面心立方铜沉淀物。当粘着性沉淀达到一个临界值 (～ 2 .4mm)时 ,出现了峰值强度。铜沉淀的量、大小和形态可影响含铜钢时效后的性能。目前 ,已试图研究等温时效期间和连续冷却过程中铜沉淀的特…     

V-N微合金化高强度铁塔用角钢的研究

利用V-N微合金化技术,在16Mn钢基础上进行铁塔用角钢的合金设计,并结合角钢的孔型轧制要求,考察了V/N合金设计以及板坯加热温度、轧制工艺参数对角钢组织性能的影响。结果表明,随着钢中V/N含量的增加,钢中弥散析出的第二相粒子数量显著增加,屈服强度显著提高,其中0.01%的钒含量对屈服强度贡献约为23 MPa。V-N微合金化角钢坯料再加热过程中V(C,N)粒子的溶解温度低于1 150℃,控制低的坯料加热温度有利于提高角钢的低温冲击韧性。终轧温度对低钒钢的屈服强度和韧性存在显著影响,但对高钒钢的组织性能影响不大。采用V-N微合金化设计后,角钢的综合性能得到显著提高,且力学性能对轧制工艺参数变化不敏感,因此,V-N微合金化技术适用于角钢的实际生产应用。     

新型高强度铜微合金材料的研究与开发

本文以提高铜管材的抗拉强度为主要内容,针对以磷脱氧铜为基体添加微量元素的铜微合金进行了机械性能等方面的分析,得出部分结论,仅供参考。     

低碳微合金钢中超细组织的热稳定性分析

研究了经过新开发的弛豫-析出控制相变RPC技术得到的钢板在650℃等温回火过程中组织与性能的演变,并与经过930℃保温1h后再淬火（RQ）工艺处理后的钢板进行了对比。回火前两种钢板均为贝氏体和少量马氏体的复合组织,经过RPC处理后的钢板回火0．5h后,金相尺度下的组织没有明显变化,但硬度下降较快,在1～7h的回火过程中组织中局部区域出现板条合并现象,此阶段硬度值变化不明显,7h之后某些区域组织的板条特征趋于消失,出现了少量的多边形铁素体,硬度开始明显下降,回火20h后,大约一半的组织转化成了多边形铁素体。而经过RQ处理后的钢板回火前硬度虽然较低,但回火过程中软化速度极快,板条组织很快消失,最终获得全部的多边形铁素体组织。结果表明超细组织的热稳定性取决于其加热历史。     

低碳高强钢中纳米析出相回火过程中的透射分析

 研究了一种800MPa级低碳高强钢中纳米析出相在回火过程中的演变规律。通过透射、高分辨电镜,并结合能谱仪系统分析了不同回火温度下析出相的形貌特征及其与基体的位相关系。研究表明,低碳高强钢中的纳米析出相主要为Nb、Ti、V、Mo等元素的碳氮化物,低温回火时主要为Nb、Ti的二元析出,高温回火后则为含Mo、V、Ti、Nb等多种元素的复合碳化物析出;钢中纳米析出相按大小分为两类,大尺寸颗粒是钢在轧制过程中形变诱导析出的,小尺寸颗粒是钢在回火过程中相变诱导析出的;同时,随回火温度的升高,钢中的析出相均慢慢长大并粗化,长大方式为典型的Oswald熟化机制;析出相与母相基体之间存在特定的取向关系,在析出的开始阶段,析出与基体的界面基本保持共格关系,析出相形状主要为球形或者类球形,随着回火温度的升高,析出逐渐长大并粗化,形状渐渐变为方形或者椭圆形,同时与基体脱离共格界面,保持的界面关系为：{100}MC∥{100}α-Fe,<100>MC∥<110>α-Fe。     

低碳微合金钢中的晶内铁素体及组织控制

回顾和评述了晶内铁素体的发现、发展及其与组织控制的关系.介绍了晶内铁素体的形核机制和影响晶内铁素体形成的因素,讨论了晶内铁素体的三维形态和长大动力学,并从以上几方面分析了晶内铁素体对低碳微合金钢组织细化的重要作用和影响.     

Ultrafine Grained Austenite in a Low Carbon Vanadium Microalloyed Steel

 Ultrafine austenite grains with average size of 2 μm were successfully obtained by combining thermo-mechanical control process followed by reheating in a vanadium microalloyed steel. The mixed microstructure transformed from pancaked austenite formed during controlled rolling has a higher density of high angle boundaries, compared to that transformed from equiaxial austenite. It contributes to increasing nucleation density of austenite grain during the reheating process. A certain volume fraction of undissolved nano-sized (Ti,V)C particles, which are formed during the controlled rolling process and/or the reheating process, effectively inhibit austenite grain growth and consequently refine austenite grain size significantly. The critical grain size of austenite calculated by Gladman model agrees well with the experimental result.     

微合金高碳硬线钢的研制

通过实验室研究与酒钢现场生产工艺相结合,对微合金高碳钢在中小型转炉条件下的生产技术进行了研究。试验表明,改进工艺后钢中ω（TO）平均降低至0．0038％,显微夹杂物数量降低了78％,大颗粒夹杂物数量降低了65%。铌微合金化处理后高碳钢线材的力学性能得到了改善。酒钢应用新工艺生产了铌微合金高碳硬线钢2980t,拉拔正常且钢丝性能优良。     

EAF-CSP流程钛微合金化高强钢板的组织和性能研究

珠钢采用Ti微合金化技术在EAF—CSP流程上成功地开发出屈服强度为450～700MPa的高强度热轧钢板。系统地研究了试验钢的组织和性能．并分析了组织与性能的关系。结果表明，随钛含量增加或成品厚度减薄钢板的屈服强度显著提高，最高达到695MPa；钛的质量分数低于0．024％时对屈服强度影响不大；当钛的质量分数低于0．045％时．钢板屈服强度的提高主要来自于晶粒细化，而当钛的质量分数大于0．045％后，钢板强度的进一步提高来自于沉淀强化。     

高碳洁净钢热轧盘条的开发实践

高效低成本洁净钢生产技术,是国家钢铁产业政策提倡的冶金技术之一。安阳钢铁股份有限公司在高碳洁净钢生产中,以转炉高拉碳技术为基础,降低增碳剂加入量,同时不断深入研究连铸、轧钢等后道工序的工艺控制参数,钢水纯净度大幅度提高。在没有铁水预处理和钢水真空脱气的条件下,以较低的成本,成功开发出C72DA和C82DA热轧盘条。性能完全满足用户要求,获得了市场的良好评价。