500 MPa级VN微合金化螺纹钢筋组织及性能研究

对比分析了500 MPa VN微合金化螺纹钢筋和余热淬火螺纹钢筋在显微组织、硬度、抗时效性上的差异.结果表明:向钢中添加一定量的VN,由于产生V(CN)沉淀析出,螺纹钢筋的组织细化;与未加VN的余热处理螺纹钢比较,500 MPa VN微合金化螺纹钢筋的强度、硬度和抗时效性均得到一定程度的提高,添加了VN的螺纹钢的硬度更均匀.     

钛微合金化高强度耐候钢成分设计及熔炼

在普通耐候钢Q450NQR1成分的基础上,通过理论计算,设计出一种钛含量为0.04%～0.10%、屈服强度为520～750 MPa的高强度耐候钢。按照成分设计要求,采用高频真空感应炉在1 873 K条件下熔炼钢样,并对不同钛加入量的钢样进行成分和组织结构分析。结果表明,熔炼的钢样中氧含量为（17～26）×10-6,氮含量为（12～66）×10-6,钛含量为0.006 1%～0.059 0%;钢样组织主要由铁素体和珠光体构成,随着钢中钛含量的增加,晶粒明显细化,钢组织渐趋均匀。SEM分析表明,钢中长方体的TiN夹杂,是以球形的Al2O3、MgO和钛氧化物夹杂为核心生长的,必要时在微合金化处理之前将钢中的氧含量降低到一定程度。     

微合金化钢的动态再结晶及其显微组织的研究

应用Ｇｌｅｅｂｌｅ－１５００热模拟试验机测定了微合金化钢在不同终轧温度下的真应力－－真应变曲线，研究了终轧温度及微合金元素含量对动态再结晶的影响，研究结果表明，Ｖ，Ｎｂ可显著抑制微合金化钢轧制过程中形变奥氏体的动态再结晶，因此，在较高的终轧温度下，仍能得到细小而均匀的显微组织。     

轧制工艺对钒铌微合金化钢显微组织的影响

应用Gleeble—1500热模拟试验机对V、Nb复合微合金化钢进行了模拟轧制,测定了形变奥氏体的动态再结晶曲线,研究了轧制工艺对铁素体晶粒大小和亚结构的影响,从而确定了能够获得细小铁素体—珠光体组织的V、Nb含量及与之相应的轧制工艺。     

微合金化稀土对结构钢相变及组织的影响

本文论述了稀土固溶的概念及稀土在钢中的存在形式。研究了稀土对几种低碳、中碳、高碳结构钢的临界点、CCT曲线和显微组织的影响。试验表明,稀土使钢的A_(cl)、A_(r1)、A_(c3)、A_(r3)、M_(s)、M_f、B_s点温度有所降低;稀土不改变CCT曲线的形状,但使其向右下方移动;在相同的冷却速度下,添加稀土元素和无稀土元素的钢比较,先共析铁素体量减少,珠光体量增加,并细化了珠光体及马氏体组织。     

Ti微合金化对3.5Ni钢低温韧性的影响

利用光学显微镜和透射电镜观察不同Ti含量3.5Ni钢试样的组织及析出物,并通过测定其-80～-120℃的夏比冲击功来研究Ti微合金化对3.5Ni钢低温韧性的影响。结果表明,与0.042Ti试样相比,0.079Ti试样在热轧态和正火＋回火态时晶粒大小相同,但其热轧态组织中珠光体细化,且正火＋回火态组织中TiN数量增多,平均尺寸约为150nm;正火＋回火处理后,0.079Ti试样在-80～-120℃的夏比冲击功为233～23J,均低于0.042Ti试样相应值（234～66J）;对于正火＋回火态试样,较粗大TiN粒子的析出是造成其低温韧性降低的主要原因。     

600MPa级钛微合金化高强钢的组织与性能研究

采用光学显微镜、透射电镜以及能谱分析等对转炉CSP流程600 MPa级钛微合金化高强钢的组织及性能进行研究。结果表明,试验钢具有良好的综合力学性能,其典型组织为多边形铁素体加粒状贝氏体;位错和位错胞的强化作用成为钛微合金钢的主要强化机制之一;钢中M/A岛在增加试验钢强度的同时并未明显降低其韧性和塑性;试验钢中存在TiN、TiC和TiS等析出物,为钢的细晶强化和析出强化提供了保证;试验钢中存在大量纳米级铁碳析出物,其沉淀强化作用不容忽视。     

微合金化制取铜基多元系合金的研究

研究了微量的锆、钛、镁、铝等元素对铜基合金的作用，分析了Ｃｕ－Ｆｅ－Ｔｉ及Ｃｕ－Ｆｅ－Ｚｒ多元合金的组织和性能，以及Ｆｅ／Ｔｉ或Ｆｅ／Ｚｒ比值对合金力学性能的影响，讨论了以采用真空熔铸法熔炼的铜基多元合金代替广泛应用在电子工业半导体集成电路的ＣｕＦｅ２Ｐ合金的优越性。     

CSP线Nb微合金化HSLA钢试验研究

为在CSP生产线利用Nb微合金化技术生产HSLA钢，通过在试验室建立了CSP铸坯模拟和CSP轧制模拟的试验方法，研究了Nb微合金化试验钢的组织和性能。结果表明试验室CSP铸坯模拟和CSP轧制模拟技术上是可行的。试验钢的铁素体晶粒尺寸为3．7μm，屈服强度为535MPa，延伸率为30％。     

微合金化高强厚钢板的强韧性

采用低硫铁水,包内脱氧,Nb、V复合微合金化,钢包底吹氩喂线精炼,全程保护浇注等技术,配以控制轧制工艺,能够以较低的成本生产厚规格590 MPa钢级的钢板.所轧制生产的20～30 mm厚度JG590钢板,不需轧后热处理屈服强度和抗拉强度分别达到450～540 MPa和590～660 MPa,-5℃V型冲击功达到49～78 J.文中讨论了钢的化学成分、非金属夹杂物和生产工艺对钢材组织和性能的影响.为使钢板获得良好的强韧性配合,利用现代大型高刚度轧机结合微合金化物理冶金原理,对厚规格高强钢板轧制规程进行优化,细化了钢的组织结构,改善了590 MPa级别高强钢低温冲击韧性.     

Microstructures and properties of 550 MPa grade high strength thin-walled H-beam steel

The microstructures and mechanical properties of 550 MPa grade lightweight high strength thin-walled H-beam steel were experimentally studied. The experimental results show that the microstructure of the air-cooled H-beam steel sample is consisted of ferrite, pearlite and a small amount of granular bainites as well as fine and dispersive V（C,N） precipitates. The microstructure of the water-cooled steel sample is consisted of ferrite and bainite as well as a small amount of fine pearlites. The microstructure of the water-cooled sample is finer than that of the air-cooled sample with the average intercept size of the surface grains reaching to 3.5 gna. The finish rolling temperature of the thin-walled high strength H-beam steel is in the range of 750 ~C-850 ~C. The lower the finish rolling temperature and the faster the cooling rate, the finer the ferrite grains, the volume fraction of bainite is increased through water cooling process. Grain refinement strengthening and precipitation strengthening are used as major strengthening means to develop 550 MPa grade lightweight high strength thin- walled H-beam steel. Vanadium partially soluted in the matrix and contributes to the solution strengthening. The 550 MPa grade high-strength thin-walled H-beam steel could be developed by direct air cooling after hot rolling to fully meet the requirements of the target properties.     

高强度耐候钢及其在桥梁中的应用与前景

为了解高强度耐候钢的性能及其桥梁中的技术应用,首先总结当前国内外高强度耐候钢在桥梁工程应用的研究进展和成果,回顾了耐候钢技术的发展历程. 然后,分析了高强度耐候钢的腐蚀机理、腐蚀环境、抗腐蚀性能以及各种腐蚀评估方法;归纳总结了高强度耐候钢的焊接性能,以及耐候钢的腐蚀疲劳性能与评估方法. 最后,阐述了高强度耐候钢在国内外桥梁工程中的应用以及中国高强度耐候钢的试验状况. 分析结果表明:虽然中国的耐候钢技术有较大发展,但中国的耐候钢桥梁技术还处于萌芽阶段;耐候钢桥梁在腐蚀作用下的强度、稳定和疲劳问题将成为今后的研究方向;关键部位采用新焊接技术可保证耐候钢桥梁的疲劳强度;中国高强度耐候钢未腐蚀状态下的疲劳和力学性能满足桥梁建设要求,腐蚀状态下高强度耐候钢的疲劳性能和力学性能有待深入研究;基于电化学腐蚀和断裂力学的腐蚀疲劳模型可用于高强度耐候钢的腐蚀疲劳寿命评估.     

Texture evolution of 440 MPa grade Nb-bearing high strength IF steel during rolling and annealing process

The texture evolution from rolling process to annealing process of 440 MPa grade Nb-bearing high strength IF steel (IF-HSS) was studied. Moreover, the texture of different section in thickness direction of steel sheet after annealing was investigated. Macro-texture measurements using XRD shows that hot rolling texture in Nb-bearing IF-HSS includes a weak γ-fiber and α-fiber, of which main texture components are {001}<110>,{111}<110> and {111}<112>. It is worthy of note that the γ-fiber skeleton line formed after hot rolling. During cold rolling, the absolute maximum shifts to {111}<112> along the γ-fiber and the maximum along the α-fiber shifts to {112} <110>. During recrystallization annealing process, the weaker α-fiber and stronger γ-fiber cold rolling texture transformed to a very strong γ-fiber annealing texture. After annealing the main components from surface to mid-section along thickness display the same character for both α-fiber and γ-fiber, while textures intensity at 1/4 section is higher than that of surface and mid-section.     

耐候钢和高性能钢腐蚀后疲劳性能2019年度研究进展

免涂装耐候钢桥梁在使用过程中长期受到腐蚀作用,影响其性能的主要有均匀腐蚀和坑蚀。坑蚀能够直接导致钢材疲劳强度降低,并且疲劳细节等级越高,坑蚀对疲劳强度的削减越严重。在钢桥设计中,疲劳设计常为控制指标,需要对耐候钢和高性能钢腐蚀后的疲劳性能进行研究。针对中国耐候钢和高性能钢开展共计20个试件的腐蚀后疲劳试验,根据ISO规范对两种钢材进行中性盐雾干/湿循环腐蚀试验,盐雾采用5%的NaCl作为腐蚀溶液,其pH值为6.5,温度控制为35℃,腐蚀120个周期;针对腐蚀后的试件进行疲劳试验,并与未腐蚀试件的疲劳试验结果对比。试验结果表明,腐蚀后耐候钢和高性能钢的疲劳强度均大幅降低;不考虑保证率时,腐蚀后HPS 485W和Q345CNH钢2×10⁶次荷载循环的疲劳强度与未腐蚀试件相比分别降低了27.8%和26.6%;考虑95%保证率,采用m=3时,分别降低了34.7%和50.1%,并且低于FAT 125要求。腐蚀作用下,两种钢材表面形成稳定锈蚀层和蚀坑,其锈蚀层具有一定强度,疲劳裂纹均萌生于表面蚀坑部位。     

炉卷轧机X70级管线钢组织与性能研究

采用低碳、低硫和微合金化成分设计,在1200-1220℃加热温度、790-830℃终轧温度、500-550℃终冷温度控制工艺下进行热轧处理,对3500 mm炉卷轧机生产的X70管线钢进行组织性能检验。结果表明,所生产的X70管线钢均满足西气东输二线X70级管线钢的技术要求。     

超高强度钢与微合金钢点焊接头的组织与性能

以超高强度钢EN 10 292 TL4225和微合金钢H340 LAD为研究对象,采用先进的中频点焊连接技术,利用合适的焊接参数实现了超高强度钢与微合金钢的优质连接。对中频点焊接头横截面进行微观组织分析和硬度分布实验,并对中频点焊接头进行拉伸实验,采用扫描电镜对拉伸断口进行研究和分析。结果表明,中频点焊接头熔合良好、组织均匀,没有发现气孔、裂纹等缺陷,具有良好的中频点焊性能,能够满足实际生产需求。     

Low cycle fatigue behavior of high strength gun steels

The low cycle fatigue (LCF) behavior of two high strength steels, with nominal chemical compositions (mass fraction, %) of 0.40(2-1.5Cr-3Ni-0.4Mo-0.2V (PCrNi3MoV) and 0.25C-3Cr-3Mo-0.8Ni-0.1Nb (25Cr3Mo3NiNb), was investigated by using the smooth bar specimens subjected to strained-controlled push-pull loading. It is found that both steels show cyclic softening, but 25Cr3Mo3NiNb steel has a lower tendency to cyclic softening. 25Cr3Mo3NiNb steel has higher fatigue ductility, and its transition fatigue life is almost three times that of PCrNi3MoV. 25Cr3Mo3NiNb steel also shows higher LCF life either at a given total strain amplitude above 0.5% or at any given plastic strain amplitude, despite its lower monotonic tensile strength than that of PCrNi3MoV. It also means that 25Cr3Mo3NiNb steel can endure higher total strain amplitude and plastic strain amplitude at a given number of reversals to failure within 10^4. 25Cr3Mo3NiNb steel is expected to be a good gun steel with high LCF properties because only several thousand firings are required for gun barrel in most cases.     

Experimental study on 830 MPa grade pipeline steel containing chromium

The diversity of microstructure and properties of 830 Mpa grade pipeline steel containing chromium was investigated by optical microscope and transmission electron microscopy. The main microstructures were multiple configurations, containing lath bainite and granule bainite. Mechanical properties test results showed that the yield strength and tensile strength improved with in-creasing chromium content. The toughness and elongation decreased at the same time, so temper process was introduced. Appling proper temper parameters, the values of toughness and elongation were improved dramatically, and the strength decreased slightly.