合金元素和控轧控冷工艺在管线钢研制中的应用

通过在管线钢中添加Mn、Nb、V、Ti和Mo等合金元素与采用控轧控冷工艺可获得良好的微观组织和综合力学性能.具体论述了控轧控冷过程中合金元素和控轧控冷工艺参数对管线铜微观组织和力学性能的影响;同时分析了微合金元素(Nb、V、Ti)碳氮化物的析出行为.结果表明,在适当范围内降低终轧温度和终冷温度,提高轧后冷却速度和增大精轧总变形量都可有效改善钢的综合性能.     

控轧控冷工艺对高强度X100管线钢组织的影响

对一种X100管线钢进行热模拟试验,研究了过冷奥氏体的相变规律,提出了一种得到以粒状贝氏体+板条贝氏体为主的混合组织的控轧控冷工艺制度,分析了精轧变形量、冷却速度及终冷温度对实验钢微观组织的影响。结果表明,随着变形量的增大实验钢的微观组织逐渐细化,高强度的板条贝氏体含量减少而粒状贝氏体含量增多;随着冷却速度的增加和终冷温度的降低实验钢组织中的板条贝氏体含量明显提高,组织也逐渐细化;组织中板条贝氏体含量较高时实验钢具有较高的强度,但过多的板条贝氏体和针状M/A岛对材料的韧性造成不利的影响。     

变形制度对低碳锰钢组织性能的影响

为了获得细晶铁素体/贝氏体的复相组织,通过控轧控冷工艺研究了低碳锰钢在奥氏体区变形时变形量、终轧温度和卷取温度对组织演变和力学性能的影响规律.研究表明,增加变形量(对应道次间隔时间缩短)可以细化铁素体晶粒,但当终轧温度降低到800℃时,变形量的增加以及开冷温度的降低不利于贝氏体组织的获得.通过调整变形量、终轧温度、可开冷温度并适当降低卷取温度,可使实验钢获得晶粒尺寸约为5μm的铁素体和10%~20%的贝氏体组织,低碳锰钢强塑性能良好.     

控制轧制和控制冷却对低碳钢板的组织和抗冷脆性的影响

本文研究了控制轧制工艺参数(奥氏体化温度、道次压下率及终轧温度)对低碳钢板轧后铁素体晶粒平均直径和脆性转化温度的影响及其相互关系。试验结果表明:轧制工艺参数中终轧温度起主要作用,决定着轧后铁素体晶粒平均直径、脆性转化温度及-40℃时的冲击韧性;在约800℃终轧,效果最好。轧后快冷时间及冷却速度对低碳钢板的组织和脆性转化温度影响的试验结果表明,延长快冷时间及加快冷却对轧后组织产生复杂影响:使魏氏组织级别增大;使伪共析珠光体量增加;使珠光体退化及细化。这样复杂的组织变化,对脆性转化温度带来复杂的影响。文中提出了低碳钢中珠光体退化的几种机制。     

控轧控冷对低碳Mn-Nb-Cu钢拉伸力学性能的影响

研究了不同终轧温度及轧后冷却速度对低碳Mn-Nb-Cu钢的力学性能(σs，σb和δ5)的影响。研究结果表明，对控轧低碳Mn-Nb-Cu钢的力学性能的影响主要决定于钢的碳当量；随轧后冷却速度的提高，σs和σb提高，δ5降低；在奥氏体未再结晶区进行轧制，终轧温度对铁素体晶粒尺寸的影响较小。     

冷却工艺对货油舱用耐蚀钢组织性能的影响

基于货油舱用耐蚀钢的服役环境设计并冶炼了一种新型耐蚀钢,根据试验钢变形奥氏体连续转变曲线,采用控制轧制和控制冷却的技术将锻后110 mm坯料减薄至16 mm。热轧板材的年平均腐蚀速率分布在0.235~0.273 mm/a,小于船级社要求的1 mm/a。利用扫描电镜、透射电镜、拉伸试验机和冲击试验机进行了耐蚀钢的显微结构分析及力学性能研究,探究了控制冷却工艺对耐蚀钢组织性能的影响规律。结果表明:在终冷温度669 ℃、冷却速度8.9 ℃/s的条件下,耐蚀钢显微组织主要为铁素体、贝氏体和退化珠光体。降低终冷温度或提高冷却速率有利于抑制珠光体转变,促进针状铁素体和贝氏体相变进程,增加小角度晶界数量,提高耐蚀钢的组织均匀性和力学性能。当终冷温度降低至597 ℃,冷却速度增大到13.1 ℃/s,耐蚀钢组织为针状铁素体、粒状贝氏体和板条贝氏体混合结构,不均匀分布且粗大尺寸的板条结构弱化了材料的抗冲击性能。     

X65管线钢控轧控冷工艺研究

本文介绍了利用热模拟试验机研究X65管线钢奥氏体连续冷却相变和组织演变规律。并进行了生产试制,研究了不同工艺参数对最终组织和性能影响。经过试验得知加热温度1200℃终轧温度780℃～820℃左右;冷却速度13℃/s～20℃/s左右,终冷温度在540℃～580℃生产的管线钢性能良好,满足要求。     

16Mn钢中交叉针状魏氏组织形成条件的研究

16Mn钢奥氏体化后冷却时,随等温温度降低及冷却速度加快,显微组织由块状铁素体变成魏氏组织;而魏氏组织中的针状铁素体由交叉分布变成平行分布。我们过去的工作表明,当形成以交叉针状铁素体为主的魏氏组织时,钢材的抗冷脆性最好。本文研究了16Mn钢中交叉针状魏氏组织的形成条件,提出了采用“双段控冷工艺”,可在较宽的工艺条件下得到交叉针状魏氏组织。     

轧后控制冷却对16MnR钢机械性能的影响

本文研究了轧后双段控制冷却工艺对16MnR钢机械性能的影响。结果表明,16MnR钢轧后采用双段控冷工艺处理,获得以交叉针状铁素体为主的显微组织,强度提高,低温冲击韧性明显改善。从而证明了文献〔4〕中提出的双段控冷工艺参数是可靠的。     

CSP流程生产低碳高强度汽车板组织性能的研究

研究了珠钢电炉CSP工艺生产低碳高强度钢板的热轧工艺与组织性能之间的关系,通过光学显微镜和力学性能试验等检测分析技术分析了控制轧制和冷却各阶段工艺参数对成品板显微组织和力学性能的影响.研究表明:降低终轧温度和卷取温度可有效细化晶粒,提高钢板的强度;采用适当的控轧控冷工艺制度,可以获得不同强度级别强韧性能良好的热轧低碳高强度汽车用钢板.     

Effect of controlled rolling/controlled cooling parameters on microstructure and mechanical properties of the novel pipeline steel

The study of controlled rolling/controlled cooling process parameters which affect the microstructure and mechanical properties of a novel pipeline steel has been optimized by the orthogonal experiment with four factors and three levels in this paper.However,the parameters of thermo-mechanical control process(TMCP)optimized by the Gleeble-3500 hot simulator could not satisfy performance requirements of the X100 pipeline steel.In order to improve the performance of this steel,the influence of finish cooling temperature(FCT) on the microstructure and property is studied in detail.It is found that,as this steel is thermo-mechanically treated by this set of parameters(the start heating temperature,finish rolling temperature(FRT),FCT and cooling rate of 1,180℃,810℃,350℃ and 35℃/s,respectively),the microstructures are mainly composed of granular bainite(GB)and acicular ferrite(AF).The effective grain sizes are below 20μm;the steel reaches the optimal balance between the strength and the toughness;the yield strength is 695 MPa;the tensile strength is 768 MPa;the elongation is 16.6%;the impact energy is 262 J at room temperature.All indexes could meet the requirements of X100 pipeline steel.     

Acicular ferrite formation during hot plate rolling for pipeline steels

Abstract

The transformation of supercooled austenite in a commercial pipeline steel was investigated by means of continuous cooling transformation (CCT) and hot simulation experiments. Based on the obtained results, an improved thermomechanical control process (TMCP) was proposed, which could produce a mixed microstructure dominated by acicular ferrite. Results indicated that an increase in the cooling rate could improve the percentage of acicular ferrite in the final microstructure under the present experimental conditions. Furthermore, the acicular ferrite dominated microstructure could be obtained by a two stage controlled rolling in the austenite recrystallisation region plus the non-recrystallisation region and controlled cooling at a cooling rate of 30 K s^-1.     

管线用超低碳钢中针状铁素体的形成及强韧化行为

通过对一种管线用超低碳钢的变形奥氏体相变工艺的分析，提出了能够获得针状铁素体为主的组织的控制热加工工艺（TMCP）制度，研究了针状铁素体的结构特征和力学特性，结果表明，与管线用中，低碳钢相比较，实验用钢尽管具有很低的碳含量（0．025％），但在当前优化的TMCP工艺下能够获得优良的力学性能，即具有相当的强度和高的冲击韧性，针状铁素体的结构特征提高了材料的力学性能。值得注意的是，在当前肝硬化的TMCP工艺下，针状铁素体晶界上存在一层薄膜，这层薄膜对管线用超低碳钢的强韧性具有重要的作用。     

Some new results in thermomechanical processing of microalloyed steels

In recent times, efforts have been directed towards a better understanding of the mechanisms associated with deformation and restoration of austenite during continuous multipass hot rolling of microalloyed steels. The correspondence between the condition of austenite before transformation and the resultant microstructure upon cooling holds the key to the attainment of interesting properties. In the present paper, some results obtained on the deformation of austenite in a microalloyed steel, using a hot compression machine, are presented. Here, the idea was to simulate actual plate rolling or hot strip rolling conditions and study the evolution of microstructure at different stages of the hot deformation process i.e. after precise reductions at given strain rate and temperature of deformation. The paper further discusses recent results obtained by us on the influence of hot deformation parameters (strain, finish rolling temperature, temperature of deformation) and cooling rates (air cooling, spray water cooling) on the microstructure of microalloyed steel. The precise conditions leading to the evolution of acicular ferrite and bainitic microstructures have been identified. New information on the influence of short tempering treatments (15 min at 550, 600 and 650°C) on the microstructure and properties of a microalloyed steel are also outlined.     

含磷和钒热轧TRIP钢组织控制及力学性能研究

为探讨含磷和钒热轧TRIP钢的组织控制和力学性能,采用不同变形温度（900和800℃）,研究其相变行为,并在此基础上进行热轧试验.研究表明：随着冷速增加,变形温度对铁素体相变开始温度（Ar3）的影响逐渐增大;相同冷速条件下,变形使贝氏体相变开始温度（Bs）升高;变形对贝氏体相变的促进作用,随着变形温度的降低而减弱.终轧...     

Effects of Processing Parameters on Microstructure and Properties of Ultra High Strength Linepipe Steel

To examine the effect of processing parameters on microstructural evolution and to obtain the excellent combination of strength and toughness,simulation of thermo-mechanical processing was conducted using the Gleeble machine.Trial production was then conducted under the conditions obtained by Gleeble tests.Based on the results of microstructure analysis and mechanical property evaluation,the relationship between microstructural features and mechanical properties was elucidated.The result shows that the volume fraction of constituted phases can be controlled through adjusting the cooling rate and finish cooling temperature in order to get different strength levels.As cooling rate increases,the volume fraction of upper bainite increases,which leads to the increase of strength.The upper shelf energy(USE) increases with increasing volume fraction of acicular ferrite in bainite base because of the small effective acicular ferrite grain size.Ductile-brittle transition temperature(DBTT) decreases with increasing acicular ferrite volume fraction.High reduction in the rough stage has great influence on grain refinement.     

极地破冰船用大线能量型高强度船板的开发

采用微合金化的设计思路,钢板成分在低C、低碳当量的基础上添加少量的Nb、Ti等微合金化元素,同时在冶炼过程中采用氧化物冶金技术,在TMCP轧制过程中采用针对低碳当量的超快冷技术,最终在成品钢板中得到低碳贝氏体+铁素体混合组织,钢板强韧性匹配良好,-60℃冲击功达到200 J以上。采用100~250 kJ/cm的线能量进行焊接后,钢板焊缝及热影响区冲击韧性良好,能够满足大线能量焊接的需要。      

An investigation of mechanical property and three-body impact abrasive wear behavior of a 0.27% C dual phase steel

The present investigation is aimed to understanding the influence of the morphologies and quantity of ferrite which was obtained by different thermomechanical controlled processes (TMCPs) on microstructure, mechanical properties and three-body impact abrasive wear behavior in a 0.27 wt% C low alloy dual phase steel. The results indicate that acicular ferrite which was obtained by controlled rolling at the low temperature with laminar cooling was partially retained after intercritical heat treatment, and leading to much better mechanical properties and abrasion resistance than in the case of polygonal ferrite. Little retained finer acicular ferrite in dual phase steel deflects the propagation of cracks and increases the impact toughness and abrasive wear resistance.     

Combined effects of high-temperature rolling and ultrafast cooling on the mechanical properties of low-carbon steel

The role of ultrafast cooling (UFC) on the grain refinement of ferrite, the precipitation behavior of cementite particles and the mechanical properties of a mild steel (Q235 grade) was evaluated by applying laminar cooling and UFC and varying the finish cooling temperature ranges during UFC after hot rolling. While UFC refined the ferrite grains, it accumulated the degeneration of pearlite, resulting in complete disappearance of the laminar pearlite at relatively low finish cooling temperatures. The minimum mean size of spheroidized cementite particles reached ~110?nm. Meanwhile, the enhancement of UFC on tensile strengths of mild steels mainly resulted from the grain refinement of ferrite and the precipitation strengthening of cementite particles; however, the contribution varied with the finish cooling temperature of UFC. A modified Ashby–Orowan model was also used for evaluating the yield strength increment of medium plates. This work will provide a theoretical basis for the diversity control of microstructure and for developing stronger and tougher mild steels by introducing UFC technology after high-temperature rolling.