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.     

Mechanical Properties and Wear Resistance of Microarc Diffusion Coatings on Steel

Metallurgist - The aim of the work is to study the influence of the structure and phase composition of diffusion coatings prepared by microarc surface alloying of steel with carbon, boron and...     

Surface Ferrite Grain Refinement and Mechanical Properties of Low Carbon Steel Plates

Considering the specialities of the steel plate production, the TMCP study has been carried out with Gleeble 2000 tester to explore the possibility of fine grained ferrite in the low carbon steel plates with the chemical composition of C 0.13--0.18, Si 0.12-0.18, Mn 0.50-0. 65, P 0. 010-0. 025, and S 0. 005-0. 028. The plates with thickness of 8. 7 mm in which the ferrite grain size is smaller than 8μm have been produced by special de- formation process in the laboratory. Furthermore, the trial production of special plain carbon steel plates of 16-25 mm in thickness and 2 000- 2 800 mm in width with fine grained ferrite has been successfully carried out in the Shougang Steel Plate Rolling Plant. The ferrite grain size is 5.5-7μm in the surface layers and 9.5-15μm in the central layer respectively. The yield strength is 320- 360 MPa, tensile strength is 440-520 MPa and the elongation is 25%- 34 %. It is very important for the rolling plants to improve the low carbon steel plates＇ mechanical properties. The results show that the ferrite grains in the surface layer can be refined effectively by the appropriate rolling process, and the strength can be also increased.     

SPHC钢薄板坯的高温力学性能

用Gleeble热模拟试验机对SPHC钢(%:0.02C、0.18Mn、0.03Si、0.04Als)70 mm×1250 mm板坯进行600～1 350℃的力学性能的研究,并借助扫描电子显微镜和能谱仪分析了拉力试样的断口。结果表明,SPHC薄板坯的第Ⅰ和第Ⅲ脆性区分别为1 200℃～固相线及600～850℃,850～1 200℃薄板坯的塑性最好;第Ⅲ脆性区试样为沿晶界断裂;晶界处夹杂物及γ→α相变中形成的片状铁素体造成了晶界脆性,降低了第Ⅲ脆性区材料塑性。     

镧提高SS400钢力学性能作用机理研究

研究了镧对SS400钢常温及低温力学性能的影响.结果表明,SS400钢的强度、塑性以及冲击韧性随镧含量的增加,能够得到明显改善,特别是低温冲击韧性.但当镧加入量过大时,会造成SS400钢的强度、塑性、冲击韧性下降.将镧加入量控制在0.016%左右能够有效提高其各项力学性能.镧提高SS400钢的力学性能,是稀土净化钢液、变质夹杂、微合金化综合作用的结果.     

热处理对TA15钛合金中厚板材组织及力学性能的影响

研究了退火温度在750—1010℃范围内对TA15钛合金中厚板材显微组织和力学性能的影响。结果表明,在750～950℃两相区退火时,随着退火温度的升高,等轴化程度提高,初生α相含量从约70％降至约30％;次生α相逐步析出并长大,900℃开始,次生α相开始粗化,950℃时,次生α相粗化明显。室温强度则随退火温度的升高先降低后升高再降低,在880℃时抗拉强度和屈服强度同时达到最大峰值,而室温塑性总体上波动较小,与强度呈相反规律变化。与两相区退火相比,β退火后由于组织中存在粗大魏氏体以及晶界α相而使强度和塑性同时急剧下降。在整个退火温度范围（750～1010℃）内,屈服强度对于退火温度的变化更敏感,其波动幅度比抗拉强度更大。     

薄板坯连铸连轧工艺参数对低碳钢组织和性能的影响

结合薄板坯连铸连轧流程的工艺特点,在Gleeble 2000热模拟试验机上研究了冷却速度、变形温度和卷取温度等工艺参数对低碳铝镇静钢组织和性能的影响.试验结果表明:降低冷却速度,提高变形温度,提高卷取温度有利于铁素体组织的粗化和热轧钢带屈服强度的降低.探讨了工业生产条件下,各种工艺参数的优化组合对铁素体组织粗化的影响.     

粒状贝氏体组织对低碳钢力学性能的影响

 在化学成分相同的条件下,分别研究了粒状贝氏体、铁素体 珠光体对低碳合金钢强度、塑性、冲击韧性的影响。结果表明：低碳粒状贝氏体钢比铁素体 珠光体钢具有更高的强度和冲击韧性,而且粒状贝氏体组织对钢的强化方式不仅仅是细晶强化和位错强化,弥散强化也是强化方式之一。     

回火温度对Q960级高强结构钢组织及力学性能的影响

 以屈服强度960MPa级高强调质结构钢板开发为目标,研究了在相同轧制及淬火条件下,回火温度对试验钢显微结构及力学性能的影响。结果表明：随回火温度的升高,试验钢强度下降,韧塑性总体上呈现升高趋势,其中在300~450℃范围内出现一个韧塑性能的恶化区。当回火温度为600℃时,试验钢呈回火索氏体组织,屈服强度为1030MPa,抗拉强度为1080MPa,伸长率为15.9%,-40℃冲击功达144J,各项指标均满足国标GB/T 16270—2009要求。并对试验钢的拉伸力学性能进行了探讨。     

热机械控制工艺对热轧TRIP钢力学性能的影响

通过实验室热轧机研究了热机械控制工艺(TMCP)对热轧TRIP钢力学性能的影响.结果表明:在热轧变形过程中应变诱导铁素体相变,低温大变形量造成铁素体晶粒细化.随终轧温度的降低和终轧变形量的增加,残余奥氏体的稳定性增加,相变诱发塑性(TRIP)效果更好.在700 ℃终轧且终轧变形量为50%时,抗拉强度、屈服强度和总伸长率分别达到791 MPa,538 MPa和36%的最大值.     

Q345B连铸坯内部质量对钢板力学性能的影响

文章研究了Q345B连铸坯低倍组织、碳偏析和钢板常规力学性能,从而找出Q345B连铸坯低倍组织对钢板常规性能的影响,为中厚板连铸坯轧制成的钢板力学性能预测提供依据。     

Effect of Single and Duplex Thin Hard Film Coatings on the Wear Resistance of 1.2343 Tool Steel

In aluminum extrusion process, tool steels used as die materials suffer from mechanical, thermal and tribological stresses causing plastic deformation, wear and heat checking during hot metal flow. Thin hard film coatings like TiN, (Ti,Al)N and CrN are preferred in order to improve the surface properties of the tools. These coatings can reduce the friction force, minimize the adhesive interaction between the die and billet pairs and decrease the plastic deformation of the tool. In this study, effect of single (CrN and AlTiN) and duplex (CrN + AlTiN) thin hard films on the hot wear behavior of DIN 1.2343 tool steel was investigated. Wear tests were performed both at room temperature and elevated temperature to simulate the conditions of aluminum extrusion process. Based on the evaluation of coefficient of friction values, specific wear rates and worn surface examinations, the duplex coating, which had the best performance in the RT wear test showed good resistance to high temperature wear under the simulated aluminum extrusion conditions.     

调质工艺对Q690D钢综合力学性能及组织的影响

 以60mm厚Q690D高强度结构钢板为研究对象,在相同轧制条件下,系统地研究了淬火、回火温度对试验钢综合力学性能及显微组织的影响,并对第二相析出进行理论分析。试验结果表明：随淬火温度升高,试验钢强度升高,韧性下降;随回火温度升高,试验钢强度下降,但韧性明显升高。该钢采用930℃淬火(保温10min)650℃回火(保温40min)的调质热处理工艺具有良好的强韧性匹配,综合力学性能最佳,满足国标GB/T 16270—2009要求。     

固溶处理温度对耐蚀马氏体时效钢力学性能的影响

 研究了固溶处理温度对耐蚀马氏体时效钢力学性能的影响。研究结果表明,800℃固溶处理后的组织遗传了锻态的晶粒形态、尺寸及高密度缺陷,使固溶处理后的马氏体也具有高的缺陷密度,并增加了组织中残余/逆转变奥氏体的含量,从而使材料具有较高的强韧性。较高温度固溶处理奥氏体发生回复和再结晶,其缺陷密度的降低使最终马氏体时效强化效应下降,而且残余/逆转变奥氏体量也下降,从而使材料的韧性水平下降。该试验钢固溶处理温度低于传统的马氏体时效不锈钢的固溶处理温度。     

Effect of the Process Parameters on the Formability,Microstructure, and Mechanical Properties of Thin Plates Fabricated by Rheology Forging Process with Electromagnetic Stirring Method

A thin plate (150 × 150 × 1.2 mm) with embedded corrugation is fabricated using the rheoforming method. Semisolid slurry is created using the electromagnetic stirring (EMS) system, and the thin plate is made with the forging die at the 200-ton hydraulic press. The cross sections and microstructures of the slurry with and without stirring are examined. To investigate the effect of the process parameters on the formability, microstructure, and mechanical properties of thin plate the slurry is subjected to 16 types of condition for the forging experiment. The 16 types included the following conditions: Whether the EMS is applied or not, three fractions of the solid phase at 35, 45 and 55 pct; two compression velocities at 30 and 300 mm s^?1; and four different compression pressures—100, 150, 200 and 250 MPa. The thin plate’s formability is enhanced at higher punch velocity for compressing the slurry, and fine solid particles are uniformly distributed, which in turn, enhances the plate’s mechanical properties. The pressure between 150 and 200 MPa is an appropriate condition to form thin plates. A thin plate without defects can be created when the slurry at 35 pct of the solid fraction (f _s) was applied at the compression velocity of 300 mm s^?1 and 150 MPa of pressure. The surface state of thin plate is excellent with 220 MPa of tensile strength and 13.5 pct of elongation. The primary particles are fine over the entire plate, and there are no liquid segregation-related defects.     

Effect of Macrosegregation on the Microstructure and Mechanical Properties of a Pressure-Vessel Steel

Macrosegregation refers to the chemical segregation, which occurs quite commonly in the large forgings such as nuclear reactor pressure vessel. This work assesses the effect of macrosegregation and homogenization treatment on the mechanical properties of a pressure-vessel steel (SA508 Gr.3). It was found that the primary reason for the inhomogeneity of the microstructure was the segregation of Mn, Mo, and Ni. Martensite, and coarse upper bainite with M-A (martensite-austenite) islands have been obtained, respectively, in the positive and negative segregation zone during a simulated quenching process. During tempering, the carbon-rich M-A islands decomposed into a mixture of ferrite and numerous carbides which deteriorated the toughness of the material. The segregation has been substantially minimized by a homogenizing treatment. The results indicate that the material homogenized has a higher impact toughness than the material with segregation, due to the reduction in M-A island in the negative segregation zone. It can be concluded that the microstructure and mechanical properties have been improved remarkably by means of homogenization treatment.