Metallurgical aspects in cold rolled high strength steel sheets

Cold rolled high strength steel sheets with yield strength from 300 to 500 N/mm² have been developed by using conventional equipment for producing commercial cold rolled steel sheet, that is, cold rolling, box annealing, and temper rolling. Effective alloying elements for strengthening are carbon, silicon, manganese, phosphorus, niobium, etc. The sheets up to 400 N/mm² yield strength grade are easily produced by selecting appropriate chemical compositions. The sheets with higher yield strength grade than 450 N/mm² are obtained by introducing the new idea that the steel with more than 2 pct manganese is annealed between A₁ and A₃ transformation temperatures, and moderately temper rolled. Increase of tensile strength does not affect deep drawability while it deteriorates stretch-forming and stretch-flanging properties. As for electric resistance spot welding, shear tension strength increases in proportion to tensile strength, but cross tension strength hardly increases or tends to decrease. These sheets have been applied to door beams and bumper reinforcements.     

Effect of water quenching processing parameters on the mechanical properties of a cold-rolled C-Mn-containing steel sheet

Cold-rolled advanced high-strength steel sheets have become the material of choice for the automotive industry because of their unique attributes of high strength and balanced mechanical properties. High-hydrogen gas jet cooling and water quenching are the most commonly used ultrafast cooling technologies for producing martensite-containing high-strength steel sheets. The water quenching technology ensures the fastest industrial cooling rate of 1 000 K/s; therefore,it has the highest potential with respect to saving alloys. In this study,the water quenching of a C-Mn-containing steel sheet is simulated during continuous annealing to investigate the effect of water quenching and tempering parameters on its mechanical properties. The results reveal that at low quenching temperatures,the strength of the steel sheet decreases as the soaking temperature increases. However,at high quenching temperatures,a high soaking temperature corresponds to increased strength after quenching,regardless of whether the material was austenitized in the single austenite zone or the inter-critical zone. Therefore,a high quenching temperature always results in a high strength and a high yield ratio after quenching. Low-temperature overaging( tempering) considerably influences the yield strength and yield ratio,and the extent of this influence is correlated with the soaking temperature.     

Effects of Prior Cold Rolling and Post Temper Rolling on the Properties of Continuously Annealed Low Carbon Dual Phase Steel

The effects of two processing variables, prior cold reduction and temper rolling, on the mechanical properties of a continuously annealed 0.05 pct C low alloy dual phase steel were studied. It was found that cold rolling affected the strength of the dual phase steel through its influence on the recrystallized ferrite grain size. The correlation between yield strength and mean free path in ferrite was shown to follow a Hall-Petch type relationship. Similarly, temper rolling also had a pronounced effect on the yield strength of the steel. The effect was strongly dependent upon the previous overaging treatment; the lower the overaging temperature, the stronger the effect. Basically, the effect of temper rolling on dual phase steel was not much different from that on mild steel and HSLA in terms of the change in yield strength and yield point elongation. Another interesting observation was the influence of quenching rate on the strength of the dual phase steel. A slower quenching rate in the heavier gauge dual phase steel caused pearlite rims to form around martensite colonies and thus decreased the strength of the steel.     

Production of thick 10XCHДΦ steel sheet of optimized composition for the construction industry

On the basis of newly developed steel, thick sheet for the construction industry may be produced, by smelting and casting, hot rolling, and subsequent heat treatment. In the oxygen-converter shop at OAO Magnitogorskii Metallurgicheskii Kombinat (MMK), a 370-t melt of steel is produced as a trial run. The metal is cast to slabs (thickness 300 mm), which are rolled on a 5000 mill to sheet (thickness 22–50 mm). A production technology for thick vanadium-steel sheet on the 5000 mill is developed: rolling with subsequent heat treatment (quenching + tempering); or controlled rolling with subsequent accelerated cooling to ensure the required strength class 390 and impact strength (KCU_?60, KCV_?20, KCA₂₀). The structure of the cast 10XCHДΦ steel sheet is investigated. Control tests of sheets used in the manufacture of metal structures for the Kazan football stadium confirm the high quality of the sheet.     

LNG用7％Ni钢快速回火工艺模拟

摘要：采用淬火膨胀仪模拟研究了LNG用7%Ni钢淬火后快速加热回火工艺,结合显微组织观察以及对回火冷却过程中膨胀曲线的分析,讨论了该工艺对钢中逆转变奥氏体含量及其稳定性的影响。结果表明,提高淬火终冷温度能显著增加组织中逆转变奥氏体的含量,且其在基体上的分布也更为均匀,但当淬火终冷温度提高至300℃时,淬火组织中残留了大量的残余奥氏体,经快速加热回火后虽然保留在组织中,但其稳定性较差,导致冷却后的最终组织中出现大量的岛状M/A。回火前的快速加热一方面抑制了残余奥氏体在加热过程中发生分解,同时也有利于碳原子在较短的时间内扩散至其中,因此不但能促进钢中逆转变奥氏体含量的增加,也有利于其稳定性的提高。     

工艺参数对热轧双相钢马氏体体积分数的影响

在正交实验的基础上，采用方差分析方法研究了４个工艺参数（终轧温度、终轧变形量、淬火温度、轧后缓冷时间）对单张热轧双相钢马氏体体积分数的影响。此外，还讨论了马氏体体积分数与双相钢力学性能的关系。     

低温高磁感取向硅钢热轧板通电加热织构研究

通过对低温高磁感取向硅钢热轧板通电加热处理,发现将热轧板以55℃/s从室温加热到1 000℃后降温,在1 000～950℃降温过程中保持时间2～5 s,可以获得与常化工艺等效的热轧板织构组分,根据所得结果,讨论了在热轧轧机后段增加电加热装置,从而代替常化工艺生产高磁感取向硅钢的可能性.     

国外汽车用钢板开发新进展

综述了国外汽车板研究开发的新进展,重点介绍了板带热轧工艺中ＩＦ钢热轧卷取温度控制、铁素体区轧制、ＴＲＩＰ钢、ＢＨ钢、冷轧与退火工艺及钢板表面质量检测与控制等汽车板品种、质量研究开发的新成果。     

Effect of annealing parameters on mechanical properties of cold-rolled martensitic steel sheets

Cold-rolled martensitic steel sheets produced on continuous annealing lines with water quenching facility,have advantages of high strength and low alloying element contents.These are in good accordance with the trend of light-weighting and fuel saving for automotive steel.In this article,a cold-rolled martensitic steel is studied to investigate the effect of annealing parameters on its mechanical properties.It is found that the quenching temperature and the slow cooling speed as well as the overageing temperature have significant influence on the strength of the experimental steel.The temperature zone at which the austenite decomposition is slow or has not started may be chosen as the quenching temperature to ensure the steel’s strength stability.The slow cooling speed also influences the steel’s strength greatly.A high cooling rate will lead to significantly higher strength.Tempering would decrease the steel’s tensile strength but would increase its yield strength.     

低碳钢盘条氧化铁皮形成机理及其控制研究

低碳钢盘条表面氧化铁皮的质量是影响冷拉丝前除磷效果影的主要因素之一,采用热模拟试验机研究了对低碳钢盘条在不同加热温度和冷却工艺下形成氧化铁皮的厚度、显微组织、相结构及其组成成分、相对含量和分布特征,分析出了生成氧化铁皮控制方向和理想的吐丝温度和冷却工艺。研究结果表明,温度过高,生成氧化铁皮疏松易脱落,温度过低,生成氧化铁皮太薄起不到保护作用;冷却速度越快,生成氧化铁皮越致密,表面质量越好,Fe3O4层的厚度较厚,冷却速度过快则氧化皮就过薄。终轧温度950℃、吐丝温度930℃、冷却速度0.5~1℃/s的冷却工艺能得到厚度适中,致密度较高的氧化铁皮,且容易机械除鳞。     

平整对罩式退火生产BH钢板力学性能和自然时效性能的影响

研究了平整对罩式退火生产的BH钢板力学性能和自然时效性能的影响。结果表明，平整对BH钢的BH性能有显著影响，平整延伸率在1．0％～2．0％之间时BH值有最大值；平整使得BH钢的屈服强度先下降而后上升，屈服强度最小时的平整延伸率消除了钢板单向拉伸时的屈服点延伸现象；足够的平整延伸率是BH钢抗自然时效性能的有效保证。实验结果在工业生产中得到了应用。     

热处理工艺对高碳高钒高速钢轧辊组织和性能的影响

研究了淬火温度、冷却方式、回火温度和回火次数对高碳高钒高速钢轧辊组织和性能的影响．确定了最佳热处理工艺参数。结果表明。盐冷高速钢轧辊具有优良的淬透性。不易出现裂纹．辊面硬度高而且均匀，耐磨性好．和高铬铸铁轧辊相比，高速钢轧辊寿命提高8．4倍。     

提高镀锡板T-4CA材抗时效性能措施的试验研究

镀锡板就是在冷轧板的表面电镀一层均匀致密的锡层.对其性能的控制可以通过炼钢的化学成分、热轧温度、冷轧压下量、退火和平整来实现.选取化学成分相近的宝钢T-4CA镀锡板,选用低温、高温两种热轧卷取温度.在冷轧连退机组采用等温时效、倾斜时效和过时效等3种退火时效方式进行快速冷却(1C)及时效处理(OA)试验,研究不同的热轧出炉温度、卷取温度以及冷轧退火不同时效处理制度对T4CA镀锡板时效性能的影响.应采用低C、N含量和高Al的化学成分,采用低温出炉、高温卷取的热轧温度制度及更优的过时效处理.     

加热温度对管线钢奥氏体晶粒尺寸和铌固溶的影响

 研究了X70管线钢的原始奥氏体晶粒尺寸随加热温度的变化。通过测试淬火后回火硬度的方法分析了加热过程中铌的固溶。结果表明,随加热温度升高,原始奥氏体晶粒尺寸逐渐增大,并在1 200 ℃附近出现粗大晶粒,而钢中铌在1 150 ℃左右已基本固溶,由此对X70管线钢在控轧控冷工艺中加热温度的选择进行了探讨。     

冷轧板折皱缺陷的分析与控制

折皱缺陷经常发生在冷轧板带钢的边部,一般出现在平整机机组工序。分析了产生折皱的主要原因,通过优化弯辊力与轧制力的匹配系数、严格控制平整机上卷温度、调整好板形、加强平整机操作人员技术培训等措施,有效地降低了冷轧板折皱的发生率。     

Features and control methods of the galvanneal furnace

The recent rapid developments in the automobile industry have demanded the extensive use of galvannealed(GA)steel sheets.In particular,the development of lightweight automobiles is putting increasingly higher requirements on the strength of GA steel sheets.The galvanneal furnace,which is used for processing galvannealed steel sheets,is typically composed of the induction heating section,holding section and fog cooling section.This paper described the structural characteristics of each component of the galvanneal furnace,and analyzed temperature control methods of the galvanneal furnace that are important for the successful production of high-strength GA steel sheets for automotive applications.     

热水器内胆用热轧搪瓷钢的开发与性能

通过180t顶底复吹转炉+LF成分控制及Ti微合金化,连铸成230 mm板坯经1200～1250℃加热,控制轧制后快速冷却至500～700℃卷取等工艺措施,山西太钢不锈钢公司成功开发了热水器内胆用热轧搪瓷钢(/％:≤0.14C,≤0.06Si,≤1.20Mn,≤0.030P,≤0.025S,≤0.10Ti)2 mm热轧...     

MULPIC冷却装置在品种钢研发中的生产实践

 舞钢新宽厚板生产线MULIPIC在线快冷装备具有高冷却速度等技术特点,结合控制轧制和在线快冷装备对船板、管线钢进行了开发研究,采用直接淬火工艺研究开发了高强工程机械用钢。结果表明： 60 mm厚度E36级TMCP船板钢,组织全部为铁素体＋珠光体,晶粒度10级以上,－40 ℃夏比横向冲击功在183 J以上;X70管线钢的组织为针状铁素体,力学性能合格率达98％;利用直接淬火（DQ）和离线回火工艺,生产出30 mm厚的WQ960D调质钢,屈服强度达到960 MPa,抗拉强度1030 MPa,－20 ℃纵向冲击功在43 J以上。     

轧制-直接淬火参数对Ti-B微合金化低碳Si-Mn钢组织和性能的影响

用0.06%(Ti+B)微合金化(%)0.17C-0.92Si-1.63Mn钢135mm连铸坯在实验室φ500mm中厚板轧机轧成24 mm板材,试验了终轧、开始和终止水冷温度对实验钢组织和力学性能的影响。结果表明,终轧920℃开冷900℃终冷180℃,冷却速度30℃/s和终轧880℃,开冷860℃终冷280℃,冷却速度22℃/s,钢的组织和性能与传统的880℃1h淬火+220℃ 6 h回火的组织和性能相当。     

高性能管线钢控制轧制与控制冷却

从加热温度、轧制变形量、终轧温度三方面论述了高性能管线钢在生产过程中的控制轧制工艺,分析了开冷温度、终冷温度、冷却速度等方面在控制冷却中对高性能管线钢最终组织结构和性能的影响,以及微合金化元素Nb、Ti、V在控轧控冷中的作用,为高性能管线钢的生产工艺参数制定提供理论基础。