低碳高硫易切削钢冷加工开裂分析

通过金相显微镜和扫描电镜分析,发现低碳高硫易切削钢开裂的原因为钢材近表面的大颗粒夹杂物。大颗粒夹杂物中含有Zr、Na、Mg等元素,是冶炼过程水口和耐火材料的严重侵蚀及保护渣卷渣造成的。     

低碳高硫易切削钢LF精炼工艺研究

硫易切削钢因其良好的可切削性能和作为含铅易切削钢的环保替代品,在机加工行业已得到广泛使用。石横特钢通过对低碳高硫易切削钢LF精炼工艺的研究,改善了钢中硫化物形态,降低了脆性夹杂物出现的机率,显著提高了该钢的切削性能,满足了用户需求。     

低碳高硫易切削钢冶炼工艺分析

通过在电炉炉后和精炼炉采用硅锰合金或锰铁合金脱氧,将钢中自由氧含量控制在100×10-6以上,电炉炉后采用硫磺粉增硫,精炼炉采用硫铁矿或硫线补硫,将钢中硫含量控制在0.35%～0.41%、Mn/S≥3.0,山东石横特钢生产了1215HS低碳高硫易切削钢,钢中硫化物形态为球形或纺锤形,切削性能良好,完全满足下游用户使用要求。     

改善低碳高硫易切削钢切削性能的工艺实践

在分析影响易切削钢AISI 1215切削性能因素的基础上,通过将钢中的碳含量从0.094%降至0.072%, LF精炼用硅锰脱氧,控制LF终点游离[o]60×10^-6~80×10^-6,140 mm×140 mm坯结晶器水流量从1 900~2 050 L/min降至1700~1 850 L/min,二冷区比水量由1.15 L/kg降至0.90 L/kg,优化轧制工艺使硫化物平均直径由原来的2.09μm增加至3.11μm等工艺措施,使低碳高硫(0.072%C,0.365%S)易切削钢盘条的切削性能明显提高,零件表面粗糙度为2μm左右,满足用户要求。     

低碳硫铋易切削钢的生产工艺实践

总结了低碳硫铋易切削钢1214Bi生产过程中为保证轧材质量在冶炼、连铸及轧制工艺上采用的关键措施。生产实践表明,1214Bi易切削钢轧材夹杂物分布均匀,钢中铋颗粒细小均匀,产品切削性能良好。     

易切削高硫钢的冶炼工艺探讨

探讨了硫在易切削钢中的作用，还原期造渣工艺和硫的加入方法对硫回收率的影响。     

低碳高硫易切削钢冷拔纵裂纹分析和改进工艺措施

对100t BOF-LF—165 mm×165 mm方坯连铸-热轧至Φ14 mm-冷拔至Φ12 mm的低碳高硫易切削钢(/%:0.07C,1.24Mn,0.06P,0.39S)冷拔材开裂现象进行系统分析,得出该钢在冶炼连铸过程中由于卷渣、氧化等原因造成钢坯内部缺陷是材料冷拔纵裂纹形成的主要原因。通过控制连铸过程结晶器冷却水量,二冷区采用弱冷工艺,比水量0.83 L/kg,拉速1.5 m/min,无氧化保护浇铸及采用1300℃粘度为0.6 Pa·s专用保护渣等工艺措施,有效避免冷拔纵裂纹的发生。     

低碳高硫易切削钢带状组织对冷拔材裂纹形成的影响

低碳高硫易切削结构钢(%:0.07C、0.86Mn、0.06P、0.32S)Φ11.5 mm冷拔材出现0.3 mm深的一次纵裂纹,造成批量废品。经取样分析表明,Φ14 mm冷拔坯(热轧材)的带状组织达4级,冷拔一次断面缩减率达32.52%,致使在冷拔过程中产生裂纹。通过控制连铸时钢水过热度,在冷拔坯连轧过程精轧温度由850℃提高到1050℃,喷淋冷却,650℃回红,使Φ14 mm冷拔坯带状组织降至1.5级以下;冷拔时一次断面缩减率降低至30.5%以下,从而避免了Φ11.5 mm冷拔材纵裂纹的产生。     

石钢Y15M高硫高磷易切削钢的冶炼试制

Y15M高硫高磷易切削钢具有易切削、易攻丝的优点,主要用于制造汽车螺栓、弹簧座等部件.简述了Y15M钢生产的技术难点、试制过程、精炼渣系的设计及控制,分析了精炼和连铸过程中的气体含量、连铸坯的夹杂物级别及其组成,为进一步完善生产工艺提供了重要依据.     

低碳高硫含锡锑复合易切削钢

对复合添加少量Sn和Sb或Sn和Bi的低碳高硫易切削钢做了切削和高温热塑性实验.结果表明:试样在长时间的高速切削条件下刀具后刀面磨损很小,其易切削性能明显优于SAE1215钢.含Sn和Sb的钢样在750~950℃温度范围内塑性较差,在1050~1300℃范围内具有良好的塑性.扫描电镜及能谱分析表明:钢中Sn和Sb元素在晶界、MnS夹杂物内及MnS边界处均存在;大部分的Bi元素附着在MnS夹杂物上,一部分弥散分布在钢的基体中;钢中MnS夹杂主要呈球状和纺锤状.     

微量铋合金对易切削钢中MnS形貌的影响

 利用Q500图像分析仪和JSM6480LV型扫描电镜研究了微量元素Bi对S-Bi易切削钢中的MnS长宽比的影响规律。结果表明,Bi在易切削钢中以3种形态存在：单独存在于钢基体中、被硫化物包裹和介于钢基体与硫化物之间。S-Bi易切削钢铸锭中w（TO）分别为0.032%,0.022%和0.024%,Bi质量分数分别为0.0002%、0.0010%和0.0020%时,MnS的长宽比均在1.0~1.6,低于硫系易切削钢的1.2~3.2（w（TO）为0.030%）。在锻造比为2.25时,钢中MnS的长宽比增长率低于1.0,且MnS夹杂物的变形率随Bi含量增加而降低。钢中Bi金属在钢锭锻造过程中可起到抑制硫化物变形的作用。     

硫易切削齿轮钢的开发

多年来我厂一直存在行星齿轮加工难问题,尤为突出的是钻孔工序与铣齿工序,经常出现打刃现象.影响齿轮加工的因素主要有3个方面:齿轮材料、齿轮毛坯的硬度及显微组织、加工齿轮的刀具.国外在解决齿轮加工难问题上,也是从这3个方面着手,如德国大众公司为使捷达传动器齿套好加工,采用一种硫含量很高的齿轮材料TL4126(28MnCr5S),毛坯采用等温退火.     

以锡代铅研制环保型易切削钢

以锡代铅研制了一种含锡的环保型易切削钢,并进行了切削及力学性能试验.结果表明,在含量小于0.05%(质量分数)时,锡能明显改善钢的易切削性能,未发现对钢的力学性能有不利的影响.     

Mn-Series Low-Carbon Air-Cooled Bainitic Steel Containing Niobium of 0.02%

 A new hot-rolled low carbon air-cooling bainitic steel containing 0.02%Nb has been developed based on alloying design of the grain boundary allotriomorphic ferrite (FGBA)/ granular bainite (BG) duplex steel.The as-rolled microstructure and mechanical properties of 0.02%Nb bainitic steel were investigated by tensile test, X-ray diffraction(XRD),Optical Microscopy (OM), scanning electron microscopy (SEM) ,and Transmission electron microscopy(TEM). The results show that (1) The addition of 0.02% niobium improves the strength obviously without sacrificing toughness of the FGBA/BG steel. Compared with Non-Nb FGBA/ BG steel, 0.02% Nb increases the tensile strength and yield strength about 20% (From 780Mpa to 937Mpa)and 17%(From 557Mpa to 650Mpa) respectively, remaining 18% elongation and 83J Akv. (2) Small addition of Nb(0.02%) not only refines the allotriomorphic ferrite grain but also promotes the nucleation of intragranular ferrite, both of which in turn contribute to the refinement of granular bainite cluster including its ferrite platelets and M-A islands. Compared with Non-Nb steel, the volume fraction of M-A island in 0.02%Nb steel increases from 21% to 31%, and the average size of M-A island decreases from 1.2μm to 0.95um.(3)There is hardly any Nb(C,N) has been observed in 0.02%Nb steel. It is suggested that the strengthening effect of 0.02%Nb can be mainly attributed to the influence of the segregation of Nb to γ/α phase boundaries(solute drag-like effect) on the phase transformation rather than the precipitation strengthening of Nb(C,N).     

Texture Development During Annealing in a Low-Carbon Formable Steel Containing Impurities from Increased Scrap Use

Metallurgical and Materials Transactions A - Impurities (Cu, Sn, Cr, and Ni) have been added to a low-carbon formable strip steel to simulate the scenario of increased use of scrap during steel...     

X1215易切削钢结晶器保护渣的开发和应用

根据炼钢厂现有结晶器保护渣FRK-2和FRK-49性能分析的结果,以FRK-2保护渣(/%:32.68SiO₂、24.42CaO、3.30MgO、9.52Al₂O₃、5.40Na₂O、3.10Fe₂O₃、3.59F^-、12.60C)为基础开发了较高碱度,保温效果好,较低粘度,有一定还原性以降低弯月面处S和O含量,并避免卷渣的X1215易切削钢(/%:0.06～0.09C、≤0.10Si、1.20～1.50Mn、0.08～0.10P、0.30～0.50S)150 mm×150 mm铸坯连铸结晶器保护渣。生产结果表明,保护渣性能达到X1215低碳高硫易切削钢的生产要求;连铸坯合金元素偏析度均为0.90～1.10,S和Mn偏析度分别为0.95～1.05和0.98～1.03,连铸坯内部质量良好。     

Microstructure and Properties of Graphitized Free-Cutting Steel

This article describes the metallographic studies and the tensile tests of quenched and high-temperature tempered samples of graphitized free-cutting steel and the experience of machining graphitized samples. The experimental results have shown that the microstructure of the graphitized steel is comprised mainly of ferrite and graphite, and graphite particles are distributed both along grain boundaries and inside them. The morphology of graphite is presented by a spherical shape (average diameter of ~10 μm). The ratio of the yield stress to the ultimate strength is 0.59, and the machinability coefficient is k_T = 5.4241. The microstructure of steel samples after quenching and high-temperature tempering is comprised mainly of secondary sorbite. In this case, the ratio of the yield stress to the ultimate strength is 0.82.