复合保护渣对钢锭增碳机理的探讨

本文针对复合保护渣在保护浇注过程中产生钢锭增碳问题,进行了不同固定碳含量保护渣的对比试验.探讨了复合保护渣在保护浇注过程中产生钢锭增碳的主要成因及途径,从而说明复合保护渣中的膨胀石墨是造成钢锭增碳的主要因素.     

复合保护渣对钢锭增碳机理的探讨

本文针对复合保护渣在保护浇注过程中产生钢锭增碳问题，进行了不同固定碳含量保护渣的对比试验。探讨了复合保护渣在保护浇注过程中产生钢锭增碳的主要成因及途径，从而说明了复合保护渣中的膨胀石墨及造成钢锭增碳的主要因素。     

模铸线材表面增碳的产生原因和对策

线材表面增碳严重影响最终产品性能,选取6024等钢种作为研究对象,重点分析模铸钢坯表面的增碳原因,通过对钢锭模内部质量、浇铸保护渣、浇铸速度和热处理工艺等因素与增碳效果进行对比试验,并根据试验结果确定相应改善钢坯表面增碳措施。结果表明,浇钢过程中使用的保护渣含碳量为18％左右成为钢锭表面增碳的主要来源,因此,采用无碳保护渣是减少钢坯或盘条表面增碳的可行方法。     

保护渣粘模机理

一、前言自60年代初我国采用混合的固体氧化物(以下简称保护渣)保护钢水浇铸以来,粘模问题一直未得到解决。尤其是近年来,考虑到使用高含量石墨保护渣造成钢锭头部和锭身表面增碳的后果,许多钢厂为了提高钢材质量,希望降低保护渣中碳含量。但是在研制低碳渣的过程中,首先遇到的被认为难以克服的技术关键问题,就是粘模问题。使用后的保护渣液渣层不规则地牢固地粘结在钢锭模表面,在钢锭模再次使用前必须清除干净。若清理不净,粘在模壁上的渣     

使用模铸保护渣时钢的增碳研究

对采用ＮＦ－３、ＺＸＤ、ＺＸＧ３种石墨型复合模铸保护渣时钢的增碳情况进行了试验研究，结果表明，３种保护渣均引起了钢锭表面增碳，以用ＮＦ－３保护渣的增碳幅度最大；在切头率不同时，３种保护渣钢材样的中心增碳各不相同。用ＺＸＧ保护渣钢的表面增碳与中心增碳尚能满足要求，但表面质量与帽口钢渣分离则尚待改进。     

模铸用复合保护渣在抚顺钢铁公司试验成功

抚顺钢铁公司原外购炼钢模铸用的保护渣存在有增碳、钢锭底部和表面夹渣等缺点,为解决这些问题,公司去年组织有关科技人员攻关,研制新型保护渣。经过几个月的努力,FS系列低碳复合模铸保护渣小型试验进行完毕,在电炉钢模铸生产中进行了对比试验,取得了较为理想的效果。     

模铸保护渣的应用研究

本文阐述了保护渣的作用与特性，对低碳、中碳和高碳复合渣的应用进行了分析研究，形成了石墨渣系高、中、低碳系列保护渣。文中指出试制的以高炉水渣－电厂灰为基配制的复合可用于钢锭保护浇注。     

Fz型复合保护渣的研制与应用

炼钢模铸采用保护渣浇注后,使钢锭的表面质量、头部质量得到改善,成坯率有了提高。特別是近年来推广绝热板帽口、保护渣、膨胀发热剂“三位一体”浇注工艺后,效果更加明显。然而,“三位一体”浇注中使用的“721”石墨渣,对低碳钢增碳严重,使用受到限制。以电厂灰为基的低碳保护渣,虽可避免增碳,但由于电厂灰成份及性     

DG805电厂灰保护渣碳含量合理确定及增碳机理的初步研究

选取DG805电厂灰保护渣的基础渣料配制了6种含碳量不同的保护渣。在实验室和到工厂进行实验研究。查明了碳对保护渣物化性能的影响和渣中碳含量对钢质量的影响。确定了DG805电厂灰保护渣含碳12—15％的合理性。得出由此渣浇注的钢锭基本上不增碳的结论。对使用含碳保护渣引起钢锭增碳的问题进行初步研究。得出在有液渣层存在时。由于液渣中碳的饱和含量很低[(C)<0.05％]渣中不同碳含量对钢锭增碳没有影响。钢液的动力学传质是引起渣中碳向钢中扩散主要的途径的初步结论。     

使用微碳保护渣解决钢材表面增碳问题

为了提高我公司的钢材质量,减少质量事故,曾对钢材表面增碳问题进行多次研究。1988年以来,我们使用微碳保护渣解决钢材表面增碳问题取得了一定的进展和较好的效果。杜绝钢材表面增碳,是一项难度较大的工作。1987年研究“角钢腿部开裂”这个问题时,就已经证明,在正常情况下,钢锭模中所含的碳不会造成钢锭表面严重增碳,在轧钢过程中一般也无增碳的可能。由此看来,要解决钢材表面增碳就应集中力量     

含碳球团熔融渗碳机理

使用CaO-SiO_2-Al_2O_3合成渣与磁铁矿、石墨粉制备含碳球团,考察了球团中渣相成分、渣量以及碳含量对铁水渗碳量的影响,并探讨了含碳球团内铁的熔融渗碳行为和机理。结果表明,熔融渗碳分为熔融还原渗碳以及铁熔体聚合过程渗碳2个阶段,前一阶段熔渣中Fe2+含量与铁的渗碳量处于动态平衡过程,主要受熔渣化学成分的影响;后一阶段的渗碳过程决定铁的物理渗碳极限,主要与铁、碳颗粒的接触条件有关,且熔渣中Fe2+的还原极限与渣相碱度和SiO_2绝对含量有关,铁的熔融渗碳量(质量分数)可以达到4%左右,满足铁锍分离要求。     

热轧板翘皮缺陷的渗碳行为和组织特征

 为了提高SPHC热轧带钢的表面质量,针对异常翘皮缺陷的成因展开研究。利用光学显微镜、扫描电镜、能谱仪和硬度仪分析了缺陷处与基体的组织、成分和硬度的差异。结果表明,翘皮缺陷主要是由连铸坯中存在大量的夹杂物所致,同时这些夹杂物碳含量较高,在板坯加热过程中对周围基体起到“渗碳”作用,渗碳层厚度可达5 727.2 μm。带钢横截面的组织差异是由表面与芯部的温差所导致的动态回复与再结晶差异造成的。在层流冷却段,渗碳区域的过冷奥氏体发生了离异共析转变,粒状渗碳体均匀弥散析出。     

高碳钢用复合渣（WFZ—2）的研究

通过实验室的正交试验,获取了不同助溶剂对基本渣熔融特性的影响参数,在此基础上研制了高碳钢用复合保护渣,用该渣浇铸高碳钢钢锭不仅改善了钢锭质量,还降低了生产成本。     

电渣连铸锭表面质量的影响因素

渣皮的厚度、均匀性和力学性能是影响抽锭电渣钢锭表面质量的主要因素。薄而均匀渣皮是获得良好连铸锭表面质量的关键。文中分析了渣池电流密度分布、结晶器壁附近的热传导条件、渣成分和"高温区"温度变化等因素对渣皮厚度的影响。生产试验表明,通过控制操作温度和渣系成分获得薄而均匀的渣皮,并确保渣系具备长渣形式和适当的高温强度及塑性可得到良好表面质量的电渣连铸锭。     

High-rate carburizing in a glow- discharge methane plasma

Carburizing at high temperature (1040°C) in a glow-discharge methane plasma signifi-cantly reduces carburizing time. Sufficient carbon to produce a 1.0 mm case on conven-tional carburizing steels can be introduced in 10 min at methane pressures in the range of 1.3 to 2.7 kPa (10 to 20 Torr). To reduce the carbon concentration at the surface to an acceptable level (007E1.0 wt pct) the plasma carburizing stage is followed by a short (007E30 min) diffusion step. To aid in optimizing the division of time between the carburizing and diffusion stages, and in separating the effects of plasma carburizing and high-temperature diffusion, a computer program was written to model the diffusion equation for appropriate initial and boundary conditions. Both model and experimental results show that a diffusion time/carburizing time ratio of at least 3: 1 is required. The diffusion model indicates that the exceptionally high carburizing rates observed arise from the rapid infusion of carbon into the surface from the plasma, during the carburizing stage and not from anomalously high diffusion rates. Exceptionally uniform cases on surfaces of irregular geometry are achieved, and significant amounts of natural gas are saved owing to both the reduced car-burizing time and the low pressures employed.     

Vacuum carburization of 12Cr2Ni4A low carbon alloy steel with lanthanum and cerium ion implantation

As bearing parts, 12 Cr2 Ni4 A is expected to have high hardness and excellent fatigue strength, so carburizing is employed to improve the inherit properties of 12 Cr2 Ni4 A. However, the traditional carburizing is limited by poor microstructure distribution and low rate of carburizing. The rare earth ion implantation is known to help improving the properties of tribology, corrosion resistance and oxidation resistance of metal. In this article, the RE implantation is employed to assist the carburizing. Lanthanum and cerium ion implantations are initially used to assist 12 Cr2 Ni4 A low pressure vacuum carburization.The microstructure, content of retained austenite, hardness, thickness of layer and carbon diffusion were analyzed by optical microscopy(OM), scanning electron microscopy(SEM), X-ray diffraction(XRD) and Rockwell/Vickers hardness tester, respectively. It was shown that lanthanum and cerium implantations can improve structure of the vacuum carburizing layer, and enhance the uniformity of carbon element distribution on the carburized surface. Meanwhile the RE implantation plays a positive role in promoting the surface hardness and carburized rate. The lanthanum element has more significant effect on surface hardness and content of retained austenite than cerium element. The surface hardness of lanthanum element implanted layer was 62.9 HRC with 9.6% content of retained austenite, while the carburizing rate of cerium implanted layer increased by 12.4%.     

Simulation of Case Depth of Cementation Steels According to Fick＇s Laws

 The carburizing process is the enrichment of the depth of low carbon steels with carbon. It leads to samples with a combination of high surface hardness and high core toughness and to an impact strength that is required for many engineering parts. The material studied is a low carbon steel. The carbon content is little in this type of steel (wC=0.2%). The calculation of case depth is very important for cementation steels that are hardened in the carburizing process. The effective case depth is defined as the perpendicular distance from the surface to a place at which the hardness is HV 550. Nowadays, a great number of studies have been carried out on the simulation of effective case depth, but no studies have been conducted to determine the numerical relation between the total case depth on one hand and the carburizing time and the effective case depth on the other hand. The steel specimens were subjected to graphite powder. Then, they were heat treated at 925 ℃ for about 3, 5, 8 and 12 h, respectively. Then, these parts were quenched in oil. To determine the effective case depth, the microhardness test was performed on the cross-section of specimens. Plotting the case depth vs carburizing time, the required conditions for obtaining the specified case depth were determined. Also, the comparison between the case depths in numerical solution and the actual position in pack carburizing was performed.     

降低电渣重熔GCr15钢的氧含量

在420mm／250mm方形结晶器的工业炉上重熔1．2t锭,比较了含高氟的二元渣系、低氟和中氟的五元渣系、重熔气氛（Ar气保护）、自耗电极表面质量、渣中aFeO值和自耗电极含氧量对重熔钢氧含量的影响。结果表明,自耗电极氧含量为5．87×10-6和10×10-6．在氮气气氛、低氟五元渣系下重熔,电渣过程是一个增氧过程,重馆过程中降低渣中aFeO值,可使GCr15钢的氧含量降至15×10-6左右。     

S08A自耗电极及电渣重熔工艺试制

本文论述了优化电炉配料、选用优质石灰、精选萤石、电炉出钢换渣工艺;电渣重熔采用四元渣系,选用提纯萤石,重熔过程全程氩气保护铝粒脱氧等工艺措施,生产出低碳、低硅、低氮及残余、五害元素符合要求的自耗电极及电渣锭,经轧制成材检验低倍组织及非金属夹杂物符合技术协议要求。     

60 t电渣炉结晶器冷却水流速计算-设计优化和重熔不锈钢的应用

采用传热学理论对大型电渣炉结晶器冷却强度的影响因素进行了分析,计算得出直径1 800 mm结晶器的最佳水流速为1.2 m/s,并提出了套层厚度为10 mm的高速水套型结晶器优化设计方案,经电压77.5 V,电流19 kA,熔速31. 6 kg/min,水流1. 2 m/s,重熔60 t 0. 030C-17.16Cr-11.80Ni-2.55Mo-0.072N奥氏体不锈钢电渣锭的生产结果表明,电渣锭成型良好,表面光洁,渣皮分布均匀,改善了电渣锭成型质量。