Optimum process of RH-MFB refining for ultra-low carbon steel

A mathematical model was established and applied to simulate thedecarburization of RH-MFB process in Pansteel Company. Study of theeffects of w_[C]0, w_[O]0, Ar flowrate, evaluation rate the MFB lanceblowing parameters on the decarburization process was car- Ried out.The results showed that this model could give the quantitativeunderstanding of the process, especially the behavior of MFB Lanceblowing. This model has realized the optimum process of RH-MFBrefining for ultra-low carbon steels in Pansteel.

Cleanliness of Ti-bearing Al-killed ultra-low-carbon steel during different heating processes

During the production of Ti-bearing Al-killed ultra-low-carbon(ULC) steel, two different heating processes were used when the converter tapping temperature or the molten steel temperature in the Ruhrstahl–Heraeus(RH) process was low: heating by Al addition during the RH decarburization process and final deoxidation at the end of the RH decarburization process(process-Ⅰ), and increasing the oxygen content at the end of RH decarburization, heating and final deoxidation by one-time Al addition(process-Ⅱ). Temperature increases of 10°C by different processes were studied; the results showed that the two heating processes could achieve the same heating effect. The T.[O] content in the slab and the refining process was better controlled by process-Ⅰ than by process-Ⅱ. Statistical analysis of inclusions showed that the numbers of inclusions in the slab obtained by process-Ⅰ were substantially less than those in the slab obtained by process-Ⅱ. For process-Ⅰ, the Al_2O_3 inclusions produced by Al added to induce heating were substantially removed at the end of decarburization. The amounts of inclusions were substantially greater for process-Ⅱ than for process-Ⅰ at different refining stages because of the higher dissolved oxygen concentration in process-Ⅱ. Industrial test results showed that process-Ⅰ was more beneficial for improving the cleanliness of molten steel.

Deformation Behavior of Ultra-low Carbon Steel in Ferrite Region during Warm Processing

The hot deformation experiments of ultra-low carbon steel in ferrite range were carried out in a hot simulator in order to research hot deformation behaviors of ultra-low carbon steel in ferrite range at low temperature. The results show that the influences of deformation parameters on flow stress are different to those in austenitic deformation. The deformation characteristic parameters were calculated for ultra-low carbon steel in ferrite region. The flow stress equation for ultra-low carbon steel in ferritic deformation at low temperature was obtained.

Mathematical Model of Decarburization of Ultra Low Carbon Steel during RH Treatment

According to the balance of carbon and oxygen, a decarburization model for the RH treatment has been developed. in which the influence of the mass transfer of carbon and oxygen in the liquid steel and the stirring energy (ε) in the vacuum vessel on decarburization rate has been considered. The conclusion that the volumetric coefficients of the mass transfer of carbon is proportional to ε(1.5) is drawn. Industrical experiment proves this model is reliable. The influence of some factors on decarburization rate has been obtained. which can provide directions for RH treatment The decarburization behavior of steel with RH-OB treatment is also studied. The OB-or-not curve, the optimized OB time and OB amount are discussed.

超低碳钢210t RH脱碳精炼工艺的优化

分析和确定了RH精炼的初始碳含量、提升气体流量和转炉终点氧含量,并进行生产实践。结果表明,RH进站初始碳含量应控制在250×10^(-6)~400×10^(-6),转炉出钢时终点氧含量应控制在250×10^(-6)~400×10^(-6)。实际生产数据统计表明,在PH处理初期(0~3 min),各炉次脱碳速率最大值可达到98×10^(-6)/min,在脱碳终点时,碳含量在12×10^(-6)左右。

RH处理超低碳铝镇静钢技术的优化

针对RH在生产超低碳铝镇静钢时提高钢水的纯净度和可浇性问题,优化了工艺和操作并取得了很好的效果。

薄板坯连铸机生产SPHD钢的RH-LF双联工艺实践

针对唐钢热轧部RH直接使用FTSC(薄板坯连铸机)生产SPHD(冲压用热轧钢板及钢带)钢时钢水可浇性差的问题,开发出铁水预处理深脱硫→150 t顶底复吹转炉冶炼→RH脱碳精炼→LF白渣精炼→FTSC薄板坯连铸机生产SPHD钢的双联工艺。生产实践表明,该工艺有效地解决了脱氧、脱硫与回硅的矛盾,生产出的SPHD钢钢水成分及可浇性均能够满足要求。

Analysis of thermodynamics and kinetics of titanium between top slag and liquid steel

： Titanium is an impurity element in some special steel grades. The existence of titanium decreases the grain size and lowers the yield strength ,resulting in low quality of these steels with regard to various properties. Thus, the titanium content should be reduced to the minimum. Based on the industrial production of ultra-low carbon A1-Si killed steel, this paper investigated the physical-chemical behaviors of titanium with and without desulfurization during RH refining. The influences of Ti content in hot metal, ladle slag composition, and ladle slag quantity, etc., on the Ti content in refined liquid steel were discussed. The results show that the partition ratio of titanium between ladle slag and liquid steel is inversely proportional to the AI content to the power of 4/3 ,and the empirical formula regressed from practical experience can be expressed as w（TiO2）/WTi=48/w[AI]4/3 Maximum partition ratio of titanium between top slag and liquid steel can be ensured W[Til WIAIIby an optimum slag composition including components of FeOx and A12 03 and an appropriate slag basicity. The contents of FetO and A1203 should be controlled above 6% and below 20% respectively and the slag basicity should be kept within 1.5 to 3.0. Moreover, desulfurization refining in the RH vacuum will decrease the partition ratio of titanium between ladle slag and liquid steel significantly. To keep the Ti content stably below 15 ×10 ^-4% in a 300 ton ladle ,the Ti content in hot metal must be lower than 500 × 10^-4% and the thickness of ladle slag carried over from BOF slag must be less than 50 ram.

用RH法生产超低碳钢

本文简要介绍国外采用RH法生产超低碳钢的工艺特点和效果,以及RH法在武钢的应用情况。

RH-LF双联精炼工艺生产低碳汽车用钢的工业实践

介绍了芜湖新兴铸管采用RH-LF双联精炼工艺生产低碳汽车用钢。生产实践表明,该工艺有效解决了转炉吹炼终点钢水过氧化严重、成品碳含量高及非金属夹杂物级别高的难题。

环流式真空脱气装置的钢水混合与循环

通过实测数据及理论参数建立了ＲＨ环流和主要影响因素间的应用关系，计算结果与工业试验数据相吻合。定量分析了顶吹方法对ＲＨ 环流过程钢包所获得的单位搅拌功率的影响。结果表明，顶吹氧射流对钢包混匀时间和循环流量的作用可以忽略。

高碳微合金非调质钢C70S6的开发和工艺实践

开发的高碳微合金非调质钢C70S6(/%:0.68~0.73C,0.15~0.25Si,0.45~0.55Mn,≤0.030P,0.055~0.070S,0.10~0.15Cr,0.04~0.08Ni,0.03~0.04V,0.0120~0.0140N)的生产流程为120 t顶底复吹转炉-LF-RH-240 mm×240 mm方坯连铸-Φ39 mm棒材轧制。生产结果表明,通过控制Mn/S≥3,采用碱度[(CaO)/(SiO_2)]4.32的LF精炼渣(/%:59.87CaO,13.86SiO_2,5.55MgO,16.34Al_2O_3,0.64S,0.072MnO),钢水过热度15~30℃连铸拉速0.65 m/min,弱二冷比水量0.5 L/t;二冷Ⅲ段采用气雾冷却,终轧温度≤880℃等工艺措施,高碳微合金非调质钢C70S6抗拉强度≥950 MPa,屈服强度≥550 MPa,伸长率≥10%,断面收缩率≥20%,硬度HB值为240~290,其各项指标均满足胀断连杆要求。

超低碳冷轧基料开发

介绍了天铁超低碳冷轧基料St13开发实践。采用铁水预处理→转炉冶炼→RH→连铸→热轧的工艺路线,充分发挥RH精炼炉脱碳、去磷、脱气、去夹杂的冶金功能;热轧采用"三高一低"的温度制度,保证钢材的加工性能,严格控制表面质量和板型质量,研制开发出的超低碳冷轧基料St13性能优异。

超低碳钢增碳因素分析

重钢通过210tLD—RH—CC试生产了7炉超低碳钢，分析了该批次超低碳钢过程[C]京戏化和废钢、合金、取样器以及耐材对钢水增碳的影响，得出耐材因素是此轮钢水增碳的主要原因，并提出了合理化建议为下一步的批量生产提供了技术支持。

RH精炼钢中全氧量变化与操作改进

为了使钢中全氧量控制在一个适当的水平,在武钢炼钢总厂RH真空脱气装置对低碳、超低碳钢进行了脱氧净化试验.结果表明,影响全氧去除的因素按作用高低依次是出钢溶解氧水平,溶解氧与钢包渣的交互作用,钢包渣,和真空处理净化时间.通过改进工艺生产了全氧量≤10×10-6,非金属夹杂物尺寸<10μm的清洁钢水,建立了一个钢包内钢水全氧浓度随时间变化的新方程,该方程考虑了全氧的表观平衡含量及环流、扩散传质对去除氧化物夹杂速率的影响.

碳氧平衡在低碳低硅钢RH轻处理工艺中的应用

通过对低碳低硅钢炼钢过程碳氧平衡进行系统计算,结合RH轻处理工艺要求,详细分析了过程碳、氧含量的控制要点,结果表明:CO分压对碳氧积的影响比钢水温度更加显著;RH生产超低碳钢时要求极限真空度和较高的平衡氧含量;RH轻处理生产低碳低硅钢的适宜条件是进站初始碳质量分数0.03%~0.04%、初始氧质量分数0.04%~0.05%、真空度5 kPa,研究规律在生产中得到了应用与验证。

采用BOF-RH-CC工艺生产低碳低硅钢

结合产品性能需求,对低碳低硅钢生产工艺控制难点及其冶炼工艺参数的优化进行了论证分析。分析认为:采用铁水预处理后,转炉终点w(S)均值控制到0.011%;在转炉C-O积为0.002 8时,终点w(C)控制在0.03%～0.05%,终点温度在1 670℃以上为宜;RH精炼过程中钢包渣w(TFe+MnO)控制在2.0%～6.0%,碱度R控制在4.0～5.0。吨钢底吹供气强度控制在0.70～1.00L/min时,钢液回Si基本可控制在0.005%以下,回P控制在0.002%以下。并对钢液w(T.O)的工序控制及冶炼参数优化进行了分析。

RH-MFB生产超低碳钢的工艺优化

在RH脱碳静态模型的基础上对RH脱碳理论进行了分析，分析结果表明，涟钢RH的实际脱碳水平还有待提高。针对影响RH脱碳速率的主要因素进行分析，结果表明：为获得最佳脱碳效果，处理时应消除压降平台，全程真空度在400Pa以下保持16min以上，同时在钢水循环开始后的3～4min控制吹氩流量为80～100m^3/h；真空度达8kPa以后（即3min左右时）为吹氧的最佳时机，此时应将氧枪高度控制在250～400cm，氧气流量控制在1200～1600m^3／h。实践证明，通过这些优化措施，可使处理后碳质量分数稳定在0．003％以下。

不同RH冶炼工艺对低碳铝镇静钢洁净度的影响

对比分析了生产低碳铝镇静钢采用RH两种不同处理模式的工艺特点和洁净度差异，结果表明：工艺路线1的RH到站渣中w（T．Fe＋MnO）：5％～12％，而工艺路线2的RH到站渣中w（T．Fe＋MnO）稳定控制在2％以内，工艺路线1精炼过程中w（Al5）损失较工艺路线2高约54×10^-6；工艺2夹杂物有效去除时间平均为64min高于工艺路线1的45min工艺路线1结晶器钢水w（T．O）较工艺路线2高13×10^-6工艺路线1结晶器钢液中的夹杂物分布面积比高于工艺路线2，同时工艺路线1钢水样中，尺寸在5“m以上的夹杂物占10．6％，高于工艺路线2的3．6％。针对不同RH精炼工艺分别提出了相应的优化措施。

超低碳钢炉外精炼工艺的优化

对LF+RH精炼超低碳钢的工艺进行了优化;研究了LF渣系、炉渣碱度、炉渣氧化性、渣量、AlS、氩气流量的控制方法以及RH强制脱碳、炉渣性质的变化和RH时间的分配;制定了合理的温度制度,并比较了优化工艺与传统工艺的生产成本。研究结果表明,优化工艺后钢液化学成分、温度及时间节点控制均满足生产要求,每吨钢成本低于传统工艺32.6元。