EAF steelmaking process with increasing hot metal charging ratio and improving slagging regime

A new electric arc furnace （EAF） steelmaking process with increasing hot metal charging ratio and improving slagging regime simultaneously was developed and applied in a 50 t electric arc furnace for more than a year at No. 1 Steelmaking Plant of Shanxi Taigang Stainless Corporation Limited. The essential fact of the new EAF steelmaking process was to charge hot metal in two portions or steps： firstly, 35wt%-40wt% hot metal was pretreated by blowing oxygen in a specially designed reactor for decar burization and improving hot metal temperature and melting premelted slag; secondly, 30wt% hot metal was charged into EAF with high basicity refining slags from ladle furnace （LF）-vacuum degassing furnace （VD） refining process. The results show that the hot metal charging ratio can reach to about 65wt%-70wt% for the new EAF steelrnaking process; meanwhile, the tap-to-tap time of a 50 t EAF can shorten by 5-10 min, the electricity consumption can decrease by 35-50 kW·h/t, the lime consumption can reduce by 10.5 kg/t of molten steel, and the content of harmful heavy metals in molten steel can be easily controlled to less than the upper limits of aimed steel specification or grade compared with the traditional EAF steelmaking process. In addition, the dephosphorization ability shows a slight strengthening, however, a small degree of lessening for desulphurization ability is observed for the new EAF steelmaking process, but the weakness of desulphurization ability cannot become an obstacle to its further application since a stronger desulphurization ability can be achieved during secondary refining of LF coupled with VD after EAF steelmaking process.

Beneficial use of stainless steel EAF slag as composite cement admixture and its heavy metals leaching risk analysis

This study analyzes the feasibility of using stainless steel electric arc furnace （EAF） slag as composite cement admixture and the risk of leaching-out of heavy metals. The results show that the stainless steel EAF slag, mainly made up of Ca2 SiO4, Ca3 Mg （ SiO4 ） 2, some Cr-containing minerals and in small particle size, is easily ground and has cementitious activity. EAF slag, when used as cement admixture, can be added with a maximum percentage of 32%. It can meet the strength requirements of the standard P · C 32.5 cement. When the mixing percentage is decreased to 25 % , the strength of the cement can be increased to that of P · C 42.5 cement. Other main quality indexes of composite cement, such as the setting time and stability, also satisfy standard requirements. The results also show that most of the heavy metals in the stainless steel EAF slag exist in a stable speciation. The concentration of heavy metals that leach out from the stainless steel EAF slag and the composite cement products is far lower than the standard limit of hazardous wastes. The main heavy metal, chromium, exists as less hazardous trivalent chromium. Therefore, the risk of heavy metals leaching out from the stainless steel EAF slag is low. The internal exposure index （IRa） and the external exposure index （Iγ） of the stainless steel EAF slag are both lower than 1.0, satisfying the standard requirements of the state for the radionuclides of building materials. Therefore, stainless steel EAF slag can be safely used as admixture to produce composite cement.

Activity of Reducing Steel Slag of EAF

Reducing steel slag （RSS） was mainly acquired from five electric-arc furnace （EAF） steelmaking plants （among them, the products of two plants were carbon steel and those of other plants were stainless steel） for research tests. The chemical properties, compound compositions, activities and contents of main expansive compounds were tested. The results showed that the field sampled RSS had a very high crystallinity and hydraulicity with main chemical compositions close to those of Portland cement. It can be known from the study that in case of C/S ratio higher than 2.0, the main compound compositions are C2S, C3S, C2F and f-CaO. However, after the RSS was stored for six months, an obvious variation occurred with potential pre-hydration in RSS, where the SO3 content was slightly reduced and the compressive activity index was obviously higher than that at the 28th day.

Extraction of Valuable Metals from Titanium-bearing Blast Furnace Slag by Acid Leaching

To realize the resource utilization of the valuable metals in the titanium-containing blast furnace slag,the process route of “hydrochloric acid leaching-electrolysis-carbonization and carbon dioxide capture-preparation of calcium carbonate” was proposed.In this study,the influences of process conditions on the leaching rates of calcium,magnesium,aluminum,and iron and the phases of the leaching residue were investigated for the leaching process.The experimental results show that the HCl solution could selectively leach the elements from the titanium-containing blast furnace slag.The better leaching conditions are the HCl solution concentration of 4 mol/L,the leaching time of 30 min,the ratio of liquid volume to solid gas of 10 mL/g,and the stirring paddle speed of 300 r/min.Under the conditions,the leaching rates of calcium,magnesium,aluminum,and iron can reach 85.87%,73.41%,81.35%,and 59.08%,and the leaching rate of titanium is 10.71%.The iron and the aluminum are removed from the leachate to obtain iron-aluminum water purification agents,and the magnesium is removed from the leachate to obtain magnesium hydroxide.The leaching residue phase is dominated by perovskite,followed by magnesium silicate and tricalcium aluminate,and the titaniumrich material could be obtained from the leaching residue by desiliconization.

EAF-LF炼钢流程中钢水回磷的热力学分析

本文对钢水回磷进行了热力学计算和分析,得知EAF LF炼钢流程中钢水回磷的根本原因是熔池温度升高、炉渣氧化性减小和炉渣碱度降低,并针对宝山钢铁股份有限公司150tEAF炉冶炼钢管钢过程、定量计算了熔池温度、炉渣氧化性及炉渣碱度变化对钢水回磷量的影响。计算结果表明,在LF精炼的热力学条件下,渣中无磷存在;EAF下渣量及铁合金种类对LF精炼钢水回磷量也有影响,EAF每下渣100kg,钢水增磷0.00032%,锰铁合金的增磷作用大于硅铁合金。每加入1kg t锰铁合金使钢水增磷不少于0.0002%。由计算及分析可知,为防止钢水回磷必须密切关注EAF终点升温过程、严格控制EAF下渣量并采用低磷锰铁合金。

以EAF还原渣为主脱硫剂配料的研究

为提高EAF还原渣脱硫的效果,选择不同的添加剂与EAF还原渣按一定比例混合制备脱硫剂,并通过脱硫效果和脱硫剂利用率的比较,在保证脱硫效果和高效利用的原则下,确定了新型脱硫剂配料方案。

EAF渣矿相组成及其短期淋溶特性

采用XRD方法研究了EAF渣矿相组成,采用静态淋溶实验方法,研究了液固比、淋溶液初始p H值和淋溶温度对EAF渣短期淋溶特性的影响。结果表明,EAF渣中存在的主要矿物为镁硅钙石、硅酸二钙、钙铝黄长石、磁铁矿、尖晶石、绿铬矿和钙钛矿。短期淋溶条件下,EAF渣淋溶液呈现强碱性和一定的还原性,EAF渣淋溶液中铬质量浓度随着液固比的升高而有所降低,强酸或强碱性淋溶液会在一定程度上提高淋溶液中铬质量浓度,温度对淋溶液中铬质量浓度影响较小;淋溶液铬质量浓度不仅受铬富集相溶解反应平衡控制,也受到淋溶液酸性影响,酸性较强时利于渣中碱性氧化物Cr(OH)3的分解,碱性较强时利于Cr(OH)4-离子的生成;EAF渣淋溶液中的铬主要以三价态存在,六价铬和总铬质量浓度均低于《危险废物鉴别标准浸出毒性鉴别》(GB 5085.3—2007)限值,在一定程度上说明EAF渣的短期淋溶毒性风险较低。

70 t DC-EAF炉泡沫渣技术的最新研究与实践

在 U HP DC- EAF冶炼过程中将成分的控制、埋弧加热、避免大沸腾、增大铁水热装率、延长炉龄有机地结合起来是当前电冶金工作者努力研究的方向。简要介绍了新 70 t DC炉泡沫渣技术所进行的突破性研究与实践结果。

150t EAF-LF-VD-CC流程生产超低硫钢的工艺实践

生产超低硫0.20%～0.24%C钢时,在150 t EAF的炉料为40%铁水+优质低硫废钢,终点[C]0.03%～0.05%,电弧炉出钢平均[S]为0.046%,LF初始平均[S]为0.017%的条件下,控制精炼终点[O]≤2.5 X10^(-6),终点(FeO+MnO)≤O.80%,控制渣量不小于22 kg/t钢,铝消耗量1.85 kg/t钢,氩气搅拌良好,成品钢中的硫含量≤0.001%。

溶解氧对EAF渣静态淋溶的影响

采用短期静态淋溶实验方法研究了溶解氧对EAF渣静态淋溶的影响。研究结果表明,溶解氧对EAF渣浸出液氧化还原电位(Eh)的影响显著,空气吹扫淋溶液浸出EAF渣时浸出液的Eh存在氧化性转变为还原性的过程(-50~40mV),氮气吹扫淋溶液浸出EAF渣时浸出液的Eh一直保持还原性状态(-100^-70 mV)。溶解氧对EAF渣浸出液铬浓度的影响显著,相较于氮气吹扫条件,空气吹扫条件下EAF渣浸出液中Cr^6+和总铬的浓度分别高出12%~23%和10%~83%。溶解氧对Cr的溶出有一定的促进作用并且在氧化钙存在的条件下能够缓慢氧化Cr^3+。

EAF-LF-VD工艺冶炼轴承钢夹杂物行为研究

对某钢厂EAF-LF-VD工艺生产的轴承钢进行取样分析,发现钢中非金属夹杂尺寸主要集中在3~8μm,并且夹杂物单位面积内数量和平均粒径在VD破空样中达到最小。钢中非金属夹杂成分受渣成分影响显著,铸坯中非金属夹杂以Al_2O_3-CaO复合夹杂为主,非金属夹杂中CaO含量基本完全受渣中CaO含量影响。发现在高碱度渣的条件下,钙铝酸盐与镁铝尖晶石很容易发生反应,同时高碱度条件下MgO-Al_2O_3-CaO系夹杂物中MgO含量也会降低。

100 t EAF-LF-VD Φ500 mm连铸坯流程高压锅炉用钢SA-210A1生产实践

生产的高压锅炉用钢SA-210A1(/%:0.08～0.11C,0.22～0.24Si,0.72～0.74Mn,0.007～0.010P,0.004～0.005S,0.010～0.015V,0.025～0.035Ti,0.012～0.018Alt)的冶金工艺流程为55%铁水+废钢-100 t EAFLF-VDΦ500 mm坯连铸-轧制成Φ130mm圆钢。通过低铝脱氧工艺-EAF终点控制[C]≤0.06%,[P]0.006%～0.010%,出钢加石灰12 kg/t,AD粉(/%:10～13A1,55～60Al_2O_3,5～8SiO_2,5～8Mg0)3 kg/t,700%Al钢芯铝3 kg/t预脱氧;LF采用5.76～6.06高碱度Al_2O_3渣系,LF终点喂0.40 kg/t钙线,软吹≥10 min;中间包钢水过热度15～25℃连铸结晶器和末端电磁搅拌,拉速0.31～0.32 m/min,铸坯缓冷≥48 h等工艺措施,SA-210A1钢中的[0]16×10^(-6)24×10^(-6),[N]65×10^(-6)～80×10^(-6),[Alt]≤0.020%,铸坯和热轧圆钢低倍组织和非金属夹杂物均满足要求。

70t UHP-EAF脱磷技术实践

对70UHP-EAF的脱磷操作及其控制要点作了详细的介绍、分析。

提高70tEAF-LF炉过程脱硫效率的实践

配置EAF-LF-CCM的短流程生产线,提高钢水的脱硫效率是提高生产作业率的关键环节之一,通过采取电炉出钢渣洗、LF大渣量及强搅拌脱硫的精炼工艺,脱硫效率有了大幅度的提高。

Controllable synthesis of nanorod/nanodisk TiO_2 from titanium-containing electric furnace molten slag

Nanostructured TiO2 with different morphologies and crystal phases was successfully synthesized from titanium-containing electric furnace molten slag by using a hydrothermal method followed by reflux process in acid solution. The effects of acid concentration, reflux time, and acid type on the formation of TiO2 were systematically investigated by scanning electron microscopy, X-ray dif- fraction （XRD）, transmission electron microscopy （TEM）, high-resolution transmission electron microscopy （HRTEM）, and X-ray fluorescence （XRF）. It is indicated that TiO2 nanorod with rutile phase is achieved in nitric or hydrochloric acid, while anatase TiO2 nanodisk is formed in sulfuric acid. With the increase of the concentration of hydrochloric acid from 0.3 to 1.5 mol-L-1, the dispersibility and crystallinity of the final product can be improved. With prolonging the reflux time from 6 to 14 h, the rutile TiO2 nanorod with uniform crystal size and high crystallinity is obtained. The growth mechanism of TiO2 nanorod and nanodisk prepared under different conditions was also discussed.

电弧炉配加直接还原铁对炼钢的影响

通过开展全废钢及配加10%、20%、30%比例直接还原铁(DRI,direct reduced iron)试验研究了Consteel电弧炉配加不同比例DRI对冶炼技术经济指标、钢水洁净度和电弧炉终渣成分的影响,并根据试验情况对金属料加入、吹氧喷碳、造渣辅料加入、排渣等冶炼控制要点进行分析。结果表明,随着DRI加入比例增加,电耗、钢铁料消耗、造渣辅料消耗和渣量等逐渐增加。且DRI加入比例在30%时,因炉渣量较大,在冶炼过程中后期有炉渣从炉门溢出。同时,电弧炉配加DRI后钢水洁净度明显升高,电弧炉冶炼终点氮、磷、硫和残余元素质量分数降低,且随着DRI加入比例增加,电弧炉终点钢水氮质量分数下降速率变小。此外,随着DRI加入比例增加,电弧炉终渣FeO质量分数呈降低趋势。DRI加入比例20%时效果较好,冶炼周期较短,与全废钢炉次相比电耗增加不高,且氮和残余元素含量较低,满足大部分钢种要求。

不锈钢冶炼电炉渣结构性质及浸出行为研究

研究电弧炉(EAF)渣的结构性质及渣中重金属离子的浸出行为。结果表明,EAF渣呈碱性,渣中Fe、Cr和Ni等金属元素主要以金属颗粒、(Cr,Al)2O3和(Fe,Mn,Mg)(Cr,Al)2O4晶体形式存在,具有较高的回收价值;电炉渣中可浸出重金属离子含量未超出国家标准,但存在Cr(III)再氧化为Cr(VI)的可能;Cr(VI)浸出量随浸出时间延长而增加,且Cr(VI)在蒸馏水中的浸出能力较冰醋酸中强。因此,EAF渣应尽量避免堆放或填埋在低pH场所,以防止其中重金属离子浸出。

电炉钛渣碱浸除硅、铝与碱浸渣的预氧化焙烧动力学

采用碱浸除杂-预氧化焙烧-活化改性-高压酸浸工艺处理云南地区电炉钛渣,制备高品位人造金红石.研究了电炉钛渣碱浸除硅、铝的机理,考察了搅拌速率、粒度、温度、NaOH浓度、液固质量比、浸出碱试剂单因素对浸出率的影响,SiO2与Al2O3浸出率高达75%和50%;正交实验结果表明,NaOH浓度为1.5mol/L、液固质量比为8、温度为沸腾温度(92.7℃)、浸出时间为1h的条件下,浸出效果较理想;通过碱浸渣预氧化,有60%的TiO2以金红石形态析出,且在低于700℃下过程受界面化学反应控制,扩散较快,表观活化能为31kJ/mol/,850℃下过程受扩散控制,随空气流量增大氧化率提高.

直流电弧炉长弧泡沫渣技术

本文指出了直流电弧炉采用长弧泡沫渣技术的必要性及该技术的发展现状。总结了炉渣物理性质、化学成分、温度和气源等对炉渣泡沫化的影响。并介绍了电炉泡沫渣的操作工艺及实际应用效果，对宝钢三期１５０ｔＤＣ－ＵＨＰ电弧炉的泡沫渣工艺提出了看法。

宝钢含锌尘泥的循环利用工艺简介

对宝钢的含锌尘泥 (转炉二次粉尘、电炉粉尘和高炉瓦斯泥 )的厂内循环利用进行了研究 ,通过将含锌尘泥分别应用于铁水三脱、转炉造渣和电炉造泡沫渣工艺对循环利用工艺进行了试验 ,具体如下 :将转炉二次粉尘和电炉粉尘的混合物取代烧结矿粉作为铁水脱磷剂 ,通过改善流动性 ,达到了与烧结矿粉相当的脱磷效果 ,在三脱处理中粉尘中的锌和铅含量得到了明显的富集 ,为下一步回收处理打下了基础。将转炉二次粉尘和电炉粉尘的混合物通过添加一定量生白云石和锰矿加工成冷压块 ,在转炉吹炼前期加入 ,促进了石灰的溶解 ,改善了前期化渣 ,提高了脱磷率 ,LT压块和矿石的耗量减少。造渣剂加入没有引起钢水的增硫明显 ,粉尘造渣剂的加入对钢水和炉渣成分没有影响。将高炉瓦斯泥通过添加一定量生石灰和生白云石并加工成冷压块后 ,在电炉熔炼期加入 ,强化泡沫渣操作 ,减少金属损失和碳粉用量。瓦斯泥压块加入后对钢水。