Effect on cleanliness of molten steel with different refining slag systems for low alloy ship plate

To study the effect of refining slag on the compositions of molten steel and inclusions, the reaction between ship plate steel and different slag systems (slag A-CaO/Al₂O₃: 1.0, SiO₂: 5 mass-% and slag B-CaO/Al₂O₃: 1.5, SiO₂: 9 mass-%) was investigated by laboratory-scale high-temperature equilibrium experiments. Results showed that the desulphurisation capacity of the two slags was very similar, and the average sulphur content for both was 0.002?mass-% in steel, but the deoxidation capacity of slag B was slightly higher than slag A. The amount of inclusions <5?μm was more in steel balanced with slag B than in that balanced with slag A. To generate inclusions smaller than 5?μm, and spherical liquid CaO–MgO–Al₂O₃–SiO₂ inclusions, and to decrease the T[O] (total oxygen) content in steel, refining slag composition should be: CaO/Al₂O₃ ～ 1.5, and SiO₂ ～ 9?mass-%. Slag system optimisation can reduce or even eliminate calcium treatment during production. T[O] content in the slab could be controlled to 15–21?ppm, with typical micro-inclusions of ≤10?μm, and CaO–Al₂O₃–MgO and CaO–Al₂O₃–CaS systems in molten steel.     

Effect of slag composition on the cleanliness of drill rod steel

In order to obtain the 55SiMnMo drill rod steel with a high cleanliness, the slag refining has been simulated by laboratory experiments. More desired spherical-shaped complex inclusions with an average diameter of about 2.7?μm, total oxygen of 4?ppm and Mg of 10?ppm after refining were obtained with initial slag basicity of 2.1 and Al₂O₃ 15?wt-%. The relationship between the slag composition and the melting temperature and viscosities of slag was achieved based on a calculation by Factsage Software and Einstein–Roscoe Equation. The refractory–slag–metal–inclusion multiphase reactions were investigated from the viewpoint of thermodynamics and kinetics by the estimation of viscosities, MgO solubility, Al₂O₃ activity in slag and sulphur capacity of slags. It is experimentally confirmed that the corrosion of MgO crucible by slag was affected by the MgO solubility and viscosity of slag. The factors facilitating to obtain low oxygen and control sulphur content were also analysed. Finally, the composition transformation of inclusions during slag refining and cooling process was discussed based on thermodynamic calculation.     

高碱度精炼渣对GCr15轴承钢洁净度的影响

 利用实验室渣-钢平衡试验研究了高碱度精炼渣对GCr15轴承钢中[w(T[O])]和夹杂物的影响。结合试验结果和热力学分析,探讨了钢中[w(T[O])、]夹杂物尺寸分布和粒径大小的变化规律,以及氧化物夹杂的转变过程。研究结果表明,碱度为6时,精炼渣(59.4%CaO-24.8%Al2O3-9.8%SiO2-6%MgO)可将钢中[w(T[O])]控制在0.000 6%以内,氧化物夹杂平均尺寸最小为2.26 μm。随着钢中[w([Ca])]和[w([Mg])]的增加,钢中氧化物夹杂转变过程为Al2O3→MgO·Al2O3→MgO→CaO-Al2O3-MgO复合夹杂物(核心为MgO,外围包裹着CaO-Al2O3)。渣-钢反应前期钢中以MgO·Al2O3为主,后期以MgO和CaO-Al2O3-MgO复合夹杂物为主。氧化物夹杂转变的试验结果与热力学分析结果相一致,大多数氧化物夹杂尺寸小于5 μm。     

精炼渣成分对高强度低合金钢中非金属夹杂物影响

采用渣钢平衡的实验方法研究了1600℃下不同碱度和不同Al₂O₃含量的强还原性精炼渣对高强度低合金钢中非金属夹杂物的影响.结果表明:渣钢反应平衡后,炉渣中CaO和SiO₂的质量比为1.9~4.5、Al₂O₃质量分数为21%~33%,钢中夹杂物主要为球状的CaO-MgO-Al₂O₃-SiO₂系,尺寸在5μm以下,炉渣成分对夹杂物的成分影响很大.夹杂物主要分布在SiO₂含量一定的CaO-MgO-Al₂O₃-SiO₂伪三元相图中1 400~1 500℃的低熔点区,随着炉渣碱度的提高和Al₂O₃含量的降低,部分夹杂物逐渐偏离低熔点区域,夹杂物的总数量逐渐减小.当渣中Al₂O₃质量分数为21.22%、碱度为3.27时,有大量夹杂物分布在高熔点区域,夹杂物的总数量最小.     

RH精炼纯循环时间和镇静时间对IF钢洁净度影响

为了优化RH处理工艺,提高RH精炼后的IF钢的洁净度水平,通过分析全氧含量和夹杂物的控制水平,研究了纯循环和镇静时间对IF钢洁净度的影响。研究表明,RH加入铝粒反应6min后钢液中全氧质量分数降低至24.7×10~(-6)。加入Ti-Fe合金后,全氧质量分数上升至30×10~(-6)。随后RH经合金化后保持6~9min的纯循环时间,全氧质量分数可降低到27×10~(-6)。延长镇静时间至25min,可使全氧质量分数降低到27×10~(-6);通过直线法计算,夹杂物数量由破空时的13.21个/mm2逐渐降低到破空25min时的7.79个/mm2。     

Study on control technology of slag composition for low-sulfur ＆ low-oxygen steel

为实现高品质低硫、低氧钢的生产，有效降低钢中T．0、S含量，在考虑转炉下渣、炉渣氧化性以及钢水氧活度的条件下，研究确定了用于低硫、低氧钢冶炼的CaO-Si02-A1：03精炼渣系，并结合转炉下渣改质技术以及LF精炼钢包渣成分控制技术等工艺措施，制定了低硫、低氧钢的钢包渣改质制度。采用该技术生产的27CrMoNbV等圆管坯钢达到了成品w（T．0）≤15×10，w（S）≤0．005％的水平，实现了低硫、低氧钢的生产。     

不同浇铸阶段IF钢连铸板坯洁净度

对采用转炉-RH精炼-连铸工艺生产的IF钢连铸板坯在不同浇铸阶段(开浇、正常、两炉交接及浇铸末期)的铸坯洁净度进行了较为细致地研究和对比分析.由于浇铸初期存在二次氧化及较大程度地增碳,开浇坯[C],[O]_T,[N]含量远高于其他时间段的铸坯,并存在较大尺寸的簇群状Al₂O₃夹杂.正常坯夹杂主要为尺寸较小(≤ 30μm)的块状及少量簇群状Al₂O₃夹杂(≤ 40μm),交接坯及尾坯仍以较小尺寸的块状Al₂O₃夹杂为主,但存在极少量大于100μm的复合夹杂.     

LF精炼渣碱度变化对304不锈钢夹杂物成分的影响

采用氧氮分析仪、扫描电镜、金相显微镜等分析手段,系统研究LF精炼渣系对304系不锈钢全氧质量分数wT[O]、夹杂物数量、尺寸及成分的影响。研究结果表明,当LF精炼渣碱度由1.5升高至2.6时,LF出站溶解氧质量分数w[O]由11.6×10~(-6)降低至4.8×10~(-6),铸坯wT[O]由47×10~(-6)降低至24×10~(-6),铸坯夹杂物总数量降低,但当量直径不大于10μm的夹杂物所占比率由77.7%增加至95.1%。热力学计算结果表明:在钢液中各元素达到平衡状态时,渣系碱度越高,低熔点夹杂物2MgO·2Al_2O_3·5SiO_2生成区域越小,MgO·Al_2O_3尖晶石类夹杂物生成区域越大,与生产试验结果一致。随着LF炉渣碱度升高,铸坯夹杂物成分中MgO和Al_2O_3的质量分数分别升高了14.4%和9.1%,当碱度不大于1.9时,铸坯中不会存在镁铝尖晶石。     

Effect of refining slag containing Ce_2O_3 on steel cleanliness

The effect of pre-melting refining slag containing different contents of Ce2O3 on the absorption and modification of Al2O3 inclusion in an Al-killed steel was investigated through the slag/steel reaction experiment at 1600 oC.It was found that the replacement of 10 wt.% Al2O3 with Ce2O3 for 50 wt.%CaO-33 wt.%Al2O3-7 wt.%MgO-10 wt.%SiO2 refining slag promoted the slag absorption ability of alumina inclusion,which made the total oxygen content determined by infrared absorption method decrease from 100 to 25 ppm in 15 min.The Mg-Al-Ce-O type inclusion was also detected in the as-solidified samples by scanning electron microscopy(SEM).Thermodynamic analysis indicated that the Ce2O3.Al2O3 type inclusions would be formed with the cerium content in the range of 6.9 ppb to 3.6 ppm when the content of aluminum was 0.01 wt.%.     

转炉合成渣洗工艺对45钢纯净度的影响

主要研究了转炉出钢合成渣洗工艺对45钢纯净度的影响。结果表明：采用合成渣洗工艺后,铸坯中的全氧质量分数有所降低,比未合成渣洗的铸坯全氧质量分数降低2588%;采用合成渣洗工艺后,铸坯中大颗粒夹杂物含量平均由966 mg/10 kg减少为512 mg/10 kg,平均减小了4700%。     

超低碳钢顶渣氧化性对钢液洁净度的影响

为探究降低顶渣氧化性对改善超低碳钢钢液洁净度的影响,在转炉终点至中间包过程中,在多位置取炉渣和钢水试样,分别进行炉渣氧化性、钢液成分和夹杂物分析.实验结果表明:转炉出钢后通过对顶渣改质,渣中T.Fe由转炉终点的19.18%降至RH进站时的4.68%,顶渣氧化性降低明显.渣中T.Fe降低导致钢中[O]的降低,T.Fe较低的炉次平均吹氧量较大,使得铝脱氧前钢中[O]较高.RH结束渣T.Fe与夹杂物数量呈线性关系,T.Fe越低夹杂物数量越少,同时RH结束后夹杂物数量与铝脱氧前钢中[O]无必然关系.顶渣(CaO)/(Al₂O₃)会影响其吸收Al₂O₃夹杂物的能力,(CaO)/(Al₂O₃)控制不合理的炉次,其夹杂物数量也较多.通过降低顶渣氧化性,热轧板卷缺陷率得到明显降低.     

Effect of ladle slag of previous heat on number of non-metallic inclusions in ladle treatment of tool steel

Abstract

Nine series of industrial trials were carried out using the same ladle in each series to examine the effect of ladle slag on the number of non-metallic inclusions in the next heat. Steel and slag samples were taken after ladle vacuum treatment for chemical composition analysis. Samples of the final steel product were examined to determine the number of non-metallic inclusions. It was found that the number of inclusions increased with SiO₂ content of the ladle slag in the previous heat. No clear trends were found for the effects of viscosity and MgO activity of the previous slag on the number of inclusions.Theoretical analysis based on the experimental results suggested that the formation of 2CaO.SiO₂ followed, but the dusting of the compound made the refractory more porous, which was reasonable for the number of non-metallic inclusions.     

RH纯循环对Ti-IF钢洁净度的影响

利用金属原位分析仪定量分析了过程Al系夹杂的数量,并用一种深度侵蚀的方法观察了夹杂物的三维真实形貌.对过程全氧(T.O)、[N]含量变化进行了跟踪.通过延长RH合金化后的纯循环时间对过程洁净度进行了评价.结果表明:RH在合金化后保持8~10 min的纯循环时间T.O可降低到30×10^-6以下;废钢加入会极大影响钢液的洁净度,合金化完毕后应避免废钢加入;加Al 5min后夹杂物数量达到最大,为7.02mm^-2,主要为大型的团簇状夹杂,经过纯循环后,夹杂物数量、尺寸均有较大的降低.     

Influence of refining slag composition on cleanness and fatigue life of 60Si2MnA spring steel

The influence of basicity and Al₂O₃ content of LF refining slag on T.[O] (total oxygen) as well as type, number and size of non-metallic inclusions in Al killed 60Si2MnA spring steel was investigated. The results showed that with the increase of slag basicity R(CaO/SiO₂) or the decrease of Al₂O₃ content in slag, the T.[O], number and size of non-metallic inclusions decreased significantly. On the one hand, as the slag basicity increased, inclusions in steel were transformed from Al₂O₃–SiO₂–CaO–MgO quaternary system to Al₂O₃–SiO₂–CaO–MgO–CaS quinary system, which made the formation of voids between inclusions and steel matrix to decrease. Furthermore, thermodynamic calculations showed that CaS could only form in steel (R?≥?3.4). Al₂O₃–SiO₂–CaO–MgO came close to the compositions of the low melting point area, while Al₂O₃–SiO₂–CaO–MgO–CaS deviated from this. On the other hand, as the Al₂O₃ content in slag increased, Al₂O₃–SiO₂–CaO–MgO–CaS came close to the compositions of the low melting point area. In conclusion, the cleanness and fatigue life of 60Si2MnA spring steel had been improved by the increase of slag basicity or the decrease of Al₂O₃ content in slag.     

水洗洁净处理对钢渣SMA性能影响的研究

介绍了路用钢渣集料洁净技术,利用洁净工艺前后的钢渣集料分别配制了钢渣沥青玛碲脂碎石混合料(SMA),得到用水清洗后钢渣最佳配合比为:1号(钢渣10~16mm)∶2号(钢渣5~10mm)∶3号(玄武岩3~5mm)∶4号(玄武岩3mm)∶5号(石灰岩矿粉)=38∶36∶8∶8∶10,最佳油石比为6.4;没有用水清洗钢渣最佳配合比为:1号∶2号∶3号∶4号∶5号=34∶38∶10∶8∶10,最佳油石比为6.4。研究了钢渣洁净技术对钢渣SMA性能影响,发现洁净技术有利于发挥钢渣SMA性能。     

气泡搅拌和炉渣成分对低碳钢水洁净度的影响

在80t氧气转炉、钢包吹氩和RH真空处理工序进行净化钢水的试验,考察反应器内氩气流量、真空脱气操作和顶渣成分对低碳钢水全氧含量的影响以及夹杂物的尺寸分布和全氧的排除速率,改进操作的结果表明,二次精炼后低碳钢水全氧w[T.O]降低到0.001%。     

Improvement of steel cleanliness by controlling slag composition

Abstract

The properties of slag are very important in the improvement of steel cleanliness. In particular, the value of %CaO/%Al₂O₃ ratio, slag basicity, fluidity, and oxygen activity in the slag are considered to affect the steel cleanliness directly. To control these values effectively, the method of deoxidation and slag composition control via additives has been changed. The effect of oxygen content before tapping was investigated. By optimising these factors, the total oxygen content of bearing steel was reduced from 12 to 8 ppm.     

精炼渣对高锰钢中非金属夹杂物的影响

 为了研究精炼渣对高锰钢中非金属夹杂物的影响,采用渣/钢平衡的试验方法研究了MgO SiO2 Al2O3 CaO系精炼渣对Fe xMn高锰钢(x=10%, 20%)中非金属夹杂物的影响。结果表明,无顶渣情况下,高锰钢中夹杂物主要为MnO类和MnO Al2O3类2类。加入精炼渣后,夹杂物类型发生了变化,主要有 MnO类、MnO SiO2类和 MnO Al2O3 MgO类3类,其中MnO SiO2类数量最多。采用ASPEX扫描电镜对夹杂物的平均成分进行分析,无顶渣时高锰钢中夹杂物的成分主要是MnO,质量分数在95%以上,并含有质量分数为4%左右的Al2O3。加入精炼渣后,夹杂物中MnO质量分数降低,SiO2质量分数显著增加,MgO质量分数增加。热力学计算结果表明,加入精炼渣后,渣/钢间反应4［Al］+3(SiO2)=2(Al2O3)+3［Si］和2［Mn］+(SiO2)=2(MnO)+［Si］的吉布斯自由能均小于零,这说明在本试验条件下,钢液中的［Al］和［Mn］会还原渣中SiO2,生成的［Si］进入钢液,进而与钢液中的［O］结合,导致夹杂物中SiO2增加。     

LF两步造渣工艺对C82DA钢中硫和铝的影响

 为了研究工艺对C82DA钢中硫和铝的影响,对帘线钢在LF精炼过程脱硫控铝进行了研究。结果表明,随着精炼碱度的降低脱硫率越来越低,碱度约为1.6时,渣中w((Fe_tO)+(MnO))约为1%,基本达到脱硫的临界值;碱度约为1.2时,随着精炼的进行开始回硫,钢液中w([Al_s])随着碱度的降低逐渐降低;碱度约为2.2时,w([Al_s])降幅显著;碱度小于1.6时,对铝的影响不明显。精炼炉采取两步造渣工艺,精炼前期高碱度渣系脱硫,精炼后期降低碱度,钢液中铝含量降低。当碱度从2.2降低至1.2时,钢液中w([S]) 和w([Al_s])分别控制在0.011%和0.001 6%。     

钢渣对炼焦煤成焦后气化反应行为的影响

高反应性焦炭可降低高炉热储备区温度,提高高炉冶炼效率.钢渣中有大量的钙和铁,是理想的焦炭气化反应催化剂.在制备高反应性焦炭的过程中,钢渣在配合煤中的粒度和添加量会影响焦炭的反应性和反应后强度.本文从宏观动力学角度研究了钢渣对焦炭反应性和反应后强度影响的原因.细焦粉和粒度为3~6 mm的焦炭分别与CO2在950,1 100和1 250℃进行了气化反应.通过细焦粉的气化曲线确定了焦炭在各温度的本征初始气化速率(r0),通过粒焦炭的气化曲线确定了受内扩散影响的焦炭表观气化反应速率(rD).对反应效率因子(ηef)和西勒模数()的分析表明,焦炭基质反应性和气孔结构两者共同决定了焦炭反应性和反应后强度.