钙处理含硫20CrMo齿轮钢夹杂物析出研究

通过热力学计算控制钢中喂钙量,把钙处理20CrMo钢中Al2O3变性为低熔点的12CaO·7Al2O3上浮去除,从而使钢中夹杂物满足评级要求;并用Thermo-Calc软件模拟钢液凝固过程中CA6、CA、CA2钙铝酸盐及MnS夹杂物的析出情况.用SEM对轧材中纺锤状夹杂物进行分析,少量夹杂物内核颜色较深,为Al2O3、CaS等夹杂,外层包裹的夹杂颜色较浅,为MnS夹杂.说明凝固过程中钢液中先析出的Al2O3、CaS等复合夹杂可以被后析出的MnS捕获作为其核心.     

20CrMnTiH1齿轮钢中CaS夹杂的形成与控制

利用Factsage软件,对20CrMnTiH1齿轮钢中(CaO)m(Al2O3)n与CaS夹杂形成进行了热力学分析.结果表明:当钢中w(Al)s=0.035％时,要使钢中夹杂物完全转变为液态(CaO)12(Al2O3)7,应控制钢中w(S)低于0.006 7％,w(Ca) /w(Al)高于0.12;本钢液成分条件下,在炼钢温度下不会自发生成CaS夹杂,当钢液温度下降到1 739.8 K时,凝固前沿的w(S)达到0.015 9％,此时会与低熔点(CaO)12(Al2O3)7夹杂表面的CaO反应析出CaS夹杂.通过对某钢厂生产的20CrMnTiH1齿轮钢铸坯中夹杂物的检验发现,实际情况与热力学计算相符合.同时,通过硫偏析方程计算得到:20CrMnTiH1齿轮钢在凝固过程中不析出CaS夹杂的条件为将硫的初始质量分数控制在0.000 318％以下.     

中碳钢钙处理夹杂物变性的“液相窗口”控制模型

 系统研究了国内某钢厂生产的中碳钢Q345B钙处理前后夹杂物类型的变化,从热力学上分析铝脱氧钢中Al2O3夹杂物变性机制及夹杂物中CaS合理控制的条件,确立了夹杂物变性的“液相窗口”模型。热力学计算表明,温度为1873K,w(［Al］)为0.016%时,Al2O3转变为液态钙铝酸盐需要使钢中w(［Ca］)为0.0017%~0.0102%。生产实践表明,钙喂入量在0.0014%~0.0017%时,钙处理可以将钢中高熔点Al2O3的夹杂物转化为低熔点的12CaO·7Al2O3和CaO·Al2O3夹杂物,MnS基本转化为CaS,且无单独CaS析出。     

L360QS钢钙处理的热力学分析与试验研究

针对管线钢L360QS,利用活度相互作用系数和Bjorkvall方法对钙处理过程进行热力学分析,并对管线钢进行了实验室的钙处理试验和工业试验。热力学分析结果表明,当钢中a(Als)=0.045%时,如果要生成12CaO·7Al2O3夹杂且避免CaS夹杂析出,则应控制钢液中a(Ca)在33.21×10-6左右,a(S)0.002 563%。钙处理试验表明,CaS夹杂数量随着钢液中钙含量的增加而增多,且含MgO·Al2O3尖晶石的夹杂物有所减少。为使氧化夹杂和硫化夹杂变性完全,应控制钢液中w(S)≈0.002%,w(Ca)=0.003 5%~0.004 0%,且w(T.Ca)/w(S)1.9。工业试验结果表明夹杂物变性良好,达到预期效果。     

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。     

非钙处理铝脱氧车轮钢夹杂物形成及变形行为

 通过采用扫描电镜对BOF-LF-RH-CC非钙处理工艺生产车轮钢系统取样样品中夹杂物的形貌、尺寸及组成的分析,研究了精炼和凝固过程氧化物夹杂的形成、上浮去除和析出过程,以及轧制过程夹杂物的变形行为。研究发现,在非钙处理条件下,LF精炼过程会形成大量MgO-Al2O3夹杂和CaO-Al2O3夹杂,并且在RH精炼过程中存在MgO-Al2O3夹杂向CaO-Al2O3夹杂的转变过程,最终导致铸坯中出现低变性CaO-Al2O3夹杂;在软吹和镇静过程中,炉渣或空气对钢液的二次氧化与钢液中夹杂物上浮去除存在动态平衡;在钢液凝固过程中,固液界面的Al2O3等氧化物夹杂为MnS的析出提供了异质形核点,形成半包裹状的Al2O3-MnS类复合夹杂物;在轧制过程中,团簇状Al2O3夹杂容易被轧碎在板卷中形成点链状,高熔点半包裹的Al2O3-MnS类复合夹杂物被轧制成小尾巴状,而低熔点的CaO-Al2O3-MnS的复合夹杂形成连续的条状。     

钙处理对成品无取向硅钢夹杂物特性的影响

通过取样检测结合热力学计算,分析了钙处理对成品无取向硅钢中夹杂物特征及硫化物夹杂的析出机制的影响。结果表明,钢中尺寸大于3μm的有害夹杂物主要是AlN、MgO-SiO2、CaO-Al2O3-SiO2类复合夹杂物及其与MgS、MnS、CaS的复合析出物。钙处理钢中没有检测到单独的Al2O3、SiO2及铝酸钙类夹杂物。钙处理钢中形成的液态3CaO·Al2O3、MgO·SiO2和Al2O3夹杂物被精炼渣吸收,改性去除了钢中大尺寸Al2O3夹杂物。钙处理钢中尺寸大于3μm的氧化物夹杂主要是含CaO和(或)CaS的Al2O3-SiO2类夹杂。硫化物在MgO-SiO2类氧化物表面的析出有利于其形貌趋于规则。钢中不同形貌的AlN夹杂物呈多尺度分布,钙处理对大尺寸AlN的析出特性影响不大。氧硫化物及其与AlN复合析出并定向长大的过程,与其晶体结构有关。氧化物夹杂的硫容量决定了其与硫复合的难易程度。钙处理钢中CaS在氧化物表面呈局部包裹析出和局部吸附析出。     

生产20CrMnTiH钢的最佳CaO-Al2O3渣系成分

 研究了某厂冶炼20CrMnTiH钢所用精炼渣的成分变化对钢液中w(T［O］)与夹杂物成分的影响。基于Factsage软件探讨了精炼渣成分变化对钢液中w(T［O］)的影响机制,指出精炼渣碱度R、w(CaO)/w(Al2O3)以及MI指数是通过改变渣中的Al2O3活度与CaO活度,提高精炼渣的“Al2O3”容量,以达到降低w(T［O］)的目的,并在此基础上提出了适合冶炼20CrMnTiH钢的精炼渣系成分(质量分数)：CaO 50%~55%,Al2O3 30%~35%,SiO2 6%~8%,MgO 5%~8%,其他不超过3%。通过工业试验发现,使用此渣系后铸坯中的w(T［O］)降至10×10-6。     

第3代汽车钢凝固过程微观偏析的耦合模型

基于Clyne-Kurz的微观偏析公式,以物理试验结果为依据,充分考虑固、液相以及夹杂物之间相互作用,建立第3代汽车钢(TG钢)凝固过程微观偏析耦合模型,研究凝固过程钢液中溶质元素和Al2O3等夹杂物分子的质量分数变化特征。结果表明:在整个凝固过程中,Al2O3分子会不断在液相中生成,但生成量比较少,而SiO2和MnO分子不会在液相中生成;铸坯枝晶间不仅有Al2O3夹杂,还有SiO2和其他复合夹杂,凝固前钢水中夹杂物有待进一步去除;凝固末期液相中MnS析出,大大减小了残余液相中S的质量分数变化,但对Mn的质量分数变化没有明显影响;包晶反应温度为1 487℃,包晶反应后凝固的固相中溶质的质量分数明显高于包晶反应前。     

49MnVS非调质钢水口堵塞原因分析

 非调质钢中含有较多的铝和硫,常在连铸过程中因水口蓄积钙铝酸盐或硫化钙而发生堵塞,影响生产的顺利进行。为了探究非调质钢的水口堵塞原因并提出预防措施,采用X射线荧光分析、X射线衍射分析和热力学计算,分析了非调质钢49MnVS的水口堵塞结瘤物。结果表明,水口堵塞物主要由CaO·6Al2O3、CaO·Al2O3、MgO·Al2O3和金属铁相组成,生产中钙的收得率仅为预期的53.33%;热力学计算表明,水口堵塞的原因是钢液中的钙铝质量比较低,生成了大量高熔点的CaO·6Al2O3和CaO·Al2O3夹杂物,夹杂物在水口处黏附聚集;同时,由于MgO-C质水口耐火材料被侵蚀,MgO在絮流区与Al2O3碰撞生成MgO·Al2O3,铁液滴在夹杂物孔隙中凝固黏结,使堵塞物进一步长大,将水口完全堵塞。因此,可以通过优化喂线操作、控制钢中的钙铝比位于0.127～0.225、改进水口材质等措施来预防水口堵塞。     

管线钢铸坯中硫化物特征及形成机理

 对管线钢铸坯中的硫化物特征进行了分析,并对其形成机理进行了讨论。发现从中间包钢液到铸坯,管线钢中夹杂物由低熔点的CaO Al2O3向CaS Al2O3类型转变,且夹杂物尺寸越小,在冷却过程中的转变越充分。根据形貌特征,含硫化物夹杂可分为以下几类,即硫化物在氧化物表面部分析出、硫化物半包裹氧化物、硫化物完全包裹氧化物、纯硫化物和在TiN上析出的硫化物。采用FactSage软件对冷却过程管线钢中的夹杂物转变进行了计算,发现随着温度的降低,液态钙铝酸盐夹杂物逐渐经历CaO·Al2O3→CaO·2Al2O3→CaO·6Al2O3→Al2O3的转变过程,同时CaS和MnS相也在冷却过程中析出,且MnS的析出温度低于CaS,这解释了铸坯中硫化物的特征和形成。     

Behavior of MgO·Al_2O_3 Based Inclusions in Alloy Steel During Refining Process

The transformation of MgO·Al2O3 based inclusions in alloy steel during refining has been studied by industrial trials.Besides Factsage software is used to study the formation and modification of spinel inclusions in alloy steel using calcium treatment during refining process.The results show that the transformation sequence of inclusions is:MgO·Al2O3→CaO-Al2O3-MgO complex inclusions→MgO·Al2O3,and under present experimental condition,in order to avoid forming MgO·Al2O3 inclusions the content of dissolved Ca in the molten steel has to reach 1×10-6.Also the results show that when more calcium was added to molten steel,the content of Al2O3 and MgO will be lower.Besides,increasing the content of CaO in the inclusions will increase even if the content of SiO2 changes little.     

喂Si-Ca线对夹杂物变性处理分析

根据冶金原理,分别对喂Si-Ca线变性A12O3夹杂物、MnS夹杂物以及喂Si-Ca线同时变性A12O3夹杂物和硫化物的过程进行了热力学计算,同时对实际生产中喂线前后钢水中夹杂物进行了分析,为探索喂Si-Ca线条件下钢中夹杂物组成和形态变化提供了理论依据。     

Effect of Calcium Treatment on Non-Metallic Inclusions in Ultra-Low Oxygen Steel Refined by High Basicity High Al2O3 Slag

 The influence of calcium treatment on non-metallic inclusions had been studied when control technology of refining top slag in ladle furnace was used in ultra-low oxygen steelmaking. A sufficient amount aluminium was added to experimental heats for final deoxidizing during BOF tapping, and the refining top slag with strong reducibility, high basicity and high Al2O3 in ladle furnace was used to produce ultra-low oxygen steel and the transformation of non-metallic inclusions in molten steel was compared by calcium treatment and no calcium treatment. The results show that the transformation of Al2O3→MgO·Al2O3 spinel→CaO-MgO-Al2O3 complex inclusions has been completed for aluminum deoxidation products and calcium treatment to molten steel is unnecessary when using the control technology of ladle furnace refining top slag to produce ultra-low oxygen steel, and the complex inclusions are liquid at the temperature of steelmaking and easily removable to obtain very high cleanliness steel by flotation. Furthermore, the problems of nozzle clogging in casting operations do not happen and the remaining oxide inclusions in steel are the relatively lower melting point complex inclusions.     

中厚板钢精炼过程夹杂物的转变

 通过工业试验研究了中厚板钢LF→钙处理→RH精炼过程中夹杂物的转变规律,并对钙处理过程夹杂物转变进行了热力学计算分析。结果表明：精炼过程钢中总氧质量分数降低,夹杂物数量密度降低,夹杂物平均尺寸升高;钙处理后夹杂物为CaO-MgO-Al2O3-CaS四元系;RH破空后夹杂物转变为CaO-MgO-Al2O3三元系,夹杂物中CaO质量分数降低,Al2O3质量分数升高;热力学计算表明,钙处理后钢液可直接生成CaS,也可与钙铝酸盐夹杂物反应生成CaS,RH破空后不能生成CaS。     

Investigations of Inclusion Modification in High Grade Pipeline Steel

SiCa line was injected into liquid pipeline steel at the end of LF refining as calcium treatment, and samples were taken from liquid steel in ladles before and after calcium treatment, liquid steel in mould, and slabs. Results show that Ca content in steel decreased obviously after calcium treatment with production, and the compositions, morphologies and sizes of inclusions in steel also varied with time; Al2O3 inclusions turned to be fine irregular CaS-CaO-Al2O3 compound inclusions after calcium treatment, and then to be fine globular CaO-Al2O3 inclusions in mould, and finally changed to be a few larger irregular CaS-CaO-Al2O3 complex inclusions in slabs; reoxidation of molten steel treated by Ca deteriorates effect of calcium treatment. Thermodynamic study revealed that inclusion variations were related with preferential reactions among Ca, Al2O3 and S and precipitation of S in high sulfur capacity CaO-Al2O3 inclusions. New calcium treatment controlling rules were put forward according to the inclusion variations and requirements of pipeline on inclusion controlling.     

钙处理钢中夹杂物行为的研究

为改善武钢CSP产线钢水的连浇性,通过工业试验对钙处理钢中夹杂物的变化进行了研究,试验结果表明,钙处理后,钢中夹杂由Al2O3和MnS转变为铝酸钙盐或CaO-Al2O3-MgO-CaS复合夹杂,由于钙处理对夹杂物的聚合变性作用,钢中夹杂物直径不小于5μm的比例增加。通过热力学计算,分析了钙处理使夹杂物变性的条件。根据试验结果对工艺进行了优化,钢水结瘤断浇次数由3.6次/月降低到1.5次/月。     

Modification of MgO· Al2O3 spinel inclusions in Al-killed steel by Ca-treatment

The modification of MgO·Al2O3 spinel inclusions in Al-killed steel by Ca-treatment has been studied by industrial trials and ther-modynamic calculations.In the industrial trials,samples were taken systematically during the refining process in which the molten steel was treated by calcium,and the characters of the inclusions were analyzed using scanning electron microscopy (SEM) and energy dispersive spectra (EDS).The effects of Ca-treatment were evaluated by tracking the compositions of the inclusions.The results show that the modifi-Al2O3→MgO.Al2O3→liquid complex inclusions.The modification of spinel inclusions by Ca-treatment was calculated by FactSage6.0 util-izing its free-energy minimization routines.The results of thermodynamic calculations indicate that spinel inclusions are easier to be modi-fied than Al2O3 inclusions and the spinel inclusions in 30CrMo steel would transform to liquid complex inclusions when the content of dis-solved Ca in the molten steel exceeds 1×10-6.Also,the results show that adding more calcium into the molten steel would lower the contents of Al2O3 and MgO and increase the CaO content of the inclusions,while the change in SiO2 content is little.     

G102Cr18Mo不锈轴承钢VIM-VAR冶炼过程夹杂物的演变

通过真空感应冶炼、真空自耗重熔,制备了 G102Cr18Mo不锈轴承钢锭,利用Aspex扫描电镜分析了夹杂物数量、尺寸、面积的变化规律,并采用SEM-EDS进一步观察夹杂物的元素分布.研究结果发现,不论是真空感应还是自耗重熔,夹杂物的组成变化不大,主要由硫化锰、铝酸钙、Al-Ca-Mn-(Ti)-O-S复合夹杂物3类夹...     

超低氧精炼时钙处理对氧化物夹杂的影响

 研究了采用LF精炼顶渣控制技术对钢液进行超低氧冶炼时,钙处理对钢中非金属夹杂物的影响。试验在转炉出钢时采用铝终脱氧,LF精炼过程采用强脱氧、高碱度、强还原性精炼顶渣对钢液进行超低氧冶炼,比较了钙处理和不钙处理的钢液中非金属夹杂物转变的情况。结果表明,采用精炼顶渣控制技术冶炼超低氧钢时,钢液不需要进行钙处理就能实现铝脱氧产物Al2O3→MgO·Al2O3尖晶石→CaO-MgO-Al2O3类复合夹杂物的转变,得到炼钢温度下呈液态的复合氧化物夹杂,这些液态的夹杂物容易通过碰撞长大上浮去除,得到高洁净度的钢液,且残留在钢液的氧化物夹杂为较低熔点的复合氧化物,在浇注过程中不会产生水口结瘤。