轴承钢精炼过程非金属夹杂物行为的研究

采用金相、SEM等分析方法，分析了某电炉厂EAF-LF-VD-CC流程冶炼GCr15轴承钢精炼过程非金属夹杂物的变化，并确定了夹杂物的主要来源。实验结果表明，LF处理后夹杂物以块状Al2O3、点状不变形夹杂物和硫化物为主；VD处理后点状不变形夹杂物明显减少，而含CaO、MgO、Al2O3、硫化物等的复合夹杂有所增加。成材试样中未发现点状不变形夹杂物，只有少量尺寸很小的Al2O3和硫化物夹杂。     

28MnCr5冶炼过程钢中夹杂物的变化情况研究

通过SEM、EDS和大样电解试验对28MnCr5冶炼过程中夹杂物的大小、形貌、数量进行了分析。结果表明：LF精炼后夹杂物多为钙镁铝氧化物及硫化钙夹杂,夹杂物的尺寸较小,多为1μm～3μm,形状为方形。经VD处理后,较LF阶段夹杂物尺寸增大,夹杂物的组成多是钙镁铝尖晶石类及MnS夹杂。连铸过程中夹杂物的成分主要为MgO-Al2O3-MnS-MnO系夹杂物,夹杂物多呈圆形,其尺寸在3μm～6μm。通过大样电解发现大部分大型夹杂物都是多元复合夹杂物,颗粒粒径多在100μm以上,对钢材性能影响极大。     

GCr15轴承钢冶炼过程钢液洁净度变化

 研究了EAF→LF→VD→软搅→CC工艺生产GCr15轴承钢冶炼过程钢中T[O]及非金属夹杂物的变化情况。通过将电炉出钢碳质量分数控制为0.2%～0.4%、出钢加铝强脱氧及造预精炼渣、LF精炼过程造高碱度强还原性炉渣、VD真空强搅拌及防止中间包二次氧化,可以生产[w(T[O])]等于8×10－6的轴承钢。在炉外精炼过程中夹杂物经历了Al2O3→MgO·Al2O3→CaO-MgO-Al2O3演变。LF精炼过程夹杂物平均尺寸减小,经过VD真空处理后尺寸增加,接着在软搅和中间包过程继续减小。利用VD真空处理可以去除高达74%的夹杂物。     

低碳铝镇静钢LF精炼过程钢中非金属夹杂物的研究

对LF精炼过程低碳铝镇静钢水中非金属夹杂物的变化进行了研究,发现在采用高碱度、强还原性炉渣条件下,Al2O3类夹杂物先向MgO-Al2O3系夹杂物并进而向CaO-MgO-Al2O3系夹杂物和CaO-CaS-Al2O3系夹杂物转变。在LF精炼结束时,钢中已基本没有对钢水可浇性影响最大的Al2O3系夹杂物,因此可以减少LF精炼后对钢水进行钙处理用的钙线量,以降低生产成本并减少由于钙处理而生成的大尺寸钙铝酸盐夹杂物的数量。     

EAF—LF—VD—CC流程生产GCr15轴承钢的洁净度及夹杂物演变

为探究GCr15轴承钢在冶炼过程中夹杂物的演变规律,基于国内某钢厂EAF—LF—VD—CC工艺过程进行全流程取样分析,系统研究了全流程杂质元素含量的变化以及夹杂物的演变.分析结果表明,轧制后的轧材钢样杂质元素Ca和Ti的质量分数较高,分别达到0.001 6%和0.001 7%,全氧(T.O)质量分数为0.000 7%.轧材中夹杂物类型主要为镁铝尖晶石、钙铝酸盐类和硅酸盐类复合夹杂物.较大尺寸的夹杂物出现在LF和VD精炼工位,且夹杂物最大尺寸超过了30μm.VD破真空后出现了大量CaO-MgO-Al₂O₃-SiO₂类复合夹杂物,成分分布均匀,个别尺寸甚至超过45μm.连铸坯和轧材中MnS和TiN夹杂物占比较高.     

管线钢K60C2精炼过程钢水洁净度的研究

研究了管线钢K60C2 LF精炼及钙处理后,钢水中杂质元素、夹杂物成分和形貌尺寸的变化情况。结果表明,精炼结束后,钢水中的硫能满足要求,T.[O]较精炼前大幅度降低,精炼和钙处理过程增氮明显,非金属夹杂物从Al_2O_3向Mg O-Al_2O_3-Ca O或Mg O-Al_2O_3-Ca O-Si O2复合夹杂物转变,钙处理后变性为钙铝酸盐类夹杂物和钙镁硅铝酸盐复合夹杂物;精炼结束后夹杂物尺寸明显变小。     

铝镇静钢LF精炼过程中夹杂物行为研究

通过对LF精炼开始3 min、通电化渣和钙处理后3个阶段的钢水进行取样,对夹杂物的数量、形态及成分进行对比分析,来研究铝镇静钢中夹杂物在精炼过程中的变化及钙处理对夹杂物性质的影响.结果表明:钙处理在提高钢水洁净度、夹杂物改性等方面效果显著.当LF炉通电化渣后,夹杂物球化率显著提高;钙处理后,球化率进一步提高.LF精炼开始3 min后,钢中的夹杂物以Al2O3-SiO2-MnO和纯Al2O3夹杂物为主;通电化渣后,钢中夹杂物以Al2O3-CaO(CaS)-SiO2为主;钙处理后,钢中夹杂物以Al2O3-CaO为主.     

超低氧石油套管钢LF-VD过程非金属夹杂物的转变

系统分析和研究了采用“EAF→ LF→VD→CC”工艺流程生产试验钢时,各工序的全氧与氮含量的变化情况、钢液中非金属夹杂物的生成与变化以及精炼初渣对夹杂物去除的影响.结果表明:试验钢在LF精炼过程中w(T.O)平均下降42.83％,经VD真空处理后w(T.O)和w(N)平均下降48.77％和10.72％.在LF精炼过程中,钢液中非金属夹杂物按“Al2O3系夹杂物→MgO-Al2O3系夹杂物→CaO-MgO-Al2O3系夹杂物”顺序转变,其中MgO-Al2O3系夹杂物向CaO-MgO-Al2O3系夹杂物转变是由外向内逐步进行,并且夹杂物中CaO与MgO互不相溶.精炼初渣碱度控制在2.5左右对于炉渣吸收夹杂较为有利.     

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。     

精炼渣碱度对304不锈钢夹杂物的影响

结合生产实际,采用定量金相和SEM+EDS统计分析方法,研究了硅脱氧条件下,精炼渣碱度对304奥氏体不锈钢在LF精炼、连铸过程夹杂物变化规律的影响。结果表明:钢水中主要形成球状CaO-Al2O3-SiO2类复合夹杂,适当高的精炼渣碱度有利于钢中细小夹杂物的形成。随精炼渣碱度的提高,复合夹杂物中CaO含量增加,SiO2含量减小,Al2O3含量变化不大。现场条件下,由FeSi合金带入钢中的Al形成的Al2O3对复合夹杂物的塑性变形影响较大。在精炼渣碱度分别为1.0和1.5时,铸坯复合夹杂物中Al2O3质量分数为25%左右,夹杂物的变形能力稍弱。     

高端抗硫管线钢非金属夹杂物研究

采用扫描电镜和大样电解等检验方法对抗硫管线钢的冶炼过程试样和连铸坯中夹杂物的数量、尺寸、成分、形貌进行系统分析。结果表明:钢液经过LF精炼后,显微夹杂物的面积比降低了34.7%;中间包钢液的夹杂物面积比较VD出站增加了6.1%。LF进站钢液中的夹杂物主要为Al_2O_3夹杂物,在LF精炼和VD真空处理过程中由于钢渣间的相互作用,形成以CaO、MgO、Al_2O_3为主要组成的复合型夹杂物。钙处理后夹杂物中的CaO和Al_2O_3的物质的量比接近12∶7,并与钢液发生了脱硫反应,形成了含CaS的复合夹杂物。中间包开浇阶段铸坯中的显微夹杂物和大型夹杂物都明显高于稳定浇铸状态;在稳定浇铸状态下,铸坯中的w(T[O])小于15×10~(-6),大型夹杂物的含量小于0.2 mg/kg;大型夹杂物的主要来源是钢包引流砂、结晶器保护渣。     

50Cr5MoV钢中非金属夹杂物及全氧

 对采用“EBT→LF→VD”工艺路线生产50Cr5MoV锻钢轧辊炼钢过程的全氧质量分数和夹杂物类型与数量进行了分析。结果表明：LF精炼后钢液中[w(T[O])]平均为0.004 7%,VD出站[w(T[O])]为0.001 4%,中间包[w(T[O])]为0.001 55%,铸坯[w(T[O])]为0.001 8%,轧材中[w(T[O])]降低至0.001 0%。LF精炼初期,钢中夹杂物主要是不规则的Al2O3夹杂,其中96.75%的夹杂物尺寸小于10 μm。LF精炼结束后,大量夹杂物转变成以CaO-Al2O3-SiO2为主要成分的0～1 0 μm复合氧化物夹杂。钢水从VD真空精炼炉向中间包转移过程中,由于保护性浇注效果差,二次氧化严重造成钢水夹杂逐渐增多,其中夹杂物主要为球形的[mCaO·nAl2O3]复合夹杂物。铸坯中99.65%的夹杂物尺寸小于10 μm,其中大部分为球形钙铝酸盐夹杂物,还有少量球状硅铝酸钙复合夹杂物。轧材中98.77%的夹杂物尺寸小于10 μm。通过对炼钢过程中各工序的工艺优化,可实现对夹杂物的有效控制, 从而确保50Cr5MoV合金铸钢的产品质量。     

Inclusion Variations of Hot Working Die Steel H13 in Refining Process

 Inclusion variations of die steel H13, including changes of species, morphologies, compositions, amounts and sizes, in the production of EAF→LF→VD→ingot casting→electro-slag refining (ESR) procedure, were investigated by systematic sampling, and analyzed with scanning electron microscope (SEM), energy dispersive spectrum (EDS), and metallographic microscope. The variation mechanism was studied by comprehensive analysis of total oxygen, nitrogen, and acid soluble aluminum as well as chemical test of refining slag. Based on the investigations, technical measures for cleanness improvement were discussed. The results show that oxide inclusions in H13 steel change from irregular Al2O3→near globular CaO-MgO-Al2O3 and CaO-Al2O3-SiO2 complex inclusions→finer CaO-Al2O3-SiO2 inclusions with higher CaO content→CaO-Al2O3-SiO2 inclusions with higher Al2O3 content and irregular MgO-Al2O3 inclusions→fine irregular MgO-Al2O3-CaS inclusions in various steps of the production; the variations are related with changes of acid soluble aluminum content, reactions between slag and steel, re-oxidation of liquid steel during casting, and refining of ESR. It is also found that Al2O3 inclusions are modified by refining slag in LF and VD refining; and ESR plays a good role in inclusion removal, especially in controlling the large linear VC-CrC-MoC inclusions distributed in grain boundaries. It is suggested that casting protection should be improved, and the basicity of refining slag and acid soluble aluminum content in steel should be raised.     

易切削钢中硫化物形态的研究

以易切削钢20CrMnTiSH为研究对象,通过喂硫线增加钢中硫化物数量,再喂入SiCa线使长条形的硫化物变性为球形或纺锤形,在改善钢材切削性能的同时不降低钢材的机械性能。对LF、VD和轧材取样进行检验。检验结果表明:钙处理后夹杂物数量增多,94%以上的夹杂物粒径集中在0～4μm之间;夹杂物纺锤率平均值达到50.73%,在钢中呈细小弥散的分布;氧、Mn/S、Ca/S是影响硫化物形态的重要因素。     

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.     

低氧高碳铬轴承钢LF-VD精炼时洁净度与夹杂物特征变化

研究了低氧高碳铬轴承钢在LF-VD精炼时洁净度与夹杂物类型、数量、尺寸等特征的变化规律,并关注了个别大尺寸夹杂物.试验中采用了二元碱度约为7、Al2 O3质量分数约30％ 的高碱度高Al2 O3精炼渣.LF精炼前期和中期钢中夹杂物主要为Al2 O3和MgO-Al2 O3:由于与钢液润湿性较差能够较好地去除,数量密度由L...     

帘线钢72A精炼过程研究

对首钢帘线钢72A精炼过程的钢液中酸溶铝、总氧、夹杂物成分和形貌进行了系统的分析,发现从LF结束到VD开始过程中酸溶铝增加很大;VD精炼处理后夹杂物熔点高.分析得出合金中铝以及喂Si-Ca丝导致了钢中酸溶铝的增加;夹杂物中CaO含量过高、SiO2含量过低导致精炼结束后夹杂物处于高熔点区.提出降低脱氧剂中Ca含量,取消喂丝以及降低精炼渣碱度的改善措施.     

Investigation on Non-Metallic Inclusions in LCAK Steel Produced by BOF-LF-FTSC Production Route

 The behavior of non-metallic inclusions in LCAK (low carbon aluminum killed) steel produced by BOF (basic oxygen furnace)-LF (ladle furnace) refining-FTSC (flexible thin slab continuous caster) production route was investigated. The results showed that, LF refining for LCAK steel could decrease the wT[O] significantly, and the inclusions were modified by Ca treatment, which prevented nozzle clogging efficiently. However, owing to the unstable casting condition in the earlier stage of casting, a severe reoxidation occurred, accompanied with mold slag entrapment. The transformation of non-metallic inclusions during the steelmaking process was Al2O3→MgO-Al2O3 type inclusion→MgO-Al2O3-CaO type inclusion with a CaS ring, and the mechanism of the transformation was proposed and discussed via thermodynamic and kinetic analysis. Besides, to avoid CaS precipitation, the product of w2[Al]×w3[S] in steel should be less than 2.0×10-10 at 1873 K, which remands higher desulfurization ratio during LF refining.