稀土处理对含铝中锰钢中夹杂物的调控机理

铝脱氧中锰钢精炼过程中易形成尖晶石类夹杂物,这类硬质夹杂物会恶化中锰钢的疲劳性能,易导致钢材功能失效引发事故。采用稀土Ce处理对中锰钢中尖晶石类硬质夹杂物进行改质处理。为了阐明夹杂物的改质机理,开展了高温模拟实验。实验结果表明,Ce处理后,尖晶石夹杂物转变为稀土夹杂物,且随着TO含量的降低,稀土夹杂物类型为CeAlO₃→CeAlO₃+Ce₂O₂S→Ce₂O₂S。铈对尖晶石夹杂物的变质机理为：铈添加到钢中后,尖晶石夹杂物中镁和铝不断被铈替代(含锰尖晶石夹杂物中锰优先被置换),尖晶石结构遭到破坏,从而形成CeAlO₃。当钢中氧含量低,相对硫含量较高时,钢中硫将参与置换反应,置换出夹杂物中的氧,因此尖晶石夹杂物和CeAlO₃夹杂物最终转变为Ce₂O₂S。最后通过热力学模型计算得出,将钢中尖晶石夹杂物完全改质为稀土夹杂物的最低铈含量与钢中氧含量呈线性关系,当钢中铈质量分数为氧质...     

高氮钢电渣重熔夹杂物控制研究

对高氮钢电渣重熔前后夹杂物进行对比研究,分析不同渣系和自耗电极氧含量对重熔后夹杂物的影响。研究发现,不同渣系对电渣钢的洁净度影响很大,适当提高w(Ca O)/w(Al2O3)可有效降低电渣锭中的夹杂物和全氧量。对高氮钢电渣重熔的脱硫进行研究,分析了不同渣系和熔炼速率对高氮钢脱硫率的影响,实验结果表明:电渣重熔后,硫化物夹杂的平均直径和单位面积数量大大减少,夹杂物的主要类型为Mn S+Al2O3复合型夹杂物,同时适度提高渣中Ca O含量实现提高硫分配比是提高脱硫效率的有效手段。脱硫动力学推导中发现重熔速率越低,脱硫效果越明显,但实验发现脱硫率随重熔速率的降低呈现先降低后升高的趋势,其原因在于渣池中发生硫化物富集,导致"回硫"现象发生。     

冷却速率对钢中MnS+Al_2O_3复合夹杂物包裹率的影响研究

通过实验室试验研究钢中MnS+Al_2O_3复合夹杂物的生成以及不同冷却速率对MnS+Al_2O_3复合夹杂物包裹率的影响。结果表明:被推动到钢液凝固前沿的Al_2O_3,会为MnS析出提供异质形核质点;随着冷却速率的增加,复合夹杂物的尺寸从4μm降至2.5μm左右,MnS+Al_2O_3复合夹杂物包裹率逐渐降低。本次试验研究为得到较优包裹程度的实验条件以及进一步改善钢材性能提供一定的理论分析。     

50CrVA弹簧钢夹杂物特性研究

采用全流程多级取样的方法,对国内某钢厂BOF-LF-CC工艺生产的50CrVA弹簧钢中夹杂物特性的演变规律进行系统分析和研究。实验结果表明:随着精炼和连铸过程的进行,钢中的夹杂物种类逐渐由SiO2-Al2O3-MnO-TiO2夹杂物转变为CaO-Al2O3-MgO和CaO-A l2O3-SiO2夹杂物。最终铸坯夹杂物中的Al2O3组元含量约为70%～75%,而Ca O含量仅为5%～10%。夹杂物熔点较高,改性不充分。建议在生产中,强化钙处理或提高炉渣碱度来实现夹杂物的低熔点化,降低其危害。     

CO_2保护浇注对45号钢钢水洁净度的影响研究

针对连铸过程中二次氧化的问题,某厂分别采用Ar和CO2保护浸入式水口,对比分析钢中洁净度水平,试验表明:在两种保护浇注条件下,钢中夹杂物去除情况较好,钢中夹杂物的面积百分比保持在10-5级别,保护浇注后为(4~5)×10-5,夹杂物粒径集中在1~5μm;夹杂物和大型夹杂物的类型及组成不变,采用CO2代替Ar进行保护浇注不会影响钢液洁净度,并且大型夹杂物平均质量减少可达16.6%。     

电解提取风电齿轮钢夹杂物研究

采用小样电解法对风电齿轮钢18CrNiMo7-6中的夹杂物进行了系统的分析检测,通过对齿轮钢中夹杂物的电解、提取、分离,较为完整地将钢中的夹杂物电解并收集,借助SEM-EDS对所收集的夹杂物进行了定性分析。结果表明:通过小样电解法可以较为完整地得到风电齿轮钢18CrNiMo7-6中夹杂物的三维形貌;Al2O3、Al2O3-SiO2类夹杂物多呈不规则多边形状,平均尺寸分别为29.7μm、15.81μm,A l2O3-MgO-CaO-SiO2复合类夹杂物通常为包裹形态的球状,平均尺寸为13.1μm,Ca O类夹杂物通常呈块状,平均尺寸为11.7μm,MnS类夹杂物形貌多呈长条状或纺锤状,平均尺寸为18.8μm,Ca S类夹杂物通常呈规则长条状,平均尺寸为9.2μm;与传统金相法相比,小样电解法在观察钢中夹杂物真实的三维形貌和尺寸时是更为行之有效的方法。     

不同冷却条件下钢中MnS夹杂物析出特性的研究

实验室以及工业试验研究发现冷却条件的不同对钢中MnS夹杂物特性变化的影响较大。研究结果表明:随着冷却速率的增加,MnS夹杂物的尺寸逐渐降低,析出的MnS的数量逐渐增加。通过实验获得的硫化物尺寸与冷却速率之间的关系式,可用于实际钢厂中硫化物的尺寸与取样方式之间关系的建立,运用此关系式,便可通过取样方式来估量硫化物的当量直径大小,提高夹杂物检测分析的效率。     

X70管线钢洁净度控制研究

针对某钢厂中厚板卷厂采用铁水倒罐→铁水预处理→转炉冶炼→出钢脱氧合金化→LF精炼炉→RH真空炉→钙处理→连铸生产X70管线钢生产工艺,采取系统取样分析,对P、S等杂质元素,N、H、O等气体的脱除规律以及夹杂物的控制规律进行了研究。研究表明,成品成分可以稳定控制水平为:w([P])≤0.004 5%,w([S])≤0.001 00%,w([O])≤0.000 85%,w([N])≤0.003 00%,w([H])≤0.000 15%,夹杂物以小于10μm的CaO-CaS为主,且单位面积总夹杂物数量小于12个/mm~2,成品钢具有很高的洁净度水平。     

60Si_2Mn-Cr弹簧钢中夹杂物演变行为分析

针对某钢厂60Si_2Mn-Cr弹簧钢的生产工艺,取不同工位处的钢样,研究夹杂物的转变效果。实验表明:微铝工艺生产钢中的夹杂物逐渐转变为Al_2O_3-SiO_2-CaO-MgO复合氧化物夹杂,形状逐渐趋于球状夹杂物尺寸逐渐减小,最终铸坯中夹杂物的平均尺寸为4.6μm。通过热力学计算,得到了不同工位下夹杂物的SiO_2+CaO-MgO-MnO+Al_2O_3相图,在中间包和铸坯中的夹杂物大多数处于1500-1 600℃温度下的液相区,减小高硬度夹杂物的危害,提高了弹簧钢的质量。     

Ca处理对55SiMnMo夹杂物行为变化的研究

研究了Consteel电弧炉-LF-VD-连铸工艺生产55SiMnMo时钙处理对钢中夹杂物行为变化的影响,对显微夹杂物、夹杂物成分变化及大型夹杂物进行分析。结果表明,喂钙线后2 min时钙处理并未反应完全,VD结束后夹杂物钙处理变性效果明显且钙主要与夹杂物表面反应。对Mg-Al-Ca类夹杂物成分分析得出,钙线的加入使钢中夹杂物Ca含量明显增加,(Al2O3)由VD入位80%～90%降低至中间包中的40%～60%,(Mg)最终降低至10%以下。钙处理对大型夹杂物影响较小。     

2205双相不锈钢硅铝复合脱氧的实验研究

在实验室进行了不同加铝量的2205双相不锈钢硅铝复合脱氧及钙处理的热模拟实验,研究了钢中铝含量对总氧含量和脱氧产物的影响。结果表明:在一定的加铝范围内,加入的铝粒越多,钢中酸溶铝Al S含量越高,最终的氧含量越低。未加铝粒的实验组中,脱氧阶段夹杂物类型为SiO_2-Al_2O_3-MnO和SiO_2-Al_2O_3-MnO-MgO。加入铝粒的实验组中,钢中w(Al_S)0.005 4%,脱氧阶段夹杂物为SiO_2-Al_2O_3-MnO和MgO-Al_2O_3,加入铝含量越多,SiO_2-Al_2O_3-MnO夹杂物成分中Al_2O_3的含量越多;w(Al_S)≥0.005 4%,脱氧阶段夹杂物只有MgO-Al_2O_3。当w(Al S)≤0.005 4%,钙处理后的夹杂物为CaO-SiO_2-Al_2O_3-MgO,加入铝量越多,夹杂物成分中Al_2O_3的含量越多;w(Al_S)=0.016%时,钙处理后的夹杂物为CaO-Al_2O_3-MgO。     

Comprehensive study on hydrogen induced cracking of electrical resistance welded API X52 pipeline steel

Different heat treatment cycles were designed in order to investigate the effect of microstructural changes on hydrogen induced cracking resistance (HIC) and mechanical properties of the electric resistance welded steel. The heat treating of the as-welded specimen improved the ductility and impact toughness. After heat treatment, the uniform hardness profile was obtained for the welded specimens. The removal of local hard zones reduced the risk of HIC. The chemical composition and clustering of inclusions have a deleterious effect on cracking resistance in the H₂S environment. Aluminosilicate compounds and MnS inclusions were favorite sites for HIC. The most promising post weld heat treatment for improving mechanical properties and the resistance to HIC was the application of two-cycle quenching followed by tempering.     

Effect of non-metallic inclusions on hydrogen-induced cracking of API5L X100 steel

In this work, the type, composition and distribution of inclusions contained in an API5L X100 steel were characterized by scanning electron microscopy and energy-dispersive x-ray analysis. A hydrogen-charging at various current densities was used to introduce hydrogen into the steel, and the correlation between HIC and the inclusions was established. The microstructure of the steel consists of a leather-like bainitic ferrite matrix, with martensite/austenite as the second phase particles. At least four types of inclusions are contained in API5L X100 steel, elongated MnS inclusions and spherical Al-, Si- and Ca-Al-O-S-enriched inclusions. In particular, the majority of inclusions in the steel are Al-enriched. Upon hydrogen-charging, hydrogen blisters and HIC could be caused in the steel in the absence of external stress. The cracks are primarily associated with the Al- and Si-enriched inclusions, rather than the elongated MnS inclusion. The critical amount of hydrogen resulting in HIC of the tested API5L X100 steel is determined to be 3.24 ppm under condition in this work.     

Mo(S,O)/(Ce,Mo)(S,O) sulfo-oxide with heterovalent metal states for efficient visible-light-driven hydrogen evolution and pollutant reduction via in-situ generated protons

The existence of the heterovalent metal states and S doping into Ce–Mo bimetallic oxide improve the photocatalytic activity by generating oxygen vacancy and narrowing the bandgap for suitable water splitting. Spherical and plate likes heterostructure Mo(S,O)/(Ce,Mo)(S,O) sulfo-oxide catalysts with heterovalent metal states and oxygen vacancy defects were synthesized by co-precipitation method for photocatalytic hydrogen evolution reaction. Catalyst labeled as 1-CeMoOS with more oxygen vacancies and high Ce³⁺/(Ce³⁺+Ce⁴⁺) ratio evolved 405.18 μmol/h H₂ and achieved AQE of 13.72%, whereas reduced 76.43% 4-NP and 91.52% RhB by in-situ generated protons. S doping, oxygen vacancy creation, Ce and Mo heterovalent states have narrowed the bandgap by substituting oxygen with sulfur, promoted the photogenerated charge carriers' effective separation, and prolonged the lifetime of electrons. The oxygen vacancy formation with a subsequently partial Ce⁴⁺-to-Ce³⁺ conversion achieves CeMoOS catalysts with excellent PHER and provides a promising way to improve photocatalysts' visible light PHER activity.     

Effect of Ce content on the hydrogen induced cracking of X80 pipeline steel

In this study, the effect of Ce content on hydrogen induced cracking (HIC) of X80 pipeline steel has been investigated. The results show that as the Ce content increased from 0 wt% to 0.0042 wt%, 0.016 wt% and 0.024 wt%, the HIC susceptibility of tested steels decreased first and then increased. The steel containing 0.016 wt% Ce possessed the lowest HIC susceptibility because Ce modified inclusions, promoted the formation of acicular ferrite, and decreased the number of hydrogen traps and intergranular cracks.     

Effect of manganese sulphide particle shape on the pinning of grain boundary

The pinning of austenite grain boundaries by manganese sulphide particles is examined experimentally as a function of the shape and size of the inclusions in a free-machining steel. With the same volume fraction, large and extremely long MnS particles are found to be more effective at hindering the motion of austenite grain boundaries than those that approximate spherical shape, even when the latter are smaller and have a higher number density.     

X1215易切削钢生产工艺实践研究

成功开发了X1215易切削钢100t转炉-1 00t LF炉-150mm× 150mm连铸-高线轧制生产工艺.通过LF期不完全脱氧及出钢时钙线调氧,控制LF精炼渣二元碱度在1.0～2.5与底吹氩气100～120L/min的工艺措施,确保了在不同工位钢中存在适当的氧含量.对X1215钢中夹杂物的检测表明,该工艺条件下钢中硫化物形貌和含量控制合理.实践表明,准确预判终点氧含量以确定脱氧剂加入量,合理的控制不同工位氧含量是达到线材产品质量稳定控制的关键.     

Comparative study of non-metallic inclusions on the critical size for HIC initiation and its influence on hydrogen trapping

In the present work, the critical crack nucleation size and the hydrogen trapping capability of inclusion were discussed with a numerical simulation considering the factors of inclusion/matrix heterojunction. The results showed that the inclusion composition had a significant effect on hydrogen capacity and its critical nucleation size of hydrogen-induced cracking (HIC). The MnS inclusions exhibited a larger critical size tolerance of HIC nucleation (approximately 2.5 μm), but for some typical oxide inclusions, it ranged between 0.1 and 0.4 μm. In addition, two sheets of steel containing different composition, morphology, and distribution of inclusions were studied by the standard-based test and thermal desorption spectroscopy (TDS) to evaluate the HIC susceptibility and hydrogen trapping behaviour. The results complementarily demonstrated that when controlling the non-metallic inclusions into the proper size and compound with MnS into the sphere, the HIC resistance of steel could be efficiently improved.