谈针对钢中非金属夹杂物的有效检验

钢中非金属夹杂物包括了外来夹杂物和内生夹杂物两大类。其中,外来夹杂物指的是钢液凝固过程中没有及时浮出而残留夹杂在钢中的耐火材料和炉渣等。而内生夹杂物指的是钢在冶炼过程中,因为脱氧剂的加入以及氮、硫等元素溶解度下降,会形成非金属性质的氧化物、硅酸盐以及硫化物和氮化物等。钢材料的韧性、塑性以及疲劳性能会因非金属夹杂物的存在而降低,并且,其危害会随着钢的强度增高而增多。因此,对钢中非金属夹杂物的检验非常有必要。     

钢中非金属夹杂物及其金相检验

文章介绍钢中非金属夹杂物种类,分析非金属夹杂物给钢性能造成的影响,探讨非金属夹杂物金相检验。结果表明,依据化学成分钢中非金属夹杂物分为氮化物系、硫化物系、氧化物系。这些夹杂物对钢的强度、塑性、疲劳性能、切削性能等都会造成不良影响,影响钢性能充分发挥的同时,缩短钢的使用寿命。不同的非金属夹杂物金相不同,可应用光学显微镜进行金相检验。     

无取向电工钢WG350生产过程中夹杂物的行为与控制

为了更好地控制WG350无取向电工钢中的夹杂物,采用扫描电子显微镜、Aspex系统分析了精炼、连铸过程和成品板中夹杂物的类型、数量及尺寸的演变规律。结果表明,氩站开始出现大尺寸含P复合夹杂物,该类型夹杂物大部分在RH脱碳后会上浮去除。RH加铝脱氧时生成的Al_2O_3以团簇状和块状为主,前者尺寸范围为0.5～5μm且大部分被去除,而块状Al_2O_3会一直遗留至成品中。RH合金化后,钢液中夹杂物数量达到最大,夹杂物类型除Al_2O_3外,主要还有复合氧化物、复合氧硫化物。成品板中夹杂物种类及数量关系为:氧硫化物氧化物氮化物氮化物+氧化物氮化物+硫化物氮-氧-硫复合物硫化物。钢中氧硫(质量分数)由49×10~(-6)降低至13×10~(-6)时,夹杂物种类及数量均会大幅度减少。     

酸溶铝和铌含量对取向硅钢夹杂物特征的影响

摘 要：为了掌握Als（酸溶铝）和Nb含量对取向硅钢中夹杂物特征的影响,借助场发射扫描电镜(FE-SEM)结合能谱仪(EDS)和图像分析软件研究了钢中夹杂物类型、数量、尺寸及尺寸分布,结合钢液凝固过程中溶质元素的微观偏析模型,重点分析了Als和Nb含量影响钢中AlN和NbN析出的机制。结果表明,钢中的夹杂物以NbN、AlN和AlN-NbN为主,夹杂物尺寸分布由Als和Nb含量综合影响。Als含量的增加使含氧复合夹杂物中Al2O3含量增加,SiO2含量降低,促进了钢中硅酸盐类氧化物夹杂的去除,但大大增加了AlN和AlN-NbN夹杂的偏析析出。Nb含量的增加使夹杂物的平均尺寸变小,促进了钢中NbN在凝固前沿的提前析出和以氧化物为核心析出。Als主要影响钢中的氧化物和氮化物夹杂,Nb通过影响与Als结合的O和N的活度影响钢中氧化物和氮化物夹杂的析出特性。     

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。     

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-SiO_2、CaO-Al_2O_3-SiO_2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Al_2O_3、SiO_2及铝酸钙类夹杂物。钙处理钢中形成的液态3CaO·Al_2O_3、MgO·SiO_2和Al_2O_3夹杂物被精炼渣吸收,改性去除了钢中大尺寸Al_2O_3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Al_2O_3-SiO_2类夹杂。硫化物在MgO-SiO_2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。     

硅锰脱氧钢中CaO-SiO2-Al2O3夹杂在固态钢中的结晶行为

 为了避免Al₂O₃、MgO·Al₂O₃等高熔点硬质夹杂物对钢材加工和产品使用性能带来危害,气门簧、切割丝用钢和手撕钢等钢种均采用了硅锰脱氧夹杂物塑性化控制工艺。夹杂物塑性化控制工艺只关注夹杂物成分是否处在相图低熔点区域是不足的,钢中硅酸盐类夹杂物之所以在非液态条件下能发生良好塑性变形,主要是因为它们具有玻璃类材料性质,其软化温度点明显低于钢材热轧温度。而硅酸盐夹杂物的热轧流变性很大程度上取决于其结晶状态,所以夹杂物从玻璃态到结晶态的转变需要予以研究和控制。从微观结构及加热软化行为方面对比了玻璃态与结晶态夹杂物的不同,指出夹杂物结晶对夹杂物塑性化控制工艺所带来的不利影响。阐明在铸坯凝固冷却和轧制前的加热过程中,玻璃态夹杂都有可能发生结晶转变。为了防止玻璃态夹杂出现严重结晶,需要结合夹杂物TTT曲线优化铸坯加热温度和时间,或控制夹杂物组成落入玻璃相更稳定区域。对于CaO-SiO₂-Al₂O₃体系夹杂物,认为磷石英、假硅灰石和钙长石三相共熔区是实现玻璃态稳定控制的理想组成区域。关于MgO及碱金属氧化物对硅锰脱氧钢氧化物夹杂结晶性能的影响规律需要进一步研究揭示,可以借助单丝法等方法来研究氧化物夹杂对应成分的TTT图。     

电工钢中钛的行为研究

为了提高电工钢的磁性能,需要促进晶粒长大和防止存在小晶粒。一般是注重氧化物、氮化物和硫化锰的存在。但是,通过采用具有夹杂物分析功能的扫描电镜的研究发现,钢中添加元素Ti后,在钢中形成大量Ti的硫化物、Ti与MnS复合物、TiAl等。含Ti的复合硫化物主要是TiS-MnS。为了提高电工钢中Mn和Al的利用率,降低夹杂物量,提高磁性能,降低电工钢中S和Ti含量是比较恰当的方法。     

化学成分体系对无取向硅钢夹杂物控制的影响

 结合工业化生产的无取向硅钢,采用非水溶液电解+扫描电镜观察方法,探讨了化学成分体系对夹杂物控制的影响。结果表明,随着Si、Al元素含量升高,氧化物夹杂数量明显减少。氮化物夹杂数量先是快速增多、而后逐渐减少。与此同时,夹杂物平均尺寸逐渐变大。低铝状态下,硫化物夹杂数量较多;高铝状态下,硫化物夹杂数量明显减少,而且CuxS夹杂消失。高硅低铝系列钢、中硅低铝系列钢、低硅无铝系列钢、高硅高铝系列钢夹杂物数量依次减少。     

普钢中非金属夹杂物快速分析方法研究

钢中非金属夹杂物习惯上系指氧化物和硫化物,而常规夹杂分析仅为耐酸浸蚀的稳定氧化物,其组成为尖晶石、硅酸盐玻璃、硅铝等复合氧化物~(Ⅲ),在半镇静钢中夹杂物绝大部分为(Mn、Fe)O,2(Mn、Fe)SiO_2,(Mn、Fe)SFeO,Al_2O_3;在镇静钢中夹杂物主要是SiO_2,Al_2O_3,     

无缝钢管中非金属夹杂物特性研究

峰位于4869 eV位置,对应于元素锡的四价氧化态。锡泥中含有的主要成分为SnO2。     

Influence of nonmetallic inclusions in rail steel on the high-temperature plasticity

The influence of nonmetallic inclusions in Э76Ф rail steel on the high-temperature plasticity is considered. In terms of the shear strain, a plasticity maximum is observed in all three zones of the continuouscast billet: the crust, the columnar-crystal zone, and the central zone of the billet. The high-temperature torsion of samples heated to 950–1250°C with 10-min holding is studied for continuous-cast billet of electrosmelted rail steel. Oxides and silicates are present in the crust; oxides and oxysilicates are found in the columnar-crystal zone; and sulfides, oxides, silicates, and alumosilicates are found in the central zone of the billet. The concentration of inclusions that impair the plasticity is greatest in the central zone of the billet.     

Microstructures and Mechanical Properties of Fe-Mn-（Al, Si） TRIP/TWIP Steels

The mechanical properties and microstructure of two low carbon high manganese steels with 23.8% （No. 1） and 33% （No. 2） （mass percent） of manganese were investigated. The results showed that No. 1 steel possesses high strength and high plasticity, and No. 2 steel has a relatively high strength and extraordinary plasticity. The No. 1 steel exhibits both TRIP （transformation induced plasticity） and TWIP （twin induced plasticity） effects during the deformation; while only TWIP effect appeared under the same deformation condition for No. 2 steel. The comparison between the microstructures and mechanical properties of two steels was made, and the strengthening mechanisms were also analyzed.     

铝含量对TWIP钢中夹杂物特征及AlN析出行为的影响

采用扫描电镜、X射线能谱仪以及扫描电镜配置的夹杂物自动扫描统计软件(INCAFeature)表征了Fe-Mn-C(-Al)系TWIP钢中夹杂物的成分、形貌和数量,考察了Al质量分数在0.002%~1.590%的四种TWIP钢中夹杂物的特征和Al含量对AlN析出行为的影响.并在此基础上,采用了适合TWIP钢中高锰高铝特点的热力学参数对AlN夹杂物进行了系统的热力学分析.研究表明,在含有相似N质量分数(0.0078%~0.0100%)的TWIP钢中,当钢中Al质量分数升高至0.75%时,AlN夹杂物开始在钢中析出,并在MnS(Se)-Al₂ O₃上局部析出形成MnS(Se)-Al₂ O₃-AlN复合夹杂;当Al质量分数升高至1.07%时,热力学计算表明AlN已经可以在TWIP钢液相中形成,经不断长大后在MnS(Se)夹杂物表面局部析出形成MnS(Se)-AlN复合夹杂物;在Al质量分数为1.59%的TWIP钢中,AlN的平衡析出温度比其液相线温度高出42℃,在液相中形成的AlN可以作为异质核心,MnS(Se)夹杂在其表面包裹形成MnS(Se)-AlN复合夹杂物.另外,在Fe-18.21% Mn-0.64% C-1.59% Al体系的TWIP钢中,AlN在液相中析出所需的最低氮的质量分数仅为0.0043%.因此,在TWIP钢的冶炼过程中,应尽可能的降低钢中的氮含量,避免生成过量的AlN夹杂.      

Behavior of sulfide inclusions during thermomechanical processing of AISI 4340 steel

The morphological and compositional modifications of sulfides in AISI 4340 low alloy steel, in which the sulfur level was raised to about 0.1 pct, were studied during hotrolling at 1223 K followed by homogenization at 1583 K for various lengths of time. The relative plasticity of sulfide inclusions with respect to the steel matrix increased with cooling rate during solidification, hence with iron content. The number of sulfides first increased with homogenization time, reached a maximum and subsequently decreased. Inclusion size exhibited the opposite variation. The sulfide matrix interface area per unit volume of sulfide decreased continuously with homogenization time. These variations were in agreement with observed morphological modifications of sulfides during homogenization. During early stages of homogenization the flattened and elongated sulfide plates in the as-rolled material coarsened and became cylindrical. The cylindrical sulfides, broken into segments which spheroidized and coarsened with time, assumed finally a faceted morphology. During homogenization iron was rejected from the sulfide phase into the surrounding matrix, whereas manganese was accepted, causing the formation of manganese depleted zone around the inclusions. This paper is based on a Ph.D. Thesis submitted by Y. V. Murty to the Department of Metallurgy, University of Connecticut.     

Evolution of Non-metallic Inclusions and Precipitates in Oriented Silicon Steel

The evolution of inclusions in oriented silicon steel during the manufacturing process was carried out by chemical composition analysis, non-aqueous electrolytic corrosion, and thermodynamic calculation. The morphology, composition, and size of inclusions were analyzed introducing field emission scanning electron microscope. The oxides were mainly formed during the secondary refining, and the nitrides, sulfides, and compounds were formed during the solidification and cooling of steel in the processes of continuous casting and hot rolling.     

Characteristics of AlN inclusions in low carbon Fe–Mn–Si–Al TWIP steel produced by AOD-ESR method

Argon oxygen decarburisation–electroslag remelting (AOD-ESR) process has been well used to produce the Fe–Mn–Si–Al twinning induced plasticity steel (TWIP) steels. The characteristics of AlN inclusions formed in TWIP steels after AOD refining, ESR and forging process were investigated by scanning electron microscopy and X-ray energy dispersive spectrometry. An automated program called ‘INCAFeature’ was used to collect statistics of inclusion characteristics. Great differences on the amount, distribution and morphologies of AlN inclusions were observed in AOD ingots, ESR ingots and forgings. The dominating inclusions in AOD ingots are mainly single Al(O)N and MnS(Se)–Al(O)N aggregate, accounting for 66.7% of the total inclusions. After the ESR process, AlN inclusions in all size range significantly decreased, which were rarely observed in ESR ingots. Thermodynamic calculations show that AlN inclusions can precipitate in the liquid Fe–Mn–Si–Al TWIP steels, which is different from the viewpoint of literatures that the precipitation of AlN inclusions took place at solidifying front or solid phase. Furthermore, the thermodynamic calculation result has been verified by high temperature laser scanning confocal microscope experiments.     

�ƴ����ѺϽ𻯸���TiN������Ϊ

The characteristics of inclusions in high strength structural steel were characterized by scanning electron microscopy and energy dispersive spectroscopy. The influence of Ti- alloying and Ca treatment on the composition of inclusions in the steel was investigated, and the effect of oxides on the precipitation behavior of TiN and its refining effect on the microstructure were studied. The results show that the inclusions in the steels are Al- Ti- Mg- O system with spherical or polygonal shape after adding Ti, which furtherly can be effectively modified into spherical inclusions after adding Ca. The TiOx in inclusions can be reduced by Ca treatment and Ti gradually diffuses into the surface of the inclusions, which promotes the local precipitation of TiN on the surface of the composite oxides. The amounts of fine oxides and nitrides in steel increase with the increase of Ti mass percentage. Therefore, Ca treatment and higher Ti content can promote the formation of the inclusions of composite oxide and TiN, and also delay the homogeneous nucleation time of TiN inclusions, reducing its size during solidification process of the steel. TiN with the size about 2-3??m not only can induce polygonal ferrite, but also induce acicular ferrite. Specially, the inclusions with TiN and MnS locally precipitating on the surface of composite oxides are conducive to the nucleation of interlocking acicular ferrites.     

高锰TWIP钢层错能的研究进展

高锰TWIP钢的高强度、高塑性和高能量吸收能力与其堆垛层错能有关。TWIP效应对应的层错能上、下限值仍未统一,尤其是TWIP向MBIP(微带诱导塑性)转变的临界判据仍有待于深入分析。XRD、TEM和EAM是测定奥氏体层错能最常用的实验方法。同一TWIP钢的层错能及其变化规律存在实验方法的相关性。正规和亚正规溶液模型、Bragg-Williams模型和双亚点阵模型是计算高锰钢层错能的常见模型。对同一TWIP钢来说,不同模型的预测值并不相同,且与实测值也存在差异。铃木效应引起层错能随间隙原子浓度非线性变化,这在计算时是不能忽略的。规范实验方法、提高设备精度和完善热力学模型及其数据库有助于获得准确可靠的层错能值。     

Effect of Zr addition on morphology characteristics of MnS inclusions in medium carbon high sulfur free cutting steel

In order to improve the morphology characteristics of MnS inclusions in medium carbon high sulfur free-cutting steel, Zr alloy with different contents were added into the 2kg vacuum induction furnace in laboratory, and the characteristics of oxides and sulfides in steel with different Zr additions were investigated with scanning electron microscope and energy dispersive spectrometer (SEM-EDS). The formation mechanism and process of different MnS inclusions were analyzed with thermodynamic software Thermo-Calc. The results show that sulfides in the experimental steel without Zr element are mainly type II MnS with cluster morphology and a small number of type I MnS with large size, and the size and spatial distribution of the sulfides are extremely uneven. After adding 0.0015 mass% of Zr element, the sulfides in the steel are mainly distributed along the grain boundary with cluster morphology. Complex sulfides account for only 01%. As the Zr content further increases to 0.0051 mass%, fine and pure ZrO2 particles are generated in the steel, which provides a sufficient oxide nucleus for MnS formation, weakens the distribution behavior of sulfides in grain boundary polymers, and improves the distribution uniformity of sulfides. Thus, oxides in steel can be used to improve the morphology of sulfides even under the condition of high S/O ratio. The key is to obtain second phase particles with fine size and efficient nucleation ability.