中碳钙硫易切削钢夹杂物形态控制

在实验室进行了1kg坩埚实验,研究了中碳高硫结构钢钙处理前后夹杂物的形态、尺寸及组成.结果表明:钢钙处理后获得了可以改善钢切削性的纺锤形夹杂物,夹杂物的平均纺锤形率为68.11%,并且随钢中[Ca]/[S]增加夹杂物纺锤形化趋势增加;钙处理后小于2.5μm的夹杂物占夹杂物总量的76.05%,夹杂物细小、弥散分布于钢基体中;夹杂物类型以钙铝酸盐芯硫化物外壳的复合夹杂物、(Mn,Ca)S形式的硫化物为主,有少量的铝酸钙与CaS的复合夹杂物;含钙硫的45钢铸态钢锭比普通45钢铸态钢锭切削性能有所改善.     

碲处理控制Y15易切削钢中MnS夹杂物形貌

 为了研究碲对钢中MnS夹杂物形貌的影响,针对Y15高硫易切削钢,利用SEM-EDS扫面电镜,结合FactSage热力学计算,分析了不同碲质量分数对钢中MnS夹杂物形貌、尺寸、长宽比的影响,同时探讨了稀散金属碲对MnS夹杂物形貌控制的机理。研究结果表明,钢液中加碲后,在MnS夹杂物的外环形成了碲、锰、铁的复合相。钢中加碲后MnS夹杂物的形貌和分布大幅度改变,当碲硫比为0.05时,链状MnS夹杂物大幅度减少,球状MnS夹杂物数量增加;当碲硫比增加到0.2时,链状MnS夹杂物基本消失;当碲硫比增加到0.5时,MnS夹杂物形貌的变化不再明显。钢中加碲显著降低了MnS夹杂物的长宽比,控制MnS夹杂物长宽比最合适的碲硫比为0.2。FactSage计算结果表明,MnTe的生成温度为1 900 ℃,在MnS的析出温度下,MnTe是作为液态夹杂物存在的。在凝固过程中,MnTe和MnS发生固溶现象,由于MnTe为液态,两者形成的固溶体会趋于球形生长。     

镁系易切削钢中夹杂物分析

为了探究Mg处理对易切削钢中夹杂物的影响,以1144高硫易切削钢为试验钢种,采用金相和能谱仪等手段研究了 Mg处理对1144易切削钢中夹杂物的形态、尺寸分布和夹杂物成分的影响.结果表明:在易切削钢铸坯中,Mg处理使得易切削钢铸坯硫化物夹杂由Ⅱ类向Ⅲ类、Ⅰ类转变,分布更为均匀,同时使得复合硫化锰夹杂物比例提升.在轧材中,...     

非金属夹杂物对钙系与钙硫系易切削钢切削性能的影响

研究了在18t钢包中采用喷粉方法生产的钙系与钙硫系易切削钢中非金属夹杂物对切削性能的影响。试验结果表明：以200m/min的速度切削Y40CrCa钢时，刀具寿命比切削40Cr钢时高6－10倍；以160m/min的速度切削Y40CrCaS钢时，刀具寿命比切削40Cr钢时高20倍。经能谱仪查明在刀具后面形成保护薄膜，它是延长刀具寿命的主要原因。     

易切削钢中夹杂物及锡的形态

研制了一种新型含锡易切削钢.在锡含量小于0.05%(质量分数)时,钢材具有良好的易切削性能,其力学性能也达到了国家标准.在扫描电镜下观察了钢中夹杂物和断口的形貌,利用能谱分析了夹杂物的成分.结果表明,钢中的复合夹杂物主要由氧化物和MnS组成.多数呈球形或纺锤形,在断口及夹杂物的表面上锡明显偏析.     

低碳高硫易切削钢LF精炼工艺研究

硫易切削钢因其良好的可切削性能和作为含铅易切削钢的环保替代品,在机加工行业已得到广泛使用。石横特钢通过对低碳高硫易切削钢LF精炼工艺的研究,改善了钢中硫化物形态,降低了脆性夹杂物出现的机率,显著提高了该钢的切削性能,满足了用户需求。     

低碳高硫易切削钢冷加工开裂分析

通过金相显微镜和扫描电镜分析,发现低碳高硫易切削钢开裂的原因为钢材近表面的大颗粒夹杂物。大颗粒夹杂物中含有Zr、Na、Mg等元素,是冶炼过程水口和耐火材料的严重侵蚀及保护渣卷渣造成的。     

易切削钢中稀土夹杂物类型的预测

论述了易切削钢中稀土夹杂物相的形成条件及其预测方法，并总结了稀土夹杂物对钢性能的影响，。初步建立了钢液成分、夹杂物类型与钢性能的关系。     

新型贝氏体易切削塑料模具钢中夹杂物的研究

本文研究了新型贝氏体易切削塑料模具钢中几种夹杂物的形态和成分，对含核心的硫化物的能谱分析证实核心为ＣａＯ．２Ａｌ２Ｏ３和ＣａＯ．６Ａｌ２Ｏ３，并对钙在硫化物的变形过程中的作用进行了初步探讨，同时发现了与硫化物复合在一起的氮化钛和氧化铝。     

镁处理易切削钢硫合金化后夹杂物演变行为研究

为开发含镁硫系易切削钢,采用高温模拟实验及热力学计算相结合的方法研究了夹杂物演变.探究了硫合金化对钢液中不同镁系夹杂物的影响及作用机理.实验结果显示,硫合金化会导致钢液中镁系夹杂物沿着MgO(s)→2MgO·SiO2(s)→MgO-SiO2-MnO(1)的路径转变.热力学计算结果表明,随着钢液中硫含量的增加,[Mg]-...     

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.     

Three dimensional morphology analysis of sulfide in 1215MS high sulfur steel billet

1215MS is a typical high sulfur free cutting steel. The morphology and spatial distribution of manganese sulfide have an important influence on the properties of the steel. The sulfide inclusions in the 1215MS cast slab were analyzed by OM, SEM, EDS, and three dimensional inclusion etching technology. The results show that the sulfide size in the chilled layer of 1215MS cast billet is small, with the mean equivalent diameter of less than 15μm. However, in the columnar grain zone the sulfide size gradually increases, and the number density of sulfides decreases. At the 1/4 of the surface of billet, the equivalent diameter of sulfide is maximum about 6μm. In the central equiaxed grain region, the sulfide sizes gradually decrease, while their number densities increase. The equivalent diameter at the center of the billet is reduced to about 46μm, while the number density of sulfide is increased to 1000mm-2. The sulfide morphology from the chilled layer to the center of the cast slab mainly includes ellipsoid, short rod, and long strips. The sulfide is uniformly distributed from the intragranular and grain boundaries of the chilled layer to gradually distributed along the grain boundary.     

1215MS高硫钢连铸坯中硫化物三维形貌的解析

摘要：1215MS是典型的高硫易切削钢,硫化锰的形貌及空间分布对钢的性能具有重要影响。借助OM、SEM、EDS、夹杂物三维腐刻技术对1215MS铸坯中硫化物夹杂进行解析,结果表明：1215MS铸坯激冷层中硫化物尺寸细小,等效直径不大于15μm;柱状晶区硫化物尺寸逐步增大,到距铸坯表面1/4位置处等效直径达到最大6μm左右;中心等轴晶区的硫化物尺寸向内逐渐减少,铸坯中心处等效直径约46μm,硫化物增加至每平方毫米1000个左右。从激冷层到铸坯中心硫化物的形貌主要包括椭球状、短棒状、长条状,硫化物由激冷层的晶内及晶界分布,逐步变为沿晶界分布。     

中高碳铝镇静钢形成MnS塑性夹杂的工艺开发与实践

 为提高中高碳钢产品的抗疲劳性能,利用中高碳钢的成分特点,研究开发了中高碳铝镇静钢中MnS以Al₂O₃为形核质点的非均质形核工艺,将钢中Al₂O₃脆性夹杂用塑性MnS包裹,解决了疲劳应力钢因脆性非金属夹杂引起的疲劳断裂问题。通过对微细、弥散Al₂O₃夹杂生成条件、MnS非均质形核析出热力学条件的研究,开展了钢中关键元素的成分设计、精炼及连铸集成工艺的设计与开发。工业实践表明,低活度氧条件下进行铝终脱氧可以形成3～5 μm微细弥散的Al₂O₃夹杂,并作为非均质形核的核心在二次枝晶晶间的凝固末端析出弥散、细小的粒状MnS;通过梯度脱氧、真空碳脱氧以及保护浇铸等操作可以有效稳定控制钢中全氧含量,提高钢水洁净度,成品T[O]质量分数平均为0.000 618%,较原工艺的0.000 739%降低了16%;成品的夹杂物中MnS及MnS包裹Al₂O₃夹杂所占比例大于96%,与世界领先产品的夹杂物控制水平相当,考虑到产品使用过程中Al₂O₃夹杂外部的MnS包裹层必须足够厚,塑性夹杂才能起作用,建立了MnS “有效包裹率” 的概念,当硬相夹杂物被MnS包裹且硬相夹杂物的最大半径不大于MnS包裹部位半径的1/2时,认为MnS对硬相夹杂物实现了“有效包裹”;MnS塑性夹杂工艺可明显提高材料的疲劳性能,成品的平均断裂韧性为83.47 MPa·m1/2,较原工艺的67.31 MPa·m1/2提高了24%。     

含钛中碳钢中钛氧化物析出热力学分析

以含钛中碳钢为研究对象,从热力学的角度分析了含钛中碳钢中钛氧化物析出行为,结果表明:浇注温度为(1535±10)℃且钢中溶解氧含量大于0.003％(质量分数,余同)时,低钛中碳钢中的溶解Ti可与钢中的溶解氧反应生成Ti3O5、Ti2O3,生成TiO2、TiO夹杂的可能性较小;高钛中碳钢中的溶解Ti可与钢中的溶解氧反应生...     

MnS夹杂对钢中氢扩散行为的影响

通过实验和有限元计算研究了MnS夹杂对钢中氢扩散行为的影响.结果表明:当MnS夹杂长度取向与氢渗透方向平行时,氢在钢中的表观扩散系数随MnS含量的增加而增加;当MnS夹杂长度取向与氢渗透方向垂直时,氢在钢中的表观扩散系数随MnS含量的增加而降低.对于具有扩散通道效应和陷阱效应的第二相,它对氢扩散的影响取决于扩散通道效应和陷阱效应的强弱以及第二相的形状、数量和取向.     

冷却强度对超高硫中碳钢方坯凝固过程MnS生长的影响

 中碳超高硫易切削钢SAE144是兼具力学性能与切削性能的结构钢,用于制造汽车发动机密封阀件等,产品多采用转炉/电炉→LF精炼→连铸小方坯→线棒材热轧→冷拉及机加工成型流程生产,近年来市场热度稳步提升。若钢中MnS尺寸过大,零件加工使用过程易发生探伤不合、切削性能差、带状组织严重、力学性能各相异性显著,甚至拉拔加工断裂等问题。MnS夹杂物多在铸坯凝固后期形成,随着轧制与钢基体同步变形,控制该类钢种铸坯内MnS原始尺寸成为控制热轧材中MnS夹杂物形态及尺寸的最关键环节。为控制热轧超高硫中碳钢盘条中MnS夹杂物,利用钢坯凝固数值模拟、第二相析出理论、Ostwald熟化理论计算分析了160 mm2钢坯中硫元素偏析及MnS的生成、长大和熟化过程。计算结果表明,当固相分数f_s为0.446、硫微观偏析比达到2.19时,铸坯在凝固末期生成MnS。凝固过程中MnS的生长过程决定了钢坯中MnS颗粒的直径。理论计算表明,当连铸二次冷却水量固定为0.6L/kg时,拉速为1.6、2.1和2.6 m/min时,160 mm2方坯中心的MnS分别增长到30.6、32.2和34.6 μm,与实际测试结果一致。控制该类钢种线材中MnS尺寸的关键是提高二冷区的冷却强度,降低连铸拉速。基于该系列计算方法,提出了160 mm2钢坯中与MnS直径控制目标相匹配的连铸工艺参数控制范围。     

硫含量对重轨钢中非金属夹杂物的影响

摘要：实际生产过程中由于原料和操作控制不精确,钢中硫含量和非金属夹杂物波动较大,严重影响钢的洁净度。为了准确控制重轨钢中硫化锰等非金属夹杂物的尺寸、形态和数量,在实验室开展了硫含量对重轨钢中非金属夹杂物的影响研究。钢中硫质量分数增至70×10-6、110×10-6、140×10-6后随炉冷却,采用全自动夹杂物分析仪对钢中非金属夹杂物进行统计,获得了硫含量与钢中非金属夹杂物成分、尺寸、形态和数量的关系。结果表明,钢中夹杂物大部分为以氧化物为形核核心的复合型MnS;随着硫含量的升高,复合型MnS、MnO-SiO2和MgO-Al2O3-SiO2-CaO型夹杂增多,CaO-SiO2和MgO-CaO-SiO2夹杂减少;夹杂物平均尺寸随硫含量的升高而增大,且不同尺寸的夹杂物均有所增加,尺寸为2~10μm增多最明显;硫质量分数为(70~140)×10-6的钢液凝固过程液相中都能单独析出MnS,且硫含量越高,MnS析出越早,含量越多。     

Effect of sulfur content on non metallic inclusions of heavy rail steel

Due to the inaccurate control of raw materials and operation in the actual production process, the sulfur content and non-metallic inclusions in the steel fluctuate greatly, which seriously affects the cleanliness of steel. To accurately control the size, shape and quantity of non-metallic inclusions such as manganese sulfide in heavy rail steel, the effect of sulfur content on non-metallic inclusions in heavy rail steel was studied in the laboratory. To investigate the changes of the number and morphology of non-metallic inclusions in steel under different sulfur contents, the sulfur content of test steel was increased to 70×10-6, 110×10-6 and 140×10-6, respectively. During the experiment, the test steel was heated and melted in a tubular furnace according to a certain heating rule, and then cooled naturally in the furnace. Subsequently, the non metallic inclusions in steel were scanned by automatic inclusions analyzer, and the relationship between sulfur content and the composition, size, form and quantity of non-metallic inclusions in steel was obtained. The results indicate that most of the inclusions in the steel are composite MnS with oxides as nucleating cores. With the increase of sulfur content, the quantity density of composite MnS, MnO-SiO2 and MgO-Al2O3-SiO2-CaO inclusions increase, while the CaO-SiO2 and MgO-CaO-SiO2 inclusions decrease. The average size of inclusions increases with the increase of sulfur content, and the number of inclusions with different sizes also increases, especially for inclusions with sizes of 2-10μm which increase obviously. During solidification, MnS can be separated from molten steel with sulfur content of (70-140)×10-6. In addition, the higher the sulfur content is, the earlier MnS inclusions precipitate and the more the MnS content is.