Nb-H13钢中一次碳化物的析出机理和控制

为了得出铌微合金化H13钢中合适的铌元素添加量,以H13钢中的一次碳化物为研究对象,通过实验室冶炼不同铌元素质量分数的H13钢,系统地研究了Nb-H13钢中一次碳化物的析出机理和合适的Nb添加量。结果表明,当H13钢中铌的质量分数小于0.03%时,Nb-H13钢中的一次碳化物主要为富钒相;当H13钢中铌的质量分数达到0.05%时,Nb-H13钢中的一次碳化物主要为富钒相和富铌相。铌微合金化H13钢中铌元素的添加量应小于0.03%。铌质量分数的高低会显著影响FCC相中碳化物的析出顺序,随着铌质量分数的增加,碳化物的析出顺序由首先析出富钒相转变为首先析出富铌相,且富铌相的热稳定性要远高于富钒相。理论计算结果与试验观察结果基本一致,工业试验结果同样论证了本研究的结论。     

合金元素对2Cr13马氏体不锈钢组织及性能的影响

Ni,Mo,V均是影响13Cr型马氏体不锈钢性能的主要元素.研究了在普通2Cr13基础上添加不同含量的Ni,Mo以及微量V对其力学性能、耐腐蚀性能的影响.研究表明:单独添加Ni或Mo元素均未能明显改善2Cr13型马氏体不锈钢的综合力学性能,但同时添加适量的Ni,Mo等合金元素能明显提高材料的力学及耐CO2腐蚀性能.     

国内外高氮马氏体不锈轴承钢研究现状与发展

 高碳铬不锈钢是应用最为广泛的不锈轴承钢,其具有较高的硬度和一定的耐蚀性,然而较高的碳、铬质量分数导致粗大碳化物的出现,轴承钢的疲劳和耐蚀性能将受到损害。相比之下,钢中添加氮元素能够减少粗大共晶碳化物的数量,同时析出大量细小的氮化物及碳氮化物,氮代碳既强化基体又改善耐蚀性,从而获得高强度与良好耐蚀性。介绍了含氮轴承钢及含氮马氏体轴承钢的发展历程,分析了不锈轴承钢中氮元素对组织结构、力学性能和耐蚀性能的作用机理;介绍国内外含氮轴承钢的研究现状并指出了含氮轴承钢研究的不足,需要在氮溶解模型、氮对组织演变及耐蚀机制等方面进行基础理论研究,同时不断研发不同系列的含氮马氏体轴承钢。     

中低碳系列马氏体不锈钢开发与生产

针对中低碳马氏体不锈钢20Cr13、30Cr13,通过差异化成分配比,开发了6个牌号系列化产品,满足不同使用需求.采用高洁净度冶炼工艺、钢板坯纵裂优化控制措施、动态轻压法及电磁搅拌、消除碳化物偏析等冶炼技术,有效降低了钢中有害重金属残余量,使产品符合欧盟食品级检测标准,质量达到国际先进水平.     

氮元素对Cr13超级马氏体不锈钢组织及性能的影响

摘要：为了提高超级马氏体不锈钢的性能以满足油气开采的使用要求,在Cr13超级马氏体不锈钢中添加质量分数为0.065%的N元素,并采用金相观察、SEM、拉伸试验、电化学测试等方法,研究N元素对Cr13超级马氏体不锈钢组织、力学性能及耐蚀性能的影响。研究发现,N元素能细化原奥氏体晶粒、对组织中的回火马氏体有一定的“短化”作用,并且能有效减少组织中的δ铁素体、增加奥氏体的含量。在力学性能方面,适量的N元素因可以细化奥氏体晶粒和短化马氏体从而增加晶界和亚晶界,所以能有效提高试验钢的屈服强度和抗拉强度。耐蚀性能方面,电化学实验表明,适量的N元素能提高钝化膜的保护能力和再钝化能力,所以在一定程度上能有效提高试验钢的耐蚀性能。     

热处理工艺对18%Cr马氏体不锈钢组织与力学性能的影响

以羰基Fe粉以及Cr_3C_2,VC,Mo_2C等碳化物粉末为原料,制备Cr含量(质量分数,下同)为18%的粉末冶金马氏体不锈钢。将不锈钢分别在1 050℃和1 150℃下淬火,然后于200~590℃下进行回火处理,研究热处理工艺对不锈钢组织与力学性能的影响。结果表明:粉末冶金18%Cr马氏体不锈钢的基体中存在M_7C_3型以及MC型碳化物,随回火温度升高,碳化物数量增多并且碳化物形态由原来的部分连续状向孤立、块状转变。1 150℃温度下淬火的不锈钢,其硬度较高,HRC最高达63.9,在较低温度下(200℃)回火时,抗弯强度为2 002 MPa,而在530℃温度下回火后,抗弯强度大幅升高至3 093 MPa。1 150℃淬火的不锈钢,其冲击韧性较低,随回火温度升高而升高。热处理后的不锈钢断裂形式均为准解理断裂。     

泰山钢铁马氏体不锈钢系列产品的开发

介绍了泰山钢铁马氏体不锈钢产品开发历程。从化学成分、组织、性能以及重点控制工艺方面,介绍了泰山钢铁开发生产的Cr13系列马氏体不锈钢、含氮耐蚀马氏体不锈钢、个性化定制马氏体不锈钢以及高端马氏体不锈钢产品的特点。     

镁对GH3625合金一次碳化物析出的影响

 GH3625合金中碳的质量分数约为0.05%,由于含有较高的铌、钼和铬元素,合金中会形成 MC型、M₆C型和M₂₃C₆型碳化物,在冶炼凝固过程中由于选分结晶的原因,易产生碳化物偏聚问题。因为碳化物回溶温度偏高,在其可锻温度区间内很难消除,所以会导致合金棒材中存在碳化物条带状聚集的问题,对其服役性能影响较大。利用Thermal-calc热力学软件计算分析了GH3625合金平衡析出相及一次碳化物的析出规律,利用金相显微镜、扫描电镜等研究了镁对GH3625合金一次碳化物形貌、尺寸及分布的影响。结果表明,GH3625合金的基体为单一的奥氏体相,MC型碳化物作为一种高温析出相,直接从液相析出,其富含铌元素,其次还有少量的钛、钼等元素。而随着凝固温度的降低,铌质量分数逐渐升高;未加镁时,GH3625合金在二次枝晶间析出了大量长条状的一次碳化物,其平均直径和面积较大;加入质量分数为0.014%的镁后,镁通过改变碳化物相与基体相的比界面能关系,不仅有效地改善了合金枝晶间和晶界碳化物的分布及形貌,还减小了一次碳化物的尺寸;当镁质量分数增加到0.037%时,一次碳化物分布更加均匀弥散,此时镁细化、球化碳化物的效果最好;同时,试验合金在水冷和空冷的条件下,由于冷却速率比炉冷时更大,一次碳化物析出尺寸也相对更细小。     

马氏体型不锈钢

它的显微组织为马氏体。这类钢中铬的质量分数为11.5％～18．0％,但碳的质量分数最高可达0．6％。碳含量的增高,提高了钢的强度和硬度。在这类钢中加入的少量镍可以促使生成马氏体,同时又能提高其耐蚀性。这类钢的焊接性较差。列入国家标准牌号的钢板有1Cr13、2Cr13、3Cr13、1Cr17Ni2等。     

高碳马氏体不锈钢8 Cr13 MoV钢铸态组织及碳化物

利用Thermo-Calc软件对8Cr13MoV马氏体不锈钢的凝固过程进行计算,利用光学显微镜、扫描电子显微镜和X射线衍射分析仪对铸态组织和碳化物形貌以及类型进行观察与分析,利用Gleeble热模拟试验机测定材料的静态连续冷却转变曲线.结果表明,8Cr13MoV在平衡凝固条件下组织为铁素体和M₂₃C₆型碳化物,而在实际的凝固条件下,组织为铁素体、马氏体、残余奥氏体、M₇C₃型和M₂₃C₆型碳化物,由于偏析导致最终组织中碳化物以M₇C₃型为主,少量M₂₃C₆以薄片或树枝状分布在晶界上.由于较高的C和Cr含量,以0.1℃·s-1的冷却速率冷却时,奥氏体也会发生马氏体转变.      

Microstructure and Mechanical Properties of Martensitic Stainless Steel 6Crl5MoV

 Martensitic stainless steel containing Cr of 12% to 18% (mass percent) are common utilized in quenching and tempering processes for knife and cutlery steel. The properties obtained in these materials are significantly influenced by matrix composition after heat treatment, especially as Cr and C content. Comprehensive considered the hardness and corrosion resistance, a new type martensitic stainless steel 6Cr15MoV has been developed. The effect of heat treatment processes on microstructure and mechanical properties of 6Cr15MoV martensitic stainless steel is emphatically researched. Thermo-Calc software has been carried out to thermodynamic calculation; OM, SEM and TEM have been carried out to microstructure observation; hardness and impact toughness test have been carried out to evaluate the mechanical properties. Results show that the equilibrium carbide in 6Cr15MoV steel is M23C6 carbide, and the M23C6 carbides finely distributed in annealed microstructure. 6Cr15MoV martensitic stainless steel has a wider quenching temperature range, the hardness value of steel 6Cr15MoV can reach to HRC 608 to HRC 616 when quenched at 1060 to 1100 ℃. Finely distributed carbides will exist in quenched microstructure, and effectively inhabit the growth of austenite grain. With the increasing of quenching temperature, the volume fraction of undissolved carbides will decrease. The excellent comprehensive mechanical properties can be obtained by quenched at 1060 to 1100 ℃ with tempered at 100 to 150 ℃, and it is mainly due to the high carbon martensite and fine grain size. At these temperature ranges, the hardness will retain about HRC 592 to HRC 616 and the Charpy U-notch impact toughness will retain about 173 to 20 J. A lot of M23C6 carbides precipitated from martensite matrix, at the same time along the boundaries of martensite lathes which leading to the decrease of impact toughness when tempered at 500 to 540 ℃. The M3C precipitants also existed in the martensite matrix of test steel after tempered at 500 ℃, and the mean size of M3C precipitates is bigger than that of M23C6 precipitates.     

铌对高碳钢奥氏体向珠光体转变规律的影响

 铌可以显著改善钢的组织，提高钢的性能。同时，铌在钢中还存在偏聚现象，可有效提高钢的淬透性，使共析点右移。因此，利用金相法和等温热处理试验，对高碳钢的微观组织进行分析，发现铌的析出和固溶将细化晶粒，同时铌的加入将推迟高碳钢的珠光体转变，并使其孕育期延长。利用合金价电子结构理论，构建了不含铌和含铌的两种体系的奥氏体合金价电子晶胞，从电子层次研究铌对高碳钢奥氏体的影响规律。理论计算结果表明，两种模型在碳质量分数为0.86%时的最大共价电子对数nA分别为0.972 5、0.962 4。铌的加入会改变体系中键的组成，并与碳原子结合形成新的最强键C-Nb键。而NbC的析出阻碍了碳在奥氏体中的扩散，推迟了珠光体的形成和长大，进而推迟了珠光体相变，导致添加铌元素后的CCT曲线右移。     

Study on microstructure and mechanical properties of martensitic stainless steel 6Cr15MoV

Martensitic stainless steel containing 12%-18%Cr have high hardness due to high carbon content. These steels are common utilized in quenching and tempering processes for knife and cutlery steel.The properties obtained in these materials are significantly influenced by matrix composition after heat treatment,especially as Cr and C content.Comprehensive considered the hardness and corrosion resistance,a new type martensitic stainless steel 6Cr15MoV has been developed.This study emphatic researches the effect of heat treatment processes on microstructure and mechanical properties of 6Cr15MoV martensitic stainless steel.Thermo-Calc software has been carried out to thermodynamic calculation;optical microscope（OM）,scanning electronic microscope（SEM） and transmission electron microscope（TEM） have been carried out to microstructure observation;hardness and impact toughness test have been carried out to evaluate the mechanical properties.Results show that the equilibrium carbide in 6Cr15MoV steel is M₂₃,C₆ carbide,and finely distributed of M₂₃C₆ carbides can be observed on annealed microstructure of 6Cr15MoV stainless steel.6Cr15MoV martensitic stainless steel has a wider quenching temperature range,the hardness value of steel 6Cr15MoV can reach to 60.8 -61.6 HRC when quenched at 1060 - 1100℃.Finely distributed carbides will exist in quenched microstructure,and effectively inhabit the growth of austenite grain.With the increasing of quenching temperature,the volume fraction of undissolved carbides will decrease.The excellent comprehensive mechanical properties can be obtained by quenched at 1060-1100℃with tempered at 100-150℃,and it is mainly due to the high carbon martensite and fine grain size.At these temperature ranges,the hardness will retain about 59.2-61.6 HRC and the Charpy U-notch impact toughness will retain about 17.3-20 J.The morphology of impact fracture surface of tested steel is small dimples with a small amount of cleavage planes.The area of cleavage planes increases with the increasing of tempering temperature.     

Characterization of (Nb,Ti, Mo)C Precipitates in an Ultrahigh Strength Martensitic Steel

A study on ultrahigh strength steel plate subjected to novel thermo-mechanical control process was presented. The mechanical properties examination showed that the investigated steel exhibited excellent combination of ultra-high strength( 2 200 MPa) and toughness( 26 J). The microstructure of the experimental steel was observed by scanning electron microscope and transmission electron microscope. Desired martensitic lath with width of about 180- 250 nm was obtained. Nanostructured carbide precipitates with sizes of 20-50 nm,which contained Nb,Ti and Mo,were observed in the lath martensitic microstructure,and confirmed to be MC-type carbides with B1 structure by means of selected area electron diffraction.The compositional characteristics revealed by energy dispersive X-ray spectrometer mapping implied that the carbide forming elements Nb,Ti and Mo distributed in the precipitates evenly. Three-dimensional atom probe tomography reconstruction further indicated that Mo incorporated into the precipitates without enrichment in the carbide-matrix interface and probably substituted for Nb and Ti to form the( Nb,Ti,Mo) C carbides.     

不锈钢酸洗污泥用作炼钢造渣剂的试验

 酸洗污泥产量大、污染严重且难处理，常规固化填埋占用土地且浪费资源，将酸洗污泥配入电炉作为造渣剂使用，在生产中回收其中金属铁、铬和镍，并发挥CaO、CaF2等辅料功能，可实现污泥在冶金过程的资源化利用。通过FactSage热力学软件计算发现酸洗污泥中的金属铁、铬和镍绝大部分可回收进入金属液中，且金属液硫质量分数最高为0.014%，不会使金属液增硫。在此基础上，将酸洗污泥制成混合造渣剂，通过静态试验与吹氧熔炼试验发现，当造渣剂与酸洗污泥质量比为1[∶]1时，硫质量分数能够满足钢液要求，铬、镍回收率分别为66.04%和97.90%。     

时效处理对05Crl7Ni4Cu4Nb马氏体沉淀硬化不锈钢力学性能及组织的影响

试验研究了 1040 ℃固溶的马氏体沉淀硬化不锈钢05Cr17Ni4Cu4Nb在480~620 ℃时效5 h的组织,强度和硬度。结果表明,随时效温度升高,马氏体基体逐渐分解,碳化物析岀而降低;在时效处理过程中,随时效温度升高,富Cu相最初以球形析出,逐渐发展成椭圆形及杆状,尺寸增大,与基体共格界面消失,强化效果减弱;05Cr17Ni4Cu4Nb钢经1040 °C固溶,480 °C 5h时效后,其HRC硬度值44.3,满足钢材HRC硬度值43的要求。     

碳化物对热连轧403Nb钢位错组态及蠕变行为的影响

对热连轧403Nb钢进行了蠕变试验,并对其蠕变前后的组织进行了研究,结果表明:403Nb钢在轧制过程中发生了动态回复及动态再结晶,组成相中,Cr23C6主要为二次碳化物,而NbC则主要源于一次碳化物。在连轧过程中,一次碳化物通过阻碍位错滑移制约动态回复,其分布影响回复后的组织结构。蠕变期间,晶内碳化物阻碍位错运动,晶界碳化物"钉扎"晶界,阻碍晶界滑动,由此提高钢的蠕变抗力。