含W的Cr15型超级马氏体不锈钢组织性能分析

采用全自动热膨胀相变仪、光学显微镜、透射电镜、高分辨电镜及能谱分析和力学万能试验机等手段,研究含W的Cr15型超级马氏体不锈钢经淬火+回火后的微观组织和力学性能.结果表明,淬火+回火后的微观组织为回火马氏体及分布在马氏体基体中的逆变奥氏体两相组织,形成的逆变奥氏体与马氏体板条符合K-S关系.在基体上弥散析出的纳米级金属化合物Laves相以及富铜相ε-Cu起到强化作用.该钢具有优良的力学性能,洛氏硬度为26～36,抗拉强度为895～1 009 MPa,延伸率为17%～21%.     

两相区热处理对9Ni钢低温韧性的影响

采用扫描电镜、X射线衍射仪等分析手段研究了两相区热处理工艺参数对9Ni钢组织和低温韧性的影响。结果表明,中间淬火温度及回火温度对低温韧性有显著的影响,温度过高和过低都会造成低温韧性的降低。同调质工艺相比,经两相区热处理后,回转奥氏体分布更加弥散、均匀,且析出数量增加。     

两相区热处理对9Ni钢低温韧性的影响

采用扫描电镜、X射线衍射仪等分析手段研究了两相区热处理工艺参数对9Ni钢组织和低温韧性的 影响。结果表明,中间淬火温度及回火温度对低温韧性有显著的影响,温度过高和过低都会造成低温韧性的降低。 同调质工艺相比,经两相区热处理后,回转奥氏体分布更加弥散、均匀,且析出数量增加。     

热穿-热轧法生产的新型贝氏体中空渗碳钢的组织和性能

用热穿-热轧法制备了新型贝氏体中空钢．研究了热处理对新型贝氏体钢和渗碳处理对中空钢组织和性能的影响．结果表明：新型贝氏体钢正火＋低温回火热处理后的组织为贝氏体铁素体和奥氏体,淬火＋低温回火后的组织由马氏体、贝氏体和奥氏体组成;正火或淬火＋低温回火后,新型贝氏体中空钢具有良好的强韧性．正火＋低温回火后,中空钢的组织为贝氏体铁素体和残余奥氏体组织．新型贝氏体中空钢渗碳后空冷,渗层的组织为高碳马氏体和残余奥氏体组织,非渗层为贝氏体铁素体和残余奥氏体组织,实体中空钢具有较好的强韧性和渗碳效果．     

高速钢的回火组织与性能及二次硬化机制的探讨

利用电子显微分析及X射线衍射分析等手段,揭示了不同温度回火给高速钢带来的组织变化,并从组织方面分析了高速钢材料的强韧性随回火温度的变化规律。研究发现,低温回火组织的高塑性决定了组织的低硬度和高抗弯强度及冲击韧性。而高温回火时特殊碳化物的析出等过程降低了回火组织的塑性,因而回火组织有很低的冲击韧性和很高的硬度及抗弯强度。同时分析认为,固溶强化是一个不容忽视的二次硬化过程中的强化过程。另外碳化物析出可能是残余奥氏体催化的重要原因。     

钢中的低碳马氏体及条间奥氏体

低碳马氏体形成时可能存在碳的扩散,使条间奥氏体富碳,以及受协作形变强化的力学稳保持至室温,形成淬火钢中马氏体条间的奥氏体,它对低碳马氏体的韧化起重要的作用。低碳马氏体形成时,碳的扩散并非必需过程;马氏体与基体间为平直界面,而贝氏体界面却存在巨型台阶;低碳马氏体也并不按贝氏体形式长大;证明低碳马氏体形成机制和贝氏体的不同。低温回火时,由于渗碳体自马氏体脱溶的形核(长大)驱动力较大,先由马氏体析出渗碳体;长时间回火时,由于条间奥氏体分解驱动力较大,又受到马氏体脱溶呈收缩的拉应力促使分解;提出回火马氏体致脆的机制为马氏体脱溶和奥氏体分解的互为关连的过程。应用低碳马氏体时须注意避免回火马氏体致脆及加强条间奥氏体的稳定性。     

Effects of Si on the stability of retained austenite and temper embrittlement of ultrahigh strength steels

Effects of silicon(Si)content on the stability of retained austenite and temper embrittlement of ultrahigh strength steels were investigated using X-ray diffraction(XRD),transmission electron microscopy(TEM),and other experimental methods.The results show that Si can suppress temper embrittlement,improve temper resistance,and hinder the decomposition of retained austenite.Reversed austenite appears gradually with the increase of Si content during tempering.Si has a significant effect on enhancing carbon(C)partitioning and improving the stability of retained austenite.Si and C atoms are mutually exclusive in lath bainite,while they attract each other in austenite.g-carbides are found in 1.8wt％ Si steel tempered at 250℃,and they get coarsened obviously when tempered at 400℃,leading to temper embrittlement.Not ε-carbides but acicular or lath carbides lead to temper embrittlement in 0.4wt％ Si steel,which can be inferred as cementites and composite compounds.Temper embrittlement is closely related to the decomposition of retained austenite and the formation of reversed austenite.     

回火温度对25SiMnNi2CrMo钢组织和性能的影响

为提高钎具产品的性能和使用寿命,采用OM、TEM、冲击和拉伸试验,研究了正火后不同回火温度对25SiMnNi2CrMo钢组织与力学性能的影响．结果表明,25SiMnNi2CrMo钢920℃正火后不同温度回火,随着回火温度的提高,材料的硬度和抗拉强度呈逐渐下降的趋势,冲击韧度值呈先升高后降低、复又升高的变化趋势,300℃回火后冲击韧度出现峰值,450℃回火出现回火脆性．试验材料在300℃回火后,具有最佳的强韧性配合,具体性能为：抗拉强度σb1391MPa、硬度HRC40、冲击韧性AKV72．5 J．300℃以下回火的组织为回火马氏体＋贝氏体＋残余奥氏体;超过350℃回火,残余奥氏体开始发生分解,组织中有碳化物析出,随回火温度提高,碳化物有聚集和球化趋势．提出了25SiMnNi2CrMo钢最佳回火热处理工艺．     

热处理对含锰6％的中锰球墨铸铁组织及性能的影响

采取不同的淬火（800℃,900℃,1000℃）和回火（200℃,400℃,600℃）热处理工艺,对含锰6％的中锰球墨铸铁组织和力学性能进行了研究．结果表明：中锰球墨铸铁的合理热处理工艺为在900℃奥氏体化保温2h水淬,在200℃回火2h水淬．淬火后的组织为大量的马氏体＋贝氏体＋残余奥氏体＋球状石墨,淬火和回火后的组织为回火马氏体＋贝氏体＋少量残余奥氏体＋碳化物＋球状石墨．热处理后试样的硬度下降,冲击韧性提高,耐磨性下降．淬火温度对试样的硬度、冲击韧性和耐磨性影响较大,回火温度对试样的硬度、冲击韧性和耐磨性影响较小．     

高碳高合金钢中残余奥氏体亚结构的研究

本文研究了高碳M2钢中残余奥氏体在系列回火过程中数量、形态及亚结构的变化规律,探讨了引起残余奥氏体亚结构变化的原因-马氏体的相硬化作用;并进一步分忻了系列回火过程中高碳M_2钢硬度的变化规律。     

热处理工艺对低合金耐磨钢组织和性能的影响

通过对低合金耐磨钢热处理工艺试验．研究了不同淬火和回火温度对材料组织和性能的影响．结果表明：经过920℃／30min水淬＋260℃／2h回火处理后,试样晶粒细小,组织为板条马氏体、碳化物和少量残余奥氏体,并具有最佳的冲击韧性和硬度．     

C90油井管的组织与性能

研究C90油井管调质后的组织与性能。结果表明,钢的组织主要由回火屈氏体与回火索氏体组成。且随回火温度的升高,回火屈氏体含量降低,回火索氏体含量增加,第二相粒子析出增加。钢的屈服强度与抗拉强度随回火温度的升高而降低。试验钢的抗腐蚀性能随回火温度的升高而增强,随浸泡时间增加而降低。C90的最佳热处理工艺为：870℃淬火,650℃回火。     

Nb变质处理铸造高速钢的组织和性能

在铸造高速钢刀具中添加质量分数为4％的Nb形成孤立粒状碳化物以细化铸态组织,研究了不同固溶温度和回火温度下的组织和硬度.结果显示:固溶处理温度为1 200℃时,碳化物呈孤立粒状均匀分布;低于此温度,晶界上的羽毛状碳化物未能完全溶解,而高于此温度则导致粒状NbC的溶解.回火温度为570℃到580℃时,可获得细针状马氏体和最少量的残余奥氏体;低于此温度,针状马氏体粗大,残余奥氏体量较多.     

Effects of Ti addition on low carbon hot strips produced by CSP process

Large quantity of fine Ti（C,N） particles, 15-30 nm in size, were observed in low carbon hot strips added to a small amount of Ti and produced by CSP process. The results showed that the precipitation of Ti（C,N） mostly took place during soaking and hot rolling, which is significantly different from that in the conventional production. These fine Ti carbonitride particles could be very effective on the austenite grain refinement by hindering grain growth of recrystallized austenite. Their precipitation behavior was discussed and compared with that of the steels produced in the conventional production.     

Semi-solid casting of high speed steel ingots using inclined slope pre-crystallization method

Semi-solid casting of M2 high speed steel ingots was investigated by inclined slope pre-crystallization method. Effects of casting temperature and slope length on the microstructure of M2 HSS ingots were investigated. M2 cast ingots of non-dendritic primary austenite and fine eutectic ledeburite network carbide structure were obtained, with the casting temperature, slope length and angle of 1480 °C, 500 mm and 60° respectively. Meanwhile, the microstructure of cast samples was quantitatively assessed by Image tool software. Results show that optimum mean equivalent diameter of primary austenite crystal grain is 50.8 μm, shape factor is 0.83, and mean thickness of network carbide is 5.21 μm.     

Effect of deep cryogenic treatment on the properties of 80CrMo12 5 tool steel

The effect of deep cryogenic treatment on the mechanical properties of 80CrMol2 5 tool steel was investigated.Moreover,the effects of stabilization (holding at room temperature for some periods before deep cryogenic treatment) and tempering before deep cryogenic treatment were studied.The results show that deep cryogenic treatment can eliminate the retained austenite,making a better carbide distribution and a higher carbide amount.As a result,a remarkable improvement in wear resistance of cryogenically treated specimens is observed.Moreover,the ultimate tensile strength increases,and the toughness of the sample decreases.It is also found that both stabilization and tempering before deep cryogenic treatment decrease the wear resistance,hardness,and carbides homogeneity compared to the deep cryogenically treated samples.It is concluded that deep cryogenic treatment should be performed without any delay on samples after quenching to reach the highest wear resistance and hardness.     

NR400高强度贝氏体耐磨钢板的组织与耐磨性能

分别采用滑动磨损和冲击磨料磨损试验,对比研究南钢NR400高强度耐磨钢板和进口SW400,JA400耐磨钢板的显微组织及耐磨性,分析磨痕形貌,探讨其磨损机制。结果表明,NR400耐磨钢板的组织由贝氏体和少量残余奥氏体组成,具有良好的强韧性及耐磨性。SW400和JA400耐磨板的组织主要为回火马氏体,基本元残余奥氏体存在。NR400耐磨钢板的耐磨性优于进口耐磨钢板。     

空冷高硅中碳低合金钢的组织与性能

研究了高硅中碳低合金钢空冷态和空冷＋回火态的显微组织和力学性能.试验钢在860℃保温0.5 h奥氏体化后空冷处理,随后分别在250℃和400℃保温1 h回火.结果表明：试验钢空冷后组织为贝氏体/马氏体和残余奥氏体的混合组织,硬度约为41 HRC;而250℃回火后组织变化不大,硬度明显升高,约为49 HRC,韧性明显增加,由44 J/cm2增加到66 J/cm2,抗拉强度、屈服强度和延伸率明显下降.回火温度进一步增加对力学性能影响不大.     

Precipitation and Hetero-nucleation Effect of V(C,N)in V-Microalloyed Steel

The precipitation behavior of V(C,N) in steels microalloyed with vanadium was researched using a thermal simulator during single-pass deformation at 800-750 ℃.The V(C,N) precipitates and its nucleation effect on ferrite were investigated by TEM and EDS.The experimental results show that there are two remarkable heterogeneous nucleation effects of V(C,N) particles precipitated before y→αphase change:primary reason is that high coherency between V(C,N) and ferrite promotes V(C,N) to become a nucleating center of intragranular ferrite;secondary reason is that the coarsening of V(C,N) causes locally solute-poor region in austenite,thus expedites the nucleation of intragranular ferrites further.Furthermore,the relationship between the size and shape of V(C,N)was studied,and identification method was provided for distinguishing interphase precipitation and general precipitation to avoid erroneous judgment and misguide.     

乙烯裂解炉管服役前后材料组织分析

观察分析了服役前后Fe-Cr-Ni耐热钢乙烯裂解炉管横截面组织。由管外壁向内,树枝晶的垂直管外壁沿径向生长的特征逐渐减弱,直至消失。服役前组织为含过饱和碳的奥氏体和沿晶界分布的碳化物。炉管服役过程的时效与渗碳导致大量碳化物的析出,其数量、大小与形态取决于服役温度和时间。析出碳化物影响炉管的性能。