Niobium alloying effect in high carbon equivalent grey cast iron

The effect of niobium on the formation of NbC phase and solidification structure in high carbon equivalent grey cast iron was investigated.The experimental results indicated that an increase in the niobium content is favorable to refining the graphite and eutectic cell;and the pearlite lamellar spacing is reduced.Based on the thermodynamic calculation the formation of NbC is prior to the eutectic reaction.The reduction in the pearlite lamellar spacing is mainly attributed to the decrease of eutectic temperature with the addition of niobium.Additionally,properties including hardness and wear resistance were improved after the addition of niobium.

Effect of Rare Earth Elements on Carbide Morphology and Phase Transformation Dynamics of High Ni-Cr Alloy Cast Iron

The effect of rare earth(RE) elements on carbide of high NiCr alloy cast iron was investigated. Meanwhile, the continuous cooling transformation(CCT) curves of cast iron with and without RE addition were determined. The results show that the carbides in high NiCr cast iron can be refined and changed from network and long strip structures into island and block ones. The phase transformation temperature was raised and incubation period of bainite transformation was shortened by adding RE element in high NiCr alloy cast iron.

Effect of Rare Earth Elements on Thermal Fatigue of High Ni－Cr Alloy Cast Iron

The effect of RE on crack forming and developing of hot rolled high Ni-Cr alloy cast iron during thermal fatigue test was investigated.It shows that the serviceable life of hot rolled high Ni-Cr alloy cast iron can be improved by RE.The number of cycle before fracture was increased by 42%～163%.The optimum of RE addition is 0.05 wt%～0.15wt%.

Effect of Ti-V-Nb-Mo addition on microstructure of high chromium cast iron

The effects of trace additions of multi-alloying elements （Ti, Nb, V, Mo） on carbides precipitation and ascast microstructure of eutectic high chromium cast iron containing 2.85wt.%C and 31.0wt.%Cr were investigated from thermodynamic and kinetic considerations. The thermodynamic calculations show that Ti and Nb exist in the multi-alloying system in the forms of TiC and NbC. The formation of VC during the solidification is not feasible from the thermodynamic consideration. XRD analysis shows that the V exists in alloy compounds （VCr2C2, VCrFes）. The first precipitated high melting point particles （TIC, NbC） can act as the heterogeneous substrate of M7C3 carbides, which results in significant refinement of the M7C3 carbides. After the addition of alloying elements, C atom diffusion is hindered due to the strong affinities of the strong carbide forming elements for carbon, which decreases the growth rate of carbides. The combined roles of the increase of nucleation rate and the decrease of carbides growth rate lead to the finer microstructure.

Effect of Rolling Process on Microstructure and Wear Properties of High Carbon Equivalent Gray Cast Iron

Rolling process based on the plastic deformation as a surface strengthening treatment was employed,aiming to improve the wear resistance ability and functional performance of the high carbon equivalent gray cast iron(HCEGCI).The microstructures and tribological performance of the untreated and rolled samples were characterized.In addition,the wear mechanism of HCEGCI samples was also studied via pin-on-disc tests.The experimental results show that the as-rolled samples possess the structure-refined layer of 15μm and work-hardened layer of 0.13 mm.In comparison with the surface hardness of untreated samples,the surface hardness of as-rolled samples increases by 84.6%(from 240HV0.1 to 443HV0.1)and the residual compressive stresses existed within the range of 0.2 mm.The wear rates of as-rolled samples were decreased by 38.4%,37.5%,and 44.4%under different loads of 5 N,10 N,and 15 N,respectively.The wear characteristics of the untreated samples mainly exhibit the peeling wear coupled with partial adhesive and abrasive wear.However,as for the as-rolled samples,the adhesive wear was limited by the structure-refined layer and the micro-crack propagation was controlled by the work-hardened layer.Therefore,the wear resistance of as-rolled samples can be improved significantly due to the low wearing degree of the friction contact zone.

Thermal and microstructural characterization of a novel ductile cast iron modified by aluminum addition

In high-temperature applications,like exhaust manifolds,cast irons with a ferritic matrix are mostly used.However,the increasing demand for higher-temperature applications has led manufacturers to use additional expensive materials such as stainless steels and Ni-resist austenitic ductile cast irons.Thus,in order to meet the demand while using low-cost materials,new alloys with improved high-temperature strength and oxidation resistance must be developed.In this study,thermodynamic calculations with Thermo-Calc software were applied to study a novel ductile cast iron with a composition of 3.5wt%C,4wt%Si,1wt%Nb,0‒4wt%Al.The designed compositions were cast,and thermal analysis and microstructural characterization were performed to validate the calculations.The lowest critical temperature of austenite to pearlite eutectoid transformation,i.e.,A1,was calculated,and the solidification sequence was determined.Both calculations and experimental data revealed the importance of aluminum addition,as the A1 increased by increasing the aluminum content in the alloys,indicating the possibility of utilizing the alloys at higher temperature.The experimental data validated the transformation temperature during solidification and at the solid state and confirmed the equilibrium phases at room temperature as ferrite,graphite,and MC-type carbides.

Electron theory study on the effect of Mn on as-cast structure of Fe-C-Cr-Mn cast irons

The valence electron structure of alloying austenite of 3C-15Cr high chromium white cast iron with different Mn contents from 1% to 6% is analyzed by BLD method and EET. Results show that the addition of Mn has major influence on the valence electron structure of the alloying austenite, especially on that of Fe-C, Fe-C-Cr and Fe-C-Cr-Mn unit cells of it. The effect becomes weak when Mn content is over 4%. Based on the effect of n~, F~~, the weighting of each unit cell and the degree of undercooling on phase transition of the aus- tenite, we can calculate the retained austenite content of as-cast structure of the high chromium white cast iron. The calculation results coincide well with those of the experiment. The phase transition characters of the austenite in high chromium white cast iron can be forecasted through valence electron structure analysis of alloying austenite by BLD method and EET on the basis of Fe-C-Cr equilibrium phase diagram.

铸态QT700-2偏心体铸件的研发

本文介绍铸态QT700-2偏心体铸件的研发过程。在铸造工艺方案上采用分层浇注,在铸件热节部位使用冷铁,并且结合保温冒口工艺,使铸件达到均衡凝固,消除铸件的缩松、缩孔缺陷;在熔炼过程通过合金化,使用低稀土球化剂,采用多次孕育处理,消除了碎块状石墨、细化了石墨晶粒、稳定了珠光体含量,生产的铸态偏心体的性能满足客户要求。

ICP-OES法测定高镍合金铸铁中锰铬镍铜

高镍合金铸铁已广泛用于制造耐高温的反应器、换热器等设备和构件以及高强度、高韧性的机械零件,先行国家标准方法对铸铁中高含量元素的测定都有局限性。本实验建立了电感耦合等离子体原子发射光谱法(ICPOES)同时测定高镍铸铁中锰、铬、镍、铜元素的方法。试验探讨了不同溶解方法对分析结果的影响,优选出最佳溶样方法:先加(1+1)硝酸溶解样品至剧烈反应后滴加浓盐酸和氢氟酸,最后加入高氯酸加热至冒烟,定容后测定。将该法应用于实际样品测定,测定结果锰的质量分数在0.05%~4%,镍的质量分数在0.05%~40%,铬的质量分数在0.05%~5%,铜的质量分数在0.05%~10%范围内。在选定的仪器工作条件下,各元素的校准曲线线性相关系数均大于0.999,方法中各元素的回收率为98.0%~105.6%,实际样品分析相对标准偏差RSD≤2.00%(n=11),将本方法应用于高镍铸铁标准物质中锰、铬、镍、铜元素的测定,结果与证书标称值吻合。

双金属液液复合界面净化剂的研究及应用

本文通过SEM元素分析、ICP等表征手段,揭示了净化剂的形貌和结构特征,发现硼酸和硅酸盐的含量以及配制方法对净化剂的性能影响较大。优化了净化剂产品配方,开发了双金属液液复合界面净化剂,将双液第一层金属液界面凝固时间缩短6~10 s,实现了快冷、防氧化和净化作用。不仅便于连续生产,同时界面扩散宽度增加49%,界面结合强度提高了41.5%,冲击韧性提高了15.6%。

基于文献计量学的高铬铸铁组织及性能研究进展

耐磨材料在工业发展中起到关键作用,其中高铬铸铁因其耐磨性能优异、成本较低得到了快速发展。高铬铸铁的研究主要集中在制备工艺、组织与性能调控、耐磨性等几个方面。本研究借助文献计量学方法对近年来的研究进行了梳理,介绍了研究的侧重点,并从耐磨性研究的最新进展、合金成分和热处理对组织及性能的影响,总结了近年来的研究现状。研究表明,M_(7)C_(3)型碳化物是高铬铸铁组织中最重要的强化相,能够显著提高基体的强度和耐磨性能。对高铬铸铁进行热处理,能够细化晶粒,提高硬度和耐磨性。另外,通过添加合金元素或者加入强化相也能提高高铬铸铁的性能,例如,添加Ti_(2)AlC后材料的力学性能明显提高。总之,对高铬铸铁的制备工艺、组织与性能调控、耐磨性等方面进行研究,有助于优化其性能并扩大其应用领域。

高强韧珠光体球墨铸铁的研究

在球墨铸铁成分优化基础上,用万能材料试验机、布氏硬度计和金相分析显微镜研究了球墨铸铁经多元合金化、型内孕育处理和等温正火后的组织和和性能。结果表明:经Cu、Mo、Sb多元合金化和型内孕育处理的球墨铸铁,其铸态和等温正火处理后的组织明显改善,共晶团数目增加,基体组织细化,石墨球形态圆整、细小,珠光体数量增多,比例均大于90%,力学性能显著提高。与未合金化的球墨铸铁比,Cu,Mo,Sb多元合金化的球墨铸铁,其铸态和等温正火处理后的屈服强度R_(0.2)、抗拉强度R_(m)和硬度HB分别提高了25%、20%,47%、17%,41%、11%,达到502、620 MPa,811、975 MPa,256HB、298HB,伸长率A均大于6%。

ZTA增强高铬铸铁的制备工艺和性能研究的现状

氧化锆韧化氧化铝(zirconia toughened alumina, ZTA)是一种陶瓷材料,可添加于高铬铸铁以提高其硬度、比强度、耐磨性、塑性和韧性等性能。综述了目前ZTA增强高铬铸铁制备工艺和性能研究的状况,制备工艺包括铸渗法、烧结法、铸造法、堆焊法和复合法,性能包括界面性能、耐磨粒磨损性能、摩擦磨损和冲蚀磨损性能及其通过合金化进一步改善。

高硬度过共晶高铬铸铁的合金化与热处理工艺研究

通过Nb、W、V和B合金化,使过共晶高铬铸铁的铸态硬度得到显著提高。高硬度主要来源于碳、硼化物比例的显著提高和碳、硼化物尺寸的明显细化。大尺寸的碳化物明显消失,微观组织更加均匀,使合金化铸态硬度达到了未合金化样品热处理态的硬度水平。将过共晶高铬铸铁在不同热处理方案下的硬度值进行对比,结果表明,快速冷却相比缓慢冷却会使过共晶高铬铸铁的硬度增加,较低的温度、较长的加热时间以及较长的固溶时间会产生更高的硬度值,炉冷或空冷等回火冷却方式对硬度值影响较小。这为过共晶高铬铸铁提高硬度值、简化热处理流程以及优化生产工艺提供了理论借鉴。

高铬铸铁中铌的研究综述

论述了高铬铸铁的发展和应用情况,介绍了铌在高铬铸铁中的形态和对组织的作用,以及含铌高铬铸铁的性能特点,在耐磨领域、堆焊领域和冷轧辊领域的应用情况;综述了国内外这些方面的研究成果。

高铬铸铁初生碳化物细化的中外研究进展

从合金化、变质处理、过流冷却三个方面对高铬铸铁中初生碳化物细化的国内外最新研究成果进行了分析研究,并且进一步提出了在研究过程中的不足和未来研究中有待研究的问题,同时展望了未来高铬铸铁中初生碳化物细化的研究发展前景。

高强度灰铸铁生产技术新进展

从优化化学成分、提高铁液纯净度和成分均匀性,强化孕育效果等方面介绍了高强度灰铸铁生产技术的最新进展。通过资料总结认为:灰铸铁生产技术的主要发展方向是高CE、高强度、高Si/C比、低应力和良好的加工性能;难点是获得高温、成分稳定、纯净度高的铁液和强化孕育。

灰铸铁表面WC颗粒-高铬铸铁铸渗层研究

采用铸渗技术，研究了在灰铸铁表面获得良好WC颗粒－高铬铸铁铸渗层工艺以及铸渗层组织和耐磨性。结果表明，在适宜工艺条件下，铸渗层平整、均匀、与基体结合良好，具有优良的抗磨粒磨损性能。用WC颗粒－高铬铸铁铸渗法制造的灰铸铁基搅拌机叶片，其使用寿命是Q235钢制叶片的三倍以上。

Fe-Cr-C系高碳高铬耐磨堆焊合金微观组织分析

研究了C元素含量6.0%左右时改变Cr元素含量和Cr元素含量40%左右时改变C元素含量两种情况下Cr及C元素各自对Fe-Cr-C合金堆焊层组织的影响。结果表明,C和Cr元素增加时,初生碳化物的量增加。初生碳化物随着C元素和Cr元素的增加,形态越来越规则,分布越来越密集,初生碳化物颗粒的单个尺寸增大。C元素含量6.0%左右,Cr元素含量增大时,初生碳化物微区Cr元素含量增加;而当Cr元素含量40%左右,C元素含量增加时,初生碳化物微区Cr元素含量反而降低。

薄壁缸体铸件中合金元素的选择

针对柴油机薄壁缸体铸件 ,试验了少量合金元素铬、铜、锑和锡对高碳当量灰铸铁抗拉强度、硬度及白口倾向的影响。结果表明 :合金元素铬和铜对灰铸铁的强度有明显的影响 ,在碳当量为3 8%～4 1 %的条件下 ,铁液中合金元素铬、铜和锑的合理含量( %)分别为 :0 20～0 25、0 40～0 45以及0 02。试验条件下 ,合金元素锡的作用不太明显。初步分析了合金元素铬和铜对灰铸铁强度及组织的影响机理。此外 ,还进行了实际薄壁缸体铸件的浇注试验。