汽车排气系统用耐热材料的抗氧化性能研究

介绍了采用氧化增重法对4种耐热材料进行高温抗氧化性能的对比试验,得出以下结论:(1)QTANi35Si5Cr2材料抗高温氧化性能较差,ZG40Cr25Ni13Nb2Si1和ZG40Cr25Ni12Si2材料抗高温氧化性能较好,ZG40Cr25Ni20Si2材料抗高温氧化性能最优;(2)ZG40Cr25Ni13Nb2Si1、ZG40Cr25Ni12Si2、QTANi35Si5Cr2材料的氧化层由外到内可分2层,一层为富含Fe、O元素的外氧化膜,另一层为富含Cr、Mn、O元素的内氧化膜,ZG40Cr25Ni20Si2材料只观察到一层富含Cr、Mn、O元素的氧化膜,4种材料的氧化层与基体间为一层富含Si元素的过渡区;(3)4种耐热材料氧化层大部分由MnxCryOz氧化物和CrxFeyOz氧化物构成;(4)奥氏体系耐热铸造材料中w(Ni)量越高,越有利于Cr元素的扩散,进而促进Cr2O3保护膜的形成。     

汽车排气系统用耐热材料的抗氧化性能研究(2)

介绍了采用氧化增重法对4种耐热材料进行高温抗氧化性能的对比试验,得出以下结论:(1)QTANi35Si5Cr2材料抗高温氧化性能较差,ZG40Cr25Ni13Nb2Si1和ZG40Cr25Ni12Si2材料抗高温氧化性能较好,ZG40Cr25Ni20Si2材料抗高温氧化性能最优;(2)ZG40Cr25Ni13Nb2Si1、ZG40Cr25Ni12Si2、QTANi35Si5Cr2材料的氧化层由外到内可分2层,一层为富含Fe、O元素的外氧化膜,另一层为富含Cr、Mn、O元素的内氧化膜,ZG40Cr25Ni20Si2材料只观察到一层富含Cr、Mn、O元素的氧化膜,4种材料的氧化层与基体间为一层富含Si元素的过渡区;(3)4种耐热材料氧化层大部分由Mn_xCr_yO_z氧化物和Cr_xFe_yO_z氧化物构成;(4)奥氏体系耐热铸造材料中w(Ni)量越高,越有利于Cr元素的扩散,进而促进Cr_2O_3保护膜的形成。     

合金元素对耐热球墨铸铁耐磨性能的影响

研究了合金元素对耐热球墨铸铁耐磨性能的影响。结果表明,球墨铸铁的磨损失重随Mn、Mo、Cr含量的增加而下降。Mn、Cr的加入均可以提高材料的硬度,并且在共析转变过程中,促进珠光体转变,稳定和细化珠光体,提高球墨铸铁的耐磨性;Mo能提高球墨铸铁组织的稳定性,细化珠光体,从而提高球墨铸铁的耐磨性。适量加入Si(4.5%)可减少铸态组织中的碳化物,提高球墨铸铁的耐磨性,但Si含量过多(5.0%)则会减少珠光体数量,降低球墨铸铁的耐磨性。球墨铸铁磨损失重和摩擦系数均随载荷的增加而增加,但低耐磨性的球墨铸铁试样磨损失重和摩擦系数的增加幅度明显高于高耐磨性的球墨铸铁试样。     

Si对FeMoCrNi高温耐磨合金的组织和抗氧化性能的影响

利用扫描电镜、X射线衍射仪等研究Si对FeMo25Cr14Ni10高温耐磨合金组织及其800℃氧化行为的影响。结果表明:合金的铸态和退火态组织均为α-Fe(Mo,Cr,Ni)+Laves相(Fe2Mo型)。随Si含量增加,合金中铸态组织形态由魏氏体组织转变为枝晶组织。Si的加入明显改善了合金的抗氧化性能,其作用机理在于提高了基体中Cr的含量,促进了致密Cr2O3氧化膜的形成;而Mo和Si在Laves相中的富集增强了中间相的稳定性,抑制了Mo的氧化与挥发。但当Si含量较低时,低熔点Mo氧化物的挥发不能得到完全抑制,外氧化膜较为疏松,并且会产生剥落现象。Si含量为3%~4%(质量分数)的FeMo25Cr14Ni10合金具有优异的抗氧化性能。     

Mn、V、Mo、Ti、Zr元素对AlFeCrCoCu-X高熵合金组织与高温氧化性能的影响

利用非自耗真空电弧熔炼技术,研究等摩尔Mn、V、Mo、Ti、Zr元素对Al Fe Cr Co Cu多组元高熵合金的组织结构、硬度及抗高温氧化性能的影响。结果表明:6组合金都是典型的树枝晶结构,合金组织成分偏析严重,Cu元素大量聚集在晶间,其中,Ti和Zr元素对合金的组织影响最大,两组合金都伴随富Cr组织析出。合金具有较强的硬度,其硬度均与添加元素原子半径成正比。热重分析实验表明:合金具有较强的抗高温氧化能力,在加热到700℃以前,质量几乎保持不变,Al Fe Cr Co Cu合金的抗高温氧化性能最好,而第6元素的添加对合金的抗高温氧化能力不利。其中,V和Mo元素的加入导致其产生的对应氧化物具有易挥发特性而严重地恶化合金的抗高温氧化性能。     

合金元素对球墨铸铁模具材料性能的影响

以废钢和生铁为主要原料,以低碳铬铁、钼铁、Mn钢以及硅铁为添加剂原料,稀土镁(RE5-Mg9)为球化剂,采用中频感应电炉及不氧化法研制球墨铸铁模具材料。探讨了Cr、Mo、Mn以及Si元素添加量对球墨铸铁机床附件模具材料抗拉强度、硬度、抗氧化性能以及耐磨性能的影响。结果表明,最佳球墨铸铁模具材料配方为H3,其抗拉强度为570 MPa,硬度值为22.7HRC,氧化增重速率为0.092 2 g/m2·h,磨损量为0.018 4 g。     

铸态QT800-5悬挂支架铸件的研制

介绍了铸态高强度、高韧性球墨铸铁QT800-5悬挂支架的研制情况,主要技术措施是:(1)选用高C、低P、低S的优质球铁生铁;(2)加入少量的Cu、Mo、Sb等合金元素进行复合强化;(3)球化剂选用Fe Si Mg8RE3,包内孕育剂选用75Si Fe,二次孕育及随流孕育采用自行配制复合孕育剂;(4)球铁原铁液的化学成分控制为:w(C)3.6%~3.8%,w(Si)2.5%~2.8%,w(Mn)0.25%~0.45%,w(S)0.02%,w(P)0.03%,w(Cu)0.2%~0.4%,w(Mo)0.1%~0.3%,w(Sb)0.01%~0.02%。试验结果表明:珠光体体积分数超过95%,含有少量铁素体,石墨球化良好,石墨球细小且均匀,力学性能检测数据符合技术要求。     

Co-Mo-Cr-Si合金组织及其耐铝液腐蚀性能

通过扫描电子显微镜和能谱仪(SEM-EDS)以及X射线衍射仪(XRD)等研究不同含量的Mo、Cr和Si对Co-Mo-Cr-Si合金的组织及其700℃耐铝液腐蚀性能的影响。结果表明:在实验范围内,当w(Si)2.8%时,基体为FCC-Co;而当w(Si)≥2.8%时,基体转变为HCP-Co。随Mo和Si含量增加,Laves相比例增加。在本工作中CoMo4Cr23.8Si0.6合金耐腐蚀性能最好,但由于是单一的固溶体相,基体很软。具有高硬度的CoMo28.5Cr16.7Six合金随着Si含量的增加,其硬度随之增加,耐腐蚀性也随之提高,腐蚀产物主要是(Co,Mo,Cr)2Al9和(Cr,Mo)7Al45。Mo含量较多时主要生成(Mo,Cr)Al5,Cr元素含量较多时主要生成(Cr,Mo)2Al13。     

科技动态

耐腐蚀性能良好的油井管用高强度高Cr钢管的研制据日刊《JFE技报》2005№9报道,日本钢管铸物研究所和知多制造所为克服API-13Cr钢油井管在井下温度超过100℃以上时耐腐蚀性能变差,在高CO2分压下不耐使用的问题,开发出HP13Cr-1、HP13Cr-2和UHP15Cr钢油井管。HP13Cr-1钢的化学成分(质量分数,%)为:C0.025,Si0.25,Mn0.46,Cr13.1,Ni4.0,Mo1.0;HP13Cr-2钢的化学成分(质量分数,%)为:C0.025,Si0.25,Mn0.40,Cr13.0,Ni5.1,Mo2.0;UHP15Cr钢的化学成分(质量分数,%)为:C0.030,Si0.22,Mn0.28,Cr4.7,Ni6.3,Mo2.0,Cu1.0;API-13Cr钢的…     

用代Ni合金生产Ni-Mo球墨铸铁轧辊

进行了用耐热钢用纳米陶瓷复合合金替代纯Ni生产镍钼球墨铸铁轧辊的试验,确定用代Ni合金生产的轧辊化学成分为:w(C)3.1%～3.6%,w(Si)1.4%～1.8%,w(Mn)0.4%～0.8%,w(S残)≤0.02%,w(P)＜0.1%,w(Ni)2.1%～2.5%,w(Cr)0.2%～0.5%,w(Mo)0.5%～0.8%.试验结果表明:加入代Ni合金后的轧辊石墨球径略微变小且球数有增多趋势,组织更加弥散均匀,渗碳体形态由块状趋向更加细小条状,抗事故性能得到了有效提高.     

Cr22合金铸铁溜槽衬板的开发与试验研究

介绍了溜槽衬板的使用工况条件及技术要求,研究开发了新型Cr22MoWVTiNbRE钢铁高炉溜槽衬板,其化学成分为:w(C)2.6%~3.2%,w(Si)0.4%~0.8%,w(Mn)0.5%~1.0%,w(Cr)21.0%~23.0%,w(Mo)0.9%~1.1%,w(W)1.1%~1.8%,w(Cu)0.4%~0.6%,w(V)0.3%~0.5%,w(Ti)0.06%~0.2%,w(Nb)0.1%~0.5%,w(RE)0.04%~0.08%,w(S)≤0.06%,w(P)≤0.06%。热处理工艺为980~1050℃淬火+280~520℃回火,得到的硬度超过63.6HRC,冲击值超过24.66J/cm2;450~520℃二次回火,金相组织为回火马氏体+共晶碳化物(M7C3)+二次碳化物+少量残余奥氏体,得到的铸件硬度超过64HRC。     

低合金钢中合金元素高温氧化行为研究

对低合金钢进行了900~1 200 ℃高温氧化实验,对钢中Si、Mn、Cu、Cr和Ni等合金元素的高温氧化行为进行了研究。结果表明：高温下Si元素与Cu元素存在明显的富集,Si元素会氧化生成Fe2SiO4,阻碍铁离子在氧化铁皮中的扩散,使钢具有一定的抗氧化性;Cu元素可以改善钢的强度、韧性与耐腐蚀性,但是高温氧化后极易形成“富铜液相”,导致出现“铜脆”现象;在1 200 ℃下,Cr元素和Ni元素也会发生富集,Cr在高温下会在氧化铁皮和基体钢之间形成FeCr2O4,同样具有一定的抗氧化性;Mn的氧化物与Fe的氧化物很相似,两者相应氧化物有很高的互溶度;Ni元素对氧化过程没有较大的影响。     

大型高Cr铸铁护套的铸造工艺

介绍了大型高Cr铸铁护套的铸造工艺:(1)确定化学成分为w(C)2.6%~2.9%,w(Si)≤1.0%,w(Mn)0.5%~1.0%,w(P)≤0.08%,w(S)≤0.08%,w(Cr)26%~30%,w(Ni)0.8%~1.0%;(2)采用碱性酚醛树脂砂造型,铸件外部和内腔全部采用砂芯组合形成、分型面设在铸件中部;(3)采用顺序凝固原则,在铸件最高部位设置顶冒口,不易放顶冒口的部位设置侧冒口;浇注温度为1 360~1 410℃,浇注时间为4~5 min。生产结果表明:铸件外表良好、冒口部位无明显缩孔缩松;磁粉探伤,未发现缺陷;尺寸测量合格,热处理后硬度在58~60 HRC。     

减少球墨铸铁管内壁夹渣的措施

研究了铁液化学成分对球墨铸铁管质量的影响,确定成分控制范围为:w(C)3.2%~3.3%,w(Si)1.95%~2.25%,w(Mn)0.4%,w(P)0.06%,w(S)0.05%。由于铸管的主要缺陷是内壁有夹渣,对冲天炉铁液氧化原因进行了分析,并提出了一些预防措施,结果使铸管的伸长率由7%~11%提高到9%~14%、一次水压合格率从97.5%提高到99%。     

Cyclic and isothermal oxidation behavior on some Ni-Cr alloys

Additions of 3 wt.% Mn and 3 wt.% Si were made to Ni-20Cr. These alloys, along with Ni-20Cr and Ni-40Cr were oxidized for 100 1-hr cycles at 1100°C and 50 1-hr cycles at 1200° C. Oxidation behavior was judged by sample weight and thickness change, metallography, x-ray diffraction, and electron microprobe analysis. These tests showed that Ni-40Cr and Ni-20Cr-3Si were about the same and were the most oxidation-resistant alloys. Ni-20Cr-3Mn was not as oxidation resistant, especially at 1200° C. Ni-20Cr was far less oxidation resistant than any of the other alloys. The Ni-40Cr and Ni-20Cr-3Si relied on a protective layer of Cr₂O₃ for their oxidation resistance. A SiO₂ layer was noted beneath the Cr₂O₃ layer on the Ni-20Cr-3Si, but had apparently only a second-order effect. The source of improved protection of the Ni-20Cr-3Mn was apparently the formation of a relatively adherent MnCr₂O₄ layer at the metal-oxide interface.     

Improving the quality of layers deposited on rolling rolls by optimising the composition of flux-cored wires

ABSTRACT

Experiments were carried out to investigate the effect of adding carbon–fluorine compounds (the waste from metallurgical production) and nickel powder to the composition of flux-cored wires of the C–Si–Mn–Cr–W–V and C–Si–Mn–Cr–V–Mo alloying systems. The results show that the addition of these compounds to the composition of the charge for producing the wires of the 35V9Kh3SF and 25Kh5FMS types improves a large number of the characteristics of the deposited layer: reduces the extent of contamination with non-metallic inclusions, increases the hardness of the deposited layer, refines austenite grains and results in the formation of fine-dispersion carbides which in practice may improve the thermal resistance of rolling rolls, and also prevents the formation of a ferrite network which may have a beneficial effect on cracking resistance. The experimental results can be used to develop new compositions of flux-cored wires for hardfacing rolling rolls protected by Russian Federation patents. The hardfacing technologies of the rolls using these flux-cored wires with the C–Si–Mn–Cr–W and C–Si–Mn–Cr–V–Mo alloying systems are now produced by the ElSib company.     

ADI拨叉的壳型铸造和等温淬火工艺

介绍了拨叉铸件的结构和技术要求。铸件采用无冒口铸造工艺生产,原铁液化学成分控制范围为:w(C)3.75%~3.98%、w(Si)1.2%~1.7%、w(S)≤0.08%、w(Mn)≤0.3、w(P)≤0.04,w(Si终)为2.5%~2.8%;出铁温度控制在1 520℃,采用喂丝法进行球化、孕育处理;采用盐浴等温淬火,奥氏体化温度为900℃,保温时间75 min,等淬温度为300~350℃,等淬时间为60 min。最终生产的铸件经过X光检测后可以达到2级甚至1级,铸态金相组织为:球径大小16~60μm,基体组织为铁素体+珠光体;淬火后的金相组织为致密的下贝氏体和20%的残余奥氏体组织,淬火后硬度为302~375 HB。     

The influence of alloying elements on the chlorine-induced high temperature corrosion of Fe-Cr alloys in oxidizing atmospheres

The effect of the alloying elements Al, Cr, Mn, Mo, Si and Ti on the corrosion behaviour of ferritic Fe-15Cr model alloys was studied in a N₂/He-5 vol.% O₂ gas mixture with and without additions of 500–1500 vppm HCl at 600°C. The main corrosion mechanism is “active oxidation”, characterized by the formation of volatile metal chlorides at the metal/oxide interface. Volatilization and subsequent conversion of the chlorides into oxides results in the formation of porous and poorly adherent oxide scales. Large mass gains were observed for Fe-15Cr, Fe-35Cr and Fe-15Cr with additions of 5 wt.% Ti, 10 wt.% Mn or 10 wt.% Mo. The specific morphology of the corrosion products depends strongly on the alloying elements. For the Fe-Cr alloys, a model for the formation of the scales, which are characterized by alternating dense and porous layers, is presented. The addition of 5 wt.% Si or Al to Fe-15Cr leads to much better corrosion resistance by the formation of protective Cr₂O₃/Al₂O₃-layers, however in the case of Al addition the behaviour depends strongly on the experimental conditions, as surface treatment and flow velocity. In Fe-15Cr-10Mo preferential removal of the more reactive metals Fe and Cr was observed resulting in a Mo-enriched porous metal zone underneath the metal-oxide interface. The effect of carbon on the corrosion behaviour was examined by addition of 0.3–0.8 wt.% C to the model alloys. Cr-rich M₂₃C₆-carbides were attacked preferentially while Mo-rich M₆C-carbides are very stable relative to the matrix and the attack occurs in regions surrounding the carbides.     

High-temperature oxidation behavior of Mo–Si–B-based and Co–Re–Cr-based alloys

Improving the efficiency of aerospace gas turbine engines requires materials that can be used at increasingly higher temperatures in aggressive environments. This paper summarizes the current stage of alloy development of Mo–Si–B-based and Co–Re–Cr-based alloys regarding the high-temperature oxidation resistance. Since refractory metals, such as Mo and Re, suffer from catastrophic oxidation, the main task of research is to find alloying elements that improve the oxidation behavior of these alloys. For Mo–Si–B-based alloys, it was observed that an addition of Zr has a significant positive influence on the oxidation resistance by reducing the time necessary for the formation of a protective borosilicate layer. An addition of 0.2 at.% Y improves the viscous properties of the borosilicate increasing the protectiveness of the oxide scale. Macroalloying with Ti yields a strong positive effect on the oxidation behavior and, in addition, notably reduces the density of Mo–Si–B-based alloys. In Co–Re–Cr-based alloys, Cr is included to achieve favorable mechanical properties and to form a protective chromia layer during oxidation. As a consequence of the synergetic effect of Cr and Si, an addition of 2 at.% Si significantly improves the oxidation behavior of the alloy. Al addition further promotes the formation of the protective chromia layer at intermediate temperatures and exhibits the potential of the formation of a protective alumina scale suitable for applications at very high temperatures. The critical evaluation of the complex oxidation behavior of both metallic systems in a broad temperature range gives insight into the underlying fundamental mechanisms, reveals the potentials of particular alloying elements and, thus, guides future development of these material classes.     

Cr对钢耐海水腐蚀性的影响

获得了５种含铬低合金钢在海水中暴露１、２、４、８（７）年的腐蚀数据,讨论Ｃｒ对钢耐海水腐蚀的影响,铬钢的耐海水腐蚀性不仅与Ｃｒ的含量有关,还与其他复合合金元素有关。短期浸泡时,钢的耐海水腐蚀性随铬含量（无其他合金元素复合）增加而提高。长期浸泡,Ｃｒ对钢的耐海水腐蚀性有害,约１％Ｃｒ与Ｍｏ（－Ａｌ）复合对钢的耐海水腐蚀性的影响与Ｃｒ的影响没有左别大于２％Ｃｒ与Ｍｏ（－Ａｌ）复合大幅度提高钢在海水中短期浸泡的耐蚀性,并使耐蚀性逆转时间明显推迟.小于1%Cr与Mn-Cu、Cu-Si-V、Ni-Cu-Si、Ni-Mn等复合对钢的耐海水腐蚀性有害。