铸态合成蠕墨铸铁的组织与力学性能研究

以RuT500蠕墨铸铁为目标选择了基本元素含量范围,采用中频感应电炉制备了废钢与高纯生铁配比分别为3∶7和6∶4的Cu、Sn合金化合成蠕墨铸铁,并采用光谱分析仪、金相显微镜和万能材料试验机测试了其化学成分、金相组织和力学性能。结果表明,当废钢与高纯生铁配比为3∶7时,铸态合成蠕墨铸铁的基体组织为85%P+15%F,蠕化率为85%,力学性能R_m、A、硬度分别为562 MPa、1.1%、235HBW;当废钢与高纯生铁为6∶4时,基体组织为95%P+5%F,蠕化率83%,R_m、A、硬度分别为572 MPa、0.7%和256HBW。     

干扰元素对铸铁组织和性能的影响

介绍了来源于铸造生铁中的S、P、Pb和废钢中的Mn、Cr、Ni、Mo等元素在铸铁中形成碳化物,影响球化,增大缩孔缩松倾向,降低灰铸铁强度的情况。提出了消除其有害影响的主要措施:(1)严格管理炉料、控制铁液的化学成分;(2)加入抗干扰元素;(3)采用高纯铸造生铁。认为使用高纯生铁是解决原材料困扰的重要途径之一。     

合成铸铁工艺的试验研究

在中频感应电炉上进行合成铸铁的试验,以50%废钢 50%新生铁的炉料配比,用鳞片状石墨充分浸润的增碳工艺,抗拉强度普遍提高10～20MPa,壁厚敏感性(不同截面硬度差)ΔHBmax降低10～20HB,三角试片白口宽度在1～3mm。合成铸铁、复合孕育再辅之以低合金化的试验铸铁(Cu:0.35%～0.45%,Cr:0.15%～0.25%),与普遍铸铁相比,抗拉强度明显高一个牌号,并且机械性能波动范围不大。     

风电用QT400-18AL合成球墨铸铁的力学性能研究

采用中频感应炉熔炼,制备了某型机用合成球墨铸铁和传统球墨铸铁,对比了两者的力学性能和断口特征,分析了两种铸铁的断裂机理。结果表明,用大量废钢加增碳剂制备的合成球墨铸铁球化率高,石墨球圆整,100%铁素体(F)基体。合成球墨铸铁冲击韧性显著提高,韧-脆转变温度为-40℃,相比传统球墨铸铁降低了60℃。合成球墨铸铁的基体塑性好,抵抗裂纹扩展能力强,拉伸试样断口上留下大量深韧窝和撕裂棱,属于韧性断裂。     

原材料对冷激铸铁凸轮轴组织和性能的影响

详细地研究了主要原材料(生铁、废钢、增碳剂)对冷激灰铸铁神龙凸轮轴组织和性能的影响.试验表明:炉料质量的好坏是生产优质凸轮轴铸件的基础,生铁等炉料的"遗传性"是铸铁冶金学中需要注意的课题,试验确定的神龙凸轮轴生产用主要炉料有Q10生铁、汽车用碳素废钢、增碳剂等;要求生铁和废钢Ti等微量元素含量低,增碳剂固定碳含量高等;同时要求生铁、废钢必须经过抛丸处理,清除表面粘砂、锈蚀和油污.炉料配比对神龙凸轮轴的材质性能影响很显著,废钢的加入会改善凸轮轴的性能,但加入量大时,铁水的白口倾向增大,需加入大量增碳剂;增碳剂会显著降低铁液的白口化倾向,改善凸轮轴轴颈断口形貌和组织性能,对凸轮桃尖硬度影响很大,因此需控制好废钢和增碳剂的最佳配比,否则会引起较高的材质废品.生产中炉料配比应稳定,试验确定的适宜炉料配比为:生铁:废钢:回炉料=20%:2.5%:77.5%,各种炉料必须按工艺要求进行仔细称量.     

高性能合成灰铸铁的凝固与组织分析

采用500kg中频感应炉熔化,生产条件下对比研究了普通和合成铸铁的组织。加入0.3%FeSi75+0.3%稀土锶钡复合孕育剂,普通铸铁基体组织为98%P+~2%F,石长0.19~0.29 mm,共晶团500个/cm~2,γ_(初生)占截面面积的50%。采用加入0.6%FeSi75普通孕育处理工艺,以60wt%(70wt%)废钢结合增碳熔炼的合成铸铁,基体组织为95%P+5%F(90%P+10%F),石长0.08~0.16 mm(0.06~0.15 mm),共晶团1000个/cm~(1040个/cm~2),发达的网状γ_(初生)占截面面积的80%(80%)。合成铸铁形成这种优异组织,是由于特殊的液态不均匀原子团簇组结构改变了铸铁传统凝固模式所致。     

合成铸铁在缸体生产中的应用

为解决铸铁熔炼所需原材料生铁价格的不断上涨,以及生铁的长期使用带来的遗传影响,使铸铁产品的力学性能和金相组织出现一定恶化等问题,在缸体类铸铁产品的生产中,采用合成铸铁,即废钢加增碳剂增碳的方式进行铸铁生产.通过试制,采用合成铸铁生产的缸体类产品力学性能和金相组织均优于传统熔炼工艺生产的铸铁产品,提高了质量,降低了成本.     

合成铸铁的生产工艺

0前言利用废钢和回炉料,在电炉中加入增碳剂进行增碳生产的合成铸铁,成本低,性能优越[1]。作者从事合成铸铁的生产多年,现就合成高强度灰铸铁的生产工艺技术作浅略的探讨。1合成铸铁的性能特点在电炉中以废钢作炉料,用增碳剂(如电极)进行增碳生产的合成铸铁件,由于炉料纯净,铁液含硫量低,纯净度高,夹杂物少,实践表明与用生铁熔炼的铸件相比,有较好的力学性能、工艺性能和使用性能。11力学性能。文献表明[2],合成铸铁在相同碳当量的条件下,其抗拉强度比普通灰铸铁高30MPa左右。在碳当量38％～40％之间,能稳定地获得HT2…     

合成铸铁生产缸体铸件的工艺技术

考虑到大量使用生铁使铁液收缩倾向增大且使铸件性能降低,以及为解决铸铁熔炼所需原材料生铁价格不断上涨等问题,在缸体类铸铁产品的生产中,采用合成铸铁,即废钢加增碳剂增碳的方式进行铸铁生产。此工艺采用增硫防止石墨长成粗大片状,适当的合金化和孕育处理,可以使铁液的收缩倾向得到明显改善。采用合成铸铁生产的缸体类产品力学性能和金相组织均优于传统熔炼工艺生产的铸铁产品。     

风电前箱体铸件的生产工艺

介绍了风电前箱体铸件的结构及技术要求,详细阐述了铸件的生产工艺:采用封闭、中注式浇注系统,在厚大部位设置冒口,并在相应位置设置多块冷铁,减少缩孔、缩松缺陷;炉料配比为80%~90%Q10生铁+5%~10%废钢+5%~10%回炉料,球化处理采用堤坝坑处理包冲入法工艺,分2次出铁,孕育剂分3次加入;浇注温度控制在1 340~1 350℃。试生产结果显示:球化率达到92%以上,基体中铁素体体积分数≥90%,抗拉强度达到400 MPa以上,屈服强度达到250MPa以上,伸长率达到21%以上,-20℃条件下V形缺口试样的冲击功为11~16 J,平均值≥14 J,超声波探伤达到1级。     

Analysis of ductile iron production on steel scrap base

The cast iron production (melting) process is commonly based on pig iron. However, economic and ecological factors necessitate that the melting process is more often based on steel scrap (with no pig iron at all). This kind of cast iron is called synthetic cast iron. This approach may, however, cause a decrease in the quality of the alloys obtained, particularly when ductile iron (DI) is produced. The following article presents an analysis of the product and some aspects of ductile iron produced exclusively on a base of steel scrap. The experiments and the charging materials are described. The results of the chemical analysis of the produced DI, the carburisation efficiency and microstructure of the obtained material are presented as well. The results of cast iron melted on a pig iron base are presented for comparison. A quantitative microstructure analysis is also presented.     

Effects of forced cooling on mechanical properties and fracture behavior of heavy section ductile iron

To develop materials suitable for spent-nuclear-fuel containers, the effect of forced cooling on mechanical properties and fracture toughness of heavy section ductile iron was investigated. Two cubic castings with different cooling processes were prepared: casting A was prepared in a totally sand mold, and casting B was prepared in a sand mold with two chilling blocks placed on the left and right sides of the mold. Three positions in each casting with different solidification cooling rates were chosen. In-situ SEM tensile experiment was used to observe the dynamic tensile process. Fracture analysis was conducted to study the influence of vermicular and slightly irregular spheroidal graphite on the fracture behavior of heavy section ductile iron. Results show that the tensile strength, elongation, impact toughness and fracture toughness at different positions of the two castings all decrease with decreasing cooling rate. With the increase of solidification time, the fracture mechanism of conventional casting A changes from ductile fracture to brittle fracture, and that of casting B with forced cooling changes from ductile fracture to a mixture of ductile-brittle fracture.     

ADI的冲击韧度和断裂韧度

论述了ADI的冲击韧度和断裂韧度。室温有缺口和无缺口ADI的冲击韧度比铸钢,锻钢要略差,但约是普通珠光体球铁的3倍,ADI的冲击韧度虽随温度降低而降低,但在-40℃条件下仍保持大约室温冲击韧度的70%。断裂力学性能是更重要的安全设计和失效分析依据,无论哪一种断裂韧度,ADI的试验数据都好于普通球铁,相当于或好于强度相当的铸钢和锻钢。     

Effect of Bi on graphite morphology and mechanical properties of heavy section ductile cast iron

To improve the mechanical properties of heavy section ductile cast iron, bismuth （Bi） was introduced into the iron. Five castings with different Bi content from 0 to 0.014 wt.% were prepared; and four positions in the casting from the edge to the center, with different solidification cooling rates, were chosen for microstructure observation and mechanical properties test. The effect of the Bi content on the graphite morphology and mechanical properties of heavy section ductile cast iron were investigated. Results show that the tensile strength, elongation and impact toughness at different positions in the five castings decrease with a decrease in cooling rate. With an increase in Bi content, the graphite morphology and the mechanical properties at the same position are improved, and the improvement of mechanical properties is obvious when the Bi content is no higher than 0.011wt.%. But when the Bi content is further increased to 0.014wt.%, the improvement of mechanical properties is not obvious due to the increase of chunky graphite number and the aggregation of chunky graphite. With an increase in Bi content, the tensile fracture mechanism is changed from brittle to mixture ductile-brittle fracture.     

高韧性等温淬火球铁力学性能的研究

根据欧洲等淬球铁标准EN1564的数据，建立各力学性能之间的数学模型。对高韧性等淬球铁铸件的生产检测结果进行了分析，发现合金化的高韧性等淬球铁铸件的力学性能之间的关系与一般非合金化等淬球铁铸件不同，其伸长率、冲击韧度、屈服强度、硬度在一定范围内随抗拉强度的提高改变不大。生产实践证明：设计合理的化学成分，经过适当的合金化，铸造优质的球铁毛坯，采用有效的热处理工艺，可大幅度提高等淬球铁的综合力学性能，稳定生产高韧性等淬球铁铸件。     

Effect of C and Si on mechanical properties of austempered ductile iron

It is well known that ductile cast iron can be strengthened and toughened by austempering. The tensile strength and the fatigue strength of austempered ductile iron (ADI) are equal to those of forged steel. Previous studies have been aimed at establishing a suitable process to obtain both strength and toughness in ADI.^1,2 These studies focused on the effect of alloying such as Mo, Ni, Mn, Cu, etc. and the austempering conditions such as temperature and holding time. In this study, a new type of ADI with higher toughness and higher elongation was developed as compared with conventional ADI. A new type of ADI with a low carbon content was achieved by reducing the initial carbon content, long annealing and ordinary austempering. The suitable silicon content was found to be 2.5% and effective alloying was 0.25% Mo and 0.7% Cu to obtain maximum impact energy and elongation.     

The influence of copper on microstructure and mechanical properties of compacted graphite iron

Abstract

The influence of copper content (0·26 to 1·31 wt-%) on microstructure formation and mechanical properties of compacted graphite iron (CGI) has been evaluated through standard metallographic analysis, colour etching techniques and tensile testing of machined test bars. The properties investigated are yield strength, tensile strength and elongation. The castings were made in an industrial environment from a combination of CGI returns, pig iron, cast iron- and steel scrap. A total of four heats were cast in specially designed sampling cups (3 different cooling rates), chill wedges as well as tensile test bars machined from sand moulded cylinders (20, 45 and 85 mm in diameter). The results clearly illustrate the combined effect of copper and cooling rate on nodularity, chilling tendency as well as pearlite content. A discussion concerning the effect of graphite morphology on the ferrite growth is also included.     

Processing of high carbon Fe3Al based intermetallic alloy

A melting procedure for air induction melting (AIM) of an Fe₃Al based intermetallic alloy Fe-15.38 wt%Al-1.1 wt%C is described. Use of an appropriate slag cover during AIM results in elimination of hydrogen gas porosity in cast AIM ingots. Criteria for slag selection and slag to metal ratio are discussed. Refining by slag-metal reactions results in significant reduction in impurity levels (S, O, N) during AIM. Consequently, low cost raw materials such as mild steel scrap and commercial aluminium were used for melting the alloy. The AIM ingot exhibited excellent tensile properties. The ductility and hot workability of the ingot may be further improved by subsequent processing through electroslag remelting. It is also argued that the presence of carbon may be necessary to get AIM castings with desirable mechanical properties.     

合成球墨铸铁技术在轧辊生产中的应用

对复合轧辊所用合成球墨铸铁的增碳原理及实际生产工艺进行了论述,并分析了采用增碳工艺后合成球墨铸铁的组织和性能,结果表明,影响增碳吸收率的因素主要有增碳剂的粒度、熔炼过程中铁液的搅拌、铁液的化学成分、铁液饱和浓度、增碳剂加入量.采用增碳工艺后,铸铁组织明显改善,石墨均匀分布,且形态得到明显改善,石墨球化良好,未出现片状组织,铸件硬度提高,硬度更加均匀.