高铬白口铸铁干滑动摩擦磨损特性的研究

研究了两种碳化物 ((Fe,Cr) 2 3 C6型碳化物和 (Fe,Cr) 7C3 型碳化物 )和 3种基体组织 (共析组织、马氏体组织和奥氏体组织 )的高铬白口铸铁与淬火 4 0Cr钢对磨时的干滑动摩擦磨损特性。试验结果表明 ,与(Fe,Cr) 2 3 C6型碳化物相比 ,(Fe,Cr) 7C3 型碳化物有利于提高高铬白口铸铁的耐磨性 ,降低其摩擦系数 ;在高接触应力情况下 ,与马氏体和奥氏体基体的合金相比 ,共析组织基体的合金具有更大的摩擦系数 ,其耐磨性也更好。     

镶铸高铬白口铁锤头的研制

本文分析锤头镶铸工艺中白口铁镶块裂纹的产生原因．指出白口铁镶块的过度升温是产生裂纹的主要原因；镶铸部位钢与铁的截面积应有合适的比例。     

Ultrahigh-carbon “wootz” from crucible carburization of molten iron: Hypereutectoid steel from “Tamil Nadu Process” at Mel-siruvalur

ABSTRACT

As European and Mediterranean accounts indicate, India has been famed for the production of steel, apparently made by crucible processes. Late medieval traveler’s accounts record the making of “wootz” steel in several places in southern India. This material was used for the fabled Damascus swords, which were later found to be of ultrahigh-carbon steel. Whereas studies on Asian crucible steel making from India, Central Asia and Sri Lanka have discussed various processes ranging from co-fusion of cast iron and wrought iron to solid-state carburization of wrought iron, it has been difficult to find clear evidence relating to an end product of ultrahigh-carbon steel. In this light, the archeometallurgical evidence from Mel-siruvalur in Tamil Nadu, presented in this paper, is significant in that it shows unmistakable remnants in crucibles of ultrahigh-carbon, hyper-eutectoid steel, with a likely production mechanism of molten carburization of wrought iron to steel. The favorable comparison with ultrahigh-carbon steel finds dated to early historic or megalithic times in Tamil Nadu and southern India also suggest that this method of crucible steel manufacture, which may be described as the “Tamil Nadu process”, might have been earlier or more archaic than the co-fusion process.     

Mechanical properties of a carbide-free bainitic cast steel with dispersed free ferrite

ABSTRACT

A high silicon, medium carbon cast steel was designed and heat-treated in order to develop microstructures composed of carbide-free bainite and small amounts of free ferrite, with the aim of obtaining high strength cast steels with improved ductility. Because of microsegregation, it was observed that ferrite present in partially austenitised samples is mostly present at the highly alloyed zones, creating an interconnected network even for low proportions of this phase. Despite the coarse solidification structure and marked microsegregation in the cast steel, the mechanical properties obtained for both fully bainitic and bainitic-ferritic microstructures largely satisfy the minimum standard requirements for high strength cast steels and are similar to those reported for wrought steels of similar microstructures.     

Microstructure and mechanical properties of high boron white cast iron

In this paper, high boron white cast iron, a new kind of wear-resistant white cast iron was developed, and its microstructure and mechanical properties were studied. The results indicate that the high boron white cast iron comprises a dendritic matrix and an interdendritic eutectic boride in as-cast condition. The distribution of eutectic boride with a chemical formula of M₂B (M represents Cr, Fe or Mn) and with a microhardness of HV2010 is much like that of carbide in high chromium white cast iron. The matrix includes martensite and a small amount of pearlite. After quenching in air, the matrix changes to martensite, but the morphology of boride remains almost unchanged. In the course of austenitizing, a secondary precipitation with the size of about 1 μm appears, but when tempered at different temperature, another secondary precipitation with the size of several tens of nanometers is found. Both secondary precipitations, which all forms by means of equilibrium segregation of boron, have a chemical formula of M₂₃(C,B)₆. Compared with high chromium white cast iron, the hardness of high boron white cast iron is almost similar, but the toughness is increased a lot, which attributes to the change of matrix from high carbon martensite in the high chromium white cast iron to low carbon martensite in the high boron white cast iron. Moreover, the high boron white cast iron has a good hardenability.     

高铬白口铁－钢双金属焊铸初探

本文初步探讨了在高铬白口铁镶件表面上镀上一定厚度的铜，然后浇注铸钢的焊铸法生产双金属，该法工艺简单，双金属结合牢固，具有实际使用价值。     

Design of a new nanostructured,high-Si bainitic steel with lower cost production

To reduce cost production, a bainitic steel with a new chemical composition was designed using MUCG83 thermodynamic model. The steel was cast as cylinder bar using a high frequency induction furnace under argon gas atmosphere. The cast cylinder was electro-slag remelted (ESR) for obtaining clean steel. Hot rolling was carried out after ESR to reduce the thickness and to change the cast structure to a wrought structure. To obtain a bainitic structure the austenitized samples were transformed isothermally at the temperature range of 200–300 °C for different times and finally were quenched into water. The microstructures were characterized by X-ray diffraction, scanning electron and transmission electron microscopes. The tensile and Charpy impact tests were carried out to evaluate the mechanical properties. The results show a good combination of high tensile strength and impact toughness which is ideal for high performance applications. The prominent mechanical properties are due to the unique microstructural characteristics which are evolved during isothermal transformation.     

Investigation of microstructure and mechanical properties of steel fibre–cast iron composites

Abstract

The aim of the present experimental study was to investigate improvement of the toughness and strength of grey cast iron by reinforcing with steel fibres. The carbon content of the steel fibres was chosen to be sufficiently low that graphite flakes behaving as cracks were removed by carbon diffusion from the cast iron to the steel fibres during the solidification and cooling stages. To produce a graphite free matrix, steel fibres with optimum carbon content were used and the reinforced composite structure was cast under controlled casting conditions and fibre orientation. Three point bend test specimens were manufactured from steel fibre reinforced and unreinforced flake graphite cast iron and then normalising heat treatments were applied to the specimens at temperatures of 800 and 850°C. The fracture toughness and strength properties of the steel fibre reinforced material were found to be much better than those of unreinforced cast iron. The microstructures of the composite at the fibre–matrix transition zone were examined.     

Reinforcement of Hadfield steel matrix by oriented high‐chromium cast iron bars

To attain a wear‐resistant material compatible with high hardness and high toughness, Hadfield steel matrix was reinforced by oriented high chromium cast iron bars, through inserting high chromium alloys flux‐cored welding wires into Hadfield steel melt at 1500 ± 10 °C. The obtained composites were investigated by XRD, SEM, micro‐hardness, three‐body abrasion wear and impact toughness testers. The results show that the alloy powders inside the flux‐cored welding wires can be melted by the heat capacity of Hadfield steel melt and in situ solidified into high chromium cast iron bar reinforcements tightly embedded in the matrix. The micro‐hardness of reinforcements of the water‐quenched composite is about four times higher than that of the matrix. The impact toughness of the water‐quenched composite is higher than that of the as‐cast composite and lower than that of Hadfield steel, and its fracture mechanism is very complicated and refers to brittle and ductile mixture fracture mode. The excellent impact toughness and better wear resistance of the water‐quenched composite are attributed to combine fully the advantages and avoid the drawbacks of both Hadfield steel and high chromium cast iron. Additionally, in industrial application, the pulverizer plate produced by this composite, has also better wear resistance compared to the reference Hadfield steel pulverizer plate.     

Nondestructive evaluation of cementite content in steel and white cast iron using inductive Barkhausen noise

A nondestructive testing method for the determination of the cementite content in iron-carbon steel and white cast iron is presented. The method is based on micromagnetic measuring parameters derived from inductive Barkhausen noise measurements taken under room temperature and with temperatures above the Curie temperature. The influence of different cementite contents and cementite modifications on the micromagnetic measuring quantities for steels with ferritic, pearlitic, martensitic annealed and martensitic soft annealed microstructure states and for white cast iron was determined. Cementite actively produces its own inductive Barkhausen noise and also influences the Barkhausen noise of the iron matrix both as a foreign body and by its stress fields of the second kind. Each influence has a different effect on steel and on white cast iron. It was shown that parameters derived from the Barkhausen noise can be used for determining the cementite content if the microstructure state is known. Moreover, when the steel grade is known, the microstructure state can be detected from the pattern of the Barkhausen noise curve by means of simple pattern recognition.This paper is dedicated to Prof. Dr. phil. Paul Hoeller ( Feb. 21, 1996), former director of the IZFP. Prof. Hoeller supported especially the scientific research work described in this article.     

Cr、Si、Mn、Cu对中低铬白口铸铁抗磨蚀性能的影响

应用磷酸盐石墨铸型浇注中低铬白口铸铁试样 ,用正交试验对它们的抗腐蚀耐磨性进行了研究。分析表明 :试样有较好的抗腐蚀耐磨性 ,最佳成分配比浇注出的试样的抗腐蚀耐磨性为正火态 2 0 #钢的 3倍 ,充分反映了磷酸盐石墨铸型的激冷能力好 ;中低铬白口铸铁的抗腐蚀耐磨性随着铬含量的增加而升高 ;硅的含量以低于 2 %为佳 ,锰和铜的含量分别以在 2 %～ 3%范围和在 1%～ 2 %范围为佳。     

Fatigue behaviour and mean effects in grey cast iron

Strain cycle fatigue concepts are well integrated into fatigue life prediction methodologt for wrought components. Concepts developed for wrought materials cannot be directly extended to cast materials because of differences in the fatigue mechanisms, but the framework of a life prediction method for cast iron components will be similar. Observations and results of constant-amplitude completely reversed fatigue tests performed in strain and load control are reported for a pearlitic grey cast iron. Mean amplitude tests in both control modes have been conducted to evaluate the effects of mean stresses and strains. A parameter of the form (σ_maxΔ∈) gives good correlation of all the fatigue tests performed and provides a simple relationship to fatigue life.     

Long-life torsion fatigue with normal mean stresses

Relatively simple fatigue tests have been performed on two common engineering materials, cast ductile iron and low-carbon steel, using two stress states, cyclic torsion and cyclic torsion with static axial and hoop stresses. Tests were designed to discriminate between normal stress and hydrostatic stress as the most suitable mean stress correction term for high cycle fatigue analysis. Microscopy shows that cracks in low-carbon steel nucleate and grow on maximum shear planes, while for cast iron pre-existing flaws grow on maximum normal stress planes. The data illustrate that tensile normal stress acting on a shear plane significantly reduced fatigue life and is an appropriate input for fatigue analysis of ductile materials. Static normal stresses did not significantly affect the fatigue life for the cast iron because the net mean stress on the maximum normal stress plane was zero. Mean torsion significantly reduced the fatigue strength of the cast iron. A critical plane long-life parameter for nodular iron which accounts for both stress state and mean stress is proposed, and is found to accurately correlate experimental data.     

Arrowheads and chainmail fragments from the Crusader Al-Marqab Citadel (Syria): First archeometallurgical approach

ABSTRACT

Selected iron arrowheads and samples of iron and copper-based chainmail fragments from the medieval citadel of Al-Marqab (Qal’at al-Marqab, Margat, Syria) were examined by the Archaeometallurgical Research Group of the University of Miskolc (ARGUM) using various methods. The examination includes X-ray screening, optical microscopy (OM), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) and microhardness tests, in order to determine the composition, microstructure and mechanical properties of the finds and the manufacturing processes (e.g., traces of forming and probable heat treatment) used by Crusader and/or Mamluk metalworkers. Although the highly saline and humid atmosphere of the coastal environment of the fortress was detrimental to the iron and even to the copper-based objects, the complex examination has been very useful to acquire an in-depth knowledge of the material characteristics of the finds. The results indicate different kinds of manufacturing processes were employed on the arrowheads made of wrought iron, and a typical technique for making the links of the chain. In terms of application, two kinds of arrowheads were unearthed. The widened leaf-shaped ones, which might have been made for the use of crossbows, are fully corroded and often cracked lengthwise. In addition, two types can be found among these wide leaf-shaped arrows, those that are slightly smaller and those that are bigger. During the manufacture of thinner spiked-shaped armor-piercing arrowheads, sufficiently hard raw materials (such as pieces of bloom containing a relatively high amount of carbon or recycled iron) or wrought iron were available for the smiths. In the case of wrought iron, obtained from bloomery process, the hardness of the material could be improved by different methods (forge-hardening or cementation), which mostly depended on the master’s professional knowledge and preference.     

奥氏体铸体和18—8不锈钢在烧碱中的腐蚀行为

用失重法和电化学方法研究了奥氏体铸铁的１８－８不锈钢在高温烧碱中的腐蚀行为。用扫描电镜观察了两种材料泵件表面的腐蚀形貌,分析了奥氏体铸铁耐碱腐蚀性能优于１８－８不锈钢的原因。     

硼白口铸铁的研究进展

白口铸铁的合金化主宰了其发展进程.介绍了硼合金化白口铸铁的研究状况,主要阐述了硼对以碳化物为耐磨相和以硼化物为耐磨相的白口铸铁中组织和性能的影响.硼不改变以碳化物为耐磨相的白口铸铁中碳化物的形态,但能提高碳化物硬度和基体的淬透性,对韧性没有明显改善.以硼化物为耐磨相的白口铸铁组织中含有硬的硼化物耐磨相和强韧的马氏体基体,具有良好的硬度和韧性组合,是一类非常具有前途的新型白口铸铁.     

Wear Behaviour of CTC/FeCrCSi Composite

To bring the excellent abrasion-resistant po-tential of carbide into full play,composites of casttungsten carbide(CTC)grains based on mainlyplate martensite and high Cr,W white cast iron aremade on substrate of grey iron by cast-in-placehardfacing process.Results of high-stresstwo-body and three-body abrasion show that:(1)Base alloy microstructures have overwhelmingdominating effects on abrasion resistances of thecomposites in two-body and especially three-bodyabrasion systems.(2)All composites have very ex-cellent abrasion-resistances which increase drasti-cally with the increase of CTC grain size.In case ofthe same CTC grain size,composite based onmartensite white cast iron is much morewear-resistant than that based on mainly platemartensite although the volume fraction of CTCgrains in the latter is considerably larger than thatin the former.In three-body abrasion system,loadhas little effect on wear rate for composites basedon martensite white cast iron,but wear rate ofconventional wear-resistant materials increaseslinearly in a very steep slope as the nominal stressincreases.     

铬系白口铸铁的热塑性及其锻前加热新工艺研究

对不同铬含量白口铸铁的热塑性，铬对白口铸铁热塑性的影响规律以及铬影响白口铸铁热塑性的机理进行了探讨，通过试验提出了可明显提高铬系白口铸铁热塑性的锻前加热新工艺。     

On the weldability of grey cast iron using nickel based filler metal

Shielded metal arc welding process using nickel based filler metal was used to join grey cast iron. The effect of post weld heat treatment (PWHT) on the microstructure and hardness was studied. PWHT included heating up to 870 °C, holding for 1 h at 870 °C and then furnace cooling. By using nickel based filler metal, formation of hard brittle phase (e.g. carbides and martensite) in the fusion zone is prevented. Before PWHT, heat affected zone exhibited martensitic structure and partially melted zone exhibited white cast iron structure plus martensite. Applied PWHT resulted in the dissolution of martensite in heat affected zone and graphitization and in turn the reduction of partially melted zone hardness. Results showed that welding of grey cast iron with nickel based filler metal and applying PWHT can serve as a solution for cast iron welding problems.     

Wear and oxidation behaviour of high-chromium white cast irons

High-chromium white cast irons can attain very hard microstructures composed of intergranular chromium carbides dispersed in a tempered martensitic matrix. Two heat-treated high-chromium white cast irons with different carbon contents were studied in this research work using compression at 500 °C, and wear and oxidation tests at 500 and 600 °C. The hot compression behaviour of these products is excellent, with high strengths and significant ductility. They also exhibited good wear and oxidation properties. Fracture micromechanisms are discussed in relation to the chemical composition and microstructure of the two alloys.