DOCSLIB.ORG

Effect of Quenching Conditions on the Microstructure and Mechanical Properties of 51Crv4 Spring Steel

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Effect of Quenching Conditions on the Microstructure and Mechanical Properties of 51Crv4 Spring Steel metals Article Effect of Quenching Conditions on the Microstructure and Mechanical Properties of 51CrV4 Spring Steel Lin Zhang 1,* , Dehai Gong 2, Yunchao Li 1, Xiaojun Wang 2, Xixi Ren 1 and Engang Wang 1,* 1 Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Wenhua Road, Shenyang 110819, China; [email protected] (Y.L.); [email protected] (X.R.) 2 CRRC Guiyang Co., LTD., Dulaying Road, Guiyang 550017, China; [email protected] (D.G.); [email protected] (X.W.) * Correspondence: [email protected] (L.Z.); [email protected] (E.W.); Tel.: +86-24-8368-3985 (L.Z.); +86-24-8368-1739 (E.W.) Received: 28 November 2018; Accepted: 11 December 2018; Published: 12 December 2018 Abstract: 51CrV4 steel is extensively used in large-size damping springs for trains and vehicles. Quenching conditions play an important role in performance enhancement. The present work investigated the effects of various oil-bath temperatures and out-of-oil temperatures on the microstructure and the mechanical properties of this steel. The morphological examination focused on both the quenched martensite and the tempered troostite. Tensile and hardness tests were carried out to evaluate the mechanical properties. The results showed that a coarsening of the martensite occurred at a high oil-bath temperature. In addition, the size and fraction of bainite islands also increased with the increase of oil-bath temperature. In contrast, the carbide size and the intercarbide spacing both increased with the increase of oil-bath temperature. Thus, the tensile strength and the hardness both decreased with increasing oil-bath temperature in accordance with the Hall-Petch relationship. Correspondingly, the ductility increased as the oil-bath temperature increased. At a relatively high out-of-oil temperature, the martensite underwent an auto-tempering process, which led to the precipitation of many tiny carbide particles in the as-quenched martensite laths. This auto-tempering effect enhanced the width of large-sized carbides and reduced their length in the final microstructure. The intercarbide spacings increased with increasing out-of-oil temperature. As the oil-bath temperature increased, the tensile strength and hardness decreased, and the ductility increased. The fracture morphology was examined to explain the results of mechanical properties. Keywords: 51CrV4; spring steel; quenching; martensite; carbides; strength; hardness 1. Introduction The development of high-speed railway trains imposes rigid requirements on the mechanical properties of coil springs used in freight car bogies. Over the last decades, considerable efforts have been made to develop high-performance spring steels. Most coil springs for railway applications are made of quenched and tempered high-strength steels. Elements such as chromium, manganese, and silicon are added to these steels [1]. 51CrV4 steel has high strength and fatigue performance due to the addition of Cr and V, which is extensively used in large-size damping springs for trains and vehicles [2]. The recommended properties of spring steel include high ductility and toughness at operating temperatures and good hardenability that provides required mechanical properties even at large dimensions [3]. One way to improve the mechanical properties of spring steel could be achieved through the control of alloy composition [4,5]. Thermodynamic calculation was used to identify the effects of element change on the phase fraction and transformation temperature in the soaking Metals 2018, 8, 1056; doi:10.3390/met8121056 www.mdpi.com/journal/metals Metals 2018, 8, 1056 2 of 16 and tempering process [6]. Thermodynamic calculation can be performed using software such as Thermo-Calc. However, composition adjustment means to change the standard of spring steels, which lack feasibility for spring manufacturers. Steels with a similar chemical composition may behave differently due to various mechanical properties as a consequence of their manufacturing route. The mechanical properties can be improved by effective heat treatment [7,8] and thermomechanical treatment [1,9]. Quenching before tempering is a key technique to enhance the mechanical properties of spring steels, in which the final structure is significantly affected by the processing parameters during heat treatment. For this reason, the heat treatment parameters of spring steel are controlled thoroughly by the producers. Large efforts have been made in recent years to investigate the effects of heat treatment parameters during soaking and tempering process [8,10–12], such as the time and temperature of soaking and tempering. The emphasis in the research of spring steels has been focused on increasing the strength while maintaining good ductility [6,13]. One way of improving steel properties is refining its microstructure [14,15], which means to reduce the ferrite grain size, the size of carbides, and the intercarbide spacing. The mechanical behavior of steel is influenced by the inclusions and precipitates, which act as stress raisers [16]. Large inclusions are most harmful to mechanical properties. Fine precipitation can be achieved through microalloying and effective heat treatment [17]. This leads to the enhancement of hardness and strength. Retained austenite is also an important structural component in the spring steel, whose stability is affected by the processing parameters during heat treatment, such as the soaking temperature and the cooling rate [18]. The present work performed soaking, quenching, and tempering on 51CrV4 steel since this kind of heat treatment is a conventional manufacturing route to improve its mechanical properties. Previous researchers have studied the effects of various parameters during heat treatment on the microstructure and mechanical properties of 51CrV4 steels [3,19–21]. However, very few researches have focused on the detailed quenching conditions such as the oil-bath temperature and the out-of-oil workpiece temperature, which is essential to obtain the required strength and ductility. In this work, the heat treatment experiments were carried out on 51CrV4 steel under various oil-bath temperatures and out-of-oil temperatures. The quenched martensite and tempered troostite were examined. The microstructure of the steel was analyzed by scanning electron microscopy. Effects of the quenching parameters on the mechanical properties were evaluated in terms of tensile strength, elongation, hardness, and fracture. The relationship between the microstructure and the mechanical properties was discussed. The purpose of this work is to obtain a technical reference to control the mechanical properties using the oil-bath temperature and out-of-oil temperature. 2. Materials and Methods 51CrV4 spring steels have been processed by soaking, quenching, and tempering. Table1 shows the chemical composition of the commercial 51CrV4 spring steel used in this work, which was identified by chemical analysis. The original specimens were cut from a hot deformed steel bar. The size of the cylinder specimen was Ø20 mm × 300 mm. This work performed the heat treatment according to a technology route usually used to fabricate a train damping spring. First, the steel bars were heated to 930 ◦C and isothermally held for 30 min to form austenite with a uniform distribution of the alloying elements. During this soaking process, nitrogen gas was injected into the furnace to protect the steel bars from oxidization. Afterward, the steel bars were quenched into a stirred oil bath which was set at various oil-bath temperatures (20 ◦C, 50 ◦C, and 80 ◦C). The cooling rates were estimated to be 34 ◦C/s, 30 ◦C/s, and 25 ◦C/s respectively. The surface temperature of the workpiece was measured during the quenching process, and the workpieces were taken out of the oil bath at various temperatures (60 ◦C, 90 ◦C, and 120 ◦C), which was defined as the out-of-oil temperature in this paper. After quenching, the workpieces were cooled in the air to room temperature (about 15 ◦C). Next, the specimens were tempered at 450 ◦C for 90 min. After tempering, the samples were water quenched. Metals 2018, 8, 1056 3 of 16 Table 1. Chemical composition of the as-received 51CrV4 steel (mass percent, %). C Si Mn S P Cr Ni Cu V Al Mo Fe 0.546 0.229 0.951 0.004 0.014 1.08 0.051 0.106 0.168 0.017 0.006 balance Each bar was subsequently sectioned and etched to reveal the microstructure. The microstructure was observed using an Ultra Plus field emission scanning electron microscope (Carl Zeiss AG, Oberkochen, Germany). Image-Pro Plus software (Version 6.0, Media Cybernetics, Inc., Rockville, MD, USA) was used to analyze the size and the area fraction of phases. The phases were identified by the X-ray diffraction analysis using a Philips X0Pert Pro MPD diffractometer (PANalytical Co., Almelo, The Netherlands). In order to evaluate the mechanical properties of the samples, tensile testing and hardness testing were performed. Hardness measurements were taken from a polished but unetched sample, using a Rockwell apparatus (Shenyang Kejing Auto-instrument Co., LTD, Shenyang, China), with a load of 150 kg and loading time of 5 s. Tensile testing was performed in a Shimadzu AG-X 100 kN testing machine (Shimadzu Corp., Kyoto, Japan) in accordance with the requirements and recommendations of the ISO 6892-1:2011 [22]. The round bone-shaped tensile testing specimens were prepared by lathe. The tensile testing specimen had an overall length of 150 mm, a gauge length of 50 mm, and a diameter of 6 mm. An extensometer was set during test to measure the strain precisely. The strain rate was about 2.3 × 10−5·s−1. 3. Results and Discussion Figure1a shows the microstructure of as-received commercial 51CrV4 steel used in this work. The microstructure of the as-received steel appeared to be spheroidite, in which many spherical carbides were distributed dispersedly in the ferrite grains. The XRD patterns of the as-received, quenched, and tempered specimens were analyzed. The XRD result of as-received steel showed a main phase of α-Fe (Figure1b), which is the matrix of the microstructure shown in Figure1a.
Load more

Recommended publications
  • Wear Behavior of Austempered and Quenched and Tempered Gray Cast Irons Under Similar Hardness
    metals Article Wear Behavior of Austempered and Quenched and Tempered Gray Cast Irons under Similar Hardness 1,2 2 2 2, , Bingxu Wang , Xue Han , Gary C. Barber and Yuming Pan * y 1 Faculty of Mechanical Engineering and Automation, Zhejiang Sci-Tech University, Hangzhou 310018, China; [email protected] 2 Automotive Tribology Center, Department of Mechanical Engineering, School of Engineering and Computer Science, Oakland University, Rochester, MI 48309, USA; [email protected] (X.H.); [email protected] (G.C.B.) * Correspondence: [email protected] Current address: 201 N. Squirrel Rd Apt 1204, Auburn Hills, MI 48326, USA. y Received: 14 November 2019; Accepted: 4 December 2019; Published: 8 December 2019 Abstract: In this research, an austempering heat treatment was applied on gray cast iron using various austempering temperatures ranging from 232 ◦C to 371 ◦C and holding times ranging from 1 min to 120 min. The microstructure and hardness were examined using optical microscopy and a Rockwell hardness tester. Rotational ball-on-disk sliding wear tests were carried out to investigate the wear behavior of austempered gray cast iron samples and to compare with conventional quenched and tempered gray cast iron samples under equivalent hardness. For the austempered samples, it was found that acicular ferrite and carbon saturated austenite were formed in the matrix. The ferritic platelets became coarse when increasing the austempering temperature or extending the holding time. Hardness decreased due to a decreasing amount of martensite in the matrix. In wear tests, austempered gray cast iron samples showed slightly higher wear resistance than quenched and tempered samples under similar hardness while using the austempering temperatures of 232 ◦C, 260 ◦C, 288 ◦C, and 316 ◦C and distinctly better wear resistance while using the austempering temperatures of 343 ◦C and 371 ◦C.
    [Show full text]
  • Evaluation of the Three-Phase, Electric Arc Melting Furnace for Treatment of Simulated, Thermally Oxidized Radioactive and Mixed Wastes (In Two Parts)
    PLEASE DO NOT REMOVE FRCM LIBRARY REPORT OF INVESTIGATIONS/1995 Evaluation of the Three-Phase, Electric Arc Melting Furnace for Treatment of Simulated, Thermally Oxidized Radioactive and Mixed Wastes (In Two Parts) 1. Design Criteria and Description of Integrated Waste Lk3 dt.!H':.(ll J '; Mil .~ " Treatment Facility f $ 1 ;~ *.,;;::wr')oMFp.·:~ '" ,,~ ~~f . \N," 00<?0 ,- , l By L. L. Oden, W. K. O'Connor, P. C. Turner, and A. D. Hartman UNITED STATES DEPARTMENT OF THE INTERIOR BUREAU OF MINES u.s. Department of the Interior Mission Statement As the Nation's principal conservation agency, the Department of the Interior has responsibility for most of our nationally-owned public lands and natural resources. This includes fostering sound use of our land and water resources; protecting our fish, wildlife, and biological diversity; preserving the environmental and cultural values of our national parks and historical places; and providing for the enjoyment of life through outdoor recreation. The Department assesses our energy and mineral resources and works to ensure that their development is in the best interests of all our people by encouraging stewardship and citizen participa­ tion in their care. The Department also has a major responsibility for American Indian reservation communities and for people who live in island territories under U.S. administration. Cover. ThenntJl waste tret1lment facility. T- ~---------- ~1 H Report of Investigations 9528 'I Evaluation of the Three-Phase, Electric Arc Melting Furnace for Treatment of Simulated, Thermally Oxidized Radioactive and Mixed Wastes !' ( (In Two Parts) 1. Design Criteria and Description of Integrated Waste Treatment Facility By L.
    [Show full text]
  • A Study of the Optimum Quenching Temperature of Steels with Various Hot Rolling Microstructures After Cold Rolling, Quenching and Partitioning Treatment
    metals Article A Study of the Optimum Quenching Temperature of Steels with Various Hot Rolling Microstructures after Cold Rolling, Quenching and Partitioning Treatment Bin Chen 1,2,3, Juhua Liang 2,3, Tao Kang 2,3, Ronghua Cao 2,3, Cheng Li 2,3, Jiangtao Liang 2,3, Feng Li 2,3, Zhengzhi Zhao 2,3,* and Di Tang 2,3 1 Institute of Engineering Technology, University of Science and Technology Beijing, Beijing 100083, China; [email protected] 2 Collaborative Innovation Center of steel Technology, University of Science and Technology Beijing, Beijing 100083, China; [email protected] (J.L.); [email protected] (T.K.); [email protected] (R.C.); [email protected] (C.L.); [email protected] (J.L.); [email protected] (F.L.); [email protected] (D.T.) 3 Beijing Laboratory for Modern Transportation Advanced Metal Materials and Processing Technology, University of Science and Technology Beijing, Beijing 100083, China * Correspondence: [email protected]; Tel.: +86-10-6233-2617 Received: 4 June 2018; Accepted: 24 July 2018; Published: 26 July 2018 Abstract: Quenching and partitioning (Q&P) processes were applied to a cold-rolled high strength steel (0.19C-1.26Si-2.82Mn-0.92Ni, wt %). The effects of the prior hot-rolled microstructure on the optimum quenching temperature of the studied steels were systematically investigated. The microstructure was analyzed by means of transmission electron microscope (TEM), electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). Compared with the ferrite pearlite mixture matrix, the lower martensite start (Ms) temperature and smaller prior austenite grain size in the cold-rolled martensite matrix are the main reasons for the optimum quenching temperature shifting to a lower temperature in the Q&P steels.
    [Show full text]
  • 1. Introduction the Biggest Polluters Among Metallurgical Facilities
    ARCHIVESOFMETALLURGYANDMATERIALS Volume 57 2012 Issue 3 DOI: 10.2478/v10172-012-0089-1 T. SOFILIĆ∗, J. JENDRICKOˇ ∗∗, Z. KOVACEVIơ ∗∗∗, M. ĆOSIĆ∗ MEASUREMENT OF POLYCHLORINATED DIBENZO-p-DIOXIN AND DIBENZOFURAN EMISSION FROM EAF STEEL MAKING PROCES BADANIA EMISJI WIELOCHLORKOWYCH DIBENZO-p-DIOKSYN I DIBENZOFURANÓW Z PROCESU WYTWARZANIA STALI W PIECU ŁUKOWYM Electric arc furnace (EAF) steel manufacturing is an important recycling activity which contributes to the recovery of steel resources and steel scrap/waste minimization. Because of the content of plastics, coatings and paintings as well as other nonferrous materials in the charge during melting, a strong emission of pollutants, including polluting substance group consists of persistent organic pollutions (POPs) represented by polycyclic aromatic hydrocarbon (PAH), polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) occurs. This study was set out to investigate emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs) from the stack of a new electric-arc furnace-dust treatment plant installed during modernisation of the Melt Shop in CMC SISAK d.o.o., Croatia. Obtained results have been compared with previously obtained results of PCDDs/Fs emission measurements from the old electric-arc furnace dust treatment without dust drop-out box, as well as quenching tower. The total PCDDs/Fs concentration in the stack off gases of both electric arc furnaces EAF A and EAF B were 0.2098 and 0.022603 ng I-TEQ/Nm3 respectively, and these results are close to previous obtained results by other authors. The calculated values of the emission factors for PCDDs/Fs calculated on the basis of measured PCDDs/Fs concentration in the stack off gases in 2008 and 2011 were 1.09 and 0.22 ng I-TEQ/ ton steel, respectively.
    [Show full text]
  • An Introduction to Nitriding
    01_Nitriding.qxd 9/30/03 9:58 AM Page 1 © 2003 ASM International. All Rights Reserved. www.asminternational.org Practical Nitriding and Ferritic Nitrocarburizing (#06950G) CHAPTER 1 An Introduction to Nitriding THE NITRIDING PROCESS, first developed in the early 1900s, con- tinues to play an important role in many industrial applications. Along with the derivative nitrocarburizing process, nitriding often is used in the manufacture of aircraft, bearings, automotive components, textile machin- ery, and turbine generation systems. Though wrapped in a bit of “alchemi- cal mystery,” it remains the simplest of the case hardening techniques. The secret of the nitriding process is that it does not require a phase change from ferrite to austenite, nor does it require a further change from austenite to martensite. In other words, the steel remains in the ferrite phase (or cementite, depending on alloy composition) during the complete proce- dure. This means that the molecular structure of the ferrite (body-centered cubic, or bcc, lattice) does not change its configuration or grow into the face-centered cubic (fcc) lattice characteristic of austenite, as occurs in more conventional methods such as carburizing. Furthermore, because only free cooling takes place, rather than rapid cooling or quenching, no subsequent transformation from austenite to martensite occurs. Again, there is no molecular size change and, more importantly, no dimensional change, only slight growth due to the volumetric change of the steel sur- face caused by the nitrogen diffusion. What can (and does) produce distor- tion are the induced surface stresses being released by the heat of the process, causing movement in the form of twisting and bending.
    [Show full text]
  • Ionic Technologies Inc. Solution Nitriding
    Ionic Technologies Inc. For additional information send inquiries to [email protected] or call at 864-288-9111 Solution Nitriding A Cost-Effective Case-Hardening Process for Stainless Steels by Bernd Edenhofer Mark Heninger Junpei Zhou June 10, 2008 Stainless steels are applied in various industries to take advantage of their corrosion resistance. Unfortunately, the most corrosion resistant are not very durable in wear or load-carrying applications. Producing a nitrogen-enriched surface layer with increased hardness and higher residual stress increases the wear resistance and load-carrying capability in addition to improving the resistance to cavitation, erosion and corrosion attack. Fig. 1. Influence of chromium content solubility of C and N in austenite at 1100°C (2010°F) Carburizing and nitriding of highly alloyed stainless steels in the normal temperature region between 500 and 1000°C (930–1830°F) is not possible without considerable loss of corrosion resistance. The reason for this is the very low solubility of these steels for nitrogen and carbon in the respective temperature range. This leads to chromium carbide and chromium nitride precipitations, which destroy the passive chromium-oxide layer. Carburizing in the range of 800–1150°C (1470–2100°F) leads to the formation of carbides of the type Cr23C6 or Cr7C3. Nitriding between 480 and 900°C (900– 1650°F) produces nitrides of the type CrN and Cr2N. A possibility to avoid chromium carbide or nitride precipitations is the lowering of the carburizing or nitriding temperature to values that do not permit their formation. This is the case for the temperature range between 350 and 400°C (660–750°F).
    [Show full text]
  • Heat Treatment of Cast Irons
    HEAT TREATMENT OF CAST IRONS Sukomal Ghosh National Metallurgical Laboratory Jamshedpur 831 007 Heat treatment in a general way improves and alters the heat treating objects. The improvements are aimed in respect of mechanical Properties, machinability, homogeneity, relieving of stresses, hardening and others. The application of heat causes certain structural changes in the object responding to subsequent improvements in the properties. CAST IRON - CHARACTERISTICS The ferrous metals, steel or cast irons are essentially an alloy of iron and carbon. The cast iron contains carbon ranging from 2 to 4%, with the element silicon playing a most important role. Silicon influences the eutectic carbon content of Fe - C alloy and with presence of silicon eutectic carbon is estimated as: Eutectic carbon % = 4.25 - 0.30 x (%Si) In cast iron, the carbon is present in two forms. A stable form shows carbon is present as free graphite and an unstable form indicates presence of carbon in a combined form (cementite, Fe3C). Grey cast irons are characterised by the presence of all or most of the carbon in the form of graphite, white cast irons are characterised by the presence of all the carbon in combined form, i.e., in the form of cementite. An iron of borderline composition which freezes partly as a white iron and partly as a grey iron under prevailing conditions of cooling is termed as mottled iron. Two more types of cast irons are also widely accepted as separate class owing to their achieved property. Thus, malleable cast iron derives its name from its ability to bend or undergo permanent deformation before it fractures.
    [Show full text]
  • Me8491 - Engineering Metallurgy Unit- I / Alloys and Phase Diagrams Part-A
    ME8491 - ENGINEERING METALLURGY UNIT- I / ALLOYS AND PHASE DIAGRAMS PART-A: 1. Write the constitution of austenite. Austenite is a primary solid solution based on γ iron having FCC structure. The 0 maximum solubility of carbon in FCC iron is about 2% at 1140 C. 2. Classify plain carbon steel. Low carbon steel – less than 0.25% carbon, Medium carbon steel – 0.25% to 0.60% carbon, High carbon steel – more than 0.60% carbon. 3. Define Alloy. It is a mixture of two or more metals or a metal and a non metal 4. What are alloying elements? The element which is present in the largest proportion is called the base metal and all other elements presents are called alloying base elements. 5. How will you explain peretectic reaction? In peretectic reaction, up on cooling, a solid and a liquid phase transform isothermally and reversibly to a solid phase having a different composition. Liquid + Solid1== solid2 6. What is steel? Steel is a composition unto 0.008% carbon is regarded as commercially pure iron those from 0.008-2% Carbon represent the steel. 7. State the condition for Gibb‟s phase rule. Pressure variable is kept constant at one atmosphere Gibb phase rule F=c-p+2; F=c-p+1(condensed Gibb phase rule). 8. Explain base metal. The element which present in the largest proportion is called the base metal 9. Differential between substitution and interstitial solid solutions. When the solute (Impurities) substitutes for parent solvent atoms in a crystal lattice, they are called substitution atoms, and the manure of the two elements is called a substitution solid solution.
    [Show full text]
  • Effect of Heat Treatment on Mechanical Properties of AISI 4147 Spring Steel
    3rd International Conference on Mechanical, Automotive and Materials Engineering (ICMAME'2013) April 29-30, 2013 Singapore Effect of Heat Treatment on Mechanical Properties of AISI 4147 Spring Steel S. S. Sharma, K. Jagannath, C.Bhat, U. Achutha Kini, P. R. Prabhu, Jayashree P. K and Gowrishankar M. C Abstract - Today steel is the most important resource in this The combination of heating and cooling operations applied to industrialized world. It forms the basic building material of today’s a metal or alloy in the solid state is termed as heat treatment. structure. Moreover steels with large chromium and vanadium The high temperature phase austenite in steel has the property percentage can be used as spring steels which form the suspension to transform into variety of room temperature phases like system. Prevention of wear and increase in steel life depends coarse pearlite, bainite & martensite depending upon the principally on the design and operation on the component, but providing some pre-use treatment on steel can also improve the cooling cycle [1-3]. These phases may be the decomposition quality to a great extent. It has been seen that most of the study products like ferrite & cementite or it may be super saturated focuses on the experimental testing of the steel component and very solid solution. Depending upon the plate thickness and few focuses on the material testing and improving its properties interlammer spacing between ferrite and cementite phases in beforehand. One of the processing routes to alter the properties is pearlite, the property of steel can be altered. The plate heat treatment.
    [Show full text]
  • Effect of Segregations on Mechanical Properties and Crack Propagation in Spring Steel
    B. Žužek et alii, Frattura ed Integrità Strutturale, 34 (2015) 160-168; DOI: 10.3221/IGF-ESIS.34.17 Focussed on Crack Paths Effect of segregations on mechanical properties and crack propagation in spring steel B. Žužek, M. Sedlaček, B. Podgornik Institute of Metals and Technology, Lepi pot 11, SI-1000 Ljubljana, Slovenia [email protected] ABSTRACT. Considerable efforts have been made over the last decades to improve performance of spring steels, which would increase the service time of springs and also allow vehicles weight reduction. There are different possibilities of improving properties of spring steels, from modifying the chemical composition of steels to optimizing the deformation process and changing the heat treatment parameters. Another way of improving steel properties is through refining the microstructure and reducing amount of inclusions. Therefore, the focus of the current investigation was to determine the effect of more uniform and cleaner microstructure obtained through electro-slag remelting (ESR) of steel on the mechanical and dynamic properties of spring steel, with special focus on the resistance to fatigue crack propagation. Effect of the microstructure refinement was evaluated in terms of tensile strength, elongation, fracture and impact toughness, and fatigue resistance under bending and tensile loading. After the mechanical tests the fracture surfaces of samples were analyzed using scanning electron microscope (SEM) and the influence of microstructure properties on the crack propagation and crack propagation resistance was studied. Investigation was performed on hot rolled, soft annealed and vacuum heat treated 51CrV4 spring steel produced by conventional continuous casting and compared with steel additional refined through ESR.
    [Show full text]
  • Engineering Materials and Their Properties
    16 n A Textbook of Machine Design C H A P T E R 2 Engineering Materials and their Properties 1. Introduction. 2. Classification of Engineering Materials. 3. Selection of Materials for Engineering Purposes. 4. Physical Properties of Metals. 5. Mechanical Properties of Metals. 6. Ferrous Metals. 7. Cast Iron. 9. Alloy Cast Iron. 10. Effect of Impurities on Cast Iron. 11. Wrought Iron. 12. Steel. 15. Effect of Impurities on Steel. 16. Free Cutting Steels. 17. Alloy Steels. 19. Stainless Steel. 20. Heat Resisting Steels. 2.1 Introduction 21. Indian Standard Designation of High Alloy Steels (Stainless The knowledge of materials and their properties is of Steel and Heat Resisting great significance for a design engineer. The machine Steel). elements should be made of such a material which has 22. High Speed Tool Steels. properties suitable for the conditions of operation. In 23. Indian Standard Designation addition to this, a design engineer must be familiar with of High Speed Tool Steel. 24. Spring Steels. the effects which the manufacturing processes and heat 25. Heat Treatment of Steels. treatment have on the properties of the materials. In this 26. Non-ferrous Metals. chapter, we shall discuss the commonly used engineering 27. Aluminium. materials and their properties in Machine Design. 28. Aluminium Alloys. 29. Copper. 2.2 Classification of Engineering Materials 30. Copper Alloys. The engineering materials are mainly classified as : 31. Gun Metal. 32. Lead. 1. Metals and their alloys, such as iron, steel, 33. Tin. copper, aluminium, etc. 34. Bearing Metals. 2. Non-metals, such as glass, rubber, plastic, etc.
    [Show full text]
  • Influence of Ferrite Content on Fatigue Strength of Quenched and Tempered 42Crmos4 Steel
    Influence of Ferrite Content on Fatigue Strength of Quenched and Tempered 42CrMoS4 Steel Mithaq Elias Hanno Master of Science Thesis Stockholm August 2012 Abstract Specimens of steel 42CrMoS4 were quenched from the austenite (γ) and the ferrite (α) + austenite + cementite phase fields to produce fully martensitic matrices with 0 – 14 % ferrite dispersed in the matrix. After tempering at 300°C or 600°C mechanical and fatigue properties were determined. As expected yield strength, tensile strength and hardness decreased with increased tempering temperature and ferrite content. Quite unexpected, the fatigue properties were mildly affected. A small amount of ferrite, approximately 3% even appears to improve the fatigue strength. Then, at even higher ferrite amounts, slightly below 20% the fatigue strength appears to decrease again. I Acknowledgments This thesis represents the final part of the materials processing, Master of Science program at the department of material science and engineering, Royal Institute of Technology (KTH) in Stockholm. The work was carried out at the department of materials technology for axle and transmission (UTMN) at Scania CV AB in Södertälje. I would like to thank my supervisor at Scania, Karin Biwersi for her great support and encouragement. I would like also to thank my supervisor and examiner at KTH, Professor Stefan Jonsson, for his valuable advices. I’m thankful to everyone at the department of materials technology at Scania that helped me with this research especially; Gustav Makander, Ninos Hawsho, Matti Näslund and Peter Skoglund for their valuable discussions; Robert Wiklund for his help with heat treatment experiments. Finally, I’m grateful to my wife Mais and daughter Mariana for their understanding and support during my Master of Science period.
    [Show full text]