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Bake-Hardening Response of High Martensite Dual-Phase Steel with Different Morphologies and Volume Fractions
(Chinese Acad Sciences, Inst Metal Research, 2014) Turkmen, Mustafa; Gunduz, Suleyman
Bake-hardening behaviour of carbon steel with different martensite morphologies and volume fraction was investigated. The specimens with fibrous and bulky martensite were prestrained in tension by 4%. After this, they were unloaded and bake hardened at 180 degrees C for 10-160 mm. It was found that dual-phase steel samples which were bake hardened at 180 degrees C for 20 min showed an increase in the yield stress (YS) and ultimate tensile stress (UTS) but a decrease in ductility. Further increase in the bake-hardening time of 80 or 160 min has reduced the YS and UTS, but increased the ductility. Delta sigma (increase in stress due to bake hardening), YS and UTS values are higher for the microstructure containing fibrous martensite compared to the microstructure-containing bulky martensite. It was also observed that at a given baking temperature Delta sigma, YS and UTS increased by volume of martensite.
Dynamic Strain Aging Behaviour in AISI 316L Austenitic Stainless Steel under As-Received and As-Welded Conditions
(Mdpi, 2017) Muhamed, Guma Alnaji; Gunduz, Suleyman; Erden, Mehmet Akif; Tastemur, Demet
In the current study, dynamic strain ageing (DSA) phenomena in 316L austenitic stainless steel was investigated under as-received and as-welded conditions. A tensile test was carried out on as-received and as-welded samples for the temperatures of 25-800 degrees C at a strain rate of 1 x 10(-3) s(-1). Microstructure and fracture surfaces were investigated by optic and scanning electron microscopes (SEM). 316L austenitic stainless steel showed different DSA behavior under as-received and as-welded conditions, which are discussed in terms of microstructure and mechanical properties.
Effect of chemical composition, martensite volume fraction and tempering on tensile behaviour of dual phase steels
(Elsevier Science Bv, 2009) Gunduz, Suleyman
In this work an investigation was conducted into the tempering effects on mechanical properties of a carbon steel and a microalloyed steel, both with dual phase microstructure. The UTS and YS decreased and elongations increased with an increase of tempering temperature. However, the loss in UTS and YS at tempering temperatures of 100, 200, 300, 400, 500 and 600 degrees C was a minimum for microalloyed dual phase steel. This is thought to be due to tempering of the martensite and precipitation in the ferrite. (C) 2009 Elsevier B.V. All rights reserved.
Effect of Different Current Values on Microstructure and Mechanical Properties of Microalloyed Steels Joined by the Submerged Arc Welding Method
(Mdpi Ag, 2016) Karabulut, Hasan; Turkmen, Mustafa; Erden, Mehmet Akif; Gunduz, Suleyman
In this study, microalloyed steels were joined by using the submerged arc welding method at different welding currents of 350 A, 400 A and 450 A. The effects of selected welding parameters on the microstructure and mechanical properties of welded materials were investigated. Tensile tests and microhardness measurements were performed. Microstructural changes have been identified in the welding zone. The results showed an increase in hardness and tensile strength depending on the current intensity. The heat affected zone was observed much wider with the increase in welding current.
Effect of different grain sizes on the static strain aging behavior of bake hardening steel
(Carl Hanser Verlag, 2019) Dugan, Tugay; Gunduz, Suleyman
In this study, the static strain aging behavior of a bake hardening steel (BH 220), suitable for cold forming and widely used in the automotive sector was investigated. Tensile specimens prepared from BH 220 steel were first subjected to a 40 minute solution treatment at 920 degrees C and 970 degrees C and then cooled in water to generate various grain sizes. Both as-received and heat-treated samples were pre-strained for 3 % tension and then aged at 180 degrees C for 10, 20, 30, 60, 180 and 300 min. Tensile tests were carried out to obtain the yield strength (YS), ultimate tensile strength (UTS), elongation (%) and bake hardening value (delta Y) of aged as-received and heat-treated samples. Results indicated that BH 220 steel exhibited static strain aging behavior under as-received and heat-treated conditions. Heat treated samples showed higher susceptibility to static strain aging as compared to the as-received samples. Increased grain size in all the as-received and heat-treated samples decreased the YS and UTS but increased the bake hardening value delta Y.
The Effect of Heat Treatment on Dynamic Strain Aging Behaviour of AISI H10 Hot Work Tool Steel
(Univ Fed Sao Carlos, Dept Engenharia Materials, 2018) Tastemur, Demet; Gunduz, Suleyman
Dynamic strain agmg (DSA) behaviour of hot work tool steel (H10) was investigated under as-received (AR) and as-quenched (AQ) conditions Hot tensile test was carried out m the temperatures of 25 degrees C-700 degrees C at a strain rate of 1x10(-3)s(-1) The tensile properties indicated that AQ samples showed an increase in yield strength (YS) and ultimate tensile strength (UTS) but a decrease in elongation at 200 degrees C or 300 degrees C consistent with DSA However, AR samples revealed a decrease in YS and UTS for the same testing temperatures. This indicated the presence of less amount of free C or N in solution of AR samples. Further increase in the testing temperature has increased the elongation. It is believed that DSA occurs in H10 tool steel at different temperatures because of interaction between dislocations and interstitial solute atoms (C or N) or substitutional atoms (Cr or Mo).
Effect of hot rolling process parameters on the microstructure and mechanical properties of continuously cooled low-carbon high-strength low-alloy (HSLA) steel
(Walter De Gruyter Gmbh, 2022) Kucukakarsu, Furkan Yilmaz; Ayhan, Ismail Irfan; Alan, Emre; Tastemur, Demet; Gunduz, Suleyman
In this work, high-strength low-alloy (HSLA) steel with 0.22 wt% carbon was produced in laboratory scale and hot rolled with a total deformation of 42% via 4, 5, or 6 passes. After multipass hot rolling process, samples were examined either in as-rolled (AR) or as-rolled and heat-treated (ARH) conditions. The results indicated that microstructural and mechanical properties of HSLA steels are influenced by hot rolling conditions for both cases. It was observed that strength values in AR samples have a tendency to increase with increment in rolling pass number. In contrast to AR samples, it was seen that the mechanical properties were slightly decreased in ARH samples that were austenitized at 1150 degrees C for 45 min and then cooled in still air. Microstructural investigations showed that finer precipitates in AR samples are obviously more than that of ARH samples, as an evidence for higher strength results by precipitation hardening. In addition to precipitation strengthening, refinement of lath bainite and amount of blocky martensite/austenite in AR samples favor the increase in strength.
THE EFFECT OF MARTENSITE MORPHOLOGY ON STATIC STRAIN AGEING BEHAVIOUR OF DUAL PHASE STEELS
(Gazi Univ, Fac Engineering Architecture, 2013) Turkmen, Mustafa; Gunduz, Suleyman
In this study, strain ageing behaviour of dual phase steel with different martensite morphology was investigated. Three different types (Intercritical annealing, intermediate quenching and step quenching) of heat treatment was applied in the critical temperature (775 degrees C). Ageing experiments after 4 % prestrain were carried out at 180 degrees C for different times ranging from 10 to 160 min. The microstructure after different heat treatments applied to the work pieces with the network, fiber, and the bulky martesite morphologies have been identified. It was found that the martensite morphology has no effect on the trend of Delta Y (an increase in strength due to strain ageing), YS and UTS at different ageing times for 180 degrees C. However, at a given ageing time for 180 degrees C Delta Y, YS, UTS and hardness values of fibrous martensite are higher than network or bulky martensite.
The effect of process parameter on the properties of spot welded cold deformed AISI304 grade austenitic stainless steel
(Elsevier Science Sa, 2009) Karci, Feramuz; Kacar, Ramazan; Gunduz, Suleyman
The electrode force, weld current, and weld time are three essential parameters of the resistance spot welding process. This paper deals with the characterization and understanding the effect of weld time and the influence of different weld atmospheres in the resistance spot weldability of AISI304 grade stainless steel deformed in tension by 5%, 10%. or 20%. Therefore, the microstructure of the weldment was evaluated and the hardness and tensile shear load bearing capacity of weldment were also determined. It was found that the final mechanical properties of weldment are directly related to the parameters of the process used, knowing the weld time and rate of deformation prior to welding. (C) 2008 Elsevier B.V. All rights reserved.
The effect of tempering and strain aging processes on the mechanical properties of AISI H10 hot work tool steel
(Gazi Univ, Fac Engineering Architecture, 2021) Tastemur, Demet; Gunduz, Suleyman
In this study microstructure and mechanical properties of AISI H10 hot work tool steel austenitised at 1050 degrees C for 1 hour and then cooled in water followed by tempering at 550 degrees C for different time intervals were investigated. In addition, the dynamic strain aging behavior of the samples tempered at 550 degrees C for 2 hours, where optimum parameters were obtained, was investigated. In the aging process, tensile tests were carried out at a temperature range of 25-700 degrees C and at a strain rate of 1x10(-3) s(-1). SEM analyzes were performed on the fractured samples after the tensile test in order to determine the effect of dynamic strain ageing on fracture behavior. The tensile test results indicated that tempered samples showed an increase in yield strength (YS) and ultimate tensile strength (UTS) but elongation remained constant at 200 degrees C or 300 degrees C consistent with dynamic strain aging. It is believed that dynamic strain ageing occurs in AISI H10 hot work tool steel at different temperatures because of interaction between dislocations and interstitial solute atoms (C or N) or substitutional atoms (Cr or Mo).
EFFECT OF THE ADDITION OF NIOBIUM AND ALUMINIUM ON THE MICROSTRUCTURES AND MECHANICAL PROPERTIES OF MICRO-ALLOYED PM STEELS
(Inst Za Kovinske Materiale I In Tehnologie, 2016) Gunduz, Suleyman; Erden, Mehmet Akif; Karabulut, Hasan; Turkmen, Mustafa
In this work, the effects of the addition of Nb and Al on the microstructures and tensile behaviours of micro-alloyed powder metallurgy (PM) steels were investigated. The microstructure of the micro-alloyed PM steels was examined by light microscope, SEM, XRD, XRF and EDS. The results indicated that the addition of (0.1, 0.15 or 0.2) % of Nb-Al increases the yield strength (YS) and the ultimate tensile strength (UTS) of the PM sintered steels. Elongation also tends to improve with an increasing Nb and Al content. In addition, the Nb and Al limit the grain growth during austenitization.
THE EFFECT OF THE PRE-STRAINING AND AGEING ON TENSILE BEHAVIOUR OF MICROALLOYED STEELS
(Pamukkale Univ, 2005) Gunduz, Suleyman
Two commercially available medium carbon and low carbon microalloyed steel were evaluated in this study. The steels were cold strained in tension 5 % and were aged at 100-450 degrees C for 1 hour. Strained and aged specimens were then retested to fracture and mechanical properties of steels were measured. Changes in mechanical properties such as ultimate tensile strength and yield strength were observed at ageing temperatures. This ageing is ass degrees Ciated with interaction between interstitial solutes and disl degrees Cations which are preferential sites for solute atom diffusion. Indications are that the medium carbon microalloyed forging steel is more susceptible to strain ageing than the low carbon microalloyed steel as evidenced an increase in yield strength and tensile strength.
Effect of vanadium addition on the microstructure and mechanical properties of low carbon micro-alloyed powder metallurgy steels
(Carl Hanser Verlag, 2016) Erden, Mehmet Akif; Gunduz, Suleyman; Karabulut, Hasan; Karabuk; Turkmen, Mustafa
In the present experimental work, the effects of vanadium additions on the microstructures and mechanical properties of powder metallurgy (PM) steel and microalloyed powder metallurgy (PM) steels were investigated. The microstructures of the PM steel and microalloyed PM steels were characterized by optic microscope, SEM and EDS. Experimental results showed that vanadium microalloyed steels can be produced by PM technology. The addition of vanadium limits grain growth during austenitization prior to air cooling and increases the strength in the sintered conditions. By limiting austenite grain growth, the precipitates result in significant improvement in strength.
Influence of ageing treatment on microstructure, mechanical properties and adhesive wear behaviour of 6063 aluminium alloy
(Emerald Group Publishing Limited, 2014) Buyukdogan, Serkan; Gunduz, Suleyman; Turkmen, Mustafa
Purpose - The paper aims to provide new observations about static strain ageing in aluminium (Al) alloys which are widely used in structural applications. Design/methodology/approach - The present work aims to provide theoretical and practical information to industries or researchers who may be interested in the effect of static strain ageing on mechanical properties of Al alloys. The data are sorted into the following sections: introduction, materials and experimental procedure, results and discussion and conclusions. Findings - Tensile strength, proof strength (0.2 per cent) and percentage elongation measurement were used to investigate the effect of strain ageing on the mechanical properties. Wear tests were performed by sliding the pin specimens, which were prepared from as-received, solution heat-treated, deformed and undeformed specimens after ageing, on high-speed tool steel (64 HRC). It is concluded that the variations in ageing time improved the strength and wear resistance of the 6063 Al alloy; however, a plastically deformed solution-treated alloy has higher strength and wear resistance than undeformed specimens for different ageing times at 180 degrees C. Practical implications - A very useful source of information for industries using or planning to produce Al alloys. Originality/value - This paper fulfils an identified resource need and offers practical help to the industries.
Influence of NbC Addition on the Sintering Behaviour of Medium Carbon PM Steels
(Mdpi Ag, 2017) Ozdemirler, Dogan; Gunduz, Suleyman; Erden, Mehmet Akif
In this work, the effects of NbC additions on the microstructure and mechanical properties were examined. In order to do this, NbC compounds were added into the Fe matrix at the weight percentage of 0.1-2 with individually to obtain powder mixture. The microstructure of the powder metallurgy (PM) steels were characterized by optic microscope, scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Experimental results indicated that NbC alloyed steels can be produced by PM technology. An increase in strength was observed when the amount of NbC compounds increased for all PM steels. The precipitation of carbides and nitrides in these steels limits austenite grain growth and increases the precipitation hardening or clustering hardening that results in significant improvement in strength.
Influence of straining and ageing on the room temperature mechanical properties of dual phase steel
(Elsevier Sci Ltd, 2008) Gunduz, Suleyman; Tosun, Atilla
In this work, changes in mechanical properties in dual phase steel containing 20% martensite volume fractions were observed at various ageing temperatures. For example, Delta Y (increase in yield strength due to strain ageing), YS and UTS exhibit maximum values at ageing temperature of 100 degrees C for the pre-strains of 2 and 4%. This is due to the formation of solute atom atmospheres around dislocation. When the ageing temperature increased to 200 degrees C, yield strength decreased due to overageing resulted from tempering that starts in martensite phase. (C) 2008 Elsevier Ltd. All rights reserved.
Influence of the heat treatment on the microstructure and machinability of AISI H13 hot work tool steel
(Springer London Ltd, 2018) Demir, Halil; Gunduz, Suleyman; Erden, Mehmet Akif
In this work, the influence of heat treatment on the microstructure and machinability of AISI H13 tool steel was investigated for the as-received (AR), water-quenched (Q), quenched and single-tempered (QST) and quenched and double-tempered (QDT) conditions. The machining tests were carried out through turning method at various cutting speeds. The results indicated that heat treatment conditions and the cutting speed affected the surface roughness of samples. However, cutting forces were not affected by steel microstructure and cutting speed except to those of water-quenched samples.
Investigation of hardness and microstructure properties of non alloyed and hardox steel combined with submerged arc welding method
(Gazi Univ, Fac Engineering Architecture, 2018) Erden, Mehmet Akif; Gunduz, Suleyman; Caligulu, Ugur; Boz, Mustafa
In this work, low carbon steel and hardox steel joined by using submerged arc welding under three different conditions. Same welding parameters (325 A, 30-32 V) were used during welding. Welded joints were characterised in terms of hardness test, macro and microstructures. The results indicated that hardox welded joints showed the highest hardness. In addition, as a result of macro and microstructure study, heat affected zone (HAZ) of structural steels were observed much larger.
INVESTIGATION OF MACHINABILITY OF COOLED MICROALLOY STELL IN OIL AFTER THE HOT FORGING WITH COATED AND UNCOATED CBN CUTTING TOOLS
(Yildiz Technical Univ, 2018) Ozlu, Barn; Demir, Halil; Turkmen, Mustafa; Gunduz, Suleyman
The aim of this study was to investigate the cutting forces and surface roughness of 38MnVS6 microalloyed steel quenched in oil following hot forging. The machinability tests were carried out by turning under dry cutting conditions using coated and uncoated cubic boron nitride (CBN) cutting tools at five different cutting speeds (120, 150, 180, 210 and 240 m / min), a constant feed rate (0.04 mm / rev) and a constant chip depth (0.6 mm). The microalloyed steel used in the experimental study was optically examined and a hardness test was applied. Scanning electron microscopy (SEM) was used to evaluate the wear on the cutting tools. The findings for the 38MnVS6 steel which was oil quenched after forging showed that due to the high cooling rate, a martensite structure had been formed and the hardness value was high. The lowest surface roughness values of 0.367 mu m and 0.164 mu m were obtained at a cutting speed of 180 m / min with the coated and the uncoated CBN cutting tools, respectively. In the turning experiments, the surface roughness values measured using the coated CBN cutting tool were about 103% higher than those measured using the uncoated CBN cutting tool and the highest cutting forces were obtained at a cutting speed of 120 m / min.
The Investigation of the Effect of Cu Addition on the Nb-V Microalloyed Steel Produced by Powder Metallurgy
(Int Inst Science Sintering (I I S S), 2022) Erden, Mehmet Akif; Erer, Ahmet Mustafa; Odabasi, Cagri; Gunduz, Suleyman
In this work, the effect of Cu content on the microstructures, mechanical properties and electrical conductivity of Nb-V added microalloyed powder metallurgy (PM) steels were investigated. Microalloyed steel samples were pressed at 750 MPa and sintered at 1400 degrees C in argon atmosphere for 1 h. The grain size and phase distribution of the microalloy steels were determined by optical microscope. The precipitates and fracture surface of samples were analyzed with the help of SEM and EDS analyses. Tensile test, hardness test and electrical conductivity measurement were carried out for the Nb-V added microalloyed steel with different Cu content. Results indicated that 10 wt.% Cu added PM microalloyed steel showed the highest values in yield strength (YS) and ultimate tensile strength (UTS). However, when the amount of Cu content increased from 10 to 15 wt.%, YS and UTS decreased. Elongation also tends to decrease with increasing Cu content. Although the electrical conductivity in general increased with the addition of Cu, a decrease in some conductivity was observed in the addition of 15 wt.% Cu.

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