ISSN (e): 2250 – 3005 || Volume, 06 || Issue, 08|| August – 2016 || International Journal of Computational Engineering Research (IJCER)
Studying the Fatigue Properties Of Hardened For Carbon Steel Dr. Mohammed Abdulraoof Abdulrazzaq Materials Eng. Dept. /University of Mustansiriyah, Baghdad, Iraq mohammedraof415@yahoo.com
ABSTRACT In this study, Medium carbon steel is one of the most important materials used in industrial applications especially it is used in applications exposed to fatigue stresses such as airplanes, automotive components and electrical engines industries. Medium carbon steels were prepared and the effect of hardening on hardening strength of medium carbon steel was studied, the flame hardening method was used at different speeds then fatigue test was done. The following results were obtained, first sample (none), second sample (3.5 mm/s), and third sample (1.75 mm /s) and forth sample (1.165 mm/s). It has been found that as the flaming speed increases, the fatigue strength of the material decreases. The fatigue test result at stress (407.44 N/mm2) was as follow: for the first sample the no. of cycles to failure was at (67511 rpm), for the second sample (95832 rpm), for the third sample (122565rpm) and for the fourth sample it was (134585 rpm).
Keywords: Medium carbon steel, flame hardening, fatigue test.
I.
INTRODUCTION
The medium carbon steels have a normal content of carbon carbon (0.45 – 0.8)that means that they are not as hard as high carbon steel neither are as strong as the Mild carbon steel. The mechanical properties of medium carbon steel were investigated in two different quenching media (water and palm oil). The properties are hardness, impact and strength of the material. Result indicated that water quenched steel produce best properties in strength and hardness; while palm oil quenched steel has its best properties in impact strength [1-3]. Some mechanical properties of medium carbon steel [4]: (1) Machinability is 60%-70%; therefore cut slightly better than low carbon steels. It is less machinable than high carbon steel since that is very hard steel. (2) Good toughness and ductility. Enough carbon to be quenched to form martensite and bainite (if the section size is small). (3) Responds to heat treatment but is often used in the natural condition. (4) The hardenability is low. (5) The loss of strength and embrittlement are decreased by both low and high temperature. (6) Subject to corrosion in most environments. All heat treating operators consist of subjecting a metal or steel to a definite timetemperature cycle which may be divided into three parts: (1) Heating the metal or alloy. (2) Holding at certain temperature (soaking). (3) Cooling [5-6]. Medium carbon steel is steel where the major interstitial alloying component is carbon. It is usually treated by using high temperatures so as to enhance ductility and strength. A 0.8% carbon steel (medium carbon steel) will begin to solidify at approximately 1470 0C. And when solidification is complete, the structure will consist of crystals of austenite of composition 0.8% carbon. As the steel cools slowly, the structure becomes uniform and no further structural change will take place. The upper and lower critical temperatures coincide and the austenitic structure transform at this temperature to pearlite. The treatment of medium carbon steel with heat significantly changes the mechanical properties, such as ductility, hardness and strength. Heat treatment of steel slightly affects other properties such as its ability to conduct heat and electricity as well. A variety of methods exist for treating steel with heat [7]. The uses for medium-carbon steel are defined by the requirement for a high tensile strength and ductility that, despite its brittleness when compared to other forms of steel, make it the preferred choice. Medium carbon steels is used for making car components such as crankshafts, gears, axles, tool shanks and heat treated machine elements. it is also used to make lead screws bright drawn bar , railway wheels , tracks , turbine discs , connecting rods , tram axles , gun parts shells rifle barrels , forging dies and spindles . Medium-carbon steels have good wear resistance, so they are often used for automobile parts and similar applications. They are also used in forging and for large parts [8]. Surface hardening is a process which is used to improve the wear resistance of parts without affecting the softer, tough interior of the part. This combination of hard surface and resistance and breakage upon impact is useful in parts such as a cam or ring gear, bearing or shafts, turbine applications. Most surface treatments result in compressive residual stresses at the surface that reduce the www.ijceronline.com
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