Çeşitli yenileme işlemlerine uğratılan SAE 4140 tank palet çeliklerinin özellikleri

Abstract

İOIO'NCU ORDU DONATIM ANA TAMÎR FABRİKASI " nda Üretilen tank paletleri servis ömrünü tamamladıktan sonra kauçuk kısımdan arındırılarak tekrar vulkanize kauçukla kaplanmaktadır. Bu yenileme işlemi sırasında vulkanize kauçuğunn temizlenmesi için yakma işlemi kullanılmaktadır. Bu amaçla orijinal hic kullanılmamış paletlerden 6 tane alınarak sırasıyla beş kereye kadar yenileme işlemine tabi tutulmuşlardır. Bu numunelere mekanik testlerden Vickers Sertlik Testi uygulanmıştır. Mikroyapısal incelemede ger çekleştirilmiştir. Sonuç olarak çelik gövdenin sertliği önemli ölçüde düşmekte ve mikroyapısal olarak incelemede martensitik yapı asın derecede kabalaşma göstermektedir. Genel olarak paletlerde kullanılan SAE 41 40 çeliğinin standart değerlerle kıyaslanmasına gerek duyulmuştur. 1010' NCU ORDU DONATIM ANA TAMİR FABRİKASINDA üretilen SAE 4140 kalitedeki çelik ve ASİL ÇELİK A.Ş'de Üretilen hadde mamülü SAE 4140 çeliği kullanılmıştır. Deneysel çalışmalarda sırasıyla tavlama, normalizasyon, su verme, su verme+temperleme işlemleri yapılmıştır. Temperleme işlemi sırasıyla 550 C, 600°C ve 650° C sıcaklıklar * da bir saat sureyle gerçekleştirilmiştir. Mekanik özelliklerden çekme, darbe ve sertlik deneyleri gerçekleştirilmiştir. Çekme deneyi sonuçları, haddeye paralel yönde, maksimum çekme ve akma mukavemetini göstermektedir. Döküm mamulü numunelerde ise minumurn çekme ve akma dayanımı görülmektedir. Deformasyon kabiliyeti acısından da, haddeye paralel yönde maksimum süreklik elde edilirken döküm mamulü numunelerde minumurn deformasyon sergilediği gözlenmiştir. Hadde mamulü numunelerde haddeye dik yönde yüksek darbe enerjisi elde edilirken, döküm marnülü numunelerde minimum darbe enerjileri elde edilmiştir. Sertlik sonuçları mukayese edildiğinde hadde mamulü numuneler döküm mamulü numunelere göre daha düşük sertlik değerleri göstermiştir. Yapılan metalografik çalışmalarda inklüzyon tipi, ""JK" inklüzyon çizelgesine göre hadde mamulünde SS 14 döküm mamulünde OG 95 seviyesinde inklüzyon tipi gözlenmiştir. Darbe enerjisinin ve sünek ligin düşük olması muhtemelen inklüzyon tipleriyle ilişkilidir. Ek çalışma olarak SAE 1040 ve SAE 41 40 çeliklerinin perlit lamelleri arası mesafelerle sertJik değişimi eride incelenmiştir.

A lot of parts using in the industry lost of properties during services time. These kinds of parts are presented to reuse either as scrab metals* or by repearing. Their service-areas are dependent on economical condi ti ons The aim of this study is to investigate whether being used as tank belts by renewing of SAE 41 40 steel. SAE 41 40 steel is a middle carbon low alloy steel and contains chromium, molibdeni urn as alloying elements. SAE 41 40 steel is used in many parts of technological areas. Some of the used areas of it are as follows, a> Various machine parts b> Forging parts c> Various bolts and nuts d> Plugs e> Crank mills f > Axl es g> Control and actuate parts h> Piston rods i > Var i ous mi 1 1 s and gear s J> Tank parts and belts This study include, whether the mechanical and microstr-uctural properties during the renewing treatment after the service times on the tank belts which was produced by 1010th Army Outfit Main Repearing Factory are changed or not. Mechanical and metal ©graphical properties of rolling SAE 4140 steel and casting SAE 4140 steel, and researching the changing of hardness in the SAE 41 40 and SAE 1040 steels according to inter lamellar spacing of pear lite in the fer rite-pear lite microstructure. Belts produced in lOlOth Army Outfit Main Repairing Factory casting Y-Block SAE 4140 steel in this factory and supplied SAE 41 40 steel and SAE 1040 sJ,eel from ASIL CELIK corporation have been used in this study. The composition of rolling SAE 4140 and SAE 1040 steels and casting SAE 4140 steels have been given in Tabl & 1. VX TABLE 1. Chemical Composition of Steel Samples The belts with metallic carcas and coated vulcanized rubber are used in tanks. Main steps of producing tank belts are as follows: a> Casting of liquid metals which was melted and balanced as chemical composition in the arc furnace» b> Cutting of Sprove and feeders of casted belts, c) Quenched and tempering treatments of casted belts6 d> Coating proces by the vulcanized rubber of belts. Required properties in belts are that, 33-36 Re hardness and tempered martensite microstructure Main problems investigated in this study are that. How to be affected steel parts with coated vulcanized rubber by burning during the renewing treatment. -Comparing by the way of mechanical and metal lographical properties of casted SAE." 41 40 steel in this factory versus standart SAE 41 40 and low rolled SAE 4140 steels by attention with rolling direction Vİİ -Inter lamel ar spacing of p®arlit© which was produced by changing the cooling rate of the sample from austenite phase, was investigated how to change the hardness of low rolled SAE 4140 steel and SAE 1040 steel with related to inter lamellar spacing oT pearl ite. The samples used for this aim are that; six original belts were fired from once upto five times by recoated vulcanized rubber and then these samples were cut and investigated the mi cr ©structures of them. They were tested by Vickers Hardness device from surface by step of O. 1 mm. upto 1 mm On the other properties of investigation, tensile test samples in the standart of ASTM E8-81 and impact test samples in the standart of ASTM E23-56T were prepared. The sesamples were heat treated of anealling, normalizing, oil quenching and tempering in term. Austenizing temperature! s costant at 870 C. Tempering temperatures were selected 500°C, 600°C, and 650°C respectively. When the heat treatment was completed, metal lographic examination and tensile test, impact test and hardness test as mechanical test were realized. At the measurement of interlamellar spacing of pear lite; rolled SAE 41 40 and SAE 1040 steels were austenized at &70°C and continuously cooled at 2°C/min., 3°C/min., and 6°C/min. velocities. Interlamellar spacing of pearlite in the ferrite- pearlite microstructures of these samples were measured at the end of heat treatment, and changing of hardness of these samples according to interlamellar spacing of pearlite were obtained. Hardness of tank belts according to renewing numbers are getting up, this value can go down from 33-36 Re to 23-24 Re. In addition to that, surface hardness of samples are greater than inner hardness of this samples and this situation went on the renewing treatment too. Tempering martensite microstructures were obtained in the metal lographical examination. The more renewing number of belts are, the more decreasing hardness of t hern are. Rolled SAE 41 40 steels have a greater tensile strength and yield strength than casted SAE 41 40 steels in the tensile test of other step of this study. At the same time its elongation and reduction area are greater too. While ultra tensile strength and ultra yield strength were obtained on quenched heat treatments, minimum tensile strength and yield strength were obtained on annealing heat treatment. While tempering temperature increases tensile strength and yield strength decrease but ¥±İİ elongation and reduction area of samples increase generally. if we consider the hardness of these samples» results are similar to tensile test results but casted steel hardness is greater than rolled steel. While minimum hardness value was obtained on the annealing heat treatment, maximum hardness value was obtained on quenched heat treatment. When the tempering temperature increases, hardness of samples decreases. If we consider the direction of rolling of the SÂE 4140 steel on the right angle direction, has got the greater hardness than parallel direction of the steel. While maximum impact energy was observed on the parallel direction of rolled steel, minumum impact energy was observed on the cast steel. We consider the heat treatments that the maximum impact energy will be obtained on the annealing heat treatments, while minimum impact energy was obtained on the quenched heat treatments. The higher tempering temperature the higher impact energy. If we compare the test results in terms of tempering temperatures versus standard values, hardness, tensile strength and yield strength are convenient; but elongation, reduction of area and impact energy are less than standart values. Cast steel has less than that of rolled steel in any case of conditions that was mentioned above. The effect of i nterl ameller spacing of pearl ite on the hardness of samples were investigated relative to the rate of continously cooling from austenite phase. 2 C/min., 3 C/min., and 6°C/min. cooling rates were sel lee ted in this study. The higher interlamellar spacing of pearlit in the f err Ite-s-pear lite microstructures. Hardness increases as long as continuously cooling rate increases. Interlamellar spacing of pearlit in SAE 41 40 steel and SAE 104O steel are getting up, When the cooling rate decreases. But it Is clear that increasing of i nterl ameller spacing of SAE 104O is higher than that of SAE 4140 steel. Since SAE 41 40 steel contains chromium and molibdenium as al 1 oyi ng el emen t s. Anealing heat treatment resulted in the microstructure. In normalization heat treating, the (ferriie+Pearlite) microstructure was not existed completely but martensitic transformation took place partially. Quenching caused lath martensitic microstructure but in case of tempering heat treatment tempered martensitic transformation was held. It was seen that the more tempering temperature, the more coarsening of martensitic structures in any case of conditions that was mentioned above. Ix Rolled steel samples have sulphure based inclusions texture while other casting samples gave sharp edged oxldic inclusions. Generally, tank belts are not reusable. Reusibility of tank belts are depend on re-heat treating processes. Casting steel samples gave f early low ductility and impact energy values and this is closely releated with inclusion texture. Elongation and reduction of area results that have belong to cast steel samples are less than rolled steel samples results. Rolled steel samples have sulphure based inclusions what is capable of deformation and hard oxide based inclusions that are belong to casting samples and inhomogenity of these samples are the main reasons for these results.