In this study, the analysis of cutting forces on medium carbon AISI 1050-to which different spheroidization heat treatments were applied-was conducted by the mixed-level Taguchi orthogonal experiment design method. In the experiments, besides the parameters of feed rate, depth of cut and cutting speed having effect on cutting forces as a factor in orthogonal design, the spheroidization time and temperature parameters were also used. By the performed orthogonal experiment design method, the values of cutting forces were estimated using the five-factor, two-and three-leveled Taguchi L36 (2 2 × 3 3 ) mixed orthogonal experiment design method. The effectiveness of the machining parameters on the cutting force was revealed by performing analysis of variance test. Moreover, the effectiveness rates of the parameters were also determined in the study as per the signal noise rates. Consequently, it has been observed that the feed rate is more effective on the cutting forces compared to other parameters.

This study aims to focus on the machinability of the AISI 1050 workpieces with cutting inserts, treated under deep cryogenic heat (−146 °C), and with untreated ones, and to investigate the optimization of cutting parameters and heat treatment conditions for surface roughness and cutting force by using Taguchi mixed design and Response Surface Methodology (RSM). The machining experiment was performed on a CNC lathe with machining parameters such as three feed rates, three cutting speeds and a constant depth of cut under dry condition and with heat treatment condition. As is known, Taguchi design L18 (32 21) consists of three factors; cutting parameters with each one of three levels and heat treatment condition with two levels. The results of machining tests were evaluated considering surface roughness, vibrations and cutting force. Furthermore, chip morphology and wear led by cryo-treated and untreated inserts were detected with the aid of a scanning electron microscope. The results demonstrated that cryo-treated (CTI) insert had lower tool wear, vibration, and cutting force than untreated insert (UI) in all conditions. In aspect of chip morphology, untreated inserts had bigger and larger serrations than the treated inserts. In addition, according to Taguchi S/N ratio, optimal cutting parameters and heat treatment conditions were obtained from CHT1, V3, and f1 for the Fc and from CHT1, V1, and f1 for the Ra, respectively. Also, the most significant control factors on surface roughness and cutting force were feed rate depending on ANOVA results and RSM. Validation test results demonstrated that RSM and Taguchi mixed design calculated the cutting force (R2RSM (CTI and UI) = 99.99% and R2Tag. = 99.95%) and surface roughness (R2RSM (CTI) = 99.76%, R2RSM (UI) = 99.59% and R2Tag. = 99.12%). Therefore, RSM and Taguchi mixed design predicts highly well match experimental data with prediction data.

In this study, the effects of microstructure differences obtained with the application of different spheroidizing heat treatment cycles on medium carbon steel on cutting forces and surface roughness values were investigated. For this purpose, a group of AISI 1050 materials was annealed at 700• C below Ac1 temperature for 720 min and cementite phases were spheroidized by the traditional method. Another group of materials was quenched after austenitization at 850• C for 15 min and then cementites were spheroidized in the ferrite matrix by over-tempering separately at 600• C for 15 and 60 min and at 700• C for 60 min. Machining of the samples was tested under dry cutting conditions in CNC turning center with SNMG 120408 cementite carbide cutting tool and proper PSBNR 2525M12 tool holder with 75-degree edge angle. Cutting forces of traditionally spheroidized samples were lower than the samples spheroidized after quenching. In addition, their cutting forces decreased due to the increase in the average sizes of spheroidal cementite. Minimum surface roughness value was obtained from the samples which were spheroidized at 600• C for 15 min after quenching. However, surface roughness rate of the sample increased as spheroidizing time increased. K e y w o r d s : spheroidizing, cutting forces, surface roughness, medium carbon steel

ÖZTornalama işlemlerinde, istenmeyen yüksek değerlerdeki yüzey pürüzlülük ve titreşim değerlerini gidermek için iş parçaları tezgâha doğru bir şekilde bağlanması gerekmektedir. Bir iş parçası; uygun bir basınç ile ayna ve punta arasına bağlanmadığında, bu, onun eksenden kaçık salgılı bir şekilde dönmesine ve ölçü tamlığının bozulmasına yol açmaktadır. Bunun sonucunda, iş parçasında istenmeyen, yüksek değerlerde yüzey pürüzlülük ve titreşim değerleri meydana gelir. Bu çalışmanın amacı, Taguchi metodunu kullanarak AISI 304 paslanmaz çeliğinin tornalanmasında en düşük yüzey pürüzlülüğü ve titreşim değerlerini elde etmek için en uygun ayna ve punta basıncını tespit etmektir. İşleme deneylerinde, sabit kesme hızı, ilerleme ve kesme derinliğinde 5 farklı ayna ve punta basıncı kullanılmıştır. Deney tasarımı için Taguchi L25 (5^2) ortogonal dizilimi seçilmiştir. En küçük en iyidir yaklaşımına göre S/N (sinyal/gürültü) oranı kullanılarak yüzey pürüzlülüğü ve titreşim değerleri için en uygun ayna ve punta basıncı belirlenmiştir. S/N oranlarına göre optimum ve en düşük titreşim değerlerini veren ayna ve punta basıncı sırasıyla 18 bar ve 5 bar iken, optimum yüzey pürüzlülük değerlerini veren ayna ve punta basıncı değerleri ise sırasıyla 18 bar ve 11 bar olarak tespit edilmiştir. Fakat en düşük yüzey pürüzlülük değeri ise ayna basıncı 18 bar ve punta basıncı 5 barda elde edilmiştir. Taguchi deney tasarımındaki S/N oranı sonuçlarına göre, yüzey pürüzlülüğü ve titreşim üzerinde ayna basıncının punta basıncından daha etkili olduğu ortaya çıkmıştır. Sonuç olarak; ayna ve punta basıncı parametrelerinin optimizasyonu için Taguchi yöntemindeki faktör tasarımının; basit, sistematik ve verimli bir yöntem olduğu anlaşılmıştır. Anahtar Kelimeler-Ayna ve Punta Basıncı, Yüzey Pürüzlülüğü, Titreşim, Taguchi Metodu, Optimizasyon1 *Sorumlu yazar iletişim: huseyin.gurbuz@batman.edu.tr (https://orcid.org/0000-0003-1391-172X) Makine Mühendisliği Bölümü, Batman Üniversitesi, Mühendislik-Mim. Fakültesi, Türkiye 2 İletişim: sehmus.baday@batman.edu.tr (https://orcid.org/0000-0003-4208-8779) Makine ve İmalat Mühendisliği Bölümü, Batman Üniversitesi, Teknoloji Fakültesi, Türkiye ABSTRACTIn turning operations, the workpieces must be correctly attached to the workbench to eliminate undesirable high values of surface roughness and vibration. When a workpiece is not attached with an appropriate pressure between chuck and tailstock, this will cause it to rotate eccentrically out-of-axis and deterioration of dimensional accuracy. As a result of this, undesirable high surface roughness values and vibrations in the workpiece occur. The aim of this study is to determine the optimum chuck and tailstock pressure using Taguchi method in order to obtain the lowest surface roughness and vibration values in turning of AISI 304 stainless steel. In the machining experiments, at constant cutting speed, feed and depth of cut, 5 different chuck and tailstock pressures, were used. For the experimental design, Taguchi L25 (5^2) orthogonal array was chosen. According to th...

No abstract