Journals / Dicle Üniversitesi Mühendislik Fakültesi Mühendislik Dergisi / 2016 / Cilt: 7 - Sayı: 1
Investigation of surface roughness in MQL milling of 430 ferritic stainless steel by using nano MoS2 particle reinforced cutting fluid
- Pages
- 151–158
- DOI
- —
Abstract
Stainless steel materials are categorized under a group of materials that are hard to machine due to high strength, low thermal conductivity and work hardening tendency during machining. It is possible that these materials can be machined by using various cutting fluids, but cutting fluids have disadvantages such as being harmful to the environment and health and cost due to using copiously. In this study, it is intended that the MQL (Minimum Quantity Lubrication) method is applied by using nano MoS2 reinforced commercial vegetable cutting fluid during milling of AISI 430 ferritic stainless steel material and the sustainable machining is realized. Stainless steel materials have been used lots of fields such as automotive, food, medical, chemistry etc. by applying machining operations although in spite of being faced with problems during machining. In literature, there are a few studies about machining of stainless steel materials by using MQL method. In this study, ferritic stainless steel material categorized under a group of materials that are hard to machine was milled without being harmful to the environment by applying MQL method using nanofluid obtained from mixing commercial vegetable cutting fluid and nano particles. Experiments were performed by using First MCV-300 CNC machining center. In experimental studies, uncoated and TiN (Titanium Nitride) coated WC (Tungsten Carbide) cutting tools were used. The stainless steel workpieces were prepared in the dimensions of 400x250x6 mm. The slots were machined under dry, MQL with vegetable cutting fluid, and MQL with nanofluid conditions. In MQL milling, Werte DKN 25 micro lubrication system was used and Eraoil KT/2000 commercial vegetable cutting fluid was selected as lubricant. MQL flow rates were applied as 20 ml/h and 40 ml/h and spindle speed, feed rate, and depth of cut were selected as 995 rpm, 180 mm/min, and 0.5 mm, respectively. The commercial vegetable cutting fluid was reinforced by nano MoS2 particles to prepare nanofluid. The nano MoS2 particles were added at 0,5%wt., 1%wt., and 2%wt. Before the addition, nano particles were dried in Termal G11420SD drying oven for 2 hours and at 120°C then added to the vegetable cutting fluid with lecithin which is a dispersant and added to the mixture to get stable nanofluid. Daihan WiseTis HG-15D digital homogenizer was used at 500 rpm to blend the mixture. Surface roughness (Ra) measurements of machined surfaces were performed by Time TR200 surface roughness tester. The cut-off length was adjusted as 0.8 mm and the resolution of tester is 0.001 μm. Five measurements were done on each surface and arithmetic means were calculated. In the result of milling experiments, it was specified that the nanofluid MQL method has advantages over dry milling and MQL method using pure commercial vegetable cutting fluid. The performance of nanofluid increased with increase of the amount of nano MoS2 particles in the nanofluid. Additionally, high MQL flow rate provided that the performance of MQL method was increased because of supplying high amount of cutting fluid/pressure air mist.
Özet
Paslanmaz çelik malzemeler, otomotiv, gıda, medikal, kimya vb. birçok alanda talaşlı şekillendirme uygulanarak kullanılmaktadırlar. Ancak bu malzemelerim düşük ısıl iletkenlikleri ve işlem sırasında gösterdikleri pekleşme eğilimi nedeniyle talaşlı şekillendirilmelerinde zorluklarla karşılaşılmaktadır. Bu malzemelerin talaşlı işlenmesinde kesme sıvıları kullanılmakta fakat kesme sıvılarının maliyeti arttırması ve çevre ve insan sağlığı açısından zararlı olması yeni yöntemlerin geliştirilmesini gerektirmektedir. Bu sebeple, AISI 430 ferritik paslanmaz çeliğin frezelenmesinde, kaplamasız ve TiN (Titanyum Nitrür) kaplamalı WC (Tungsten Karbür) kesici takımlar ile nano MoS2 (Molibdendisülfür) takviyeli ticari bitkisel kesme sıvısı kullanılarak MQL (Minimum Quantity Lubrication - Minimum Miktarda Yağlama) yönteminin uygulanması bu çalışma kapsamında incelenmiş ve sürdürülebilir talaşlı şekillendirilmenin gerçekleştirilmesi amaçlanmıştır. Çalışmada, kesme sıvısı olarak kullanılan ticari bitkisel yağa, performansını arttırabilmek amacıyla ağırlıkça %0,5-%1-%2 oranlarında nano MoS2 parçacıklar katılmıştır. Frezeleme işlemleri, MQL yöntemi uygulanarak elde edilen sonuçların karşılaştırılabilmesi amacıyla kuru işleme uygulanarak da tekrarlanmıştır. Nano parçacıkların, katkı oranlarının ve MQL akış hızının frezelenmiş yüzey pürüzlülük değerlerine etkileri belirlenmiştir. Frezeleme deneyleri sonucunda, nano akışkan MQL yönteminin kuru işleme ve ticari bitkisel kesme sıvısı kullanılan MQL yöntemine göre avantaj sağladığı belirlenmiştir. Nano MoS2 parçacık katkı oranının arttırılmasıyla nano akışkan performansının arttığı belirlenmiştir. Ayrıca, MQL akış hızının arttırılması da ortama gönderilen kesme sıvısı-basınçlı hava karışım miktarını arttırdığından MQL performansının artmasını sağlamıştır.