XCrNi18-8 Paslanmaz çeliğin kimyasal işlenmesi

Abstract

Geleneksel olmayan imalat yöntemlerinden bir tanesi olan kimyasal işleme yöntemi uygun kimyasal aşındırıcı içerisinde malzemenin kontrollü olarak aşındırılarak şekillendirilmesi olarak tanımlanabilir. Yöntem her türlü malzemenin işlenmesinde rahatlıkla uygulanmakta ve yaygın olarak uçak, elektronik ve medikal endüstrilerinde hassas ve karmaşık şekilli parçaların imalatında kullanılmaktadır. Mikro işleme yöntemi olarak da kullanılabilen kimyasal işleme yöntemi mikro elektro-mekanik sistemler için mikron boyutunda parçaların imalatında da kullanılabilmektedir. Bu çalışmada, X5CrNi18-8 paslanmaz çeliğinin kimyasal işlenmesi konusu deneysel olarak araştırılmıştır. Mühendislik uygulamalarında yaygın olarak kullanılan paslanmaz çeliğin kimyasal işlenmesi için demir klorür (FeCl3) kimyasal aşındırıcısı kullanılmıştır. Daldırma metodu ile kimyasal işleme yönteminde belirlenen işleme parametreleri kimyasal aşındırıcının yoğunluğu ve kimyasal işleme sıcaklığıdır. Bu amaçla 28°Bé, 32°Bé ve 36°Bé kimyasal aşındırıcı yoğunlukları seçilmiş; kimyasal işleme sıcaklıkları olarak 30 °C, 50 °C ve 70 °C kabul edilmiştir. Kullanılan kimyasal işleme sıcaklıklarından 70 °C deneysel çalışmalarda ilk defa kullanılmıştır. Belirlenen işleme parametrelerinin aşındırma miktarı ve yüzey pürüzlülüğü üzerine etkileri araştırılmıştır. Yapılan deneysel çalışma sonucunda 32°Bé yoğunluklu FeCl3 çözeltisinin işleme derinliği ve yüzey pürüzlülüğü açısından uygun olduğu belirlenmiştir. Ayrıca kimyasal işleme sırasında seçilen işleme sıcaklığının artması ile işleme derinliğinin arttığı görülmüştür. Yüzey kalitesi açısından kullanılan her üç aşındırıcı yoğunluğu da benzer sonuçlar vermiştir. Yüksek işleme sıcaklıklarında yüzey pürüzlüğü değerlerinin azaldığı görülmüştür

Keywords

• Kimyasal işleme, paslanmaz çelik, kimyasal aşındırıcı

Chemical machining of XCrNi18-8 stainless steel

Abstract

Chemical machining is applied in many manufacturing industries such as electronics, aerospace, medical and aotumotive to etch, cut or engrave metal plates. The process relies on controlled corrosion of workpiece material in acidic or alkaline etchant. The process is also called in different names like chemical etching, etching, chemical milling, wet etching in literature. It can be used to shape steal titanium, nickel, copper and its alloy,aluminium and its alloys and every kind of materials to manufacture stencils, brake motor, fuel cell, printed circiut boards, plates, stamping dies, signs, jewelry, plaques, printing plates etc. The process is known with different names in literature such as chemical milling, etching, chemical etching, wet etching etc. The history of chemical machining goes back to Ancient Egypt, it was used to produce jewelry from copper with citric acid solution. Development of electronics industry made the process more attractive, because high precision and small parts were heavily required. Main industrial application of chemical machining started in 1950’s, the process was used to etch aluminium parts for aircrafts and rockets.Nowadays, chemical machining is used as micromachining in the production of micro electromechanic system part as well. The major advantage of chemical machining is producing high precision parts in a short machining time with low production cost. The process does not require special tooling. Moreover, the product parts are burr free. However, chemical machining is not environmentally friendly machining process because of hazardous effects of etchants on environment. This problem is almost overcomed by using regeneration of waste etchant and recovery of etched material. The most suitable system is combination of regeneration and recovery simultaniously. The main parameter of chemical machining is the selection of suitable etchant for workpiece material. Various chemical etchants can be named for this purpose. Ferric chloride (FeCl3) etchant is commonly used for iron based alloys, copper and aluminium. This etchant is called “universal etchant” due to wide application in chemical machining .Copper chloride and alkaline etchants are widely used for copper etching in electrronics industry. Stainless steel is commonly etched with FeCl3 etchant solution. Various studies have been carried out to investigate etching performance of this material. These studies concluded that FeCl3 etchant is the most suitable etchant solution for chemical machining of stainless steel. The etchant conmcentration sould be around 36-42°Bé at 50 °C etching temperature. The additions of some additives such as hydrochloric acid, also improves etching performance in chemical etching of stainless steel. However, there are stil some problems about chemical machining of this material such as the real influence of etchant concentration and etching temperature on etch rate and surface roghness. The purpose of this study is to investigate the chemical machining behaviour of XCrNi18-8 stainless steel with FeCl3 etchant solution. Three etchant concentrations 28°Bé, 32°Bé ve 36°Bé of FeCl3 were selected. The other parameter was etching temperature, values of 30°C, 50°C and 70°C were applied for experimental study. The effects of selected chemical machining parameters on etch rate and surface roughness were experimentally investigated. The experimental study was carried out in a beaker as immersion etching method. The prepared etchant solution was placed on hot plate with magnetic stirrer and etching temperature was kept ± 2°C. The total etching time was 15 mins and each measurements of thickness and surface roughness were taken every 5 mins. It was concluded that etchant concentration is important factor on etch rate and surface roughness. 32°Bé of FeCl3 etchant produced better etch rate in comparison to 28 and 36°Bé etchant concentrations. Moreover, etching tempertature was effective parameter, lower etching temperature (30°C) provided high surface roughness. The use of higher etching temperature gave better surface quality.

Keywords

• Chemical machining, Stainless steel, Etchant