Investigation of the Effect of Heat Treatment on the Mechanical Properties of Copper Clad Steel Pipes

Abstract

Copper-clad steel pipes are essential components of hydraulic systems for many products, especially automobile brake systems. The mechanical properties of copper-clad steel pipes produced for the use in automotive industry have been determined by acceptance criteria. However, in addition to these mechanical properties, the shaping capabilities (ductility) of the pipes are also very important for processes such as countersink boring during the production phase stage. In this study, it was aimed to improve the ductility values of copper-clad steel pipes by heat treatment. In this context, the microstructural and mechanical properties of copper-clad steel pipes without heat treatment and copper-clad steel pipes obtained with 6 different heat treatment parameters were investigated comparatively. The optimum annealing heat treatment parameter is 450 °C and 120 min. obtained with values as, 118.7±0.6 HV Vickers hardness, 315.7±0.6 MPa tensile strength, 262.7±10.3 MPa yield strength, 36.9±0.9% elongation at break and 1260 Bar bursting strength. Therefore, by this heat treatment, approximately 7.05% decrease, 8.84% decrease, 6.49% increase and 16.00% decrease are observed in the hardness, tensile strength, yield strength, bursting strength values of the copper-clad steel pipe, respectively, the elongation at break is approximately increase as 55.04%.

Keywords

• Copper clad steel pipe
• Mechanical properties
• Microstructure
• Fracture surface
• Annealing.

Isıl İşlemin Bakır Kaplı Çelik Boruların Mekanik Özelliklerine Etkisinin Araştırılması

Öz

Bakır kaplı çelik borular, özellikle otomobil fren sistemleri olmak üzere birçok ürünün hidrolik sistemlerinin temel bileşenleridir. Otomotiv endüstrisinde kullanılmak üzere üretilen bakır kaplı çelik boruların sahip olmaları gereken mekanik özellikler kabul kriterleri ile belirlenmiştir. Ancak bu mekanik özelliklerin yanı sıra üretim aşamasında havşa açma gibi prosesler için boruların şekillendirilme kabiliyetleri (süneklilikleri) de oldukça önemlidir. Bu çalışmada, ısıl işlem ile bakır kaplı çelik boruların süneklilik değerlerinin iyileştirilmesi amaçlanmıştır. Bu bağlamda, ısıl işlemsiz bakır kaplı çelik borunun ve 6 farklı ısıl işlem parametresi ile elde edilmiş bakır kaplı çelik boruların mikroyapısal ve mekanik özellikleri karşılaştırmalı olarak incelenmiştir. Optimum tavlama ısıl işlem parametresi ile 450 °C ve 120 dk. ’da 118,7±0,6 HV Vickers sertlik, 315,7±0,6 MPa çekme mukavemeti, 262,7±10,3 MPa akma mukavemeti, 36,9±0,9% kopma uzaması ve 1260 Bar patlatma dayanım değerleri elde edilmiştir. Dolayısıyla, ısıl işlem ile bakır kaplı çelik borunun sırasıyla, sertlik, çekme mukavemeti, akma mukavemeti, patlatma dayanımı değerlerinde yaklaşık %7,05 düşüş, %8,84 düşüş, %6,49 artış, %16,00 düşüş görülürken kopma uzamasında ise yaklaşık %55,04 artış gerçekleştiği elde edilen sonuçlardan görülmüştür.

Anahtar Kelimeler

• Bakır kaplı çelik boru
• Mekanik özellikler
• Mikroyapı
• Kırık yüzey
• Tavlama.
• Copper clad steel pipe
• Mechanical properties
• Microstructure
• Fracture surface
• Annealing.

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