No abstract

Kırarak ayırma, otomobil motorlarında kullanılan biyel kollarının üretiminde son yıllarda geliştirilen modern bir metoddur. Bilinen yöntemlerle karşılaştırıldığı zaman bu yöntemin avantajları oldukça fazladır. Bu metot üretim proseslerini azaltır, alet ve ekipman yatırımını azaltır, daha az enerji kullanılmasını sağlar. Sonuç olarak, toplam üretim maliyetinde % 25 gibi önemli bir oranda tasarruf sağlar. Ayrıca yüksek kalite ve hassasiyette biyel üretimi sağlanır. Kırarak ayırma yöntemi çok ilgi çekmiş, halen teknolojik olarak bir çok modelde kullanılmaktadır. Bu makalede C70S6 çeliğinden yapılmış biyel kolu darbeli yük ile kırılarak kırma parametreleri incelenmiş, kırılan yüzeylerin optik ve SEM analizleri yapılmıştır. Yük ve hız parametreleri incelenmiş olup, uniform dağılan darbeli kuvvet etkisi ile başlangıç çentiğinin gevrek-klevaj kırılma tipine neden olduğu sonucuna varılmış, iç yapının bu gevrek kırılmaya neden olduğu ve tokluğu azalttığı sonucuna varılmıştır.

High-speed cutting is one of the key issues in mould manufacturing. But to apply high-speed milling to mould manufacturing, unlike conventional milling, it is necessary to define specific cutting parameters. This article aims to define the influence of milling strategies and cutting parameters, such as cutting speed, feeding speed, cutting tool tilting angle, on the process stability.Long tool life and cutting strategy have a major influence on the results of machining hardened steel. Machining with drawing cut and down-cutting in copper and with drawing cut and up-cutting in hardened steel gave the best results with respect to tool wear and surface quality. Tool approach across the feeding direction results in heavy impact loads on the tool which lead to heavy tool wear and substantial dimensional deviations.Good surface quality is achieved in machining of a work piece of 2 363 steel (X100CrMoV51) hardened to 60 HRC, using the strategy of up-cutting with drawing cut and a tool approach with a tilting angle of 15 degrees. While up-cutting allows for achieving better surface quality, down-cutting provides longer tool life than up-cutting for all angles of approach.

The main microstructure of the crackable C70S6 steel is pearlite (%90 of the structure is about pearlite). Changing the microstructure by various heat treatment applications such as hardening&quenching, annealing, tempering can be economic and technologic alternatives to the use of crackable C70S6 steel. In this study, the microstructure and the metallography of the crackable C70S6 steel is examined by various heat treatment applications. Besides this, some fracture experiments has been carried out for each heat treatment application. Finally, it has been seen that tempered martensite structure can be an important alternative to the pearlitic crackable C70S6 connecting rods.

Microalloyed high carbon steels (such as C70S6, SMA40 and FRACTIM) have been considered to be economic alternatives to powder metal and conventional steel, having been used as main crackable con-rod materials in recent years. Compared with powder metal and conventional steel, these microalloyed high carbon steels have remarkable advantages. One of the main advantages is that cost reduction can be achieved by changing the micro-structure of the con-rod. Sawing and machining processes of the rod and cap, in order to mate two faces can be eliminated, and is believed to reduce the production cost by 25%. Another advantage of this production method is that fracture-splitting connecting rods exhibit 30% higher fatigue strength and 13% less weight than conventional connecting rods, and can be splitted into two pieces (big body and cap) by fracturing with an instant impact load. Compared with powder metal and cast con-rods, it also has lower cost for the whole manufacturing process. Hence, it provides more advantageous production opportunities, and is prefered in manufacturing technology mostly. In this article, the metallographic and fracture surface analysis have been investigated using optical and SEM method. Hardness of C70 steel is also determined. In the article it has been made clear that, the microstructure of the fracture-split con-rod has a fine grain size with densely pearlite because of its high carbon content. Also it is shown that a high hardness value is determined approximately 280-300 HB. Almost no deformation exhibits after splitting into 2 pieces, which is what any con-rod productor would like to expect when utilizing C70S6 crackable steel in production phase.