Sabri Ozturk

Effects of Nickel Coating of Mold Plates on Star Crack Defects

Star crack defects encountered during the continuous casting of slab are elucidated in the current article. Trials were carried out to obtain basic information on the behavior of the star cracks under same casting conditions for different grade materials. It is important that star cracks form in the mold, and increase later in the casting process during the straightening. Star crack defects are clearly seen when using copper-based molds. The influences of steel carbon content, material grades, and mold type have been discussed. It is believed that defects in continuously cast products are minimized while using a nickel-coated mold wall in casting.

Effect of burnishing parameters on the surface quality and hardness

In industrial manufacturing applications to improve the surface quality of cylindrical parts such as valves, pistons of hydraulic or pneumatic cylinders, pump shafts and bearing bores, some surface-finishing processes such as grinding, super finishing and honing are applied. Nevertheless, none of them provides to improve fatigue, wear and corrosion resistance. Shot peening and case hardening can improve these properties, but they are expensive and application of them takes more time. Burnishing can increase the surface hardness by generating compressive stresses on the surface and as a result, it improves fatigue and corrosion resistance in addition to providing better surface quality. Roller burnishing is a very simple and very low consumption power process and can be applied on a conventional or computer numerical control lathe. The effect of the burnishing parameters on the surface quality and the burnishing force were examined with experimental study. The experiments were carried out using AISI 1040 carbon steel material. It was concluded that the burnishing feed is the most significant factor affecting the surface quality. Experimental results were tested with analysis of variance.

Position of the separation point in machining with a rounded-edge tool

In this article, the effect of separation point on metal flows and the behavior of the material in front of the tool face with a rounded-edge tool are experimentally examined. The character of metal flow near the rake face has obvious significance to the partial problems of the surface finish and accuracy. Analysis of variance is used to determine the most significant parameter for the separation point height from the machined surface. As the distance between the separation point and the machined surface increased, the cutting edge radius grew. It is demonstrated through experiments that the edge radius of the cutting tool affects the machining and material flow process.

Metallographic Analysis of the Dead Metal Zone In Metal Cutting With a Rounded-Edge Tool

Abstract The experimental results show that a small dead region is seen in front of the rake face during cutting with a rounded-edge cutting tool. Although this fact was accepted, metallographic analysis of the dead metal zone had never been conducted. A quick stop device was used to obtain chip root samples that are representative of the deformation taking place during dynamic (actual) cutting conditions. A metallographic analysis was performed on selected specimens to identify the microstructure and formation. The photomicrographs were analyzed and an effort made to explain the dead metal zone microstructure.

Design of a computer aided quick-stop device for study of dead metal zone formation

The use of quick-stop device allows observing a sequence of frozen images focused on the chip formation area when machining in orthogonal turning tests. This work records the development of a quick-stop device employing a servo motor. The present invention relates generally to a quick stop device, for combination with a cutting machine that is able to abruptly interrupt the cutting process between a cutting tool and the surface being cut. A dead metal zone is clearly seen when using rounded-edge cutting tools. In this study, variation of the dead metal zone is examined with the computer aided quick-stop device (CAQSD). It is clear from the experimental photomicrographs that as the cutting edge radius increases, dead metal zone increases.

A Slip-Line Approach to the Micro-Cutting Process with a Rounded-Edge Tool

The effect of tool edge roundness attracts growing attention due to increasing applications of precision, micro-and nanomachining technologies. A new slip-line model and its associated hodograph are proposed for cutting with a rounded-edge tool in this paper. New model considers stagnant metal region called as dead metal zone formed in front of the rake face of tool during cutting process. Dewhurst and Collinss [ matrix technique for numerically solving the slip-line problem is employed in the mathematical formulation of the new model. The unknown slip-line angles were solved depending on the force data obtained from experiments and variation of the sub-regions with cutting edge radius was determined.

Grinding of flat glass with Fe- and Cu-based diamond tools

Preparation of grinding wheels is the most important effective factor in glass machining. This article presents the comparison of the iron- and copper-based grinding tools. The performance of the tools is investigated based on technical and commercial aspects using same cutting speeds, feeds, and sizes of diamond grits. Scanning electron microscope is used in order to observe the microstructures of cutting tools. The service life of the grinding tools is determined on the production line in a flat glass plant. A lifetime of Fe-based diamond tools is longer compared to the copper-based wheels. The impact of metal bond materials on the service life is examined. The results show that the Fe-based tools are more economical and more useful for grinding of glass. The holding of Fe-based bonding to diamond grit is stronger than the copper-based ones.

An experimental study on dead metal zone in orthogonal cutting with worn rounded-edge cutting tools

A dead metal zone is formed by the negative rake angle effect of the rounded-edge and it affects the cutting forces during machining operations. Therefore, investigating the size of the dead metal zone and changing it with cutting edge radius and flank wear rate are important. In this study, the dead metal zone was investigated experimentally for unworn and worn rounded-edge cutting tools and it was defined by changing the flank wear rate and cutting edge radius. It was observed that the size of the dead metal zone increased with increase of the cutting edge radius and it became smaller with increasing the flank wear rate. In addition, cutting force and thrust force were investigated. It was proven that both forces increased with increase of the cutting edge radius and the flank wear rate.