This study aims to investigate the effect of an aluminum chromium nitride (AlCrN) coating on tool wear and hole quality in the conventional drilling process of carbon fiber-reinforced plastic (CFRP) composites, titanium alloy (Ti), and CFRP–Ti stack workpieces popular in the aerospace industry. The advanced arc plasma acceleration (APA) method of physical vapor deposition (PVD) was used for all AlCrN coatings. The drilling experiments were conducted with uncoated drills as well as AlCrN-coated drills. When drilling CFRP only, the AlCrN coating was removed at the drill cutting edges and the margin area, which suggests the carbon fibers abraded the coatings. When drilling Ti only, the AlCrN-coated drill mitigated the Ti adhesion formation, which resulted in less tool wear. In addition, hole quality for both CFRP and Ti was improved when the coating was used versus the uncoated tool. The machinability of CFRP–Ti stacks in the drilling process was improved by utilizing the advanced AlCrN coating on the WC tool in terms of drilling forces and hole quality parameters such as average hole size, average hole roundness, hole surface roughness, and Ti exit burr height.

The connecting rod is one of the most important parts in automotive engines, transforming the reciprocalmotion of a piston generated by internal combustion into the rotational motion of a crankshaft. Recent advances in highperformance automobile engines demand corresponding technological breakthroughs in the materials for engine parts. Inthe present research, the powder metallurgy (P/M) process was used to replace conventional quenching and/or temperingprocesses for mass production and ultimately for more cost-efficient manufacturing of high strength connecting rods.The development of P/M alloy powder was undertaken not only to achieve the improvement in mechanical properties,but also to enhance the machinability of the P/M processed connecting rods. Specifically MoS2 powders were added aslubricants to non-normalizing Fe-Cr-Mn-V-C alloy powder to improve the post-sintering machinability. The effects ofMoS2 addition on the microstructure, mechanical properties, and machining characteristics were investigated.

The development of machining technology has coincided with the recent development of a diverse amount of materials and tools. The developed materials largely consist of hardened steel for vehicle and the mechanical industry. The machining of the hardened steel is performed in a lathe and many kind of machining centers, but it is difficult to machine because its hardness is the most difficult-to-cut materials. Hard-turning is a kind of machining process which omits the final grinding process and replaces it with a single accurate cutting process. In this paper, the turning of SKD 11(HRC 58) was performed using the CBN tool in order to recognize the optimum process conditions. The cutting force, tool life and wear, surface roughness were measured. Examining the machining characteristics when cutting of high hardened steel, low cutting speed and high conveying speed were identified to be effective in cutting conditions of SKD 11. Tool life was most effective in the conditions with 65m/min of cutting speed and 0.193mm/rev of feedrate and approximately 0.5um of very good surface profile was acquired at 0.079mm/rev of feedrate. Therefore, when cutting with Low CBN tool, it could be considered to be sufficient in reducing the steps of precision machining or replacing the polishing

As the demand for car industry increase worldwide and car models diversify, industry of automobile parts also keep pace and grows day by day. However, since industry of automobile parts is staying small and there are only few study on basic knowledge of productivity, financial competitiveness is greatly insufficient. Among accessory processing, there are more parts such as key home or bolt hole rather than general turning operation, therefore, currently study on intermittence process is exigent. This thesis studied on machinability of Ductile cast iron(FCD 500) which is used for car break desk to help this kind of situation. Also it studied machinability by using Taguchi method which can get the best performance with few tests.

Mirror surface machining for large area flattening in the display field has a problem such as a tool wear and a increase in machining time due to large area machining. It should be studied to decrease machining time and tool wear. In this paper, multi-tool machining method using a PCD tool and a SCD tool was applied in order to decrease machining time and tool wear. Machining characteristics (cutting force, machined surface and surface roughness) of PCD tool and SCD tool were evaluated in order to apply PCD tool to flattening machining. Based on basic experi- ments, the PCD/SCD multi-tool method and the SCD single-tool method were compared through surface roughness and machining time for appllying large area mold machining.

Ti₂AlN composites are a laminated compounds that posses unique combination of typical ceramic proper- ties and typical metallic(Ti alloy) properties. In this paper, the powder synthesis, SPS sintering, composite characteristics and machinability evaluation were systematically conducted. The random orientation characteristics and good crystalli- zation of the Ti2AlN phase are observed. The electrical and thermal conductivity of Ti2AlN is higher than that of Ti6242 alloy. A machining test was carried out to compare the effect of material properties on micro electrical discharge drilling for Ti2AlN composite and Ti6242 alloy. Also, mixture table as a kind of tables of orthogonal arrays was used to know how parameter is main effective at experimental design. Consequently, hybrid Ti2AlN ceramic composites showed good machining time and electrode wear shape under micro ED-drilling process. This conclusion proves the feasibility in the industrial applications.

목적: 본 연구의 목적은 새롭게 개발하여 국산화한 안경테용 셀룰로오스 아세테이트(Cellulose Acetate; CA) 소재의 가공품질 및 생산성 향상을 위해 절삭성에 관한 연구를 수행하였다. 방법: 다양한 절삭 및 이송속도의 변화조건 하에서 절삭성이 평가되었다. CA 소재의 절삭실험은 절삭력, 표면조도 및 칩형상 등의 분석이 이루어졌으며, 이를 통해 절삭성을 평가하였다. 결과: 주축회전수 20,000과 30,000 rpm을 제외하고 고속영역에서 절삭력이 낮게 나타났으며, 고속회전 시 표면조도가 저속회전 조건 보다 우수하였다. 절삭력과 표면조도의 상관관계는 고속회전 조건에서는 크지 않은 것으로 나타났다. 결론: 국산화를 위해 새롭게 개발한 안경테용 CA 소재의 고품위 가공의 절삭성 평가를 수행한 결과 주축 회전수 20,000과30,000rpm을 제외하고 고속영역에서 절삭성이 양호하였으며, 표면조도는 날당이송 0.1mm 이외의 조건에서 주축회전수가 증가할수록 양호해졌고, 칩형상도 고속회전 및 저이송 조건으로 갈수록 균일 한 형태의 칩이 발생됨을 알 수 있었다. 이상과 같은 실험결과를 종합하여 새롭게 개발된 CA 소재의 절삭성을 평가할 수 있는 기초자료를 확보할 수 있었다.

목 적: 본 연구는 안경테 소재용 셀룰로오스 아세테이트(Cellulose Acetate; CA)의 최적 가공조건을 규 명하여 안경테 전용 가공기의 설계조건 선정에 활용하고자 한다. 방 법: CA안경테 소재의 가공성 평가를 위해 절삭력, 표면조도 및 형상, 칩 형상 등을 분석하였다. 절삭 속도와 이송속도를 가공변수로 다양한 실험을 수행하여 적정 가공조건을 선정하였다. 결 과: CA안경테의 반경방향 절삭력은 절삭속도에 변화에 따른 영향이 미미한 반면, 이송방향 절삭력은 20,000과 30,000 rpm에서 증가하는 경향을 보였다. 표면조도는 날당 이송이 작은 0.05 mm 경우 절삭속도가 증가하면서 양호해지는 결과를 얻었다. 결 론: 안경테 소재용 CA의 가공성을 절삭력과 가공면의 상태를 고려하여 평가하였다. 절삭력을 고려했을 때 절삭속도가 25,000 rpm이 가장 적정한 조건으로 나타났다. 표면조도를 고려했을 경우에는 저 날당 이 송, 고 절삭속도가 최적 가공조건이었다. 따라서 이를 종합했을 때 절삭력은 전체적으로 낮은 값을 가지므로 표면조도를 주요 인자로 고려하여 날당 이송 0.05 mm, 절삭속도 20,000~ 30,000 rpm이 적정 가공조건으 로 나타났다.

The powder forging (PF) process is used to produce fully dense powder metallurgy (PM) parts for high performance automotive applications. PF connecting rods have been widely accepted in the US, Japan, and other countries due to higher performance and lower manufacturing costs when compared to conventionally forged steel connecting rods [1]. In order to meet and exceed requirements for higher fatigue strength and better machinability of PF connecting rods, a newly developed machinability enhancer, named KSX, was introduced [2]. A comparison study between powder forged materials prepared with 0.3% MnS and with 0.1% KSX additions showed excellent properties in the case of the mix with KSX.

We investigated that the effect of based compound on machinability of two types of PM steels. One is a copper steel which is selected as a general PM steel, and the other is a diffusion alloyed steel selected as a high strength PM steel. It is found that based compound addition improves machinability in drilling of both of the PM steels. Although the compound addition degrades the mechanical properties of PM steels, it is considered that decrease of the properties can be compensated by increasing density.

Sintered materials have been applied widely in Valve Seat Inserts (VSI). The demands for VSIs are not only good heat and wear resistance but also good machinability. The sintered materials, which are made of a mixture of manganese containing iron powder and certain types of sulfide powder, have superior machinability due to precipitation of the fine MnS particles in the matrix. This report introduces a new VSI material, which has both superior machinability, and wear resistance due to applies of this "MnS precipitation" technique.

Machinability and machining mechanism were examined in the case where resin impregnation treatment was conducted to the Mo-Co hardening particle dispersed iron-based sintered alloy. As a result, the force required for machining decreased significantly compared with the case where resin impregnation treatment was not conducted. This effect is considered to be attributable to the embrittlement of cutting chips produced by the minimization of the cut material deformation.

Machining of sinter-hardened PM steels provides a challenge for part makers. To facilitate machining of these materials, a new additive (MA) has been developed to increase tool life during the machining process. Hard turning tests were performed to evaluate the effect of this new additive. Sintered compacts with the MA additive were compared to compacts without a machining aid and to compacts that contained the MnS additive. This paper discusses the improvement in machinability with this new additive in sinter-hardenable PM steels.

Free-machining agent 'KSX' contains complex calcium oxide is developed. The effect of admix ratio of KSX on mechanical properties and machinability with two different cutting speeds is reported. KSX displays improved machinability without deterioration of mechanical properties up to 0.3mass% addition. It was observed that KSX is effective with a small addition of 0.1mass% at slower cutting speed, and increased of admix ratio is effective at faster cutting speed.

원심 분무법으로 제조된 P/M 2011 AI 합금 압출재의 절삭성을 조사하였다. 압출재 내에 분포된 Pb-Bi 입자들은 매우 균일하고 미세하게 분포된다. 절삭속도가 증가할수록 미세한 칩이 생성되며 이송량이 0.1mm/rev 이하에서부터는 연속칩이 생성된다. 표면의 상태는 이송량에 크게 의존하며 절삭깊이와 절삭속도에는 크게 의존하지 않는다. 불연속칩은 분산된 AI2O3입자와 공정 Pb-Bi 개재물의 존재로 인해서 생성된다.