• Tribology and Lubricants
• /
• 제33권3호
• /
• pp.98-105
• /
• 2017

A pin-on-disk test is performed to measure the wear volume of a ductile cast iron (DCI) roll when it wears down using a high carbon steel and two alloy steels at different sliding velocities between the roll and the material (steel). Normal pressure is set as constant and test temperatures are 400, 500 and $600^{\circ}C$. In addition, thermal softening behavior of the DCI roll is examined using a high-temperature micro-hardness tester and the surface hardness variation of the DCI roll is expressed in terms of temperature and heating time. Based on experimental data, a wear coefficient used in Archard's wear model for each material is obtained. The wear volume is clearly observed when the test temperature is $400^{\circ}C$ and sliding velocity varies. However, it is not measured at temperatures of $500^{\circ}C$ and $600^{\circ}C$ even with variations in sliding velocity. From the optical photographs of the pin and disk, the abrasive wear is observed at $400^{\circ}C$ clearly, but no at $500^{\circ}C$ and $600^{\circ}C$. At higher temperatures, the pin surface is not smooth and has many tiny caves distributed on it. It is found that wear volume is dependent on the carbon contents rather than alloy contents. Results also reveal that the variations of wear coefficients are almost linearly proportional to the carbon contents of the material.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2004년도 제5회 압연심포지엄 신 시장 개척을 위한 압연기술
• /
• pp.223-230
• /
• 2004

In order to improve the productivity and quality of the hot rolled products, many morden mills have continuously required advanced roll materials. The introduction of HSS rolls in early stands of the Hot Strip Mill brought the excellent performance in wear resistance and surface roughness. Ni-grain rolls used in the later stands was needed to improve the roll performance. Therefore, the carbide reinforced Ni-grain roll was developed. The present paper will describe the development of carbide reinforced rolls made by INI STEEL and the results of mill tests. The wear resistance was increased upto $40\%$ and the anti-accident ablility was remarkably improved compared to the normal Ni-rain roll.

• 한국정밀공학회지
• /
• 제10권4호
• /
• pp.128-134
• /
• 1993

Work roll wear in the cold rolling of mild steel strip is strongly affected by rolling materials, rolling conditions and lubrication. The tests were performed to find the effects of rolling materials under the same lubrication conditions. The obtained results are as follfws; 1) The decrease in surface roughness of work roll is more rapid in that case of continuously cast A1-killed steel strip than ingot cast steel strip. In rolling of continuously cast A1-killed steel strip, worn powder rich in A1$\_$2/O$\_$3/sticks to the work roll surface, and so it makes the mirror surface of work roll accelerate. 2) Amount of work roll wear is small in rolling of continuously cast A1-killed strip. 3) In rolling of continously cast A1-killed steel strip, it is necessary to put up the intial surface roughness of work roll in order to prevent work roll slip.

• 소성∙가공
• /
• 제6권2호
• /
• pp.161-175
• /
• 1997

The effects of various process paramenters on the detailed aspects of the thermo-mechanical behavior of work roll and on the roll life are investigated via a series of process simulation, using a mathematical model presented previously. The process conditions are discussed that are favorable or optimal in terms of reducing roll wear in the front finishing stands.

• 한국정밀공학회지
• /
• 제14권2호
• /
• pp.58-65
• /
• 1997

Work rolls used in cold rolling mills must have outstanding wear resistance and very little plastic defor- mation. Thus, these rolls require a higher surface hardness and harding to a greater depth. To meet these requirements, the rolls, in general, have basic chemical composition of 0.7 to 1.0% carbon and 1.0 to 5.0% Cr(chromium), plus a small amounts of special elements, and are subjected to intensive water quenching and tempering at low temperature to provide a surface hardness of over 90 shore. This test results are as follows. Deflection and fracture load of 5% Cr material are than those of 3% Cr material and show flat curve from surface to subsurface. It will be clear that 5% Cr work roll has a superior resisti- bility against wear and abrasion comparing with 3% Cr work roll. The improvement of wear and abrasion in 5% Cr work roll will be achieved by the large amount of wpheroidal carbide. In grindability and polish, 5% Cr work roll will be a little inferior comparing with 3% Cr work roll.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
• /
• pp.74-80
• /
• 1999

Work roll wear in the cold rolling of mild steel strip is strongly affected by rolling materials, rolling conditions such as roll arrangement in the cold rolling mill and lubrication. The tests were performed to find the effects of roll arrangement n the cold rolling mill on the work roll wear under the same lubricating conditions. The obtained results are as follows:If the distance of cold rolling is about 60km, the surface roughness of its was reduced by half(Ra 0.49${\mu}{\textrm}{m}$) and Pc(peak count) also was decreased to 60 ea/cm.It is easier for CC(Continuous casting) to make a slip on rolling than IC(Ingot casting). It is due to surface mirror in which first residual product appears and iron powder included Al2O3 is sticked. Because bending degree of 4Hi-rolling mill is higher than 6Hi-rolling mill, the first surface mirror was occurred to its center-point which is loaded strongly. 6Hi-rolling mill shape-controlled by intermediate roll doesn't need the initial crown to work roll. Therefore, fatigue and wear would appear a little bit.

• 한국정밀공학회지
• /
• 제10권3호
• /
• pp.69-80
• /
• 1993

It is important to prevent roll failure in hot rolling process for reducing maintenance coat and production loss. Roll material and rolling conditions such as the roll force and torque have been intensively investigated to overcome the roll failures. In this study, a computer roll life prediction system under working condition is developed and evaluated on IBM-PC level. The system is composed and fatigue estimation models which are stress analysis, crack propagation, wear and fatigue estimation. Roll damage can be predicted by calculating the stress anplification, crack depth propagation and fatigue level in the roll using this computer model. The developed system is applied to a work roll in actual hot rolling process for reliability evaluation. Roll failures can be diagnosed and the propriety of current working condition can be determined through roll life prediction simulation.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1992년도 춘계학술대회 논문집
• /
• pp.306-312
• /
• 1992

The prevention of roll breakage in hot rolling process is improtant to reduce maintenance cost and production loss. Rolling conditions such as the roll force and torque have been intensively studied to overcome the roll breakage. in the present work, a model for life prediction of work rolls under working condition was developed and discussed. The model consists of stress analysis, crack propagation, wear and fatigue calculation model. Roll life can be predicted by stress, crack depth and fatigue damage calculated from this model. The reliability of stress analysis is backed up by the FEM analysis. From the result of simulation using by pressent model, although the fatigue damage of back up roll reachs 80% of practical limit, that of workroll was less than 40%. In edge section of workroll stress amplification is found by wear and bender effect. We can judge that workroll failures are not due to fatigue damage, crack propagation by bending stress but stress amplification by wear and bender in present working condition.

• 한국정밀공학회지
• /
• 제28권9호
• /
• pp.1062-1069
• /
• 2011

In electro-galvanizing line to manufacture the electro-galvanized steel sheet, polishing system is required to maintain clean surface of conductor roll and to secure the quality of the steel sheet. At the same time, prediction and decision of the replacement cycle for felt material and its brush installed in the polishing system is also important because the brush is directly contacted on the conductor roll surface. In this study, the polishing system has been designed which the brush is repetitive translating according to the longitudinal direction of the conductor roll. Furthermore, the prediction on the wear-life of the felt material used for the brush is performed using the contact pressure extracted by finite element analysis. And to verify the predicted wear-life of the felt material, the experimental study is also carried out. From the comparison result between the predicted and the measured wear-life of the felt material, it is presented that the wear-life and the replacement cycle of the felt material are well predicted by considering a wear compensation factor, and the wear compensation factor is useful and reasonable.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2003년도 춘계학술대회논문집
• /
• pp.84-87
• /
• 2003

Microstructural evolution and dry sliding wear behavior of ultra-fine grained 5052 Al alloy obtained by an accumulative roll-bonding process have been investigated. After 7 ARB cycles, ultra-fine grains with large misorientations between neighboring grains were obtained. The grain size was about 0.2$\mu\textrm{m}$. The hardness, tensile and yield strengths of the ultra-fine grained alloy increased as the amount of accumulated strain increased with the ARB cycles. Sliding wear teats of the ultra-fine grained 5052 Al alloy were conducted at room temperature. Wear rate of the ultra-fine grained alloy increased in spite of the increase of hardness. Surfaces of the worn specimens were examined with SEM to investigate wear mechanism of the ultra-fine grained alloy.