• 소성∙가공
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• 제17권4호
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• pp.272-277
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• 2008

A constitutive equation of the electrical steel strip used for a raw material of transformer is proposed. The stress-strain behavior of electrical steel strip is quite different from that of common carbon steel and/or alloy steel. A series of tensile tests were performed with the specimens made from cold rolled strip. Several thicknesses of the strip were produced by a two-high (with upper and lower rolls) cold rolling pilot mill as reduction ratio increases from 10% to 90%. Its initial thickness of the strip was 2.5mm. Tensile specimens are cut out from the cold rolled strips. Mechanical properties of the steel are examined through rolling direction. Ramberg-Osgood model and the proposed equation are combined to describe the total behavior of stress-strain including instability region. The stress-strain curves calculated from the present constitutive equation are compared with those from experimentally obtained at each test condition of reduction ratios of specimen. Results show that the predicted stress-strain curves are in overall in a good agreement with measured ones.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.142-146
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• 2001

In this study, it was investigated the influence of cold rolling factors on the edge drop. Edge drop was highly affected by the shape of work roll, the amount of work roll shift and the crown of hot strip, but the effect of bending force at the front stand was relatively small. The used numerical model was examined by comparing to the result of measured field data, and it showed a qualitative agreement with each other.

• 소성∙가공
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• 제29권2호
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• pp.97-102
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• 2020

Wire drawing is a metalworking process used to reduce the cross-section of a wire by pulling the wire through multi-stage drawing dies. The aim of this study is to fabricate a drawing wire using 2 stage drawing process. The finite element analysis of wire drawing was conducted to validate the efficiency of the designed process and the experiment was performed to validate the designed wire drawing process using 2 stage tungsten carbide die. Dry lubricant with powder was applied for producing a wire of desired diameter. Finally, a drawing wire using 2 stage die for cold rolling mill was developed.

• 동력기계공학회지
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• 제14권2호
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• pp.40-47
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• 2010

This paper proposes a fault detection system to detect the strip rupture in six-high stand Cold Rolling Mills based on transient current signal of an electrical motor. For this work, signal smoothing technique is used to highlight precise feature between normal and fault condition. Subtracting the smoothed signal from the original signal gives the residuals that contains the information related to the normal or faulty condition. Using residual signal, discrete wavelet transform is performed and acquire the signal presenting fault feature well. Also, feature extraction and classification are executed by using PCA, KPCA and SVM. The actual data is acquired from POSCO for validating the proposed method.

• 한국정밀공학회지
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• 제7권4호
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• pp.140-148
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• 1990

A mathemetical medel has been developed for the purpose of estimating the rolling force required for computer control of cold strip mills. The model consists of equations of rolling force. flow stress. friction coefficient and tension. By applying the model to a 6-High cold tandem mill, the computer simulation is then been possible for all kinds of steels except stainless steel and the effectiveness of the model has been confirmed in the practice.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
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• pp.132-141
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• 1999

No. 1 PL(Pickling Line) and No. 1 TCM(Tandem Cold Rolling Mill) at Pohang works started up in 1977 and have been operating successfully keeping high productivity for productivity thin gauge sheat such as BP, CR and silicon steel. On the other hand, customer's requirements of quality level are rasing higher continuously, so that Pohang works has combined and revamped No. 1 PL and No. 1 TCM in order to improve labor productivity, thickness accuracy and shape control capability, and so on in the period of 1977∼1999. This paper introduce the applied facilities, technologies and recent operations after revamping.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.157-160
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• 1999

Aluminum 4343(filler thickness ; 10${\mu}{\textrm}{m}$/Al 3N03(core 80${\mu}{\textrm}{m}$)/Al 4343(filler 10${\mu}{\textrm}{m}$) clad sheet which is recently developed as brazing sheet materials for automotive condensers was fabricated by castinglongrightarrowhot rollinglongrightarrowcold rollinglongrightarrowintermediate annealing(IA)longrightarrowfinal cold rolling(CR). and the effect of IA/CR conditions on microstructure and sagging resistance were investigated the sheet which were fabricated by optimum conditions (IA'ed at 42$0^{\circ}C$ followed by CR'ed to 20~45%) showed good sagging resistance because the core obtained a coarsely recrystallized grain structure during brazing and consequently inhibited filled alloy penetration into the core.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.220-226
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• 1995

A study on the spalling causes of work roll for cold rolling was performed in the cold rolling mill. Performance of work roll is dependent to a great extent on spalling sothat both roll manufactures and users show great interest in spalling. So this paper shows that spalling origin on the roll surface. As being well known, spalling mostlyoccurred due to developing fatigue fracture originated a crack on a roll. But such spalling can be prevented by proper roll maintenance, The spalling accidents have sharply decreased since 1981 because of the use of ultrasonic test to detect cracks on a roll.

• 대한기계학회논문집A
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• 제35권8호
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• pp.855-861
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• 2011

본 연구에서는 극박 압연 이론과 6 단 압연기 수식 모델을 이용하여 압연 후 판 형상 예측에 대하여 제안하였다. 폭 방향에서 롤 사이의 접촉 압력과 판과 워크롤 사이의 압연하중은 6 단 압연기의 형상학적 구조와 경계조건을 이용한 수식모델을 통하여 계산된다. 그리고 압연 방향의 압연하중 분포는 Fleck 의 극박 압연 이론을 이용하여 계산하였다. 워크롤의 3 차원 탄성 변형량은 폭 과 압연방향의 압력분포에 의하여 계산된다. 이때, 3 차원 판 형상은 워크롤의 탄성변형에 의하여 얻어진다. 또한 3 차원 판 형상은 극박 압연 실험과 유한요소해석을 통하여 검증하였다.

• 소성∙가공
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• 제6권2호
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• pp.136-144
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• 1997

(Ag-10%Ni)/Cu clad metals for electric contact switch were fabricated by cold-roll bonding process. 2 or 3 passes of cold-rolling was carried out for each process to investigate the effect of the rolling passes on the bonding property. The effect of the annealing temperature of copper before the cold-roll bonding on the bond strength was also studied. The specimen bonded with copper annealed below 30$0^{\circ}C$ before roll bonding showed good bond strength. This is because high stored energy in copper promoted the short range diffusion and the grain refinement of copper by the static recrystallization increased the degree of the interfacial coherency. The maximum peel strength of clad metals bonded with Cu annealed below 30$0^{\circ}C$ was 120N.