• 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.

• 대한기계학회논문집
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• 제19권5호
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• pp.1149-1157
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• 1995

The research for variation of coolant film thickness and separating force has been investigated following the examination for friction profile of work roll and roughness change of strip surface in rolling mill producting actual commercial products. The obtained results are as follows ; (1) Coolant film thickness in cold rolling has been increased relative to the circumferential velocity of work roll, and formation of coolant films has decreased with the smaller diameter of work roll. (2) Separating force is related to the formation of coolant film, and large separating force is needed to the formation of coolant film but it is constant after formation of appropriate film. (3) Wear and roughness alleviation of work roll is larger in bottom-roll than in top-roll on cold surface is larger in the direction of width than in roll direction, and changes of roughness and strip surface hardness rarely occurred after 3 passes.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 제5회 압연심포지엄 신 시장 개척을 위한 압연기술
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• pp.349-358
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• 2004

The strip temperature history of finishing mill process is one of the most important factors to stabilize the facilities and to achieve the better product quality including a better prediction of roll force etc. The ultimate goal of this study is to improve scientific understanding of the finishing mill process in the view of heat transfer science. Finishing mill cooling facilities of KwangYang $\#3$ hot rolling are introduced and heat transfer analyses from FET to FDT are particularly focused in this study Three major tasks are successfully achieved as follows: 1) The temperature Prediction Models are developed. 2) The average absolute error is found to be less then 10 Celsius degree (about $8.5^{\circ}C$). 3) Prediction rate (less then $\bar{+}20$) are $10.2\%$ improved $(80.1\;\rightarrow\;90.3\%)$.

• 대한기계학회논문집
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• 제19권1호
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• pp.292-300
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• 1995

According to the number of cold-rolled coils, the amount of roll wear and thermal expansion, and roll gap profile were calculated, by using the actual data from the finishing mill. Also, based on those data, the calculations of the deflection, the flattening, and the contact pressure of vwork rolls and backup rolls were made respectively. Specially, in the calculation of contact pressure, the numerical results were obtained not only during the normal rolling, but also during the abnormal rolling, by modeling mathematically the dynamic impact force which occurs when the head section of the strip is threading through rolls. With those results the growth of the fatigue region and the fatigue damage of rolls were predicted. Also the optimum roll-grinding depth was determined to maximize the roll life.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1680-1689
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• 2002

This paper studies on the design of a looper control system for hot strip mill finisher using ILQ(Inverse Linear Quadratic optimal control) control method. The loopers are placed between each rolling stands and looper control plays an important role in regulating strip tension. The strip tension is controlled by raising and lowering the looper and by changing the speed of main work rolls. Firstly, it is shown from a nonlinear dynamic simulation that the strip tension is more influenced by difference of rolling speed than that of the looper angle. Secondly, a servo controller of the looper is designed using ILQ control method of which the characteristics and algorithms are simply introduced. Finally, the performances of the ILQ servo controller are compared with those of the LQI servo controller from computer simulation. In result, it is shown that the proposed ILQ servo controller has the better performances and robustness far parameter perturbations and disturbances than those of LQI controller.

• Advances in materials Research
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• 제4권4호
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• pp.215-226
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• 2015

Experiment on roughness and micro pit defects of SUS 430 ferrite stainless steel was investigated in laboratory. The relation between roughness and glossiness with reduction in height, roll surface roughness, emulsion parameters was analyzed. The surface morphology of micro pit defects was observed by SEM, and the effects of micro pit defects on rolling reduction, roll surface roughness, emulsion parameters, lubrication oil in deformation zone and work roll diameter were discussed. With the increasing of reduction ratio strip surface roughness Ra(s), Rp(s) and Rv(s) were decreasing along rolling and width direction, the drop value in rolling direction was faster than that in width direction. The roughness and glossiness were obtained under emulsion concentration 3% and 6%, temperature $55^{\circ}C$ and $63^{\circ}C$, roll surface roughness $Ra(r)=0.5{\mu}m$, $Ra(r)=0.7{\mu}m$ and $Ra(r)=1.0{\mu}m$. The glossiness was declined rapidly when the micro defects ratio was above 23%. With the pass number increasing, the micro pit defects were reduced, uneven peak was decreased and gently along rolling direction. The micro pit defects were increased with the roll surface roughness increase. The defects ratio was declined with larger gradient at pass number 1 to 3, but gentle slope at pass number 4 to 5. When work roll diameter was small, bite angle was increasing, lubrication oil in micro pit of deformation zone was decreased, micro defects were decreased, and glossiness value on the surface of strip was increased.

• 대한기계학회논문집A
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• 제37권2호
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• pp.271-277
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• 2013

냉간압연 및 소둔공정에서의 조질압연 과정은 강종별로 적정 연신율을 부여함으로서 프레스 가공시 항복점 연신 현상을 제거해주는 중요한 공정이다. 적정 연신율 확보를 위해서는 강종별, 사이즈별 정확한 압연하중 예측이 필수이다. 열간 및 냉간압연과는 달리 조질압연에서는 2%이내의 연신율을 부과하는 공정이므로 압연하중 작용 시 롤 바이트 내 에서의 롤의 탄성변형 거동이 복잡하여 정확한 압연하중을 예측하기가 어려워 예측모델이 정립되어 있지 않다. 그럼에도 불구하고 최근 인장강도 590MPa 급 이상의 자동차용 고강도강 개발이 가속화 됨에 따라 조질압연시 정확한 압연하중의 예측은 더욱더 중요하게 되었다. 따라서 본 연구에서는 조질 압연 시 롤 바이트 내에서 롤의 변형거동이 유사하다고 알려져 있는 호일(foil)압연 이론 식을 이용해 조질 압연 시 전체 생산 강종을 대상으로 압연하중 예측 가능성에 대해 검토하였다. 그 결과 인장강도 350MPa 이상 980MPa 이하의 강종에 대해서는 non circular model 이 circular 모델보다 압연하중 예측 정도가 우수하며, 이 영역에서 압연하중 예측 모델로의 적용이 가능함을 확인하였다.

• 소성∙가공
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• 제8권1호
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• pp.65-77
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• 1999

In recent years, the quality requirements from the customers of hot rolled steel strip have been steadily increasing in diversity and strictness. To meet these quality requirements as well as to improve productivity, steel mills have been doing their efforts for developing high performance Automatic Gauge Control (AGC) system. However, it is very time consuming and also needs a lot of money to develop the new technologies of AGC in actual mill. So, there has been a demand for developing the Dynamic Hot Rolling Simulator since late 80's. It is a kind of software packages and can analyze the dynamic behaviors of hot finishing rolling process without laborious experiments in actual mill. It can also be used as a designing tool of Automatic Gauge Controller. In this work, the Dynamic Hot Rolling Simulator which is applicable to 6 sands hot strip mill rolling was developed. The MATLAB with SIMLINK was used as a software developer for making the main part of simulator because it is very powerful tool for modeling, integrating, controller design, and simulation. In this paper, the structures and the mathematical models of the simulator were briefly described and the results of simulation on the transient phenomena of hot rolling process with actual mill data were also presented.

• 대한기계학회논문집A
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• 제20권3호
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• pp.861-871
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• 1996

In this study, a fuzzy control algorithm was developed for the randomly irregular shape of cold-rolled strip. Currently developed fuzzy control algorithm consists of two parts: the first part calculates the changes of work and intermediate roll bender forces based on the symmetric part of the irregular strip shape, and the second part calculates the weighting factors based on the asymmetric part and modifies the pre-determined roll bender forces according to the weighting factors. As a result of this, bender froces applied at the both sides of the cold-rolled strip were different. In order to simulate the continuous shape control. fuzzy controller developed was linked with emulator which was developed based on neural network. The fuzzy controller and emulator developed simulated the cold rolling process until irregular shape converged to a tolerable range in producing uniform cross-sectional strip shape. The results obtained from the simulation were reasonable for various irregular strip shapes.

• 품질경영학회지
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• 제45권1호
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• pp.25-38
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• 2017

Purpose: Hot strip rolling mill consists of a lot of mechanical and electrical units. In condition monitoring and diagnosis phase, various units could be failed with unknown reasons. In this study, we propose an effective method to detect early the units with abnormal status to minimize system downtime. Methods: The early warning problem with various units is defined. K-means and PAM algorithm with Euclidean and Manhattan distances were performed to detect the abnormal status. In addition, an performance of the proposed algorithm is investigated by field data analysis. Results: PAM with Manhattan distance(PAM_ManD) showed better results than K-means algorithm with Euclidean distance(K-means_ED). In addition, we could know from multivariate field data analysis that the system reliability of hot strip rolling mill can be increased by detecting early abnormal status. Conclusion: In this paper, clustering-based monitoring and fault detection algorithm using Manhattan distance is proposed. Experiments are performed to study the benefit of the PAM with Manhattan distance against the K-means with Euclidean distance.