• Title/Summary/Keyword: cold rolled steel

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A Micro-defect Detection of Cold Rolled Steel (냉연 강판의 미세 결함 검출 기술)

  • Yun, Jong Pil
    • Journal of Institute of Control, Robotics and Systems
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    • v.22 no.4
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    • pp.247-252
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    • 2016
  • In this paper, we propose a new defect detection technology for micro-defect on the surface of steel products. Due to depth and size of microscopic defect, slop of surface and vibration of strip, the conventional optical method cannot guarantee the detection performance. To solve the above-mentioned problems and increase signal to noise ratio, a novel retro-schlieren method that consists of retro reflector and knife edge is proposed. Moreover dual switching lighting method is also applied to distinguish uneven micro defects and surface noise. In proposed method, defective regions are represented by a black and white pattern. This pattern is detected by a defect detection algorithm with Gabor filter. Experimental results by simulator for sample defects of cold rolled steel show that the proposed method is effective.

Developments and applications of high strength cold rolled steel sheets for automobiles (자동차용 고강도 냉연강판의 개발 및 적용현황)

  • Kim S. J.;Chin K. G.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.08a
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    • pp.45-52
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    • 2004
  • Continuing pressure for the weight reduction of vehicles and improvement of collision safety is driving the development of new high strength steel with excellent formability. The formable high strength steels which have excellent drawability have been developed and applied to the complicated inner panels. Although BH steel have mainly occupied the material market for outer panels, it is challenged by DP steel which have low yield strength and good bake hardenability. The advanced high strength steel, TRIP steels and DP steels which have excellent formability are new alternatives to conventional HSLA steel for structural parts such as members and pillars. HSLA steels also have been used for automotive bumper reinforcements due to their high yield ratio. Higher grade complex phase steel(CP) were developed for bumper reinforcements by addition of precipitation hardening to transformation strengthened steel. The usage of the advanced high strength steel ale increasing and will become the main material in structural parts near future. This paper describes the features of newly developed high strength cold rolled steels for automobiles.

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A Study on the Measurement of Residual Stress in Rolled Steel for Automobile using X-ray Diffraction (X선 회절을 이용한 자동차 압연강의 잔류응력 측정에 관한 연구)

  • 홍순혁;이동우;조석수;주원식
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.6
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    • pp.150-157
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    • 2002
  • In textured material, diffraction angle $2{\theta}$ usually shows a nonlinear relation against $sin^2{\psi}$ due to elastic anisotropy of crystals. SPHD and SPCD steel is cold-rolled carbon steel for automobile. The characteristics X-ray for stress measurement is Cr $K_{\alpha}\;and\;Mo\;K_{\alpha}$ characteristic X-ray. The $2{\theta}-sin^2{\psi}$ diagram under elastic strain seems to have a linear behavior using regression line of data but has a nonlinear behavior in distribution of data by Cr $K_{\alpha}$ characteristic X-ray. As the plastic strain of specimen increases, the nonlinearity of $2{\theta}$ with respect to $sin^2{\psi}$ increases remarkably. On the other hand, the diffraction angle $2{\theta}$ by Mo $K_{\alpha}$ characteristic X-ray shows a good linearity on $2{\theta}-sin^2{\psi}$ diagram under plastic strain as well as elastic strain. Therefore, this paper presents the measurement of residual stress in cold-rolled carbon steel for automobile using penetration depth of Mo $K_{\alpha1}$ characteristic X-ray and multiplicity factor of crystal diffraction plane.

Finite element modeling of rolled steel shapes subjected to weak axis bending

  • Saliba, Najib G.;Tawk, Issam;Gergess, Antoine N.
    • Steel and Composite Structures
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    • v.29 no.2
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    • pp.161-173
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    • 2018
  • Point bending is often used for cambering and curving structural steel girders. An analytical solution, applicable in the elasto-plastic range only, that relates applied loads to the desired curve was recently developed for inducing horizontal curves using four-point bending. This solution does not account for initial residual stresses and geometric imperfections built-in hot-rolled sections. This paper presents results from a full-scale test on a hot-rolled steel section curved using four-point bending. In parallel, a numerical analysis, accounting for both initial geometric imperfections and initial residual stresses, was carried out. The models were validated against the experimental results and a good agreement for lateral offset and for strain in the elasto-plastic and post-plastic ranges was achieved. The results show that the effect of initial residual stresses on deformation and strain is minimal. Finally, residual stresses due to cold bending calculated from the numerical analysis were assessed and a revised stress value for the service load design of the curved girder is proposed.

Effect of drawbead process parameters on the drawing characteristics of sheet metals for automotive parts (자동차용 판재 성형시 드로우비드 공정인자별 인출특성에 대한 연구)

  • 김원태;이동활;강우순;서만석;문영훈
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2003.10a
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    • pp.140-143
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    • 2003
  • The drawbead is an important part in sheet metal forming for automotive part and its effect is affected by various process parameters. Therefore in this study, drawbead friction test was performed at various process parameters - panels (cold rolled and galvanized sheet steel), lubricants (having three different viscosities), bead materials(steel, iron) and surface treatment of bead (Cr plating). Circular shape bead has been used for the test. The results show that friction and drawing characteristics were mainly influenced by the nature of zinc coating, viscosity of lubricants, surface treatment of a bead and hardness of coated layer.

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Surface Flaw Detection of Cold-Rolled Steel Strips using Intensity Gradient (광강도차를 이용한 냉연강판 표면결함 검출)

  • 공선곤
    • Journal of the Korean Institute of Intelligent Systems
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    • v.10 no.2
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    • pp.75-82
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    • 2000
  • This paper presents a method of detecting surface flaw of cold-rolled steel plate using image processing technique and a neural network classifier. The amount of steel plate surface image data is reduced by the wavelet transform. Features are extracted from the co-occurence matrix of the partial image corresponding to the low-frequency region, and a MLP neural network classifies into predetermined surface flaw categories. Simulations show the neural network classifier outperforms conventional vector quantization method.

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Resistance Spot Weldability of Cold Rolled HT80 Grade Steel for Automobile Application (80kg/mm$_2$급 高張力 冷延鋼板의 熔接性)

  • 김기철;이기호;장래웅
    • Journal of Welding and Joining
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    • v.10 no.1
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    • pp.52-59
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    • 1992
  • Resistance spot weldability of cold rolled 80kg/mm$^{2}$ and 45kg/mm$^{2}$ grade high strength steel sheets for automobile structure was investigated focussing on the influences of welding parameters such as welding current and welding time on the weld strength and the nugget formation. The results of this study showed that the optimum ranges of welding current for the grade 80 and grade 45 were 5.0 cycle(250 m sec.) It was also shown that the tensile shear strength of the resistance spot weld was strongly influenced by both current and time applied in welding procedure, however, the tensile shear strength was mainly affected by welding time for the higher strength steel.

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Structural strength evaluation of Freight Car Carbody for transportation of cold-rolled coils (냉연코일 수송화차 차체의 구조 강도 평가)

  • Kwon, Sung-Tae;Kim, Jeong-Guk;Seo, Jung-Won
    • Proceedings of the KSR Conference
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    • 2007.05a
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    • pp.775-779
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    • 2007
  • The structural strength assessment of a carbody was performed using F.E. analysis and static test to verify the structural safety of newly manufactured carbody of a freight car. The freight car for the transportation of cold-rolled coils in steel making company was designed with SS400 steel for underframe and SM490A steel for bracket. Prior to the evaluation of structural strength, commercial finite element method(FEM) software was used for the stress and structural analyses on stress distribution in a carbody of freight car. The strain gages were attached on the carbody based on the FEM results. The actual vertical loading test and horizontal compression loading test were conducted, and the stress and displacement were obtained. Finally, the structural strength of carbody was evaluated by using a engineering techniques.

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Magnetic Shielding Effectiveness Measurement of Magnetic Steel Sheets in ELF Range

  • Yeon, Kyo-Heum;Son, Derac;Park, Eon-Byeong;Lee, Jae-Young;Do, Kyung-Hwan;Park, Jae-Seg
    • Journal of Magnetics
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    • v.13 no.4
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    • pp.173-176
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    • 2008
  • In this study, a new kind of instrument for measuring the magnetic shielding effectiveness (MSE) was developed using a double yoke; one a magnetizing yoke and the other a sensing yoke. Using the developed instrument, the MSE could be measured for a steel sheet specimen in the ELF range, where the magnetic permeability contributes to the MSE at low frequencies and eddy currents contributes to the MSE high frequencies with < 0.1 dB reproducibility. The developed measuring method can be applied to quality control in a steel sheet company producing EMI/EMC shielding materials.

Effect of Subzero Treatment on the Mechanical Properties of Cold-Rolled High Manganese Austenitic Stainless Steel (냉간압연한 고 Mn 오스테나이트계 스테인리스강의 기계적 성질에 미치는 서브제로처리의 영향)

  • Hwang, T.H.;Jung, M.H.;Lee, J.Y.;Lee, H.B.;Kang, C.Y.
    • Journal of the Korean Society for Heat Treatment
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    • v.25 no.5
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    • pp.233-238
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    • 2012
  • The effect of subzero treatment on the mechanical properties of cold rolled high manganese austenitic stainless steel was investagated. ${\alpha}$'-martensite was formed by cold rolling, and it was formed with surface relief and specific direction or crossing each other. The volume fraction of martensite increased by subzero treatment, and it was increased with longer time of subzero treatment and higher temperature of subzero treatment. The hardness and strength increased by subzero treatment, while the elongation decreased. With the increase of volume fraction of martensite, the hardness and strength was increased steeply with proportional relationship, elongation was decreased slowly. The results show that the hardness and strength was strongly controlled by the volume fraction of martensite, and the elongation was affected by transformation behavior of deformation induced martensite in the initial stage of deformation.