Process Design for Manufacturing 1.5wt%C Ultrahigh Carbon Workroll: Void Closure Behavior and Bonding Strength

Lim, H.C.; Lee, H.; Kim, B.M.; Kang, Stephen Dongmin

doi:10.5228/kstp.2013.22.5.269

Cited by 3 publications

(1 citation statement)

References 9 publications

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“…These voids have to be eliminated by an appropriated process like forging to prevent sudden failure of the forged part in operation. Numerous researchers studied the effects of process parameters on void closure behavior during forging to investigate the relationships among process design, process parameters and behavior of the void closure using the low or middle carbon steel [1][2][3][4][5][6]. It was also revealed from numerical anlyses that hydrostatic pressure and effective strain has a strong influence on the void closure [7][8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Microstructures and Crack Formation in Hot Compression Test of Ultrahigh Carbon Steel

Kang

Lim

Lee

2014

KEM

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Experimental works were carried out to investigate microstructure and crack formation during compression tests of 1.9wt%Cultrahigh carbon steel according to temperature and strain rate. As-received ultrahigh carbon steel is composed of precipitated cementites and pearlite matrix. In addition, numerous voids were observed in the matrix of as-received material. The compression tests at 800oC showed that the voids within the matrix are closed with increase of reduction ratio. On the other hand, when the reduction ratio increased numerous micro-cracks were newly formed in the bulky cementites and at the interfaces between hard cementite and soft matrix. It was also observed that because the volume fraction of cementite is reduced when temperature increased, volume fraction of newly formed micro-crack significantly decreased. Cast microstructures were observed after compression test at 1130oC due to local melting. From experimental results and microstructure anlayses, it was concluded that the forging temperature should be controlled at the temperature of more than 900oC and less than 1130oC.

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Section: Introductionmentioning

confidence: 99%

Microstructures and Crack Formation in Hot Compression Test of Ultrahigh Carbon Steel

Kang

Lim

Lee

2014

KEM

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Improved Ultrasonic Dead Zone Detectability of Work Rolls Using a Convolutional Neural Network

et al. 2022

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Rolled carbon steel sheets used in industrial and construction sites are formed by passing metal stock between two rotating rolls using a rolling mill, and the work roll is an essential part of the rolling mill. As the work rolls are in direct contact with the workpiece, the process quality is highly sensitive to their surface integrity, which is maintained through rough and finish cuttings; ultrasonic inspection is often performed after rough cutting the surfaces of work rolls. Ultrasonic inspection signals comprise signals reflected from and below the surface. Depending on the size of the subsurface defects, the thickness of the finish cutting is determined. The signals reflected by defects close to the surface overlap with those from the work roll surface, which is referred to as the ultrasonic dead zone and makes defect detection difficult. Since visual detection of flaws is not possible from signals collected from the dead zone, finish cutting is commonly performed up to the dead zone depth; this requires unnecessary cost and process time, which must be improved. Therefore, in this study a convolutional neural network is used to improve defect detection performance in the ultrasonic dead zone during the inspection of work rolls.

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Forging of 1.9wt%C Ultrahigh Carbon Workroll : Part II - Void Closure and Diffusion Bonding

Kang¹,

Lim²,

Lee³

2013

Transactions of Materials Processing

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In the previous work, a new forging process design, which included incremental upsetting, diffusion bonding and cogging, was suggested as a method to manufacture 1.9wt%C ultrahigh carbon workrolls. The previous study showed that incremental upsetting and diffusion bonding are effective in closing voids and healing of the closed void. In addition, compression tests of the 1.9wt%C ultrahigh carbon steel revealed that new microvoids form within the blocky cementite at temperatures of less than 900 o C and that local melting can occur at temperatures over 1120 o C. Thus, the forging temperature should be controlled between 900 and 1120 o C. Based on these results, incremental upsetting and diffusion bonding were used to check whether they are effective in closing and healing voids in a 1.9wt%C ultrahigh carbon steel. The incremental upsetting and diffusion bonding were performed using sub-sized specimens of 1.9wt%C ultrahigh carbon steel. The specimen was deformed only in the radial direction during the incremental upsetting until the reduction ratio reached about 45~50%. After deformation the specimens were kept at 1100 o C for the 1 hour in order to obtain a high bonding strength for the closed void. Finally, microstructural observations and tensile tests were conducted to investigate void closure behavior and bonding strength.

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Process Design for Manufacturing 1.5wt%C Ultrahigh Carbon Workroll: Void Closure Behavior and Bonding Strength

Cited by 3 publications

References 9 publications

Microstructures and Crack Formation in Hot Compression Test of Ultrahigh Carbon Steel

Microstructures and Crack Formation in Hot Compression Test of Ultrahigh Carbon Steel

Improved Ultrasonic Dead Zone Detectability of Work Rolls Using a Convolutional Neural Network

Forging of 1.9wt%C Ultrahigh Carbon Workroll : Part II - Void Closure and Diffusion Bonding

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