• Title/Summary/Keyword: 냉간금형강

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Characteristics on Surface Hardening by using of Continuous Wave Nd:YAG Laser of Cold-Work Die Steel(STD11) about Variation of Focal Lens F-number (초점렌즈 F-수 변화에 의한 냉간금형강 STD11 의 연속파 Nd:YAG 레이저 표면경화 특성)

  • Hwang, Chan-Youn;Yang, Yun-Seok;Lee, Ka-Ram;Yoo, Young-Tae
    • Journal of the Korean Society for Precision Engineering
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    • v.29 no.4
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    • pp.395-408
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    • 2012
  • An experimental investigation with 2.8kW Nd:YAG laser system was carried out to study the effects of different laser process parameters on the microstructure and hardness of STD11. The optical lens with the elliptical profile are designed to obtain a wide surface hardening area with uniform hardness. The Laser beam is allowed to scan on the surface of the work piece varying the power (1600, 1800 and 1900kW) and traverse speed (200, 400, 600, 800 and 1000mm/min) at three different F-numbers of lens. After laser surface treatment three zones, In the microstructure have been observed : melted zone(decarburization), heat affected zone(martensite), and the substrate.

Microstructure and Hardness of Yb:YAG Disc Laser Surface Overlap Melted Cold Die Steel, STD11 (Yb:YAG 디스크 레이저로 표면 오버랩 용융된 냉간금형강, STD11의 미세조직과 경도)

  • Lee, Kwang-Hyeon;Choi, Seong-Won;Yun, Jung Gil;Oh, Myeong-Hwan;Kim, Byung Min;Kang, Chung-Yun
    • Journal of Welding and Joining
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    • v.33 no.5
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    • pp.53-60
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    • 2015
  • Laser surface Melting Process is getting hardening layer that has enough depth of hardening layer as well as no defects by melting surface of substrate. This study used CW(Continuous Wave) Yb:YAG and STD11. Laser beam speed, power and beam interval are fixed at 70mm/sec, 2.8kW and 800um respectively. Hardness in the weld zone are equal to 400Hv regardless of melting zone, remelting zone overlapped by next beam and HAZ. Similarly, microstructures in all weld zone consist of dendrite structure that arm spacing is $3{\sim}4{\mu}m$, matrix is ${\gamma}$(Austenite) and dendrite boundary consists of ${\gamma}$ and $M_7C_3$ of eutectic phase. This microstructure crystallizes from liquid to ${\gamma}$ of primary crystal and residual liquid forms ${\gamma}$ and $M_7C_3$ of eutectic phase by eutectic reaction at $1266^{\circ}C$. After solidification is complete, primary crystal and eutectic phase remain at room temperature without phase transformation by quenching. On the other hand, microstructures of substrate consist of ferrite, fine $M_{23}C_6$ and coarse $M_7C_3$ that have 210Hv. Microstructures in the HAZ consist of fine $M_{23}C_6$ and coarse $M_7C_3$ like substrate. But, $M_{23}C_6$ increases and matrix was changed from ferrite to bainite that has hardness above 400Hv. Partial Melted Zone is formed between melting zone and HAZ. Partial Melted Zone near the melting zone consists of ${\gamma}$, $M_7C_3$ and martensite and Partial Melted Zone near the HAZ consists of eutectic phase around ${\gamma}$ and $M_7C_3$. Hardness is maximum 557Hv in the partial melted zone.