冷卻速率和持溫時間對AISI H13鑄鋼在機械性質與顯微組織上的影響

The Effects of Cooling Rate and Holding Time on the Microstructure and Mechanical Properties of AISI H13 Casting Steel

陳志威(Chih-Wei Chen)

指導教授 ： 張世賢

國立臺北科技大學/工程學院/材料科學與工程研究所/碩士(2011年)

https://doi.org/10.6841/NTUT.2011.00528

摘要

本研究是使用高週波感應電爐在大氣中熔煉的方式，以製造熱作AISI H13鑄鋼，實驗設計設定兩種冷卻速率，分別為室溫氣冷(Air Cooling, AC)和加壓氣體冷卻(Gas Cooling, GC)，以及三種不同持溫時間(1分鐘、10分鐘與30分鐘)，並利用XRD、OM與SEM觀察，以及硬度、拉伸和衝擊試驗等分析，來比較AISI H13鑄鋼在不同製程下，其顯微組織與機械性質的變化。
實驗結果顯示， 退火前的AISI H13鑄鋼之基地顯微組織在GC部份以麻田散鐵為主，AC部份以下變韌鐵為主，而析出在晶界上的網狀結構為初析之合金碳化物，且隨著冷卻速度的下降與持溫時間的增加，金屬和非金屬介在物以及孔洞的類缺陷也隨之增加，此為影響其機械性質的主因之一。經熱處理後，AISI H13鑄鋼的基地顯微組織為明顯的回火麻田散鐵，並散佈著二次析出碳化物。
硬度測試結果顯示，GC的平均值為HRC 47~48 之間，而AC部份為HRC 46~48 之間；常溫衝擊試驗結果，GC的平均值為3.9~4.7 J之間，AC部份則為3.9~4.0 J 之間；而在抗拉試驗中，GC部份的最大抗拉強度為1526~1589 MPa之間，而AC部份為1523~1560 MPa 之間。使用GC冷卻時，鑄件的硬度與強度明顯上升，但會隨著持溫時間的增加而機械性質下降，而使用AC冷卻時，則產生相反之趨勢，隨著持溫時間的增加而機械性質上升。

關鍵字

AISI H13鑄鋼 ； 冷卻速率 ； 持溫時間 ； 熱處理 ； 回火麻田散鐵

並列摘要

In this study, the melting and production of the hot work of AISI H13 casting steel was done by a high-frequency induction furnace at an atmosphere condition. In the research, we designed two different cooling rates and three holding times for the casting procedure. The different cooling rates were normal air cooling (AC) and pressurized gas cooling (GC), and the holding times were 1, 10 and 30 min, respectively. In addition, to compare the effects of the microstructural and mechanical properties on AISI H13 casting steel by various processes, XRD, OM and SEM microstructural inspections, hardness tests, tensile and impact tests were performed.

The experimental results showed that the martensite’s microstructure of AISI H13 casting steel could be obtained by the GC process, and lower bainite mainly appeared in the AC process before the annealing treatment. Furthermore, the network structures of primary alloy-carbides precipitated on the grain boundaries. The metal and non-metallic inclusions and pore defects increased as the cooling rate decreased and the holding time increased; these were the main effects of the mechanical properties on AISI H13 casting steel. The tempering martensite clearly appeared in the matrix of AISI H13 casting steel, and precipitated secondary carbides after heat treatment.

The hardness test results showed that the average value of hardness by the GC process was between HRC 47~48, and by AC, it was HRC 46~47. At a room temperature condition, the impact test result indicated that the average value of toughness was 3.9~4.7 J by the GC process, and by AC, it was 3.9~4.7 J. Moreover, the tensile test results also showed that the maximum tensile strength was between 1526~1589 MPa by the GC process, and 1523~1560 MPa by AC. The hardness and strength of the castings were obviously increased by the GC cooling process; however, the mechanical properties decreased as the holding time increased. Conversely, different results were obtained by the AC cooling process, whereby the mechanical properties of H13 casting increased as the holding time increased.

並列關鍵字

AISI H13 Casting Steel ； Cooling rate, ； Holding Time ； Heat treatment ； Tempering Martensite

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