Effect of Carbon Potential Control on the Heat Treatment Properties of Carbon Tool Steel
Date Issued
2007
Date
2007
Author(s)
Cheng, Wen-Pin
DOI
zh-TW
Abstract
The atmosphere produced from the decomposition of methanol is generally used in the industry. In order to control the carbon potential of atmosphere effectively, different ratio of distilled water was mixed with methanol in advance. Additionally, the decomposed temperature of methanol or heating temperature of workpiece was adjusted to produce atmosphere with different carbon potential and then these experimental data were analyzed with linear regression method of statistics. The carbon potential could be expressed by a linear equation in terms of decomposed temperature of methanol, heating temperature of workpiece and addition amount of distilled water. Referred to this equation, it is capable of generating the atmosphere with a specific carbon potential to satisfy the requirement of different heat treatment. Besides, the workpiece of high carbon tool steel was heated in the atmosphere with various carbon potential before quenching. The effect of carbon potential of the atmosphere on the hardness and toughness are investigated. The results obtained are as follows:
1.For a given temperature of workpiece, the carbon potential of the atmosphere will be raised, when the decomposed temperature of methanol increases. For a given temperature of methanol, the carbon potential of the atmosphere will be decreased, when the heating temperature of workpiece increases. If the decomposed temperature of methanol and heating temperature of workpiece are fixed, the carbon potential of the atmosphere will be decreased, when the ratio of distilled water to methanol increases.
2.The influence of the decomposed temperature of methanol, heating temperature of workpiece and addition amount of distilled water on the carbon potential of the atmosphere can be understood quantitatively by linear regression analysis. The carbon potential can be estimated accurately by the regression equation. The error is less than 0.1%.
3.The thin workpiece of high carbon tool steel which has been heated in the atmosphere with a higher carbon potential before quenching will possess a higher hardness and a lower toughness after tempering. Whereas for the workpiece heated in the atmosphere with a lower carbon potential, its hardness will decrease fast during tempering, but its toughness is better.
4.For the thin workpiece of high carbon tool steel quenched and tempered to the same hardness level, those tempered at 330℃ are tougher than those tempered at 400℃.
5.The thin workpiece of high carbon tool steel will possess the best toughness for the same hardness level after quenching and tempering, when the carbon potential of the atmosphere is 0.70%~0.80%.
6.Although either raising the carbon potential of the atmosphere, the carburizing temperature, or the carburizing time can enhance the hardened depth, a hyper-eutectoid structure will be formed near the surface. It will result in lowering the hardness on the surface.
Subjects
木精
碳勢
迴歸分析
韌性
滲碳
Methanol
Carbon Potential
Regression Analysis
High Carbon Tool Steel
Toughness
Carburizing
Type
thesis
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