SK5工具鋼鋸齒局部感應熱處理硬化研究

Abstract

工具鋼由於加工容易，易得到高硬度與耐磨性，在工業上通常應用於各種刀具、手工具等。工具鋼也有缺點，如硬化深度淺、回火軟化抵抗力小等。要提升工具鋼的機械性質必須施以適當的熱處理。 本研究的對象為SK5製作的木工手鋸鋸齒，利用高週波感應技術能讓工件局部加熱的特點，並配合後續的熱處理方法，希望得到鋸齒的前緣、尖點具有高硬度以及耐磨的特性，而鋸齒後方要具有適度韌性，使用上才不會造成斷裂。 實驗時以：高週波淬火、高週波淬火後進行低溫回火、高週波淬火後進行二次淬火、高週波淬火後進行二次淬火再低溫回火等不同條件對鋸齒施以熱處理，並以硬度量測、金相試驗與磨耗測試等評估方法比較熱處理的效果。 研究結果顯示SK5鋸片以高週波感應加熱衝風淬火後再以150℃回火30分鐘的條件，於鋸齒前鋒線處有較高的硬度值，並於磨耗試驗上有較佳的表現。 若鋸齒尖點的硬度值高，但鋸身處沒有較柔軟的質地吸收鋸切時的作用力，會形成齒尖的破裂，降低鋸片使用的壽命。

Tool steels usually are used in a variety of cutting tools and hand tools, because they are easy to process, can achieve high hardness and have good wear resistance. However, tool steels have some drawbacks, such as low hardenability and temper softening. Tool steels must impose the appropriate heat treatment to improve the mechanical properties. The material of this study is JIS SK5 tool steel often used in Japanese woodworking handsaw blade. High frequency induction heating could heat a specific part of workpiece. To make use of this characteristic together with subsequent heat treatment, we hope to make an ideal saw tooth which have high hardness on the cutting edges and good wear resistance. However, if the saw don’t have appropriate toughness in the saw body, it will shorten the life of saw blade. The heat treatments in this study were high-frequency induction heating and air quenching, low temperature tempering after high-frequency induction heating and air quenching, double quenching after high-frequency induction heating and air quenching, and low temperature tempering after double quenching. To evaluate the effect of heat treatments we measured the hardness distribution on the saw teeth, examine the micro-structures of the teeth and wear testing. The results showed that the saw teeth treated with high-frequency air quenching and tempering for 30 minutes at 150℃had higher hardness on the cutting edges and better wear performance. On the other hand, the saw teeth rupture and shortening the life of the saw blade were caused by hard teeth tip without soft body texture to absorb the cutting force.