and hardened through immediate cooling after austenitizing steel. The austenitizing temperature for hypoeutectoid steel should be Acz hypoeutectoid steel, and the quenching temperature for it should be set between Ac, and Acm. There are water quenching, oil quenching, martempering, and austempering as quenching methods. Select a

quenching medium and a method, and perform it depending on the materials and product properties.

-Tempering : It is a heat treatment process of reheating a quench-hardened steel below the eutectic tempera  keeping it at that temperature for an appropriate period, and air cooling immediately to improve ductility and toughness, remove residual stress, and stabilize a structure. Feature It is commonly used in the mass-production of small products of 5 kg unit weight or less. It requires fewer personnel due to easy operation through automation. Non-oxidizing is available by using CH3OH, RX-GAS, and DX-GAS for ambient gas.

• Normalizing

It is a heat treatment proces of cooling the steel after heating the steel up to a proper temperature austenite range above the transformation range (hypoeutectoid steels Ac₃ and hypoeutectoid steel Acm).