The purpose of quenching and tempering treatment of die blank is to obtain fine spheroidized body or ultra-fine grain carbide with hardness of 18O ~ 320hb. At present, many new steel grades have been introduced in China, and the metallurgical quality of existing steel grades has been continuously improved to meet the needs of tools and dies. Similarly, many improvements have been made in the heat treatment methods. In addition to the continuous use of new equipment (vacuum heat treatment), new processes and new technologies for heat treatment, great changes have been made to the traditional pre heat treatment, which has attracted extensive attention in the industry. For example, spheroidizing annealing or isothermal spheroidizing annealing, which was widely used in cold and hot working dies, has been changed to quenching and tempering or ultra-fine treatment. Reasonable quenching and tempering process can obtain good original structure, so as to improve the quenching process performance and improve the strength and toughness after quenching.

1）调质处理的主要作用

1) Main function of quenching and tempering treatment

⑴获得分布均匀、颗粒细小、形状圆整的碳化物。

(1) obtain carbides with uniform distribution, fine particles and round shape.

⑵可有效地克服粗大珠光体、二次碳化物网或轻微带状偏析，以及大截面模块心部的铸态组织。

⑵ it can effectively overcome coarse pearlite, secondary carbide mesh or slight banded segregation, as well as the as cast structure in the center of large section module.

⑶可充分加工后的残余应力，减少淬火变形。

⑶ it can fully eliminate the residual stress after processing and reduce quenching deformation.

⑷可作为预硬化处理。

(4) it can be used as pre hardening treatment.

2）调质处理的典型用途

2) Typical application of quenching and tempering treatment

⑴改进表面加工质量如碳工钢或低合金工具钢退火后硬度过低，加工后表面光洁度太差，可补充调质成硬度为183～229HB的细球化体组织，能显 著改善表面加工质量。对40Cr、45等中碳钢，调质到260～300HB时，精加工后能获得高的光洁度。

(1) improve the surface processing quality. For example, if the hardness of carbon steel or low alloy tool steel after annealing is too low and the surface finish after processing is too poor, it can be supplemented and tempered into a fine spheroidized structure with a hardness of 183 ~ 229hb, which can significantly improve the surface processing quality. For medium carbon steels such as 40Cr and 45, when quenched and tempered to 260 ~ 300hb, high finish can be obtained after finishing.

⑵防止淬火开裂

(2) prevent quenching cracking

用于冷态辗轧、校直的成型轧辊，大多采用9Cr2或Cr2钢制作，一般采用喷水淬火或用氢氧化钠水溶液浸淬，由于形状复杂，易于淬裂，例如在精加工前，调质为硬度197～229HB的细球化体既能保证良好的淬透性，又可以有用地降低淬裂倾内。

The forming rollers used for cold rolling and straightening are mostly made of 9Cr2 or Cr2 steel. They are usually quenched by water quenching or using sodium hydroxide solution. Because of their complicated shape, they are easy to crack. For example, before refining, the fine spheroidizing quenched and tempered with hardness of 197 to 229HB can ensure good hardenability and can effectively reduce quenching and cracking.

⑶保证淬硬性

(3) ensure hardenability

φ30mmCr2钢轧辊，盐浴加热淬火后的硬度与毛坯的预处理工艺有关。退火毛坯的淬火硬度为65～66.5HRC，平均66HRC；调质（毛坯850℃淬油，660～680回火，229HB）的淬火硬度为66～67HRC，平均66.8HRC，且硬度高而均匀，未发生淬裂。

φ The hardness of 30mmcr2 steel roll after salt bath heating and quenching is related to the pretreatment process of blank. The quenching hardness of annealed blank is 65 ~ 66.5hrc, with an average of 66hrc; The quenching hardness of quenched and tempered (Rough 850 ℃, oil quenching, 660 ~ 680 tempering, 229hb) is 66 ~ 67hrc, with an average of 66.8hrc, and the hardness is high and uniform without quenching crack.

⑷用于预硬化模块的强化处理铝合金压铸模采用渗氮表面强化时，均应采用调质工艺进行预强化处理。塑料模具、冲压有色金属薄板或箔料的凹模，也可采用调质预强化。调质后再进行精加工。

(4) strengthening treatment for pre hardening module. When nitriding surface strengthening is adopted for aluminum alloy die casting die, quenching and tempering process shall be adopted for pre strengthening treatment. For plastic molds, concave molds for stamping non-ferrous metal sheets or foils, quenching and tempering pre strengthening can also be adopted. Finish machining shall be carried out after quenching and tempering.