1. What are the main structural defects in low alloy cold working die steel? What are the causes? 

低合金冷作模具钢中组织缺陷主要有：网状碳化物、碳化物呈带状偏析、碳化物液析。

The main structural defects in low alloy cold working die steel are network carbide, banded segregation of carbide and liquid segregation of carbide.

① 现现网状碳化物，是由于钢材在轧制或锻造成形时，停轧或停锻温度较高而冷却速度过缓，二次碳化物沿奥氏体晶界呈网状析出，有时还会出现魏氏组织的碳化物，呈针状伸入晶内。

① The present network carbide is due to the slow cooling rate due to the high temperature of stop rolling or stop forging when the steel is rolled or forged. The secondary carbide precipitates along the austenite grain boundary in network form, and sometimes there are widmanstatten carbides extending into the grain in needle form.

② 碳化物呈带状偏析，是由于钢锭冷却时，微观结晶出现偏析，在树枝晶之间的凝固区域，富集着碳和铬等溶质元素，凝固后析出聚集着大量碳化物，在锻轧过程中它逐步沿热加工方向延伸成带状。

② The segregation of carbide is due to the segregation of micro crystal during ingot cooling. In the final solidification area between dendrites, solute elements such as carbon and chromium are enriched. After solidification, a large amount of carbide precipitates and accumulates. During forging and rolling, it gradually extends along the hot working direction to form a strip.

③ 碳化物液析，是由于铸锭在冷却时会出现元素偏析，在凝固区溶质含量高，形成碳及合金元素的富集区，当在晶界附近成分达到共晶成分时，凝固后会出现共晶莱氏体。这种亚稳定的共晶莱氏体在缓慢冷却的过程中，或在轧制加热时会形成离异共晶，离异出来的碳化物，经轧制后，呈白色多角状碎块沿轧制方向分布成链状或带状，常出现于钢材的中心地带。

③ Carbide liquidus is due to element segregation in ingot during cooling, high solute content in final solidification zone, forming enrichment zone of carbon and alloy elements. When the composition near grain boundary reaches eutectic composition, eutectic ledeburite will appear after solidification. This kind of metastable eutectic ledeburite will form divorced eutectic in the process of slow cooling or rolling heating. After rolling, the separated carbides will appear as white polygonal fragments, which are distributed in chains or belts along the rolling direction, and often appear in the center of the steel.

⒉低合金 冷作模具钢中组织缺陷对模具使用有何影响？如何低合金冷作模具钢中组织缺陷？

2. What is the effect of microstructure defects in low alloy cold working die steel on die use? How to eliminate the structure defects in low alloy cold working die steel?

低合金冷作模具钢中组织出现网状碳化物、碳化物呈带状偏析、碳化物液析等缺陷，导致模具在服役时出现工作面剥落、崩刃或开裂。也给模具的热处理带来不利的影响，往往会造成模具在淬火时出现淬裂。

The defects such as network carbide, banded segregation of carbide and liquid segregation of carbide appear in the structure of low alloy cold working die steel, which lead to the spalling, chipping or cracking of working face in service. It also brings adverse effects to the heat treatment of the mold, which often causes the mold to crack during quenching.

① 网状碳化物的方法，是采用正火处理

① The method of eliminating network carbide is normalizing

② 碳化物呈带状偏析的方法，是对钢材重新进行合理锻造，锻造后控制冷却或锻造后淬火处理，热处理时再采用固溶双细化处理工艺。也可以根据偏析程度，直接采用固溶双细化处理工艺。

② The method to eliminate the banded segregation of carbides is to re forge the steel reasonably, control cooling after forging or quenching after forging, and then adopt the solid solution double refining process during heat treatment. According to the degree of segregation, the solution double refining process can also be used directly.

③ 碳化物液析的方法，是采用扩散退火处理，或固溶+急冷处理，或锻造后利用余热进行淬火处理。

③ The method to eliminate the precipitation of carbides is to adopt diffusion annealing treatment, or solid solution + quenching treatment, or quenching treatment with waste heat after forging.