Analysis Of 40Mn2 Forging Ball Defects And The Preparation Process Optimization Research

In recent years, steel forging ball by the majority of mines, cement and other need to be broken in favor of abrasive industry because of the low cost, simple manufacturing process, suitable performance. 40Mn2 as a kind of effective forging ball material used for forged ball manufacturers. However, in practical process, the properties of 40Mn2 materials is difficult to fit the reality of the conditions and problems, such as hardness and toughness so that can not make a very good balance.A forging factory found forging ball crack and center hole defect in the production of40Mn2 forging ball. In this paper, the defects of forging ball production in the process of a casting & forging plant, the cause of the defects, the optimizing preparation technology are systematacially analyzed.The results of the study show that the failure form of 40Mn2 forging ball is the holes and cracks at the center. Forging blank has banded structure, and also,there are widmanstatten structure and a small amount of martensite structure in the quenched forging ball core structure.The Mn element segregation of forging blank leads to the appearance of martensite at the center of the organization after quenching. It is the center martensite that promote the initiation and development of cracks. 1200℃×12h can eliminate the banded structure of forging billet, but the energy consumption and the cost is too exorbitant for the forging factory. The combined treatment(860℃×1h+840℃×1h) which can significantly eliminate the banded structure and the segregation of Mn element is a suitable heat treatment process.Widmanstatten structure in the quenched forging ball core structure will come out once quenching at 920℃ and cooling at the speed of 7.3 ℃/s. You can not find widmanstatten structure in the quenched forging ball core structure if quenching at860℃ and cooling at the speed of 7.0℃/s~3.9℃/s,.The final optimized preparation process is that: two normalizing for forging blank+heated to 1100℃+forged it into a ball + quenching ball at 860℃+ tempering(250℃×2h). There is a considerable improvement in the structure and properties after the optimization.what is more,hardness is increased by 3HRC, hardened layer increased by 4mm, impact toughness is increased by 35J/cm2.