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Influence of Trimming on Open Die Forging Process

1. The Role of Trimming in Open Die Forging Process

Die forging refers to the process that metal blank is forced deform in die forging cavity under the action of pressure equipment. During die forging, the surplus metal in the final forging die bore flows into the trimming groove to form a circle of trimming around the forging. In the open die forging process, trimming is the main factor causing material waste. Moreover, too much trimming also aggravates die wear. In actual production, people always try their best to reduce trimming. However, should the trimming be as small as possible in the open die forging process? If not, what size should the trimming be?

2. The Influence of Trimming on Die Forging Process

Judging from the feedback in the actual forging production, it is obvious that the trimming should not be as small as possible. Due to the location of the blank, an excessively small blank design will result in a high rejection rate. However, some equipment factories and some forging factories which lack theoretical basis and relevant experience in forging forming pursue small trimming and no trimming, which is very unscientific and undesirable.

The role of trimming in die forging is obvious.

First, it can contain excess metal. 

Secondly, it can increase the resistance of metal flowing into the cavity and make the metal fill the cavity better.

Thirdly, the proper size of trimming also plays a certain role in buffering the blow of upper and lower dies and reducing the damage to dies and forging equipment. The reason why the parts need to be forged is to improve the mechanical properties of the parts.

The main reason why forgings can improve the mechanical properties of materials is that the open die forging process can limit the loose defects of forging blanks, thus eliminating the influence of looseness on the overall quality of parts to the greatest extent. Looseness has great harm to the mechanical properties of parts. In the heat treatment of parts, looseness provides stress concentration points for heat treatment cracks. The worse the looseness grade is, the easier it is to have heat treatment cracks. Looseness also provides stress concentration points for parts subjected to alternating loads, increasing its harmfulness. With the improvement of quality and safety awareness, the quality requirements of forgings are getting higher.

Therefore, in the open die forging process, we should not blindly pursue less trimming and no trimming. The trimming should be controlled in a reasonable range.