What preparations should be made for forging dies before use?

2022-06-22

First, technical inspection



The forging die needs to check its manufacturing quality before use, generally with forging lead method or directly with forgings to check the size of the die bore, and the wrong displacement of the upper and lower die (allowing the wrong displacement of 0.2~0.4mm) meets the requirements; During the use of the forging die, it is necessary to spot check whether the forging is out of tolerance; After the forging die is used, it is necessary to check whether the forgings are out of tolerance and whether the mold is damaged, in order to recover and reuse.



Two, mold installation



When installing the mold, attention must be paid to installing and tightening the mold. The dimension and levelness of the mold mounting surface should conform to the allowable deviation; The base surface of upper and lower die dovetail should be parallel to each other and perpendicular to the direction of movement, the supporting surface of the dovetail should be parallel to the parting surface of the forging die, and the parting surface of upper and lower die should be parallel to each other. The non-parallelism between dovetail inclined plane and hammerhead supporting inclined plane and the non-parallelism on both sides of the inclined wedge shall not be greater than 0.06mm/300mm. No clearance is allowed between dovetail base surface and supporting surface. Every time the mold is replaced, the installation surface of the equipment should be carefully observed and repaired in time, especially the dovetail support surface of the hammer head and the support surface of the anvil base should be repaired in time.

Under the condition of ensuring normal operation, the clearance between hammer head (or slider) and guide rail should be minimum. If the gap is too large, it is easy to damage the mold when forging forging parts.

Three, the preheating of the forging die

The risk of forging die cracking occurs in the beginning of production, when the temperature difference between forging die and blank is large, the effect of alternating thermal stress is the most obvious, easy to produce hot cracking; And the forging die temperature is low, plasticity, toughness is poor, but also impact cracking. When the forging die is preheated to more than 250℃, the temperature difference between the forging die and the blank decreases, and the impact toughness of the forging die is also significantly improved, and the risk of cracking is reduced. And the forging die after preheating, help to blank heat preservation, can reduce the number of hammer, is conducive to reduce the load and wear of the forging die, but also can improve productivity. Therefore, the forging die must be preheated evenly to 150~350℃ before working (the preheating temperature of high alloy steel should be higher, and the preheating temperature can be appropriately reduced in areas with higher room temperature). Stop forging time is longer, it should be repreheated, especially in winter can not be ignored.

The method of forging die preheating is as follows.

1. Bake with hot iron. The red iron heated to about 1000℃ is baked on the non-working surface of the forging die. Do not contact the die bore directly, can be separated by round steel or iron plate. Make sure the mold is heated thoroughly and the temperature inside and outside is consistent. The preheating temperature shall not be too high, the preheating time shall not be too long, so as not to reduce the annealing hardness.



2. Gas jet baking, generally with mobile gas nozzle. The nozzle is connected with the gas line by rubber hose. This method reduces the preheating time, the die surface of forging forging is not damaged, easy to operate.



3. Power frequency induction heating, using the induction heater to heat the mold to 250~300℃ only 25~30min, 1.5~2 times faster than using red iron preheating.



The test method of preheat overflow is as follows.



1. Sprinkle water on the surface of the forging die, and judge the temperature of the forging die according to the evaporation of water.



2. Test with a temperature measuring pen, when the drawn color turns into the specified color within 1s, it indicates that the specified preheating temperature is reached.



3. Determine the preheating temperature by contacting the die directly with a thermometer.