Daewon Forging Co. Ltd., which is a company specialized in forging

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Technology

Forging swage / lubrication / defects

DAEWONFORGING

Forging swage / lubrication / defects

Forging swage

Most of forgings, especially big-sized products are hot-forged.

strength and character
in high temperature

resistance to mechanical
or heat shock

uniform
stiffening ability

abrasion resistance
abrasion resistance
to scale in hot forging

Conditions
needed for
swage material

To select the proper material for swaging, the size, property, complexity, temperature, work type, price, quantity of the forging need to be considered. The heat transfer from the high-temperaure material to the swage is also important

Usually the swage materials used have chrome, nickel, molybdenum, and vanadium in them. Swaging is shaped after forming the material into wanted shape, then machine-processed and then finished. Swage can be damaged from improper heat treatment, design, over heating and heat loaded high-temperature crack, abrasion, and overloading.
To decrease the heat crack or damage, the preheat the swage under 150~250℃

Lubricant

Lubricant affects abration and friction, and liquidization and liquidization and movement inside the swage and forging loads.
Lubricant keeps the heat from the low-temperature swage and the heated material, slows down the cooling speed of the material, and improves the metal movement speed. It can be used as a release agent, preventing the forging from sticking to the swage, and to make the removal easier. Various types of lubricants are used in forging. In hot forging, graphite, bisulfide molybdunum and glass are used. In cold forging, petrolatum or soap water are used. In hot forging, Iubricants are applied on the swage, in cold forging on the material. The method of using lubricants and the uniformity of the membrane thickness affect the quality of product.

Product defects

Among the many surface defects occurring during forging, use of inappropriate material movements inside the swage can cause other types of defects.
When material amount is excessive in the web, buckling forms during forging. To avoid this defect, the web has to be thicker. However when the web is too thick the common area of swage gets filled in too fast, the swage closes, and the material inside gets out of the range and become defective. The radius of the swage is very important. The common area of the swage, irregular transformation, forging process in terms of temperature, changes of direction can also cause inner defects.

Forging dects cause fatigue failure during the use of the product, and can lead to corrosion and abrasion. Generally the product needs to be tested before using the forgings. Defects of the forgings cannot be found easily by bare eyes if the defects are not big. Therefore the following tests need to be performed after forging.

  • Surface inspection
    tests the evenness and crease on the surface, folding of the material, burnt structure,
    and excessive scales.
  • Cut inspection
    cut the forging and find the inner defects.
  • Corrosion test
    commonly used as a defect inspection for steel forging. Put the specimen in the heated acid,
    and test the crease, folding, and cracks on the surface.
  • Nondestructive inspection
    Inner defects are inspected without cut-opening the forging. Methods include ultrasonic
    examination, x-ray radiographic examination, magnetic test, and penetration test.