The cold extrusion mold or die has seven main characteristics – 1. Strength, hardness, and stiffness, 2. High wear resistance, 3. Larger smoother arc, 4. Interchangeability and versatility, 5. Combined with press-stress, 6. Made of carbon steel, and lastly, 7. Balances upper and lower template to pressure to reduce the probability of crushing.
There are three main factors that could lead to cold forging die working problems, and they include 1. Fracture failure like fatigue fracture failure, low-stress brittle breaking failure, or plastic fracture failure. 2. Excessive deformation failure is another problem caused by plastic deformation failure or excessive elasticity. 3. Cavity surface damage like corrosion failure and surface fatigue could lead to problems.
There are several problems you need to pay attention to when designing and producing cold extrusion molds. That’s to ensure improved service life, strength, stiffness, and precision of the mold. 1. Ensure that the cold forging material and stiffness. 2. Check the right size of bump mode to avoid stress and reduce the squeeze pressure. 3. Check the toughness and wear resistance properties of the mold material. 4. Ensure better interchangeability for ease of replacement of fragile parts. 5. Ensure simple operations and the safety of the operators.
There are many advantages and weaknesses associated with the cold forging process. For the advantages, they include 1. Cold forged products do not produce oxidizing skin. 2. Better precision. 3. Reduced strain hardening that increased strength and stiffness of the forged product. 4. Hot heat treatment requires, and 5. No heating costs are incurred. For the limitations, they include 1. Plasticity and toughness reduction. 2. Higher deformation or compression force is needed. 3. Residual stress occurs in the material. 4. The deformation of the metal grains and 5. The longevity of the material is lower compared to hot extruded material.
Forging technology has been used for centuries for the manufacturing of various metal products. But hot forging has been the longest used method of forging tools. However, cold forging did not come just the other day, as most people tend to think. It is believed that cold forging was used in China around 2000 D.D. for manufacturing ornaments from red copper, gold, and silver flakes. But in the 19th century, cold forging starts being used in machinery manufacturing with the invention of the forging hydraulic presses and motor-driven splinter hammer. The modern cold forging process has been improved to handle even tough metals such as iron and carbon steel.
One of the major technical features of cold forging is the temperature of the material to be formed. The cold forging means extruding the material below the crystallization point. But this temperature must be forgeable. So, some of the hard metals, such as iron, may require heating them a little bit to make extruding easy. The other thing you must get right is the compression force. The press force must be accurate to avoid damaging the die or reducing the quality of the products.
For the cases where pre-forging heating is needed, several heating methods can be used. But there are two main types, and they include 1. Flame heating method. This type of heating method uses fuels in the furnace to heat the workpiece. Some of the fuels include such as coal, gas, diesel oil, and heavy oil, among others. 2. Electric heating. As the name suggests, this type of heating uses electricity. There are two main types of electric heating – induction heating and contact heating.
Cold forging offers near net shapes. Therefore it is one of the forging technology that offers some of the best dimension accuracy details. However, many other factors might determine the accuracy of the product. The mold and press force plays a role in the accuracy of the dimensions. So, you need to get both of them right when cold forging.
There is more that you need to do to improve the quality of the cold forging process. One of them is that the entire process must be carried out in the most conducive environments. Make sure that the machine is set correctly to produce the required press force. Then use the right material. Lastly, use the right finishing work for the product you are producing.
When cold forging tools, it is recommended that you include surface treatment. That’s because the friction produced during extrusion can cause deformation of the metal. Friction also affects the quality of the forged part as well as the extrusion pressure. The best surface treatment is lubrication. It reduces external friction between the punch, blank, and the mold. Some of the lubricant used for surface treatment includes vegetable oils, mineral oil, sodium stadiate, graphite, and many others.