Manufacturing processes for various components in industrial settings involve intricate procedures, often prone to specific challenges that can impact product quality. From oblique cutting to end cracks and gas cutting cracks, each issue poses unique risks during manufacturing and forging operations. Addressing these challenges requires a comprehensive understanding of their causes and potential solutions to ensure the integrity and reliability of the final forged parts.
Oblique Cutting
Oblique cutting, or slant cutting, refers to the angular deviation of the end face of a blank relative to its longitudinal axis during loading and unloading on sawing or punching machines. Severe slanting can cause the material to fold during forging, leading to defects in the final product. Therefore, it is essential to mitigate slanting issues to ensure the integrity and quality of the manufactured components.
Burr Formation at the End of Blanks
During the feeding and unloading process on cutting or punching machines, the end of the blank may become bent and develop burrs. This occurs when there is excessive clearance between the scissors or cutting die edge, or when the edge is dull. Consequently, the blank bends before it is properly cut, causing some of the metal to be squeezed into the clearance of the blade or die, resulting in the formation of protruding burrs.
Blanks with burrs are susceptible to local overheating and excessive burning during heating processes and are prone to folding and cracking during forging. Addressing burr formation is crucial to preventing defects and ensuring the quality of the manufactured parts.
Concave End Faces on Blanks
Concave end faces can occur during the cutting process when there is insufficient clearance between the cutting blades. This causes the metal section to experience cracks and misalignment, leading to a double shearing action and partial metal detachment, forming a concave-shaped end face.
Blanks with concave end faces are highly susceptible to folding and cracking during forging operations. Addressing the root causes of concave end faces is imperative to mitigate defects and ensure the integrity of the forged components.
End Cracks in Blanks
End cracks frequently occur in large-section alloy steel and high-carbon steel bars shortly after cold shearing, typically within 3 to 4 hours post-shear. This issue arises due to excessive unit pressure applied by the blade, causing circular-section blanks to deform into an oval shape and accumulate significant internal stress.
As the compressed end surface attempts to revert to its original shape, the built-up internal stress often leads to crack formation hours after cutting. Additionally, materials with uneven hardness or severe segregation are more prone to shear cracks. During forging, blanks with end cracks pose significant challenges, as the cracks tend to propagate further under pressure. Optimizing blade pressure and ensuring material uniformity are essential to preventing end cracks and ensuring the integrity of forged components.
Cracking from Gas Cutting
Gas cutting cracks typically manifest at the ends of billets due to residual stresses and thermal stresses induced by cutting without preheating the raw material. These cracks tend to propagate further during forging. To mitigate this issue, it is advisable to clean the billet thoroughly before forging to remove any surface imperfections. Proactive measures, such as meticulous cleaning and inspection, are essential to addressing gas cut cracks prior to forging.
Cracking Due to Convex Core Formation
During lathe blanking processes, the end face of the bar often exhibits a convex core at its center. This convex core poses challenges during forging due to its reduced plasticity resulting from its smaller section and rapid cooling. Stress becomes concentrated at the junction of the sudden section change, exacerbating the discrepancy in plasticity between the convex core and surrounding material. Under the force of the hammer, this stress concentration renders the area surrounding the convex core susceptible to cracking.
To mitigate the risk of convex core cracking during forging, careful consideration should be given to the material's plasticity, forging temperature, and forging technique. Additionally, optimizing the lathe blanking process to minimize the formation of convex cores can help alleviate this issue and improve the overall quality of forged components.
By understanding and addressing these common challenges in manufacturing and forging processes, manufacturers can ensure the production of high-quality, reliable forged parts.
