Analysis & Control Of Forging Folding Causes In Modern Forging Production
This article analyzes and explains the form, cause, on-site control, and elimination method of folding from several aspects, such as the forming process, blanking, release agent use, steel surface defects, etc., which are all practical methods for on-site quality control, and the new production line and new forging production method are also talked about.
With the introduction of forging automatic production lines and precision equipment, the forging level has been greatly improved. In fact, forgings have developed in the direction of small-margin and precision forging. The robot is replacing part of the manpower, and the continuous production cycle time of the automatic forging production line is in seconds, along with the overall forging production capacity with high efficiency.
The improvement of the degree of automation puts forward higher requirements for all aspects of support. It also requires that the defects in the forging process can be controlled. Otherwise, it will cause great losses. While defects that can be detected by visual and measured inspections are easy to control, hidden defects are difficult to control. Forging folding is one of them:
Understanding Forging Folding
Forging folding refers to the defect where the metal surfaces fold over themselves, creating layers within the forged component. These folds can result in weak spots, compromising the mechanical properties and leading to potential failure under stress. Forging folding can be categorized into surface folds and internal folds, both of which require different approaches for detection and prevention.
The forging fold defect is the most difficult to control because it is not easy to detect. This is because folding is formed by the convergence with the oxidized surface metal during the deformation flow of the metal. Folding not only reduces the load-bearing area of the part but also tends to be a source of fatigue due to the stress concentration here when working.
In the subsequent process, especially heat treatment of the folded parts, the folded end often expands. So, cracks may form in the part that expands later. The end is pointed, and its surface is generally free of oxidation and decarburization. Fold becomes a cause of cracks, so folding is extremely harmful to forgings.
Causes of Forging Folding
This defect is mainly caused by factors inside the production line. The choice of the metal forged and the conditions surrounding such as the temperature in the room and so on. Not heating the billet to the recommended temperature can also be the reason. Improper follow-up processes, improper use and maintenance, or design and the following are the major causes:
Improper Material Flow
Die Design Flaws: The design of the forging dies significantly influences material flow. Incorrectly designed dies can cause uneven distribution of material, leading to areas where metal folds over itself. For instance, sharp corners or abrupt changes in die geometry can impede smooth material flow.
Inadequate Lubrication: Insufficient lubrication between the die and the workpiece can result in high friction, causing localized resistance to material flow. This resistance can force the material to fold rather than flow smoothly into the desired shape.
Material Properties: Variations in material properties, such as differences in hardness or ductility within the workpiece, can lead to uneven deformation during forging. This uneven deformation is a primary cause of folding.
Process Parameters
Temperature Control: Forging temperature is critical in determining the material’s behavior during deformation. If the material is too cold, it may not flow adequately, resulting in folding. Conversely, if it is too hot, excessive oxidation can occur, which can also contribute to folding.
Press Speed: The speed at which the forging press operates can influence the occurrence of folds. Rapid press speeds can cause the material to flow unevenly. This is if the die is not designed to accommodate such speeds.
Forging Force: Insufficient or excessive forging force can lead to folding. If the force is too low, the material may not fill the die cavity completely, causing folds. On the other hand, excessive force can cause overfilling and subsequent folding.
Die Wear and Maintenance
Wear and Tear: Dies that are worn out can have irregular surfaces, leading to improper material flow and folding. Regular maintenance and timely replacement of worn dies are essential to prevent this issue.
Die Alignment: Misalignment of the die components can cause uneven pressure distribution during forging, resulting in folding. Ensuring precise alignment of dies is crucial for uniform material flow.
Operator Skills and Training
Skill Level: The expertise of the operators plays a significant role in preventing forging defects. Skilled operators can identify and correct potential issues before they lead to defects like folding.
Training Programs: Continuous training programs that focus on the latest forging techniques and quality control measures can significantly reduce the incidence of forging defects.
Control Measures for Forging Folding
To mitigate forging folding, implement optimized die designs using CAD for smooth transitions, ensure proper lubrication to reduce friction, and maintain strict temperature control with preheating and cooling systems. Use adjustable press parameters and real-time monitoring to regulate speed and force. Conduct regular die maintenance for wear and alignment. In addition, enhance operator skills through continuous training programs focused on quality control and defect prevention.
Optimized Die Design
Computer-Aided Design (CAD): Utilizing CAD software and other simulation software to design dies allows for precise control over die geometry. Simulations can predict material flow and identify potential problem areas that could lead to folding.
Smooth Transitions: Ensuring smooth transitions in die geometry can prevent abrupt changes in material flow, thereby reducing the likelihood of folding.
Proper Lubrication Practices
Lubricant Selection: Choosing the right lubricant for the specific forging process and material can significantly reduce friction and improve material flow.
Application Techniques: Implementing consistent and adequate lubrication application techniques ensures that the entire die-workpiece interface is covered, reducing the risk of folding.
Strict Temperature Control
Preheating and Cooling Systems: Implementing precise preheating and controlled cooling systems ensures the material is at the optimal forging temperature, reducing the risk of folding.
Temperature Monitoring: Continuous monitoring of the workpiece and die temperatures can help maintain the optimal forging conditions, preventing defects.
Controlled Press Speed and Force
Adjustable Press Parameters: Modern forging presses with adjustable speed and force settings allow for fine-tuning of the forging process, reducing the risk of folding.
Real-Time Monitoring: Utilizing real-time monitoring systems to track press parameters ensures that deviations from the optimal settings are quickly corrected.
Regular Die Maintenance
Routine Inspections: Implementing a schedule for routine die inspections and maintenance can identify wear and misalignment issues before they cause defects.
Precision Alignment Tools: Using precision tools for die alignment ensures uniform pressure distribution during forging, reducing the risk of folding.
Enhanced Operator Training
Skill Development Programs: Regular training programs that focus on enhancing the skills of the operators can lead to better identification and correction of potential issues.
Quality Control Training: Training operators on the latest quality control techniques and defect detection methods can help in the early identification and prevention of folding.
Summary
According to the above analysis of the cause of “folding,” folding and steel surface defects in the forging process are two aspects of folding. The manufacturer’s forging workshop should adopt the screening and isolation of this forging process to detect these defects. When distinguishing forging folds and material cracks, technicians should use the method of mutual confirmation and elimination. Analyzing the appearance and formation process of defects is also crucial. The bottom line is that forging folding control is possible.