HOW TO REDUCE SEIZURE OF METALS – WHAT IS SEIZURE? & WAY TO EVALUATE SEIZURE WITH CAE ANALYSIS

WHAT IS SEIZURE？

Seizure is a phenomenon in which friction between a tool and a workpiece raises the temperature of the workpiece, causing the workpiece to be welded to the tool. This phenomenon is often seen in products that are subjected to a large amount of friction, such as cutting tools and press dies.

CAUSES OF SEIZURE

The main causes of seizure are as follows:

• Inadequate type or amount of lubricant
• Insufficient lubrication due to machining conditions beyond the performance of the lubricant
• The friction surface between the tool and the workpiece becomes hotter, and the metal melts
• The surface roughness of the tool and the workpiece

HOW TO PREVENT SEIZURE

To prevent seizure, the following must be taken care of:

• Adequate type and amount of lubricant between the tool and the material should be applied.
• Surface modification such as increasing tool surface roughness, coating, etc.. is recommended.
• Use a tool material that is less prone to adhere to the work material.

CASE STUDY: CAE ANALYSIS TO EVALUATE SEIZURE DEGREE

Now, we will focus on automotive gear products and introduce examples aimed at reducing seizures.

Seizure is generally said to be evaluated by combining surface pressure and velocity by utilizing CAE software.
However, in gear forming such as in this case, although we knew that differences in gear introduction shapes affect seizure, we were unable to evaluate seizure because the surface pressure and velocity indicated similar distributions.

It is said that gears with a spear-like introduction shape are more prone to seize, while those with conical shapes are less prone to seize. The seizure severity for a keel/hull-like shaped gear is considered to be in between the two.

EVALUATION FACTORS IN CAE ANALYSIS

So, in addition to surface pressure and velocity—the original evaluation factors—we defined the Surface Expansion Ratio as one of the factors to assess seizure with CAE(Computer Aided Engineering) analysis. This allows us to predict material surface expansion, which varies depending on the gear introduction geometries.

In addition to the simulation results of the surface expansion ratios, we evaluated the degree of seizures that were caused by the differences in gear introduction shapes.

The actual results are below:

Although it looked like they had no significant differences in surface pressure and velocity evaluation results, we could clearly see the differences in the material surface expansion by each gear introduction shape.

As a result, we learned that the Surface Expansion Ratio is a reliable factor in evaluating seizure.

CONCLUSION

How did you like it?
As we explained earlier, by utilizing CAE analysis, the degree of seizure occurrence can be determined at the design stage, and appropriate gear introduction shapes can be selected. This enables you to select appropriate gear introduction shapes and improve the design quality. Although we focused on gear product seizures in this article, we also offer verification services for other products and other types of damages.
Please feel free to contact us if you have any problems with your production.