The Problem with 12.9 Bolts in Seeders
In seeders, 12.9 bolts operate under particularly demanding conditions: constant vibration generated by the ground, repetitive dynamic loads, and continuous exposure to moisture, fertilizers, and accumulated dirt.
These conditions subject 12.9 bolts in seeders to a higher level of stress than in other industrial applications.
In practice, the bolts usually meet the mechanical specification. However, failures such as the following occur in service:
- Loosening
- Premature corrosion
- Unexpected breakage
This explains why 12.9 bolts fail in the field: the problem lies not only in the material, but also in the behavior of the entire system.
Where are 12.9 bolts used on a seed drill?
They are used in joints subjected to high loads and vibration, where stability is critical.
Primarily in:
- Seeder wheel bolts
- Seeder unit fastenings
- Structural connections
In these applications, the combination of mechanical load, vibration, and harsh environments demands a reliable fastening system.
3 Types of Failures in 12.9 Bolts in the Field
1. Loosening Due to Vibration in Seeders
Loosening due to vibration is one of the main causes of failure in 12.9 bolts.
During field work:
- Vibrations generate micro-movements
- The bolt preload is lost.
- The joint begins to move.
This process directly impacts the reliability of fasteners such as seeder wheel boltswhere the loss of preload can lead to progressive failure.
2. Corrosion
Corrosion in seeders is another critical factor.
The fasteners are exposed to:
- Fertilizers
- Humidity
- Accumulated dirt
This generates phenomena such as:
- Localized corrosion
- Under-deposit corrosion
In addition to deteriorating the material, corrosion modifies the friction between the threads, affecting the torque and stability of the joint.
3. Hydrogen Embrittlement
Hydrogen embrittlement is a critical problem in 12.9 bolts.
This phenomenon occurs when processes such as electroplating introduce hydrogen into the material.
Hydrogen embrittlement can cause:
- Internal microcracks
- Loss of ductility
- Sudden failures in service
This is one of the main reasons why 12.9 bolts fail without prior warning.
The most common failure in 12.9 bolts
It is still used in many applications:
- Electrolytic zinc plating
- Dichromated (yellow zinc plating)
This occurs due to:
- Cost
- Historical use
However, in 12.9 bolts in seed drills, these solutions present problems:
- Risk of hydrogen embrittlement
- Low corrosion resistance
- Unstable behavior in the field
Therefore, yellow zinc plating is one of the main causes of failure in agricultural fasteners.
How to prevent failures in 12.9 bolts?
Laurentcoat® + Precote®
The most effective way to prevent failures in 12.9 bolts is through a coating and fastening system designed for real-world conditions.
Laurentcoat®:
- Non-electrolytic coating –> prevents hydrogen embrittlement
- High corrosion resistance
- Controlled thickness –> does not affect threads
- Stable friction –> improves torque
Precote®:
- Prevents loosening due to vibration
- Maintains preload
- Improves joint reliability
This type of solution is especially effective in critical applications such as Wheel Bolts on Seeders.
Conclusion
Failures in 12.9 bolts on seeders are not solely due to the material, but to a combination of loosening, corrosion, and embrittlement under real operating conditions.
If you are experiencing problems with loosening, corrosion, or breakage in the field, we can analyze your application and propose a specific solution to improve the reliability of your fasteners.
You can contact us at info@chousa.com.ar and get in touch with our technical team.