Causes of Cracks in Diamond Saw Blade Cores

This article explores the causes of cracks in the core of a diamond saw blade by analyzing material defects and failure mechanisms. The structural integrity of the saw blade core plays a critical role in the blade’s overall performance and longevity.

Cracks Caused by Material Defects in Diamond Saw Blade Cores

Currently, the core material of most diamond saw blades is made from medium- to high-carbon spring steel. Defects such as non-metallic inclusions, structural inconsistencies, microcracks, and surface imperfections in this type of steel can all act as potential sources of fatigue cracks, ultimately leading to premature failure of the blade core.

Key contributors to reduced service life in diamond saw blade cores include non-metallic inclusions, surface defects, and banded segregation. The presence of pits, subsurface carbides, or segregated structures on the surface of the blade core accelerates fatigue failure. Moreover, the inherently low fracture toughness of the material increases the likelihood of early fatigue fractures.

1. Non-Metallic Inclusions

In diamond saw blade core steel, non-metallic inclusions like Al₂O₃ and TiN are mainly introduced during the smelting process. Their impact on fatigue performance depends on their type, quantity, size, shape, and distribution. Large, brittle inclusions with weak bonding to the steel matrix are particularly detrimental.

As the strength level of spring steel increases, the negative impact of inclusions on fatigue resistance becomes more pronounced, severely weakening the performance of the diamond saw blade core.

2. Surface Defects

Surface quality issues typically fall into three categories:

• Rolling defects such as folding and edge laps, often caused by outdated equipment and poor billet grinding techniques.
• Surface cracks appearing as longitudinal lines, typically from pre-existing billet cracks or improper cooling and stress control.
• Scratches and scaly surfaces from improper handling during packaging and transportation.

These surface imperfections often serve as the origin of fatigue failure. Even small pits, scratches, or blisters—though sometimes within acceptable standards—can weaken the blade core, especially when its overall plasticity is low. Such flaws are often overlooked in failure analysis because they may be damaged or missed during sampling.

3. Banded Segregation

In the continuous casting of high-carbon spring steel, negative segregation bands (also known as “white bright bands”) may form due to inadequate electromagnetic stirring or unstable cooling processes. Carbon segregation leads to uneven composition during solidification.

In these negatively segregated areas, carbon content is lower. During heat treatment, carbon diffusion is hindered by elements like Si and S. Consequently, the resulting martensitic or tempered sorbite structures in these bands contain lower carbon levels than surrounding areas, creating weak zones in the diamond saw blade core.

These segregated regions are more prone to fatigue crack initiation under cyclic loading. They also experience grain coarsening during quenching, which increases the risk of cracking. Additionally, non-metallic inclusions tend to accumulate along grain boundaries, weakening structural cohesion and promoting quenching cracks.

Conclusion

The fatigue failure of diamond saw blade cores is closely linked to the presence of non-metallic inclusions, surface defects, and banded segregation in the steel. These material imperfections act as crack initiation sites and reduce the mechanical integrity of the blade core. Improving material quality and production processes is essential for enhancing the lifespan and performance of diamond saw blades in demanding stone cutting applications.