Uneven wear of jaw plates in jaw crushers: mechanism analysis and countermeasures for the lower service life of the bottom compared to the top

In the actual operation of jaw crushers, a common and significant phenomenon is that the wear rate of the bottom (discharge port area) of the fixed jaw plate and the movable jaw plate is much higher than that of the top (feed inlet area), and their lifespan is often only 1/2 to 2/3 of that of the top. This uneven wear is not only the direct cause of the material not being fully utilized, but also a key factor leading to gradually coarser product particle size, decreased production capacity, and increased energy consumption. This article aims to professionally analyze the mechanics and wear mechanisms behind this phenomenon and propose systematic management ideas.

1. Core mechanism: Non-uniform cavity structure and differentiated crushing effect

The uneven wear of jaw plates originates from the inherent cavity design of the jaw crusher and the resulting variations in the crushing process.

Variable cross-section stroke difference and "clamping angle" effect:

The motion trajectory of the movable jaw is not a simple parallel movement; its top stroke is relatively small, while its bottom stroke is larger. This results in more frequent squeezing of materials between the movable jaw plate and the fixed jaw plate near the discharge opening, and a longer sliding friction path. Meanwhile, from feeding to discharging, the "clamping angle" formed by the two jaw plates causes materials to mainly endure the final crushing force that meets particle size requirements in the lower cavity area. Therefore, the bottom area undertakes a more significant task of fine crushing.

Crushing ratio gradient and "lamination crushing" strength:

At the top of the chamber, the material has the largest size, and its crushing is primarily due to impact and fracturing. As the material falls, the particle size decreases, and in the bottom area, the crushing mechanism gradually transitions to being dominated by high-stress squeezing and grinding. This means that the bottom jaw plate experiences higher contact pressure per unit area from numerous small, already crushed materials, and the abrasive wear characteristics are more pronounced.

Material flow rate and friction duration:

The material falls naturally under the influence of gravity and moves relatively slowly near the discharge opening at the bottom, resulting in a significant extension of the contact and interaction time between the jaw plate and the material (especially hard and wear-resistant particles) in this area, thereby exacerbating wear.

II. Consequences and Impacts: Systemic Issues Beyond Material Losses

Premature failure of the bottom not only incurs the cost of replacing the jaw plate itself.

Decreased crushing efficiency and economy: As the bottom tooth profile becomes worn and the cavity contour changes, the effective crushing stroke of the crusher is shortened, resulting in a reduced proportion of qualified particle sizes in the product, an increased return rate, and an increase in energy consumption per unit of output.

Difficulty in particle size quality control: The size of the discharge opening increases invisibly due to wear, resulting in a continuous coarsening of the average particle size of the final product, which affects the stability of subsequent process steps.

Triggering cascading failures: Severe uneven wear may lead to local perforation or fracture of the jaw plate, and the detached metal fragments may enter downstream equipment, causing secondary damage.

III. Response strategy: systematic management based on mechanism

To address the issue of uneven wear of jaw plates, it is necessary to implement comprehensive management throughout the entire process, from design and material selection, to usage and maintenance, and ultimately to replacement strategies.

Material selection and application adaptability:

Considerations for the Applicability of High Manganese Steel: Traditional high manganese steel (ZGMn13) relies heavily on intense impact to produce work hardening. Under high-pressure and multi-extrusion conditions at the bottom of the jaw plate, its hardening effect is relatively sufficient; however, at the top where the impact is relatively weaker, its initial hardness may not be sufficient to resist wear. Therefore, for the bottom part where wear is particularly severe, modified ultra-high manganese steel or medium manganese steel may be considered to obtain higher initial hardness and appropriate work hardening capacity.

Application of composite materials: By adopting the bimetallic composite casting process, embedding wear-resistant alloy blocks with higher hardness (such as high chromium cast iron) at the severely worn parts of the jaw plate bottom, while ensuring sufficient toughness and strength in the matrix, is a highly targeted solution.

Optimization of usage and maintenance strategies:

Regular replacement and flipping: The most direct and widely adopted method is to swap the upper and lower jaw plates when the bottom of the jaw plate is worn to a certain extent (not yet failed). For symmetrically designed jaw plates, they can also be flipped from left to right, utilizing the tooth-shaped area that has not yet been worn to continue working, thereby extending the lifespan of a single set of jaw plates by 30%-50%.

Rational application of build-up welding repair: For large jaw plates, build-up welding with wear-resistant electrodes can be carried out on the severely worn bottom tooth area to restore the tooth profile. This requires precise control of the welding process to prevent thermal stress cracks.

Guarantee of uniform feeding: Ensure that the material is evenly distributed across the full width of the crushing chamber, avoiding uneven feeding that can lead to abnormal funnel-shaped wear in localized areas (usually the middle and lower parts).

Cavity design and parameter monitoring:

Modern crusher designs have increasingly emphasized "curved" cavity shapes, aiming to achieve a more reasonable compression ratio of materials throughout the cavity and mitigate uneven wear. During operation, it is essential to regularly inspect the size of the discharge opening and promptly adjust the position of the jaw plate to stabilize the particle size of the discharged material.