Analysis of Defects Caused by Improper Water‑Cooling Parameters in Solution‑Annealing Treatment of Fixed Jaw Plates

As the core wear‑resistant component of jaw crushers, fixed jaw plates are mostly manufactured from high‑manganese steel. Solution‑annealing heat treatment serves as the key process to obtain a single‑phase austenite structure and guarantee work‑hardening capacity as well as impact resistance. The initial water‑cooling temperature and cooling rate are critical parameters governing heat‑treatment quality, which must be precisely adjusted according to casting wall thickness and material composition. Improper parameter control will directly alter metallographic structures and induce various internal defects barely visible to the naked eye, ultimately resulting in shortened service life and frequent equipment failures on site.

The conventional industrial control range for the initial water‑cooling temperature is 1000 ℃‑1080 ℃. Deviation from this reasonable range damages the microstructure in terms of grain morphology and carbide distribution. When the initial temperature is excessively high, the austenite matrix grains of the casting remain at high temperature for too long, which tends to cause grain coarsening, reduce grain‑boundary area and degrade matrix toughness. Meanwhile, the internal‑external temperature difference of thick‑walled jaw plates increases sharply, and thermal stress rises significantly during cooling. Micro thermal cracks are likely to form at stress‑concentrated positions such as tooth roots and abrupt cross‑section transitions. Such cracks propagate gradually under repeated impact during crushing operations, triggering tooth fracture and matrix cracking. In addition, an overly high initial temperature increases the thickness of the surface oxidation and decarburization layer of castings. Insufficient carbon content in the surface matrix directly weakens the work‑hardening effect and leads to obviously accelerated initial wear rate after the jaw plate is put into service.

When the initial temperature is too low, the casting undergoes excessive pre‑cooling after furnace discharge. Once the temperature drops to the carbide precipitation range, carbon elements in austenite precipitate along grain boundaries in the form of carbides, forming continuous or semi‑continuous network structures that break the continuity of the matrix. Even after subsequent water cooling, these network carbides remain within the microstructure, drastically lowering the toughness and impact resistance of jaw plates and giving rise to failures such as edge chipping and block spalling during operation. Furthermore, insufficient austenitization occurs at excessively low initial temperatures, where partial regions fail to complete structural transformation. Pearlite‑type structures form after cooling, resulting in poor overall structural uniformity, insufficient work‑hardening capacity and marked deterioration of wear resistance.

The cooling rate is jointly determined by water‑cooling medium temperature, water flow rate and casting water‑entry mode. It exerts a direct influence on structural transformation and stress distribution. Thick‑walled fixed jaw plates are more sensitive to cooling rate. An excessively fast cooling rate creates a sharp discrepancy in cooling speed between the casting surface and core, producing superposition of structural stress and thermal stress. Stress concentrates at locations including tooth roots and back transition zones, which readily induces quenching cracks. Meanwhile, over‑quenched surface layers exhibit increased brittleness, and surface spalling and tooth‑face block loss may occur when processing hard ore. By contrast, an excessively slow cooling rate keeps castings in the intermediate‑temperature range for an extended period. Austenite decomposes and large quantities of granular carbides precipitate along grain boundaries and within grains, making it impossible to obtain single‑phase austenite and resulting in failed solution‑annealing treatment. For heavy‑section fixed jaw plates, the core cools even more slowly with more severe carbide precipitation. This creates large discrepancies in microstructure and performance between the surface and core. The core becomes a structural weak zone, where fatigue cracks tend to initiate internally under long‑term service.

Hunan Xiangjian Machinery Technology Co., Ltd. specializes in mining wear‑resistant parts. We have established a specification‑specific heat‑treatment process control system for various models of fixed jaw plates. Metallographic inspection and mechanical‑property verification are carried out batch‑by‑batch to ensure products meet working‑condition requirements for ore crushing, sand making and construction solid‑waste disposal. For further process details or customized products, please visit our official website: https://www.xjgmg.com for inquiries and cooperation.