Heat treatment constitutes a critical procedure in the manufacturing of Baiyun brake pads. By precisely regulating heating, holding and cooling cycles, the internal microstructure and surface properties of brake pads can be substantially modified, thereby enhancing their performance stability. The fundamental principle of brake pad heat treatment is a metal thermal processing technique that manipulates solid-state materials via heating, thermal insulation and cooling to acquire target microstructures and mechanical properties. For Baiyun brake pads, heat treatment effectively relieves residual internal stresses within materials and mitigates thermal expansion deformation of friction linings during service, which is particularly vital for self-adjusting clearance braking assemblies.
The standard heat treatment workflow for brake pads consists of four core stages: preheating, formal heating, thermal holding and cooling. Preheating is implemented at a relatively low temperature to achieve uniform temperature rise across brake pads and prevent thermal stress induced by excessive temperature gradients. The heating stage refers to raising the brake pad temperature to the preset target value, where the heating rate must be rigorously controlled to guarantee homogeneous microstructural transformation inside the material. During the thermal holding stage, components are maintained at the target temperature for a specified duration to complete anticipated microstructural evolution and stress relief. The cooling stage involves cooling brake pads from high temperature down to ambient temperature; the cooling rate exerts a decisive impact on final product performance.
Non-uniform temperature distribution or insufficient holding duration during heat treatment may trigger thickness deformation. Therefore, process parameters such as uniform heating and holding time must be precisely calibrated to guarantee dimensional accuracy. Heat treatment can adjust the porosity of friction materials; microporous structures formed after gas evacuation facilitate heat dissipation and suppress friction coefficient fading under high-temperature conditions. For instance, heat treatment improves the stability of dynamic friction coefficients for wet paper-based friction discs. Combined with multi-layer heat-dissipating void design, heat treatment further elevates heat dissipation efficiency and avoids braking failure caused by thermal fade.
Primary functions of brake pad heat treatment include boosting hardness and wear resistance, improving dimensional stability, optimizing friction performance and heat dissipation capacity, as well as strengthening fatigue resistance and high-temperature tolerance. Thermal treatment processes such as quenching, carburizing and nitriding can form hard compound layers (e.g., carbides or nitrides) on friction lining surfaces, drastically elevating wear resistance and extending service life. Adjustments to heat treatment temperature and holding time enable optimization of internal material microstructures (e.g., martensitic transformation), balancing hardness and toughness to eliminate brittle cracking risks stemming from excessive hardness.
Thermochemical heat treatment (e.g., nitriding) generates high-temperature resistant surface layers, enhancing the anti-fatigue performance of friction linings under frequent braking or heavy-load operating conditions. Heat-treated materials can better withstand high-temperature and high-pressure environments during braking, reducing the risks of thermal cracking and delamination. Synergistic application of heat treatment and surface finishing technologies (such as film deposition and coating) jointly improves the corrosion resistance, vibration damping and noise suppression performance of friction linings. For example, progressively bonded structural designs optimize interlayer bonding strength via heat treatment to boost overall durability.
Specific heat treatment parameters shall be determined according to the material grade and performance requirements of brake pads. Semi-metallic brake pads generally adopt a low-temperature regime (150–200 °C) with extended holding durations (2–4 hours). In contrast, ceramic or carbon fiber brake pads demand higher temperatures (200–300 °C) and stringent time control. Heat treatment temperature selection must take the glass transition temperature and decomposition temperature of materials into account to prevent material degradation or over-curing during processing. Holding time is determined by material thickness and thermal conductivity, ensuring sufficient heat penetration into the material core.
The selection of heat treatment equipment significantly impacts processing outcomes. Common heat treatment facilities include box furnaces, vacuum furnaces and continuous heat treatment production lines. Box furnaces feature simple structures and are suitable for small-batch production; vacuum furnaces provide an oxygen-free atmosphere and apply to oxidation-sensitive materials; continuous heat treatment lines support mass automated manufacturing. Thermal control systems for furnaces require high precision and reliability, typically equipped with PID controllers and thermocouple sensors to achieve a temperature control accuracy of ±5 °C. Uniform furnace temperature distribution is also essential, with permissible internal temperature deviation limited to ±10 °C to ensure consistent heat treatment effects across all workpieces.
Quality control for brake pad heat treatment shall be implemented from multiple dimensions. Firstly, key process parameters including temperature, holding time and cooling rate must be strictly regulated and precisely configured based on material characteristics and product specifications. Secondly, real-time monitoring of heat treatment processes shall be carried out with recording of critical parameters to guarantee consistent process execution. Thirdly, post-heat-treatment performance testing shall be conducted on finished products, covering hardness testing, dimensional inspection and friction property characterization to verify heat treatment efficacy. Finally, a comprehensive quality traceability system shall be established to retrieve full heat treatment parameter records for each batch of products, providing data support for quality analysis and process optimization.