The Impact of Cooling Water Temperature on Crystal Pulling/Extrusion Molding Processes

 

C temperature is a critical process parameter in both crystal pulling and extrusion molding, directly determining product quality, production efficiency, and equipment stability. Its influence spans the entire process, with significantfferences in the effects of different temperature ranges, requiring precise control tailored to the core requirements of the process. The following details the specific impacts of cooling water temperature on these two processes, explaining control points in the context of actual production scenarios.

 

 

I. Impact of Cooling Water Temperature on Crystal Pulling Process

 

The core of the crystal pulling process (including singlestal and polycrystalline growth) is to achieve the orderly growth of crystals from the melt to the solid state through precise control of the thermal field. Cooling water temperature prima acts on the furnace cooling system, indirectly regulating the temperature gradient at the solid-liquid interface, thereby affecting crystal quality and growth efficiency.

 

When the water temperature is too high, the coolystem's heat dissipation capacity is insufficient, leading to elevated and unstable thermal field temperatures within the furnace. On one hand, the solid-liquid interface moves upward and becomes steep, di the orderly growth of the crystal. This easily generates defects such as dislocations, slips, and grain boundaries, exacerbates impurity segregation, and reduces crystal purity and mechanical propertiesevere cases, it can cause crystal cracking and growth interruption. On the other hand, residual heat from the thermal field cannot be dissipated in time, extending the crystal growth cycle and reducinn efficiency, while accelerating the aging of furnace components and shortening equipment service life.

 

 

 

 

When the water temperature is too low, it leads to excessive cooling, causing the thermal field tempera to drop too quickly and creating an excessively large temperature gradient at the solid-liquid interface. This results in uneven crystal growth rates, prone to issues such as diameter fluctuations and rough saces. Simultaneously, excessive thermal stress is generated within the crystal, making it prone to cracking during subsequent processing. Furthermore, excessively low water temperatures may cause condensation or freezing in coes, blocking the lines, affecting the normal operation of the cooling system, and even damaging the furnace sealing structure.

 

 

In actual production, the cooling water temperature for crystal pulling must be preciseset based on the crystal material (such as silicon, germanium, sapphire) and growth process parameters. It is usually controlled between 20-35°C, maintaining stable watermperature to avoid large fluctuations, ensuring a flat solid-liquid interface and stable thermal field, thereby obtaining high-quality crystals.

 

 

II. Impact of Cooling Water Temperature on Extrusion Moldg Process

 

 

In extrusion molding (applicable to high molecular materials such as plastics and rubbers), cooling water temperature acts directly on the melt after extrusion, affecting product shaping, dimensioal accuracy, and mechanical properties. The rationality of its control directly determines the final product pass rate.

 

 

When the water temperature is too high, the cooling rate is too slow, extendmelt shaping time. This easily leads to uneven product shrinkage, excessive dimensional deviations, and defects such as surface sink marks and ripples. For heat-sensitive materials (sucas PVC, PE), excessively high water temperatures can cause secondary softening, leading to sticking and deformation issues, while also extending the production cycle and reducing efficiency. Additionally, insufficient cooling prevents internal stresse being fully released, making the product prone to warping and cracking during subsequent use.

 

 

 

 

When the water temperature is too low, the cooling rate is excessively fast, causing the melt surface to solidify rapidly while the interior reains molten. This easily results in a large temperature difference between the inside and outside, leading to internal stresses within the product and issues such as cracking and embrittlement. At th time, rapid cooling reduces the surface gloss of the product, causing appearance defects like pitting and scratches; for thin-walled products, it may also lead to incomplete molding and excessrrs on edges and corners.

 

 

Different extrusion materials have different requirements for cooling water temperature. For example, the water temperature for rigid PVC extrusion is typically controlled bween 15-25°C, soft PVC at 25-30°C, and polyethylene and polypropylene at 20-30°C. During production, water temperature be flexibly adjusted based on material properties, product dimensions, and shape, while maintaining uniform water temperature to avoid product defects caused by uneven local cooling.

 

 

 

 

In summary, the impact of cooling watermperature on both crystal pulling and extrusion molding processes revolves around "temperature gradient control" and "product shaping/growth stability." Both excessively high and low water temperatures will lead to a decline in product quality and reduced production efficiency. In actual production, it is necessary to set a reasonable water temperature range based on process requirements and material properties, and equip with a precise waterture control system to ensure process stability and improve product pass rate and production benefits.