通風管道變形的原因主要有以下四點：

The main reasons for the deformation of ventilation ducts are as follows:

1、鎂水泥在自然養護條件下其體積是一個連續膨脹過程，其線膨脹率為0.1-0.2%，體積膨脹率約為1%。

1. Magnesium cement undergoes a continuous expansion process under natural curing conditions, with a linear expansion rate of 0.1-0.2% and a volume expansion rate of approximately 1%.

2、菱鎂礦在服燒過程中不可避免地產生局部過燒，使一部分MgO呈死燒狀態，過燒的MgO水化過程很慢，當已形成強度的水泥石中的MgO再遇水進行水化時，生成Mg(OH)2，體積膨脹120%。

2. During the sintering process of magnesite, local overburning is inevitable, causing a portion of MgO to be in a dead burning state. The hydration process of overburned MgO is slow. When MgO in the cement stone that has formed strength is hydrated again with water, it generates Mg (OH) 2, with a volume expansion of 120%.

3、輕燒氧化鎂中游離CaO水化時體積膨脹90%，而鹵片中存在著 SO42-，當Ca(OH)2轉化成石膏時，固體體積將增加2倍以上，導致制品變形，這也是限制輕燒氧化鎂中游離CaO含量、鹵片中SO42-含量的原因。

3. During the hydration of free CaO in lightly burned magnesium oxide, the volume expands by 90%, while there is SO42- present in the brine sheet. When Ca (OH) 2 is converted into gypsum, the solid volume will increase by more than twice, causing deformation of the product. This is also the reason for limiting the content of free CaO in lightly burned magnesium oxide and SO42- in the brine sheet.

4、MgO-Mg-C12-H2O系統水化過程是一個強烈的放熱反應過程，而生產的管道體積又大，若環境溫度較高，則反應升溫過程，板材本體溫度過高，反應不充分，造成較大的結晶應力和熱膨脹應力，使制品體積膨脹。

4. The hydration process of MgO-Mg-C12-H2O system is a strong exothermic reaction process, and the volume of the produced pipeline is large. If the ambient temperature is high, the reaction temperature will rise, and the temperature of the board body will be too high, resulting in insufficient reaction and causing significant crystallization stress and thermal expansion stress, causing the volume of the product to expand.

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