耐火砖砌筑的膨胀缝怎么留｜Setting Expansion Joints in Refractory Brick Masonry

摘要：砌筑窑衬的损坏常从拱顶挤裂开始：砖体受热膨胀没有去处，应力集中把砖挤碎。讲不同材质的线膨胀量估算、膨胀缝的留设位置、宽度与填充材料。
Abstract: Lining damage often starts at the crown: heated brick has nowhere to expand, so stress concentrates and spalls the joints. Estimating linear expansion by material, and where to put joints, how wide, and with what filler.

正文： 新窑烘到中段拱顶掉砖，查材料没问题、砌筑也没问题，最后发现是膨胀缝没留够。膨胀缝是砌筑里最不起眼的一笔，却是决定窑衬寿命前两个冷热循环能不能活下来的关键。
Main text: A new kiln drops crown bricks mid-bake. Material checks out, masonry checks out, and the finding is insufficient expansion joints. The least glamorous detail in masonry decides whether a lining survives its first two thermal cycles.

一、先算膨胀量再定缝宽
1. Calculate expansion before sizing the joint

不同耐火砖千度线膨胀差别很大：硅砖百分之一点二上下，高铝砖百分之零点六到零点八，镁砖接近百分之一点五。缝的总宽度按膨胀量扣除砖缝吸收量再留余量，宁可将留缝分散成多条窄缝，不留一条宽缝。
Linear expansion at 1000 C varies widely: silica brick about 1.2 percent, high-alumina 0.6 to 0.8, magnesia close to 1.5. Size total joint width from expansion minus what mortar joints absorb, with margin. Prefer several narrow joints over one wide joint.

二、位置比宽度更要紧
2. Placement matters more than width

• 拱顶沿轴线分段留缝，两拱接头处必须留。
  Leave joints along the crown axis, always at the meeting of two arches.
• 直墙按 1.5 到 2 米间距留纵缝，转角与金属锚固件附近必留。
  Vertical walls take joints every 1.5 to 2 m, always at corners and near steel anchors.
• 缝内填陶瓷纤维毡或纸板，严禁用砂浆填死。
  Fill joints with ceramic fibre felt or board; never pack them with mortar.

三、烘炉后的复查
3. Recheck after bake-out

第一次烘炉结束降温后进窑看缝：被砖挤闭合的说明不够，要开复查记录；缝隙均匀微合的是正常状态。这份记录留着，检修时比任何图纸都有用。
After the first bake-out, inspect the joints cooled: joints squeezed shut were too narrow — log it; joints closed evenly and slightly are normal. That log outperforms any drawing at the next overhaul.