永久线性变化 meaning in English

permanent linear change

Method of test for permanent linear change on castable refractories
注块耐火材料的永久线性变化的试验方法
Testing method for the rate of linear change of castable refractories
注块耐火材料的永久线性变化率的试验方法
Method of test for permanent linear change on light weight castable refractories
轻质可铸耐火材料的永久线性变化率的试验方法
Method of test for permanent linear change on high alumina and fireclay plastic refractories
高矾土和塑性耐火土材料永久线性变化的试验方法