| 摘要 |
PROBLEM TO BE SOLVED: To provide a vitrified grindstone of a high porosity which has an abrasive grain rate below 45 vol.% and prevents appropriately local clogging, glazing and falling of grindstone and scorching of a material to be ground.SOLUTION: In a vitrified grindstone of a high porosity, abrasive grains are bonded through a vitrified bond in such a state that pores are formed between abrasive grains and has an abrasive grain rate of 45 vol.% or lower. In the frequency distribution of abrasive grain area ratios representing the ratio of solid including abrasive grains per unit area at a plurality of sites in the cross section of the grindstone, the vitrified grindstone has homogeneity with a standard deviation of 10 or smaller, giving homogeneity with a high abrasive grain area ratio in the cross section of the vitrified grindstone and thereby preventing appropriately local clogging, glazing and falling and scorching of a material to be ground. |
