The thermal stability of refined grain of trace B and an additional trace Zr modified brass HPb59-1 during holding at thermal processing temperature range was examined. The results showed that the normal growth of refined grain at the pertinent thermal processing temperature range and holding time has no deteriorative effect on the refinement

i.e.

the refined grain was still much finer than unmodified grain. However

an abnormal rapid growth of the refined grain up to couple of mm from surface toward center of the alloy took place with prolonging holding time or relevant high temperature. Although an additional trace Zr has the slight effect on modification and normal growth rate of refined grain

it can inhibit effectively the above mentioned abnormal grain growth of refined grain.