PURPOSE: To improve the close adhesiveness of a low thermal expansion material or an intermediate material by constituting a high thermal expansion material of an Fe-Ni-Cr alloy containing boron and nitrogen.

CONSTITUTION: A high thermal expansion member is constituted of an Fe-Ni-Cr alloy having a composition containing C 0.2% or less, Si 1.5% or less, Mn 1.0% or less, A 0.03% or less, Ni 15 - 30%, Cr 1 - 15%, B 0.001 - 0.01% and N 0.001 - 0.01% and consisting of the remainder of Fe and inevitable impurities. At the time of annealing after cold rolling in a process preparing the high thermal expansion member from said alloy, B and N contained as alloying components are diffused and migrated to the surface part of the member to become a state present in a bonded BN form and the surface part becomes hard to be reduced in plastic deformation capacity and therefore, an active new surface becomes easy to form at the time of clad rolling and close adhesiveness is enhanced.