Max temp for K6 line :
AHX core : 60°C
AFX core : 65°C
AFR core : 70°C
Normal range is 40°-50°C. If you want to overclock, the CPU must stay below 40-45°C.
Your system must have a cooling problem. If CPU temp exceed 60°C, you might fry your chip.
Use thermal paste in place of the thermal pad. Add case fans. Try to have a good air flow inside the case (must stay closed).