As the steel is heated above the critical temperature, about 1335°F (724°C), it undergoes a phase change, re-crystallizing as austenite. Continued heating to the hardening temperature, 1450°F - 1500°F (788°C - 816°C) ensures complete conversion to austenite. At this point the steel is no longer magnetic, and its color is cherry-red, normalizing has a slower rate of cool than annealing and this accounts for the springs having a greater strength than the annealed spring, and also accounts for it being harder and less ductile than the annealed springs