The tested stainless steel 17-4PH (/% : 0.02 ~ 0. 03C

0.40 ~ 0.50Si

0.41 ~0. 60Mn

0.018 ~ 0. 026P

0. 001S

15. 56 ~ 15.75Cr

4. 31 ~ 4. 50Ni

3. 21 ~ 3.40Cu

0. 20 ~ 0.25Nb

0. 013 〜0. 067N) is melted by 20 t EAF + LF + VOD + ESR process and forged to Φ150 mm bar products. Test results show that with increasing N content in steel from 0

013% to 0. 067%

the ferrite content in steel increases from 0. 5% to 6%

the strength and hardness of steel increase and the plasticity of steel decreases. As to control the N content in steel 0. 020% ~0. 045%

the ferrite content in steel is 1% 〜3% and the mechanical properties of steel quenched at 1040 ℃ for 1 h

water cooling + 480 °C for 2 h

air cooling

the mechanical properties of test steel are qualified; and the HB hardness value of so Ed-solution-treated steel is ≤325

so the workability of steel is improved.