PROCESS FOR MANUFACTURING A BAR AND A PROJECTILE OF CALIBER 30 MM FROM MARAGING 300 STEEL

The invention relates to a process for manufacturing bars of Maraging 300 steel hardenable by precipitation, required for producing armour-piercing tracer projectiles - of caliber 30 mm of AP-T type. According to the invention, the process has the following steps: 1. smelting a Maraging 300 steel in a vacuum induction furnace CIA followed by double remelting in a vacuum atmosphere on the VAR installation and ingot casting; 2. hot rolling or forging the ingot until an electrode with a diameter Φ = 50 mm in annealed and peeled state is obtained, the end deformation temperature being 800°C, with water cooling, 3. applying a soaking heat treatment in a solution at a temperature of 830°C for at least 40 minutes and cooling in water, 4. carrying out a severe plastic deformation in two stages with a reduction of the cross-section from Φ = 50 mm to Φ = 32 mm, the reduction per section being 60%, by cold radial forging with the change of the deformation direction in order for the Bausinger effect to occur and develop as follows: a first stage of cold deformation with a 42% reduction per section from Φ 50 mm to Φ 42 mm and finally to Φ 38 mm, followed by a change of deformation direction and a second stage of deformation with a 30% reduction per section from Φ 38 mm to Φ 34 mm and finally to Φ 32 mm, 5. heat treatment in a solution at a temperature of 820°C for 15 minutes with cooling in water, 6. precision cutting out at the weight of the projectile of caliber 30 mm with positive tolerances, 7. final cold forming of the projectile by rotary forging with profiled tools, 8. degreasing, 9. final heat treatment with double precipitation at a temperature of 450°C, for 4 hours, with cooling in air, and 10. final dimensional control of the projectile, hardness control per section and metallographic analysis of the grain size structure.