300M
Alloy Steel300M
Aerospace Cr-Ni-Mo-V Q&T ultra-high-strength steel. (GJB 5218; equiv AMS 6411 / 4330V). Nominal values—confirm mill certificate.
Chemical Composition (%)
| C | 0.4 |
|---|---|
| MN | 0.65 |
| SI | 1.45 |
| NI | 1.65 |
| CR | 0.7 |
| MO | 0.3 |
| V | 0.05 |
| P | 0.01 |
| S | 0.01 |
Mechanical Properties
Tensile:≥1860 MPa;Yield:≥1515 MPa;Elong:≥10%;RA:≥30%
Chinese Standard
GJB 5218 300M
Equivalent Standards
AMS 6411
Equivalent Grades
4330V
Applications
航空用Cr-Ni-Mo-V调质超高强钢。,"Bar
Available Forms
Forging"
Uses
Spring steel with high elastic limit and fatigue strength for coils, leaf springs, clips and suspension parts. Silicon (≈1.625%) raises elastic limit and tempering resistance. Supplied as strip, wire and bar; shot-peened after forming for longer service life.
Heat Treatment
Austenitize 830–880 °C (oil quench) and temper at 400–520 °C; stress-relieve formed springs at 230–320 °C after coiling.
Precautions
Preheat and control interpass temperature when welding; post-weld heat treatment or stress relief is recommended to avoid hard-zone cracking. Use low-hydrogen electrodes. Protect from decarburization during heating (controlled atmosphere or protective coating). Shot-peen after coiling to improve fatigue life; avoid sharp bends and surface defects.
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