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1.1Common Grades: Ti-6Al-4V (Grade 5).
1.2Advantages: High strength-to-weight ratio, exceptional corrosion resistance, high-temperature stability, biocompatibility.
1.3Disadvantages: High raw material cost, challenging machining, strict welding protection requirements.
2. 4130N Alloy Steel
2.1 Composition: Low-alloy steel (Cr-Mo steel), carbon content ~0.30%.
2.2 Advantages: High strength, good toughness, low cost, mature machining and welding processes.
2.3 Disadvantages: High density (~7.85 g/cm³), susceptibility to corrosion (requires surface treatment), poor high-temperature performance.
| Criteria | Titanium Alloys | 4130N Alloy Steel |
| Machinability | Difficult: Low thermal conductivity, tool adhesion risks; requires low RPM, high feed rates, and specialized carbide tools. | Easier: Good machinability in annealed state; supports high-speed machining with longer tool life. |
| Hot Formability | Requires high temperatures (800–900°C), prone to oxidation, needs inert gas protection. | Lower hot-forming temperature (~900°C), simpler process. |
| Cold Formability | High springback; requires multiple forming stages or intermediate annealing. | Excellent cold rolling/bending performance with controllable springback. |
| Surface Treatment | Typically no anti-corrosion coating needed; anodizing possible. | Requires anti-rust treatments (e.g., galvanizing, phosphating, or painting). |
| Cost | High material and machining costs (rapid tool wear). | Low material and machining costs. |
| Criteria | Titanium Alloys | 4130N Alloy Steel |
| Welding Methods | Primarily TIG/MIG welding; strict inert gas shielding (front/backside). | TIG, MIG, or stick welding; no special shielding required. |
Preheating/Post-heat Treatment | No preheating typically needed, but interpass temperature control critical. | Preheating (150–300°C) required to prevent cold cracks; post-weld slow cooling or tempering. |
| Weld Quality | Sensitive to oxygen/nitrogen contamination (causes embrittlement); strict surface cleaning required. | Risk of hydrogen-induced cracks; requires low-hydrogen electrodes and pre-drying. |
| Welding Distortion | Low thermal expansion coefficient minimizes distortion. | Higher thermal expansion; fixtures needed to control distortion. |
| Filler Material | Requires matching filler (e.g., ERTi-5). | Common fillers: ER80S-D2 or E7018 electrodes. |
| Application Scenario | Recommended Material | Rationale |
| High Lightweight Demand(Aerospace, racing components) | Titanium Alloys | Superior strength-to-weight ratio, fatigue resistance, significant weight reduction. |
| Cost Sensitivity(Automotive chassis, general structures) | 4130N Alloy Steel | Cost-effective with low machining/welding expenses. |
| Corrosive Environments (Marine, chemical equipment) | Titanium Alloys | No additional anti-corrosion treatment needed; long service life. |
| High-Temperature Use (Engine parts, exhaust systems) | Titanium Alloys (≤500°C) | Better high-temperature strength vs. 4130N (which requires thermal coatings). |
| Complex Welded Structures | 4130N Alloy Steel | Mature welding processes, ease of repair, controllable hydrogen cracking. |
1.Material Selection Priority:
Titanium Alloys: Ideal for weight-critical, corrosion-prone, or high-temperature applications but require acceptance of high costs and complex processes.
4130N Alloy Steel: Suitable for general high-strength needs with budget constraints and standard machining/welding conditions.
2. Process Optimization:
Titanium: Invest in inert gas shielding systems and advanced tooling (e.g., diamond-coated tools) to improve machining efficiency.
4130N Steel: Apply post-weld tempering (600–650°C) to relieve stress and shot peening to enhance fatigue resistance.
3. Hybrid Solutions:
Consider mixed structures (e.g., titanium critical components + steel support frames) to balance cost and performance.
4. Final Recommendation:
Base material selection on core application requirements (lightweight, cost, corrosion resistance) and evaluate whether production capabilities (e.g., welding equipment, machining tools) meet the stringent demands of titanium alloys.
