Key Conclusion in a Nutshell
For the same specifications: Pure titanium bolts are inferior to high-strength steel bolts; Gr5 (Ti-6Al-4V) titanium alloy bolts have a strength equivalent to approximately Grade 10.9 steel, which is significantly weaker than Grade 12.9 steel; however, titanium's specific strength (strength ÷ density) is far superior to that of steel.
1｜Comparison of Basic Data (Common Grades)
Grade 4.8/8.8 carbon steel: Low tensile strength; easily surpassed by Gr5 titanium
Grade 10.9 alloy steel (40Cr): Tensile strength ≥ 1040 MPa
Grade 12.9 alloy steel (42CrMo): Tensile strength ≥ 1220 MPa
Gr5 Titanium Alloy Ti-6Al-4V: Tensile strength ≈ 860–1100 MPa (typically ~900 MPa in the standard annealed condition)
Pure Titanium Gr2: Tensile strength ≈ 400–500 MPa, comparable only to Grade 8.8 steel, and far weaker than Grades 10.9 and 12.9
Comparison Summary:
Gr2 pure titanium bolts → Absolute strength < Grade 10.9 and 12.9 steel
Gr5 titanium alloy → Upper limit approaches Grade 10.9 steel, but does not reach Grade 12.9
However, titanium has a density of only about 60% that of steel (titanium 4.51, steel 7.85)
Specific strength (strength-to-weight ratio): Gr5 > 12.9 steel
Meaning: For the same strength, titanium bolts are lighter; for the same weight, titanium is stronger-it's not simply that titanium bolts of the same size are harder or sturdier.
Other Key Differences (Significantly Affecting "Durability/Ruggedness")
Advantages of Titanium
Excellent corrosion resistance: Does not rust in seawater, chloride-ion, or weak acid environments; alloy steel requires a coating
Excellent fatigue properties; performs very well under alternating vibration conditions
Non-magnetic, good low-temperature performance, and low coefficient of thermal expansion
No hydrogen embrittlement (a significant risk with electroplated high-strength steel)
Quick Selection Guide
Goal: For bolts of the same size, maximize tensile strength → Choose 12.9 steel, which is stronger than titanium
Goal: Weight reduction + corrosion resistance + vibration fatigue (racing, aviation, seawater equipment) → Gr5 titanium alloy is more suitable
Standard indoor racks, heavy-duty fastening → Best value: 10.9/12.9 steel
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