Knowledge of bolt material grades
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I would like to ask: for bolts whose material is designated as 35CrMoA, what does the letter A stand for? And what are the differences in performance between such bolts and those made of 35CrMo?
I. What is 35CrMoA material? Answer: Alloy structural steel. II. What does A stand for? Answer: A stands for high-grade quality steel. B and C refer to grade 2 and grade 3 steel, or what is known as medium-grade steel. Thirdly, what are the chemical composition and mechanical properties of this material? What standards should be referenced? Answer: 1. Chemical composition: C: 0.32–0.4%, Si: 0.2–0.4%, Mn: 0.4–0.7%, Cr: 0.8–1.1%, Mo: 0.15–0.25%. 2. Mechanical properties: ① When the cross-sectional dimension is ≤40 mm, σb = 95 kg/mm², σ0.2 = 80 kg/mm², δ = 10%, Ψ = 40%, σk = 5 kg·m/cm², HB = 293–321 ； ②When the cross-sectional dimension is ≤70 mm, σb=88 kg/mm², σ0.2=70 kg/mm², δ=12%, Ψ=45%, σk=6 kg·m/mm², HB=277–302 ； ③When the cross-sectional dimension is ≤100 mm, σb=80 kg/mm², σ0.2=60 kg/mm², δ=14%, Ψ=45%, σk=6 kg·m/cm², HB=241-277 ； ④When the cross-sectional dimension is ≤150 mm, σb=70 kg/mm², σ0.2=50 kg/mm², δ=15%, Ψ=45%, σk=6 kg·m/cm², and HB=217–255. 3. Reference standard: GB/T3077-1999 \"Alloy structural steel\".
Question: Could someone upstairs mention a brand of bolts in China that are rated at 10.9 grade and 12.9 grade? !