Take the 10.9 level as an exampl ∑★e: 10 represents the nominal₩φ‌ tensile strength (1000MPa), aα↔nd 9 represents the yield streng'®Ωth ratio (0.9). The rest ca× ↑<n be deduced by analogy.
No other grades are currently seen, ↑↓and grade 12.9 is relatively rar ₽λ e.
The materials used for grade 8.8 a∏α£♠nd 10.9 are 42CrMo, 42CrMoA, 35C >rMo, 42CrNiMo, 40Cr steel≠®.
The occasions used at a♣ ll levels should be determ≥"←ined by calculation, mainly c•↓↔σalculating their shear str₽←¥$ess, frictional force, an≤≈←≈d compressive stress.
The performance level of bolts is diΩ§∞vided into 3.6, 4.6, 4.8, 5.6, 5.8, 6.8♣×←✘, 8.8, 10.9, 12.9 from γ♦small to large.
This marking method means taking♥÷₩δ 10.9 as an example
10 indicates 1/100 of the tensile sδ¥✘∏trength of the bolt, which meα™β​ans that the tensile→↑↔ strength of this grade of bolt must reΩ‍≥±ach 1000MPa, which may ‍±★actually be higher than 1000MPa.
GB/T3098.1 stipulates that the m₩"inimum tensile strength​λ of this grade of bolts must be £♦★•greater than 1040MPa≠♠↓.
The indicated yield ra≈≥tio after the decimal point is the bo​×lt's (yield strength/tensile st←¶∞♠rength) = 0.9
That is, the yield str φength=1000*0.9=900MPa, the yieφ<•ld strength of this grade of b££₽αolt must be higher thλ★→an 900MPa to be qualified.✔¶©
Usually we call the three grades of  ✔  bolts 8.8, 10.9, and 12.9 as®☆§‍ high-strength bolts.
It should be noted tha‍‍€t GB/T3098.1 does noγ★t give specific valu↔‍£↑es ​​of yield strength for∏×>δ these three grades of bolts, beca↑¶♥use for high-strength bol₩​≠ts 0.8 and 0.9 are the minimum  ↓‍¥yield strength ratiosσ§ specified by this grade. Bδ$ ☆ecause high-strength bolts are used ↔£¥↕for very important links₽'β, there is no spot on thα♠e market and must be ordered with the∞< bolt manufacturer. There♦¥fore, the specific yiel¶ δd ratio is generally produced ¥£≥by the buyer’s specific v←•€alue.