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The table contains information on the chemical composition of steels for the manufacture of boltsdevided by classes of strength. Chemical composition of materials is binding only on those boltsthat can not be tested by tensile test.

Strength classMaterialsChemical composition %Tempering temperature
C min.C max.P max.S max.
3.61)Carbon steel-0,200,050,06-
4.61)-0,550,050,06
4.81)
5.60,150,550,050,06
5.81)-0,550,050,06
6.81)
8.82)Carbon steel with additives B, Mn, or Cr, case-hardened and tempered 0,153)0,400,0350,035425
Carbon steel, case-hardened and tempered0,250,550,0350,035
9.8Carbon steel with additives B, Mn, or Cr, case-hardened and tempered0,153)0,0350,0350,035425
Carbon steel, case-hardened and tempered0,250,550,0350,035
10.94)Carbon steel with additives B, Mn, or Cr, case-hardened and tempered0,153)0,350,0350,035340
10.95)Carbon steel, case-hardened and tempered0,250,550,0350,035425
Carbon steel with additives B, Mn, or Cr, case-hardened and tempered0,203)0,550,0350,035
Carbon steel, case-hardened and tempered0,200,550,0350,035
12,95) 6)Carbon steel, case-hardened and tempered0,200,500,0350,035380
  1. Strength for these classes is permissible automat steel with the following maximum shares of S, P and Pb: S = 0.34%, P = 0.11%, Pb = 0.35%.
  2. For nominal diameter over 20 mm is necessary to use the material strength class 10.9 for reasons of sufficient hardness.
  3. Carbon steel with additives B and C content less than 0.25% (according tavebního analysis)Mn content must be at least class 8.8 0.6% for class 9.8 and 10.9 at least 0.7%.
  4. For articles of these steels must be label-class strength underlined.
  5. Material for this property class must be sufficiently hardenable to be sure that the composition of the nucleus in the threaded part will be available approximately 90% of blindness in themartensite state before tempering.
  6. For strength class 12.9 is admissible metallographically detectable white phosphorous enrichedlayer on the surface, which is tension.
  7. Alloy steel must contain at least one of the following elements: Cr, Ni, Mb, Va.
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