|Designation GOST Cyrillic||20-КХС|
|Designation GOST Latin||20-KXC|
|By chemical elements||20-CoCrС|
Steel 20-kkhs used: for the production of flat steel longitudinal electric-welded pipeline pipes with improved resistance to local corrosion for a working pressure up to 7.4 MPa strength class K52 diameter 530 — 1020 mm and a diameter of 114−530 mm strength classes K48 and K52 used for the construction of oil gathering networks (to transport corrosive gas, oil and formation water) and pipeline system at the pressure more than 7.4 MPa (75 kgf/cm2), for operation at a minimum ambient temperature of minus 60 °C.
|Steel pipes and fittings to them||В62||TU 14-1-5433-2005, TU 14-1-5491-2004|
According to TU 14-1-5491-2004, deviations from the chemical composition are permissible: for carbon ± 0.010%, for manganese ± 0.050%, for sulfur + 0.0010%, for phosphorus +0.0030%, for nitrogen +0.0030% , silicon ± 0.020%, chromium +0.020%, vanadium +0.020%, aluminum +0.010%, niobium + 0.010%.
The carbon equivalent C eq is calculated by the formula and should not exceed 0.43%: C eqv = C + Mn / 6 + (Cr + Nb) / 5 + (Ni + Cu) / 15, where C, Mn, Cr, Nb, Ni, Cu - mass fractions of the basic elements that make up the steel.
According to TU 14-1-5433-2005, deviations from the chemical composition are permissible: for carbon ± 0.010%, for manganese ± 0.050%, for sulfur + 0.0010%, for phosphorus +0.0030%, for nitrogen +0.0030% , for niobium + 0.010%.
|Section, mm||sT|s0,2, MPa||σU, MPa||d5, %||KCU, kJ/m2|
|The main metal tube: heat-treated, in the state of delivery on the other 14-1-5433-2005. In the graph the impact strength values KCU-60/KCV-20|
|The main metal tube: heat-treated, in the state of delivery on the other 14-1-5491-2004|
Description mechanical marks
|sT|s0,2||Yield strength or limit of proportionality with a tolerance for residual deformation of 0.2%|
|σU||Limit short-term strength|
|d5||Elongation after rupture|
|Toughness||Basically the metal pipe on the other 14-1-5491-2004 impact strength KCU-60 when pipe wall thickness up to 15 mm inclusive, must be ≥to 39.2 j/cm2(392 kJ/m2), and the pipe wall thickness more than 15 mm 49,0 j/cm2 (490 kJ/m2). The percentage of the viscous component in the fractured impact specimens KCV-20 is not less than 50%. The impact strength and the percentage of the viscous component is defined as the arithmetic average of the results of the three samples. One of the three samples may reduce impact toughness 9.8 j/cm2 (98 kJ/m2), percent of a viscous component by 10%. The value of toughness and yield strength for material of the welded connection shall not be less than the norms of the base metal for all wall thickness, KCU-60 > = 39,2 j/cm2 (392 kJ/m2). For the material of welded joints of pipes on the other 14-1-5433-2005 impact strength KCU-60 for all classes of strength and wall thickness should be ≥ to 24.5 j/cm2 (245 kJ/m2).|