Designation
| Name |
The value |
| Designation GOST Cyrillic |
20ГМЛ |
| Designation GOST Latin |
20GML |
| Transliteration |
20GML |
| By chemical elements |
20MnMo |
Description
20ГМЛ steel is used: for the manufacture of castings 1, 2 and 3rd parts of valves, operating at low temperatures (from -60 to +450 °C) in neutral environments, for cast and welded structures were test impact strength KCU-60≥300 kJ/m2 (3.0 kgs·m/cm2); casting parts of valves, operating in environments containing hydrogen sulphide (H2 S) at temperatures from -40 to +80 °C test of impact strength KCU-40≥300 kJ/m2 (3.0 kgs·m/cm2)
Standards
| Name |
Code |
Standards |
| Steel castings |
В82 |
OST 26-07-402-83, TU 26-0304-55-95, TU 4112-091-00220302-2006, ST ЦКБА 014-2004 |
Chemical composition
| Standard |
C |
S |
P |
Mn |
Cr |
Si |
Ni |
Fe |
Al |
Mo |
Ca |
Ce |
| ST ЦКБА 014-2004 |
0.12-0.2 |
≤0.03 |
≤0.03 |
0.8-1.2 |
≤0.5 |
0.2-0.4 |
≤0.5 |
Rest |
≤0.08 |
0.25-0.35 |
0.05-0.15 |
0.05-0.1 |
Fe is the basis.
According to CT CKBA 014-2004, the content of calcium, cerium and aluminum is introduced by calculation and is not an obligatory delivery characteristic. When smelting 20GML steel in electric furnaces with acid lining intended for casting parts of pipeline fittings of the northern version, the mass fraction of sulfur and phosphorus is allowed up to 0.040%, provided that the required mechanical properties are ensured.
Mechanical properties
| sT|s0,2, MPa |
σU, MPa |
d |
y, % |
KCU, kJ/m2 |
| Casting parts of valves for neutral media. Normalization at 900-920 °C, air cooling + vacation at 600-650 °C, air cooling KCU+20/-60 |
| ≥240 |
≥420 |
≥18 |
≥30 |
≥500/300 |
| Casting parts of pipe fittings for environments containing hydrogen sulfide. Normalization at 900-920 °C, air cooling + vacation at 600-650 °C, air cooling KCU+20/-40 |
| ≥240 |
≥420 |
≥22 |
- |
≥800/300 |
Description mechanical marks
| Name |
Description |
| sT|s0,2 |
Yield strength or limit of proportionality with a tolerance for residual deformation of 0.2% |
| σU |
Limit short-term strength |
| d |
Elongation after rupture |
| y |
The relative narrowing |
| KCU |
Toughness |
Technological properties
| Name |
The value |
| Surfacing |
Surfacing of sealing surfaces of valves in accordance with OST 26-07-2028-81 is made by manual arc welding electrodes type e-20X13 with plaster SSSI-13НЖ, NII-48, NII-48Ж-1 or SV wire-12H13 or SV-20X13. Surface preparation for overlay welding is performed by machining. Surfacing is performed with preliminary and accompanying heating to 400-450 °C is not less than 3 layers with thickness not less than 4 mm, excluding allowance for machining. Heat treatment after welding is produced by tempering at 550-600 °C (delay of 2-5 h) hardness HB=301-350, at 600-650 °C (delay of 2-5 h) hardness HB=240 to 300, at 400-450 °C (delay of 2-5 h) hardness HB=351-400. The temperature of the furnace when loading the details for the home should be no more than 300 °C. |
