Steel 20HML

Designation

Name	The value
Designation GOST Cyrillic	20ХМЛ
Designation GOST Latin	20XML
Transliteration	20HML
By chemical elements	20CrMo

Description

20HML steel is used: for the manufacture of castings, gears, joints, bushings, gear wheels, cylinders, clips and other parts operating for a long period of time at temperatures up to +500 °C; casting parts for gas turbines and axial compressors operating at temperatures up to +510 °C; casting groups 1, 2, 3 parts of valves and actuators to it, working in non-aggressive environments at temperatures from -40 to +540 °C without restriction of the nominal working pressure; castings of body parts, shipbuilding, operating at temperatures of 400−500 °C; stationary parts of steam turbines operating at temperatures up to +520 °C; casting equipment parts (valves) for nuclear power stations, heat supply stations, heat and power plants, experimental and research nuclear reactors and installations.

Note

Heat-resistant steel pearlitic class.

Standards

Name	Code	Standards
Steel castings	В82	GOST 977-88, OST 108.961.04-80, OST 26-07-402-83, OST 5Р.9285-95, TU 26-02-19-75, TU 4112-091-00220302-2006, ST ЦКБА 014-2004, TU 5.961-11151-92
Castings with special properties (iron and steel)	В83	OST 108.961.02-79, OST 108.961.03-79
Welding and cutting metals. Soldering, riveting	В05	RTM 108.020.122-78

Chemical composition

Standard	C	S	P	Mn	Cr	Si	Ni	Fe	Cu	Mo
OST 108.961.03-79	0.15-0.22	≤0.025	≤0.025	0.5-0.8	0.5-0.8	0.2-0.45	≤0.3	Rest	≤0.3	0.4-0.6
TU 5.961-11151-92	0.15-0.25	≤0.04	≤0.04	0.4-0.9	0.4-0.7	0.2-0.42	-	Rest	-	0.4-0.6
OST 108.961.02-79	0.15-0.25	≤0.025	≤0.025	0.5-0.8	0.5-0.8	0.2-0.45	≤0.3	Rest	≤0.3	0.4-0.6
OST 5Р.9285-95	0.15-0.25	≤0.04	≤0.04	0.4-0.9	0.4-0.7	0.2-0.42	≤0.3	Rest	≤0.3	0.4-0.6

Fe is the basis.
According to OST 108.961.04-80, the total sulfur and phosphorus content should be ≤ 0.050% for all possible tolerances.
According to OST 5R.9285-95, the content of nickel to 0.50% and copper to 0.40% is not a defect condition provided that the requirements of the standard are observed and if there are no special instructions in the technical conditions of the order or drawing.
According to TU 5.961-11151-92 for castings of grades 1 and 2 the mass fraction of cobalt in steel should not exceed 0.20%, and for castings in the direct irradiation zone - 0.15%.

Mechanical properties

Section, mm	s_T\|s_0,2, MPa	σ_U, MPa	d	y, %	KCU, kJ/m²	HB, MPa
Normalization with 880-890 °C + Vacation at 600-650 °C, air cooling
100	≥245	≥441	≥18	≥30	≥294	-
Normalization at 890-910 °C (extract 8 hours) + Vacation at 640-660 °C (exposure 8 h), cooling to 300 °C at a speed of 40-50 °C/h.
-	305-390	470-550	12-28	27-66	-	-
Casting without heat treatment
	365-570	540-670	6-16	15-24	100-340	-
Normalization at 890-910 °C (extract 8 hours) + Vacation at 640-660 °C (exposure 8 h), cooling to 300 °C at a speed of 40-50 °C/h.
-	345	430	17-21	59-62	-	-
Casting parts of gas turbines. Normalization when 880-910 °C, air cooling + Vacation at 620-650 °C, cooling with the furnace to 300 °C, air cooling
-	≥245	≥461	≥18	≥30	≥290	135-180
Normalization at 890-910 °C (extract 8 hours) + Vacation at 640-660 °C (exposure 8 h), cooling to 300 °C at a speed of 40-50 °C/h.
-	295	380	22	69-75	-	-
Casting parts, cylinders, clips stationary steam turbines. Normalization at 880-900 °C + Vacation at 600-650 °C, air cooling
-	≥250	≥470	≥18	≥30	≥294	135-180
Normalization at 890-910 °C (extract 8 hours) + Vacation at 640-660 °C (exposure 8 h), cooling to 300 °C at a speed of 40-50 °C/h.
-	195-235	290	28	82	-	-
Castings for shipbuilding. When normalizing 890-920 °C + vacation at 630-670 °C, air cooling
-	≥250	≥450	≥18	≥30	≥300	135-180
Annealing at 880-900 °With (extract 8 hours)
-	365	460	17-22	41-51	-	-
-	295-325	390-410	14-24	64-79	-	-
-	245-265	305-345	24-26	73	-	-
Castings with wall thickness up to 100 mm in the delivery state on the other 5.961-11151-92. Normalization at 880-920 °C + Vacation at 600-650 °C. the Critical temperature of brittleness of TKO ≤ 50 °C.
-	≥245	≥441	≥18	≥30	≥490	-
-	≥230	≥430	-	≥35	-	-
-	≥220	≥420	-	≥52	-	-
-	≥200	≥400	-	≥55	-	-

Description mechanical marks

Name	Description
s_T\|s_0,2	Yield strength or limit of proportionality with a tolerance for residual deformation of 0.2%
σ_U	Limit short-term strength
d	Elongation after rupture
y	The relative narrowing
KCU	Toughness
HB	Brinell hardness number

Physical characteristics

Temperature	r, kg/m³	a, 10^-6 1/°C
0	7800	-
20	7800	-
100	7780	109
200	7750	124
300	7720	128
400	7690	131
500	7650	136
600	7620	136
800	-	139

A description of the physical symbols

Name	Description
Е	The normal elasticity modulus
r	Density
l	Coefficient of thermal conductivity
С	Specific heat

Technological properties

Name	The value
Weldability	Limited weldability. The welding process - SMAW. When welding requires preheating. After welding and repair of defects by welding is used vacation at 600-650 °C.
Склонность к отпускной хрупкости	Tend not.
Machinability	In the normalized and tempered condition at NV 135-180 and blower SB=460 MPa Kn b.St.=0,85.
Welding defects	Welding defects of castings after cutting is carried out with preliminary and attendant heating up to 350-400 °C. for semi-automatic welding in carbon dioxide environment used wire SV-08ХГСМФА with a diameter of 2 mm at a current of 300-350 A. Welding defects by manual welding is done with electrodes ЦЛ45. When heat treated after welding defects to cool in the oven to 100-150 °C at a rate of 30-50 °C/h and further in the air.