DIN 20MnCr5 1.7147 / ASTM 5120 Case Hardening Alloy Steel

20MnCr5 / 1.7147 is an alloyed carburized steel belonging to the European standards EN 10084 and EN 10250-3. It is widely used in several industries, such as automotive manufacturing, heavy machinery and highly loaded transmission components. You can find equivalents in different national standards, such as American Standard ASTM 5120 (ASTM A29/A29M) and Chinese Standard 20CrMn (GB/T 3077).

20MnCr5 is part of the Mn-Cr steel series, with a carbon content ranging from 0.17-0.22%. This steel is particularly valued for its ability to achieve a balance between surface hardness and core toughness after undergoing carburizing and heat treatment processes. Its excellent wear resistance and fatigue strength make it a preferred choice for components subjected to high stress and friction. Commonly used in the production of gears, shafts, and other transmission parts, 20MnCr5 is ideal for applications where durability and reliability are critical.

1: Steel equivalent

2: Chemical composition

3: Mechanical properties .

Steel grades 20MnCr5 according to minimum tensile strength as a function of diameter after hardening and tempering at 200℃ according to EN10084.

Mechanical properties for reference test bar in the simulated case-hardening condition according to ISO 683-11-1987.

Sampling and preparation of test pieces for 20MnCr5 case-hardening steel.

1): According to EN10084, all samples shall be taken at a distance of 1/4 of the diameter or thickness below the heat-treated surface.

2): As stipulated in the contract between buyer and seller.

4: Surface hardness and hardenability.

Where the steel is ordered by using the symbols for normal (+H) or restricted (+HL, +HH) hardenability requirements, the hardenability values should apply below:

Scatter bands for the Rockwell - C hardness in the end quench hardenability test.

Key

X   distance from quenched end of test piece, mm

Y   hardness, HRC

1   upper limit

2   upper limit, +HL grades

3   lower limit, +HH grades

4   lower limit

5: Supply size & Tolerance & Stock size

Qilu steel stock hot rolled bar and forged bars more than ten thousands tons every month, below our our stock size.

1): Stock diameter for hot rolled bar

Since the stocks change everyday, if you want to know our stock available information, please contact our salesman.

6：Forging processing

Pre-heat: 600-700℃

Initial temperature: 1150-1200℃. Should not exceed 1200°C to avoid overheating or coarse grains.

Final temperature: 800-850℃. Need to finish forging above Ar3 line to avoid cracks caused by low temperature forging.

Slow cooling after forging, cooling in the sand or in the furnace.

7: Heat treatment

Soft annealed:

Heat 20MnCr5 steel to 650-700℃

Cooling in the furnace

Normalized:

Heat 20MnCr5 steel to 840-870℃

Cooling in the air

End quench test Austenitizing temperature: 870℃

Carburizing temperature: 880-980℃

Core-hardening temperature: 860-900℃

Case-hardening temperature: 780-820℃

Quenching and tempering:

Heat 20MnCr5 steel to 830-840℃

Quench in water or oil

Temper steel at 150-200℃ in the furnace

Cooling in the air.

Remark: The conditions given above are for guidance, at the temperatures at the lower end of the range are generally applicable to hardening in water and those at the upper end for hardening in oil.

8: Weldability

20MnCr5 steel has limited weldability due to its alloy composition. While the carbon content of 20MnCr5 is around 0.17%-0.22%, which is below the 0.25% threshold where weldability typically starts to decline, the presence of manganese and chromium can still pose challenges. Manganese increases hardenability, and chromium contributes to the formation of hard microstructures in the heat-affected zone (HAZ), which can lead to cracking during welding. To achieve successful welding, preheating to around 150°C - 250°C and using low-hydrogen electrodes are recommended. Additionally, post-weld heat treatment may be necessary to relieve residual stresses and improve the toughness of the welded joint.

9：Application

20MnCr5 steel is a low carbon alloy steel with good hardenability, strength and toughness. The following are its main application uses.

1): Automotive Industry:

(1): Gears: used to manufacture transmission gears, differential gears, etc.

(2): Shaft parts: such as drive shafts, half shafts, etc.

(3): Clutch parts: such as clutch plates, pressure plates, etc.

2): Mechanical Manufacturing:

(1): Transmission parts: such as sprockets, pulleys, etc.

(2): High-strength bolts and nuts: for connecting parts that require high strength.

3): Construction Machinery:

Excavator and loader parts: such as gears, shafts, etc.

4): Aerospace:

High-strength and wear-resistant parts: such as landing gear parts, transmission parts, etc.

5): Other Industries:

Molds: for manufacturing plastic molds, die-casting molds, etc.

Tools: such as wrenches, pliers and other hand tools.