EN19 Steel Properties and Key Applications Overview

EN19 Steel, also known as 4140 steel, is a medium-carbon alloy steel that falls under the category of low-alloy steels. It is primarily characterized by its excellent strength, toughness, and wear resistance, making it a popular choice in various engineering applications. The primary alloying elements in EN19 steel include chromium (Cr) and molybdenum (Mo), which enhance its hardenability and strength.

Comprehensive Overview

EN19 steel is classified as a medium-carbon alloy steel, which typically contains carbon content ranging from 0.30% to 0.60%. The addition of chromium and molybdenum not only improves the steel's mechanical properties but also contributes to its resistance to wear and fatigue. The unique combination of these elements allows EN19 to achieve a good balance between hardness and ductility.

Key Characteristics:
- High Strength: EN19 exhibits high tensile and yield strength, making it suitable for heavy-duty applications.
- Good Toughness: The steel maintains its toughness even at low temperatures, which is crucial for applications subjected to impact loading.
- Wear Resistance: The alloying elements provide enhanced wear resistance, making it ideal for components that experience friction and abrasion.

Advantages:
- Excellent mechanical properties, including high tensile strength and fatigue resistance.
- Versatile applications across various industries, including automotive, aerospace, and manufacturing.
- Good machinability and weldability when properly treated.

Limitations:
- Prone to stress corrosion cracking in certain environments.
- Requires careful heat treatment to achieve desired properties, which can complicate fabrication processes.

Historically, EN19 has been widely used in the production of high-strength components such as gears, shafts, and axles, establishing its significance in the engineering sector.

Alternative Names, Standards, and Equivalents

Standard Organization	Designation/Grade	Country/Region of Origin	Notes/Remarks
UNS	G41400	USA	Closest equivalent to EN19
AISI/SAE	4140	USA	Commonly used designation
ASTM	A829	USA	Standard specification for alloy steel
EN	19	Europe	European standard designation
DIN	1.7225	Germany	Equivalent with slight compositional differences
JIS	SCM440	Japan	Similar properties, but different alloying elements
GB	42CrMo	China	Comparable grade with minor differences

The table above highlights various designations and standards for EN19 steel. Notably, while grades like SCM440 and 42CrMo are often considered equivalent, they may have subtle differences in alloying elements that can affect performance in specific applications. For instance, SCM440 may have a slightly different carbon content, which can influence hardenability.

Key Properties

Chemical Composition

Element (Symbol and Name)	Percentage Range (%)
C (Carbon)	0.38 - 0.43
Cr (Chromium)	0.90 - 1.20
Mo (Molybdenum)	0.15 - 0.25
Mn (Manganese)	0.75 - 1.00
Si (Silicon)	0.15 - 0.40
P (Phosphorus)	≤ 0.035
S (Sulfur)	≤ 0.040

The primary alloying elements in EN19 steel play crucial roles:
- Chromium (Cr): Enhances hardenability and corrosion resistance.
- Molybdenum (Mo): Improves strength at elevated temperatures and contributes to wear resistance.
- Manganese (Mn): Increases toughness and hardenability.

Mechanical Properties

Property	Condition/Temper	Typical Value/Range (Metric - SI Units)	Typical Value/Range (Imperial Units)	Reference Standard for Test Method
Tensile Strength	Quenched & Tempered	850 - 1000 MPa	123 - 145 ksi	ASTM E8
Yield Strength (0.2% offset)	Quenched & Tempered	600 - 800 MPa	87 - 116 ksi	ASTM E8
Elongation	Quenched & Tempered	15 - 20%	15 - 20%	ASTM E8
Hardness (Rockwell C)	Quenched & Tempered	28 - 34 HRC	28 - 34 HRC	ASTM E18
Impact Strength (Charpy)	-40°C	27 J	20 ft-lbf	ASTM E23

The mechanical properties of EN19 steel make it suitable for applications requiring high strength and toughness. Its ability to withstand significant loads and resist deformation under stress is particularly beneficial in structural applications.

Physical Properties

Property	Condition/Temperature	Value (Metric - SI Units)	Value (Imperial Units)
Density	-	7.85 g/cm³	0.284 lb/in³
Melting Point	-	1425 - 1540 °C	2600 - 2800 °F
Thermal Conductivity	20°C	45 W/m·K	31 BTU·in/(hr·ft²·°F)
Specific Heat Capacity	20°C	0.49 kJ/kg·K	0.12 BTU/lb·°F
Electrical Resistivity	20°C	0.0000017 Ω·m	0.0000017 Ω·in

The density and melting point of EN19 steel indicate its robustness, while its thermal conductivity and specific heat capacity are relevant for applications involving thermal stresses. These properties are essential for components that may experience rapid temperature changes.

Corrosion Resistance

Corrosive Agent	Concentration (%)	Temperature (°C/°F)	Resistance Rating	Notes
Chlorides	3-5	25°C / 77°F	Fair	Risk of pitting
Sulfuric Acid	10	25°C / 77°F	Poor	Not recommended
Sea Water	-	25°C / 77°F	Fair	Moderate resistance
Alkaline Solutions	5-10	25°C / 77°F	Good	Better resistance

EN19 steel exhibits moderate resistance to corrosion, particularly in environments with chlorides and alkaline solutions. However, it is not recommended for use in acidic environments, such as sulfuric acid, where it can suffer from significant degradation. Compared to stainless steels, EN19's corrosion resistance is limited, making it less suitable for applications in highly corrosive environments.

Heat Resistance

Property/Limit	Temperature (°C)	Temperature (°F)	Remarks
Max Continuous Service Temp	400 °C	752 °F	Suitable for high-temperature applications
Max Intermittent Service Temp	500 °C	932 °F	Short-term exposure only
Scaling Temperature	600 °C	1112 °F	Risk of oxidation at this temperature
Creep Strength considerations begin around	400 °C	752 °F	Creep resistance decreases significantly

EN19 steel performs well at elevated temperatures, maintaining its mechanical properties up to 400 °C. However, beyond this temperature, the risk of oxidation and scaling increases, which can compromise the material's integrity.

Fabrication Properties

Weldability

Welding Process	Recommended Filler Metal (AWS Classification)	Typical Shielding Gas/Flux	Notes
MIG	ER70S-6	Argon + CO2	Good results with preheating
TIG	ER80S-Ni	Argon	Requires preheat to avoid cracking
Stick	E7018	-	Suitable for thicker sections

EN19 steel can be welded using various methods, but preheating is often necessary to prevent cracking. The choice of filler metal is crucial, as it should match the mechanical properties of the base material to ensure a strong weld.

Machinability

Machining Parameter	EN19 Steel	AISI 1212	Notes/Tips
Relative Machinability Index	70	100	Moderate machinability
Typical Cutting Speed (Turning)	50-70 m/min	80-100 m/min	Use carbide tools for best results

EN19 steel has moderate machinability, which can be improved with proper tooling and cutting conditions. It is essential to use high-quality cutting tools to achieve optimal results.

Formability

EN19 steel exhibits good formability, allowing for both cold and hot forming processes. However, it is important to consider work hardening effects during cold forming, which can increase the material's strength but may also lead to cracking if not managed properly. Bend radii should be carefully calculated to avoid failure during forming operations.

Heat Treatment

Treatment Process	Temperature Range (°C/°F)	Typical Soaking Time	Cooling Method	Primary Purpose / Expected Result
Annealing	600 - 650 °C / 1112 - 1202 °F	1 - 2 hours	Air or Furnace	Softening, improving machinability
Quenching	850 - 900 °C / 1562 - 1652 °F	30 minutes	Oil or Water	Hardening, increasing strength
Tempering	400 - 600 °C / 752 - 1112 °F	1 hour	Air	Reducing brittleness, improving toughness

Heat treatment processes significantly influence the microstructure and properties of EN19 steel. Quenching increases hardness, while tempering reduces brittleness, allowing for a balance between strength and ductility.

Typical Applications and End Uses

Industry/Sector	Specific Application Example	Key Steel Properties Utilized in this Application	Reason for Selection (Brief)
Automotive	Gears	High strength, wear resistance	Essential for durability
Aerospace	Landing gear components	Toughness, fatigue resistance	Critical for safety
Manufacturing	Shafts	High tensile strength, machinability	Suitable for precision parts
Oil & Gas	Drill bits	Wear resistance, toughness	High-performance requirements

Other applications include:
- Heavy machinery components
- Structural parts in construction
- Tooling and dies

EN19 steel is often selected for applications requiring high strength and toughness, particularly in environments where wear and fatigue are concerns. Its versatility across various industries highlights its importance in engineering.

Important Considerations, Selection Criteria, and Further Insights

Feature/Property	EN19 Steel	AISI 4140	SCM440	Brief Pro/Con or Trade-off Note
Key Mechanical Property	High strength	High strength	Moderate strength	Similar strength, but EN19 has better toughness
Key Corrosion Aspect	Fair resistance	Fair resistance	Good resistance	SCM440 offers better corrosion resistance
Weldability	Good	Moderate	Good	EN19 requires preheating
Machinability	Moderate	Good	Excellent	AISI 1212 is easier to machine
Formability	Good	Moderate	Good	EN19 can be more challenging to form
Approx. Relative Cost	Moderate	Moderate	Moderate	Costs are generally comparable
Typical Availability	Common	Common	Common	Widely available in various forms

When selecting EN19 steel, considerations include mechanical properties, corrosion resistance, and fabrication characteristics. Its balance of strength and toughness makes it suitable for demanding applications, while its moderate cost and availability enhance its appeal.

In summary, EN19 steel is a versatile and robust material that serves a wide range of engineering applications. Its unique combination of properties, coupled with careful consideration of fabrication and environmental factors, makes it a preferred choice in many industries.