10B38 Steel: Properties and Key Applications

10B38 steel is a medium-carbon alloy steel primarily classified as a low-alloy steel. It is characterized by its significant alloying elements, including manganese, chromium, and molybdenum, which enhance its mechanical properties and overall performance in various applications. The presence of these elements contributes to improved hardenability, strength, and wear resistance, making 10B38 suitable for demanding engineering applications.

Comprehensive Overview

10B38 steel is particularly valued for its balance of strength and ductility, which allows it to withstand significant mechanical loads while maintaining structural integrity. Its primary alloying elements, such as manganese (Mn), chromium (Cr), and molybdenum (Mo), play crucial roles in defining its properties. Manganese enhances hardenability and tensile strength, chromium improves corrosion resistance and hardness, while molybdenum contributes to strength at elevated temperatures.

Advantages (Pros)	Limitations (Cons)
High strength and toughness	Limited weldability
Good wear resistance	Susceptible to stress corrosion cracking
Excellent machinability	Requires careful heat treatment for optimal properties
Versatile for various applications	May not perform well in highly corrosive environments

Historically, 10B38 has found its niche in the manufacturing of components that require high strength and durability, such as gears, shafts, and other critical machine parts. Its market position is solid, particularly in industries where performance under stress is paramount.

Alternative Names, Standards, and Equivalents

Standard Organization	Designation/Grade	Country/Region of Origin	Notes/Remarks
UNS	G10450	USA	Closest equivalent to AISI 4130
AISI/SAE	1038	USA	Minor compositional differences to be aware of
ASTM	A29/A29M	USA	General specification for alloy steels
EN	1.0540	Europe	Equivalent to 10B38 with slight variations
JIS	S45C	Japan	Similar properties but different alloying elements

The table above highlights various standards and equivalents for 10B38 steel. Notably, while grades like AISI 4130 and S45C may appear similar, they can differ in specific alloying elements and mechanical properties, which can significantly affect performance in specific applications.

Key Properties

Chemical Composition

Element (Symbol and Name)	Percentage Range (%)
C (Carbon)	0.35 - 0.45
Mn (Manganese)	0.60 - 0.90
Cr (Chromium)	0.40 - 0.60
Mo (Molybdenum)	0.15 - 0.25
Si (Silicon)	0.15 - 0.40
P (Phosphorus)	≤ 0.035
S (Sulfur)	≤ 0.035

The key alloying elements in 10B38 steel play significant roles:
- Carbon (C): Increases hardness and strength through heat treatment.
- Manganese (Mn): Enhances hardenability and tensile strength.
- Chromium (Cr): Improves wear resistance and corrosion resistance.
- Molybdenum (Mo): Contributes to strength at elevated temperatures and improves toughness.

Mechanical Properties

Property	Condition/Temper	Typical Value/Range (Metric)	Typical Value/Range (Imperial)	Reference Standard for Test Method
Tensile Strength	Annealed	600 - 800 MPa	87 - 116 ksi	ASTM E8
Yield Strength (0.2% offset)	Annealed	350 - 500 MPa	51 - 73 ksi	ASTM E8
Elongation	Annealed	20 - 25%	20 - 25%	ASTM E8
Hardness (Brinell)	Annealed	170 - 210 HB	170 - 210 HB	ASTM E10
Impact Strength (Charpy)	-40°C	30 - 50 J	22 - 37 ft-lbf	ASTM E23

The mechanical properties of 10B38 steel make it suitable for applications that require high strength and toughness. Its tensile and yield strengths indicate that it can withstand significant loads, while its elongation percentage reflects good ductility, allowing it to deform without fracturing. The hardness values suggest that it can resist wear, making it ideal for components subjected to friction and abrasion.

Physical Properties

Property	Condition/Temperature	Value (Metric)	Value (Imperial)
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	0.46 kJ/kg·K	0.11 BTU/lb·°F
Electrical Resistivity	20°C	0.0000017 Ω·m	0.0000017 Ω·ft

The physical properties of 10B38 steel, such as its density and melting point, indicate its robustness and suitability for high-temperature applications. The thermal conductivity suggests that it can effectively dissipate heat, which is beneficial in applications where thermal management is critical.

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
Sodium Hydroxide	5%	25°C/77°F	Good	Moderate resistance

10B38 steel exhibits moderate corrosion resistance, particularly in environments with chlorides and alkaline substances. It is susceptible to pitting corrosion in chloride-rich environments and should be avoided in applications involving strong acids like sulfuric acid. Compared to other grades, such as 4140 and 4340, 10B38 may show inferior performance in highly corrosive settings, making it essential to consider the operating environment when selecting materials.

Heat Resistance

Property/Limit	Temperature (°C)	Temperature (°F)	Remarks
Max Continuous Service Temp	400°C	752°F	Suitable for moderate temperatures
Max Intermittent Service Temp	500°C	932°F	Limited exposure recommended
Scaling Temperature	600°C	1112°F	Risk of oxidation beyond this limit

At elevated temperatures, 10B38 steel maintains its strength but may begin to lose hardness and toughness. Its oxidation resistance diminishes at temperatures above 600°C, necessitating careful consideration in high-temperature applications.

Fabrication Properties

Weldability

Welding Process	Recommended Filler Metal (AWS Classification)	Typical Shielding Gas/Flux	Notes
MIG	ER70S-6	Argon + CO2	Preheat recommended
TIG	ER70S-2	Argon	Post-weld heat treatment may be needed
Stick (SMAW)	E7018	-	Requires careful control to avoid cracking

10B38 steel presents challenges in welding due to its medium carbon content, which can lead to cracking if not properly managed. Preheating and post-weld heat treatment are often necessary to mitigate these risks and ensure the integrity of the weld.

Machinability

Machining Parameter	10B38 Steel	AISI 1212	Notes/Tips
Relative Machinability Index	70	100	Good machinability with proper tooling
Typical Cutting Speed (Turning)	50-80 m/min	100-150 m/min	Adjust based on tooling and operation

10B38 steel offers good machinability, though it requires appropriate tooling and cutting speeds to achieve optimal results. The relative machinability index indicates that while it is machinable, it may not perform as well as some free-machining steels like AISI 1212.

Formability

10B38 steel can be formed through both cold and hot processes. Cold forming is feasible, but care must be taken to avoid excessive work hardening. Hot forming is preferred for complex shapes, as it reduces the risk of cracking and allows for better control over the final properties.

Heat Treatment

Treatment Process	Temperature Range (°C/°F)	Typical Soaking Time	Cooling Method	Primary Purpose / Expected Result
Annealing	600 - 700 / 1112 - 1292	1 - 2 hours	Air	Softening, improved ductility
Quenching	800 - 850 / 1472 - 1562	-	Oil or Water	Hardening
Tempering	400 - 600 / 752 - 1112	1 hour	Air	Reducing brittleness, improving toughness

Heat treatment processes significantly influence the microstructure and properties of 10B38 steel. Quenching increases hardness, while tempering is essential to reduce brittleness and enhance toughness, making it suitable for dynamic applications.

Typical Applications and End Uses

Industry/Sector	Specific Application Example	Key Steel Properties Utilized in this Application	Reason for Selection
Automotive	Gears	High strength, toughness	Durability under load
Aerospace	Structural components	Lightweight, high strength	Performance at high stress
Machinery	Shafts	Wear resistance, machinability	Precision and longevity

• Other applications include:
• Tooling components
• Fasteners
• Heavy machinery parts

10B38 steel is chosen for applications requiring a combination of strength, toughness, and wear resistance. Its properties make it particularly suitable for components that experience dynamic loads and require high durability.

Important Considerations, Selection Criteria, and Further Insights

Feature/Property	10B38 Steel	AISI 4140	AISI 4340	Brief Pro/Con or Trade-off Note
Key Mechanical Property	High strength	Higher toughness	Higher fatigue resistance	10B38 is more cost-effective
Key Corrosion Aspect	Moderate resistance	Good resistance	Excellent resistance	10B38 is less suitable for corrosive environments
Weldability	Moderate	Good	Moderate	10B38 requires careful handling
Machinability	Good	Fair	Fair	10B38 is easier to machine than 4140
Formability	Good	Fair	Good	10B38 is versatile in forming processes
Approx. Relative Cost	Moderate	Higher	Higher	10B38 is a cost-effective option
Typical Availability	Common	Common	Less common	10B38 is widely available

When selecting 10B38 steel, considerations such as cost-effectiveness, availability, and specific application requirements are crucial. Its balance of properties makes it a versatile choice for various engineering applications, though its limitations in corrosive environments and welding should be carefully evaluated.

In summary, 10B38 steel is a robust medium-carbon alloy steel that offers a blend of strength, toughness, and machinability, making it suitable for a wide range of applications in demanding environments.