C35 Steel: Properties and Key Applications

C35 steel is classified as a medium-carbon alloy steel, primarily composed of iron with a carbon content of approximately 0.35%. This steel grade is known for its balance of strength, toughness, and wear resistance, making it suitable for various engineering applications. The primary alloying elements in C35 steel include manganese, which enhances hardenability and strength, and silicon, which improves deoxidation during steelmaking.

Comprehensive Overview

C35 steel exhibits several significant characteristics that define its utility in engineering applications. It possesses good machinability, weldability, and can be heat treated to enhance its mechanical properties. The steel's medium carbon content allows for a good balance between ductility and strength, making it suitable for components that require both toughness and resistance to wear.

Advantages and Limitations

Advantages:
- Strength and Toughness: C35 steel has a good tensile strength and impact resistance, making it ideal for structural applications.
- Versatility: It can be used in various forms, including bars, plates, and forgings, allowing for a wide range of applications.
- Heat Treatability: The steel can be heat treated to achieve desired mechanical properties, enhancing its performance in demanding environments.

Limitations:
- Corrosion Resistance: C35 steel is not inherently corrosion-resistant and may require protective coatings in corrosive environments.
- Limited High-Temperature Performance: While it performs well at room temperature, its mechanical properties may degrade at elevated temperatures.

C35 steel holds a significant position in the market due to its versatility and cost-effectiveness. It has been widely used in the manufacturing of components such as shafts, gears, and axles, and has historical significance in the development of medium-carbon steels.

Alternative Names, Standards, and Equivalents

Standard Organization	Designation/Grade	Country/Region of Origin	Notes/Remarks
UNS	G10350	USA	Closest equivalent to C35
AISI/SAE	1035	USA	Minor compositional differences
ASTM	A36	USA	Common structural steel, lower carbon
EN	C35E	Europe	Equivalent with slight differences in composition
DIN	1.0501	Germany	Similar properties, used in Europe
JIS	S35C	Japan	Comparable grade with different standards
GB	Q345B	China	Higher yield strength, used in construction

The table above highlights various standards and equivalents for C35 steel. It is important to note that while these grades may be considered equivalent, subtle differences in composition and mechanical properties can affect performance in specific applications. For instance, A36 steel has a lower carbon content, which may result in reduced strength compared to C35.

Key Properties

Chemical Composition

Element (Symbol and Name)	Percentage Range (%)
C (Carbon)	0.32 - 0.38
Mn (Manganese)	0.60 - 0.90
Si (Silicon)	0.10 - 0.40
P (Phosphorus)	≤ 0.035
S (Sulfur)	≤ 0.035

The primary alloying elements in C35 steel play crucial roles in determining its properties. Carbon is the key element that influences hardness and strength; manganese enhances hardenability and toughness, while silicon contributes to deoxidation and improves strength at elevated temperatures.

Mechanical Properties

Property	Condition/Temper	Typical Value/Range (Metric)	Typical Value/Range (Imperial)	Reference Standard for Test Method
Tensile Strength	Annealed	600 - 700 MPa	87 - 102 ksi	ASTM E8
Yield Strength (0.2% offset)	Annealed	350 - 450 MPa	51 - 65 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)	-20°C	30 - 40 J	22 - 30 ft-lbf	ASTM E23

The mechanical properties of C35 steel make it suitable for applications requiring good strength and toughness. Its tensile strength and yield strength indicate its ability to withstand significant loads, while the elongation percentage reflects its ductility, allowing it to deform without fracturing.

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	50 W/m·K	34.5 BTU·in/h·ft²·°F
Specific Heat Capacity	-	0.46 kJ/kg·K	0.11 BTU/lb·°F
Electrical Resistivity	-	0.0006 Ω·m	0.00002 Ω·in

The density of C35 steel indicates its mass per unit volume, which is important for weight-sensitive applications. The melting point is critical for processes involving high temperatures, while thermal conductivity and specific heat capacity are vital for applications involving heat transfer.

Corrosion Resistance

Corrosive Agent	Concentration (%)	Temperature (°C)	Resistance Rating	Notes
Chlorides	3%	25°C	Fair	Risk of pitting
Sulfuric Acid	10%	20°C	Poor	Not recommended
Sodium Hydroxide	5%	25°C	Fair	Susceptible to SCC

C35 steel exhibits moderate corrosion resistance, particularly in environments with chlorides and alkaline substances. It is susceptible to pitting and stress corrosion cracking (SCC) in chloride-rich environments. Compared to stainless steels, C35 steel's corrosion resistance is significantly lower, necessitating protective coatings or treatments in corrosive applications.

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	Short-term exposure only
Scaling Temperature	600°C	1112°F	Risk of oxidation at higher temps

C35 steel maintains its mechanical properties up to moderate temperatures but may experience oxidation and scaling at elevated temperatures. Its performance can degrade if exposed to high temperatures for extended periods, making it less suitable for high-temperature applications compared to alloy steels specifically designed for such environments.

Fabrication Properties

Weldability

Welding Process	Recommended Filler Metal (AWS Classification)	Typical Shielding Gas/Flux	Notes
MIG	ER70S-6	Argon + CO2	Good for thin sections
TIG	ER70S-2	Argon	Clean welds, low distortion
Stick	E7018	-	Requires preheat

C35 steel is generally considered to have good weldability. Preheating may be required to minimize the risk of cracking, especially in thicker sections. Post-weld heat treatment can enhance the properties of the weld area, ensuring a strong bond.

Machinability

Machining Parameter	C35 Steel	AISI 1212	Notes/Tips
Relative Machinability Index	70	100	C35 is less machinable than 1212
Typical Cutting Speed	30 m/min	50 m/min	Use high-speed steel tools

C35 steel has moderate machinability, making it suitable for various machining operations. Optimal cutting speeds and tooling can enhance performance, but care must be taken to avoid work hardening.

Formability

C35 steel can be formed using both cold and hot processes. Cold forming is feasible but may require higher forces due to work hardening. Hot forming is preferred for complex shapes, as it reduces the risk of cracking and allows for easier manipulation of the material.

Heat Treatment

Treatment Process	Temperature Range (°C/°F)	Typical Soaking Time	Cooling Method	Primary Purpose / Expected Result
Annealing	600 - 700 °C / 1112 - 1292 °F	1 - 2 hours	Air	Softening, improving ductility
Quenching	800 - 850 °C / 1472 - 1562 °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 affect the microstructure and properties of C35 steel. Annealing softens the material, making it easier to work with, while quenching increases hardness. Tempering is crucial to relieve stresses and improve toughness after hardening.

Typical Applications and End Uses

Industry/Sector	Specific Application Example	Key Steel Properties Utilized in this Application	Reason for Selection
Automotive	Axles	High strength, toughness	Load-bearing components
Machinery	Gears	Wear resistance, machinability	Precision components
Construction	Structural beams	Strength, weldability	Structural integrity

C35 steel is widely used in the automotive and machinery industries due to its strength and toughness. It is often selected for components that must withstand significant mechanical loads and wear.

Important Considerations, Selection Criteria, and Further Insights

Feature/Property	C35 Steel	AISI 4140	S235JR	Brief Pro/Con or Trade-off Note
Key Mechanical Property	Good strength	Higher strength	Lower strength	C35 is versatile but less strong than 4140
Key Corrosion Aspect	Fair resistance	Better resistance	Poor resistance	C35 requires coatings in corrosive environments
Weldability	Good	Moderate	Excellent	C35 is suitable for welding with precautions
Machinability	Moderate	Good	Excellent	C35 is less machinable than S235JR
Formability	Good	Moderate	Excellent	C35 can be formed but requires care
Approx. Relative Cost	Moderate	Higher	Lower	C35 is cost-effective for many applications
Typical Availability	Common	Less common	Very common	C35 is widely available in various forms

When selecting C35 steel, considerations include its mechanical properties, corrosion resistance, and fabrication characteristics. Its balance of strength and toughness makes it a cost-effective choice for many applications, although its susceptibility to corrosion may necessitate additional protective measures.

In summary, C35 steel is a versatile medium-carbon alloy steel that offers a good balance of properties for various engineering applications. Its historical significance and continued relevance in modern manufacturing underscore its importance in the materials science field.