33 KSI Steel: Properties and Key Applications

33 KSI Steel is classified as a medium-carbon alloy steel, specifically recognized for its yield strength of approximately 33,000 psi (or 227 MPa). This steel grade typically contains a balanced mix of carbon, manganese, and other alloying elements that enhance its mechanical properties and performance in various applications. The primary alloying elements in 33 KSI Steel include:

• Carbon (C): Generally in the range of 0.25% to 0.30%, carbon is crucial for increasing hardness and strength through heat treatment.
• Manganese (Mn): Typically around 0.60% to 0.90%, manganese improves hardenability and tensile strength while also aiding in deoxidation during steelmaking.
• Silicon (Si): Usually present in small amounts (0.15% to 0.40%), silicon enhances strength and is beneficial for the steel's resistance to oxidation.

Key Characteristics and Properties

33 KSI Steel is characterized by its excellent strength-to-weight ratio, good weldability, and moderate corrosion resistance. It is often used in applications requiring high strength and toughness, such as structural components, automotive parts, and machinery.

Advantages and Limitations

Pros	Cons
High yield strength and tensile strength	Moderate corrosion resistance
Good machinability	Limited ductility compared to lower grades
Suitable for welding	Requires careful heat treatment management
Cost-effective for high-strength applications	May be susceptible to stress corrosion cracking in certain environments

Historically, 33 KSI Steel has been a popular choice in the construction and automotive industries due to its balance of strength, cost, and availability. Its market position remains strong, particularly in regions where medium-carbon steels are favored for structural applications.

Alternative Names, Standards, and Equivalents

Standard Organization	Designation/Grade	Country/Region of Origin	Notes/Remarks
UNS	G10400	USA	Closest equivalent to AISI 1040
AISI/SAE	1040	USA	Minor compositional differences
ASTM	A36	USA	Common structural steel grade
EN	S235JR	Europe	Comparable but lower yield strength
JIS	SS400	Japan	Similar applications, lower strength

The table above highlights some of the standards and equivalents for 33 KSI Steel. While grades like A36 and S235JR are often considered equivalent, they typically have lower yield strengths, which may affect performance in high-stress applications. Understanding these nuances is crucial for material selection.

Key Properties

Chemical Composition

Element (Symbol and Name)	Percentage Range (%)
Carbon (C)	0.25 - 0.30
Manganese (Mn)	0.60 - 0.90
Silicon (Si)	0.15 - 0.40
Phosphorus (P)	≤ 0.04
Sulfur (S)	≤ 0.05

The role of key alloying elements in 33 KSI Steel is significant. Carbon increases hardness and strength, making it suitable for load-bearing applications. Manganese enhances hardenability and toughness, while silicon contributes to strength and oxidation resistance.

Mechanical Properties

Property	Condition/Temper	Test Temperature	Typical Value/Range (Metric)	Typical Value/Range (Imperial)	Reference Standard for Test Method
Yield Strength (0.2% offset)	Annealed	Room Temp	227 MPa	33 ksi	ASTM E8
Tensile Strength	Annealed	Room Temp	450 - 620 MPa	65 - 90 ksi	ASTM E8
Elongation	Annealed	Room Temp	20%	20%	ASTM E8
Hardness (Brinell)	Annealed	Room Temp	160 - 190 HB	160 - 190 HB	ASTM E10
Impact Strength	Charpy V-notch	-20°C	27 J	20 ft-lbf	ASTM E23

The mechanical properties of 33 KSI Steel make it suitable for applications that require high strength and toughness, such as structural beams and automotive components. Its yield strength allows it to withstand significant loads without permanent deformation, while its tensile strength ensures it can handle dynamic stresses.

Physical Properties

Property	Condition/Temperature	Value (Metric)	Value (Imperial)
Density	Room Temp	7.85 g/cm³	0.284 lb/in³
Melting Point	-	1425 - 1540 °C	2600 - 2800 °F
Thermal Conductivity	Room Temp	50 W/m·K	29 BTU·in/h·ft²·°F
Specific Heat Capacity	Room Temp	0.46 kJ/kg·K	0.11 BTU/lb·°F
Electrical Resistivity	Room Temp	0.0000017 Ω·m	0.0000017 Ω·in

The density and melting point of 33 KSI Steel indicate its robustness, while its thermal conductivity and specific heat capacity suggest it can effectively dissipate heat in applications involving thermal cycling.

Corrosion Resistance

Corrosive Agent	Concentration (%)	Temperature (°C/°F)	Resistance Rating	Notes
Chlorides	3%	25°C / 77°F	Fair	Risk of pitting
Sulfuric Acid	10%	20°C / 68°F	Poor	Not recommended
Sodium Hydroxide	5%	25°C / 77°F	Good	Moderate resistance

33 KSI Steel exhibits moderate resistance to various corrosive environments. It is susceptible to pitting in chloride-rich environments, which can be a concern in marine applications. Compared to grades like A36, which has similar corrosion resistance, 33 KSI Steel's higher strength may make it preferable in applications where mechanical loads are significant.

Heat Resistance

Property/Limit	Temperature (°C)	Temperature (°F)	Remarks
Max Continuous Service Temp	400 °C	752 °F	Suitable for structural applications
Max Intermittent Service Temp	500 °C	932 °F	Short-term exposure only
Scaling Temperature	600 °C	1112 °F	Risk of oxidation at high temps

At elevated temperatures, 33 KSI Steel maintains its strength but may experience oxidation. Careful consideration of service temperatures is essential to prevent degradation of mechanical properties.

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	Excellent for precision work
Stick	E7018	-	Requires preheat

33 KSI Steel is generally weldable using common processes such as MIG and TIG. Preheating may be necessary to avoid cracking, especially in thicker sections. Post-weld heat treatment can enhance the properties of the weld zone.

Machinability

Machining Parameter	[33 KSI Steel]	AISI 1212	Notes/Tips
Relative Machinability Index	70%	100%	Good for turning and milling
Typical Cutting Speed (Turning)	60 m/min	90 m/min	Adjust for tool wear

33 KSI Steel offers good machinability, though it is less machinable than free-machining steels like AISI 1212. Optimal cutting speeds and tooling should be selected to minimize wear.

Formability

33 KSI Steel can be cold and hot formed, though its medium carbon content means it may require higher forces compared to low-carbon steels. The material exhibits work hardening, which can affect bend radii and forming processes.

Heat Treatment

Treatment Process	Temperature Range (°C/°F)	Typical Soaking Time	Cooling Method	Primary Purpose / Expected Result
Annealing	700 - 800 °C / 1292 - 1472 °F	1 - 2 hours	Air or Furnace	Softening, improved ductility
Quenching	800 - 900 °C / 1472 - 1652 °F	30 minutes	Water or Oil	Hardening, increased strength
Tempering	400 - 600 °C / 752 - 1112 °F	1 hour	Air	Reducing brittleness, improving toughness

Heat treatment processes significantly influence the microstructure of 33 KSI Steel. Annealing softens the steel, while quenching increases hardness. Tempering balances hardness and toughness, making it suitable for various applications.

Typical Applications and End Uses

Industry/Sector	Specific Application Example	Key Steel Properties Utilized in this Application	Reason for Selection (Brief)
Construction	Structural beams	High yield strength, good weldability	Essential for load-bearing structures
Automotive	Chassis components	High tensile strength, good machinability	Durability and performance under stress
Machinery	Gear shafts	Toughness, impact resistance	Reliability in dynamic applications

Other applications include:

• • Agricultural equipment
• • Heavy machinery
• • Oil and gas pipelines

33 KSI Steel is chosen for these applications due to its ability to withstand high loads and its versatility in fabrication processes.

Important Considerations, Selection Criteria, and Further Insights

Feature/Property	33 KSI Steel	A36 Steel	1040 Steel	Brief Pro/Con or Trade-off Note
Yield Strength	227 MPa	250 MPa	400 MPa	33 KSI is lower than 1040 but offers better weldability
Corrosion Resistance	Moderate	Moderate	Poor	33 KSI performs better in some environments than 1040
Weldability	Good	Good	Fair	33 KSI is easier to weld than 1040
Machinability	Good	Fair	Good	33 KSI is less machinable than A36
Approx. Relative Cost	Moderate	Low	Moderate	Cost-effective for high-strength applications
Typical Availability	Common	Very Common	Common	33 KSI is widely available but may vary by region

When selecting 33 KSI Steel, considerations include its mechanical properties, cost-effectiveness, and availability. Its balance of strength and weldability makes it a preferred choice for many structural applications. However, potential users should be aware of its limitations in corrosive environments and ensure proper fabrication techniques are employed to maximize performance.