1.2312 Steel (P20+S): Properties and Key Applications

1.2312 Steel (P20+S Type) is a high-performance tool steel primarily classified as a medium-carbon alloy steel. This grade is specifically designed for applications requiring high toughness and good machinability, making it a popular choice in the manufacturing of molds and dies. The primary alloying elements in 1.2312 include chromium, nickel, and sulfur, which significantly enhance its mechanical properties and performance characteristics.

Comprehensive Overview

1.2312 Steel is a modified version of the P20 tool steel, enriched with sulfur to improve its machinability. This steel grade is characterized by its excellent toughness, good wear resistance, and high hardness after heat treatment. The addition of sulfur not only enhances machinability but also contributes to the steel's ability to maintain strength at elevated temperatures.

The main advantages of 1.2312 Steel include:

• High Machinability: The sulfur content allows for easier cutting and shaping, reducing tool wear and improving production efficiency.
• Good Toughness: This steel exhibits excellent toughness, making it suitable for applications where impact resistance is critical.
• Versatile Applications: It is widely used in the production of molds for plastics and die-casting applications.

However, there are some limitations to consider:

• Corrosion Resistance: 1.2312 Steel is not as corrosion-resistant as stainless steels, which may limit its use in certain environments.
• Cost: Compared to lower-grade steels, the cost of 1.2312 may be higher, which could be a consideration for budget-sensitive projects.

Historically, 1.2312 has gained popularity in the tool-making industry due to its balance of toughness and machinability, making it a go-to choice for many engineers and manufacturers.

Alternative Names, Standards, and Equivalents

Standard Organization	Designation/Grade	Country/Region of Origin	Notes/Remarks
UNS	T51620	USA	Closest equivalent to P20 with improved machinability
AISI/SAE	P20+S	USA	Enhanced sulfur content for better machinability
ASTM	A681	USA	Specification for tool steels
DIN	1.2312	Germany	Equivalent to P20+S with minor compositional differences
JIS	SKD61	Japan	Similar properties, but with different alloying elements
ISO	4957	International	General standard for tool steels

The differences between these grades often lie in their specific alloying elements and heat treatment processes, which can affect their performance in particular applications. For instance, while both 1.2312 and SKD61 offer good toughness, SKD61 may provide slightly better wear resistance due to its higher chromium content.

Key Properties

Chemical Composition

Element (Symbol and Name)	Percentage Range (%)
C (Carbon)	0.40 - 0.50
Cr (Chromium)	1.80 - 2.10
Ni (Nickel)	0.80 - 1.20
S (Sulfur)	0.03 - 0.08
Mn (Manganese)	0.30 - 0.50
Si (Silicon)	0.20 - 0.40

The primary role of the key alloying elements in 1.2312 Steel includes:

• Carbon (C): Increases hardness and strength through heat treatment.
• Chromium (Cr): Enhances wear resistance and hardenability.
• Nickel (Ni): Improves toughness and ductility.
• Sulfur (S): Significantly enhances machinability, allowing for better cutting performance.

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	10 - 15%	10 - 15%	ASTM E8
Hardness (HRC)	Quenched & Tempered	28 - 32 HRC	28 - 32 HRC	ASTM E18
Impact Strength	Room Temperature	30 - 50 J	22 - 37 ft-lbf	ASTM E23

The combination of these mechanical properties makes 1.2312 Steel particularly suitable for applications involving high mechanical loading, such as in mold making where both toughness and wear resistance are critical. Its high tensile and yield strength ensure that it can withstand significant forces without deforming, while its good impact strength provides resilience against sudden loads.

Physical Properties

Property	Condition/Temperature	Value (Metric - SI Units)	Value (Imperial Units)
Density	Room Temperature	7.85 g/cm³	0.284 lb/in³
Melting Point/Range	-	1425 - 1470 °C	2600 - 2700 °F
Thermal Conductivity	Room Temperature	25 W/m·K	14.5 BTU·in/(hr·ft²·°F)
Specific Heat Capacity	Room Temperature	460 J/kg·K	0.11 BTU/lb·°F
Electrical Resistivity	Room Temperature	0.00065 Ω·m	0.00038 Ω·in

The practical significance of key physical properties includes:

• Density: Affects the weight and structural integrity of components made from 1.2312 Steel, influencing design choices in mold and die applications.
• Thermal Conductivity: Important for applications involving heat transfer, ensuring that molds can dissipate heat effectively during processing.
• Melting Point: Determines the maximum service temperature for components, critical for applications involving high-temperature processes.

Corrosion Resistance

Corrosive Agent	Concentration (%)	Temperature (°C/°F)	Resistance Rating	Notes
Water	0 - 100	20 - 100	Fair	Risk of rusting
Acids (HCl)	0 - 10	20 - 60	Poor	Susceptible to pitting
Alkalis	0 - 10	20 - 60	Fair	Limited resistance
Chlorides	0 - 5	20 - 60	Poor	Risk of stress corrosion cracking

1.2312 Steel exhibits moderate resistance to corrosion, particularly in atmospheric conditions and fresh water. However, it is susceptible to pitting and stress corrosion cracking in chloride environments, making it less suitable for marine applications or areas with high salinity. Compared to stainless steels like 1.4401 (AISI 316), which offers excellent corrosion resistance, 1.2312 is significantly less resistant, necessitating protective coatings or surface treatments in corrosive environments.

Heat Resistance

Property/Limit	Temperature (°C)	Temperature (°F)	Remarks
Max Continuous Service Temp	300 °C	572 °F	Above this, properties may degrade
Max Intermittent Service Temp	400 °C	752 °F	Short-term exposure only
Scaling Temperature	600 °C	1112 °F	Risk of oxidation at prolonged exposure

At elevated temperatures, 1.2312 Steel maintains its mechanical properties up to a certain limit, beyond which it may experience oxidation and loss of strength. This makes it suitable for applications that involve intermittent high temperatures but requires careful consideration of service conditions to avoid degradation.

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	Requires post-weld heat treatment

1.2312 Steel is generally weldable, but care must be taken to avoid cracking due to its high carbon content. Preheating before welding is recommended to minimize thermal stresses, and post-weld heat treatment can help relieve residual stresses and improve toughness.

Machinability

Machining Parameter	1.2312 Steel	AISI 1212	Notes/Tips
Relative Machinability Index	100	130	1.2312 is good but less than AISI 1212
Typical Cutting Speed (Turning)	80 m/min	100 m/min	Adjust tooling for optimal performance

1.2312 Steel offers excellent machinability due to its sulfur content, which reduces tool wear and improves surface finish. Optimal cutting speeds and tooling should be selected based on the specific machining operation to maximize efficiency.

Formability

1.2312 Steel exhibits good formability, allowing for both cold and hot forming processes. It can be bent and shaped without significant risk of cracking, although care should be taken with bend radii to avoid work hardening effects.

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	Reduce hardness, improve machinability
Quenching	850 - 900 °C / 1562 - 1652 °F	30 minutes	Oil	Increase hardness and strength
Tempering	200 - 300 °C / 392 - 572 °F	1 hour	Air	Reduce brittleness, enhance toughness

The heat treatment processes for 1.2312 Steel lead to significant metallurgical transformations. Quenching increases hardness through the formation of martensite, while tempering reduces brittleness and enhances toughness, making the steel suitable for demanding applications.

Typical Applications and End Uses

Industry/Sector	Specific Application Example	Key Steel Properties Utilized in this Application	Reason for Selection (Brief)
Automotive	Injection molds	High toughness, good wear resistance	Essential for durability
Aerospace	Die-casting molds	Excellent machinability, toughness	Reduces production costs
Consumer Goods	Plastic molds	High hardness, good surface finish	Ensures quality and precision

• Other Applications:
• Molds for rubber products
• Tooling for machining operations
• Components in manufacturing equipment

1.2312 Steel is chosen for these applications due to its excellent balance of toughness, machinability, and wear resistance, making it ideal for producing high-quality molds and dies that require precision and durability.

Important Considerations, Selection Criteria, and Further Insights

Feature/Property	1.2312 Steel	AISI P20	AISI D2	Brief Pro/Con or Trade-off Note
Key Mechanical Property	High toughness	Moderate toughness	High wear resistance	1.2312 offers better machinability
Key Corrosion Aspect	Fair	Fair	Poor	1.2312 is more versatile than D2
Weldability	Good	Moderate	Poor	1.2312 is easier to weld than D2
Machinability	Excellent	Good	Fair	1.2312 is superior for machining
Approx. Relative Cost	Moderate	Moderate	High	Cost-effective for high-performance applications
Typical Availability	Common	Common	Less common	1.2312 is widely available in tool steel markets

When selecting 1.2312 Steel, considerations include its cost-effectiveness, availability, and suitability for specific applications. Its excellent machinability and toughness make it a preferred choice for mold-making industries, while its limitations in corrosion resistance necessitate careful application in environments prone to corrosion.

In summary, 1.2312 Steel (P20+S type) is a versatile tool steel that balances toughness, machinability, and wear resistance, making it suitable for a wide range of applications in the manufacturing sector. Its unique properties and performance characteristics provide significant advantages in mold and die production, while careful consideration of its limitations ensures optimal use in engineering applications.