DMR 249A Steel: Properties and Key Applications
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Table Of Content
Table Of Content
DMR 249A Steel is a medium-carbon alloy steel primarily used in the manufacturing of components that require high strength and toughness. Classified as a low-alloy steel, it typically contains alloying elements such as manganese, chromium, and nickel, which enhance its mechanical properties and resistance to wear. The presence of these elements contributes to the steel's ability to withstand high stress and impact loads, making it suitable for various engineering applications.
Comprehensive Overview
DMR 249A Steel is characterized by its excellent mechanical properties, including high tensile strength, good ductility, and toughness. These properties are essential for applications in the automotive and construction industries, where components must endure significant mechanical loads and environmental conditions. The steel's ability to be heat-treated further enhances its performance, allowing for tailored properties based on specific application requirements.
Advantages:
- High Strength: DMR 249A exhibits superior tensile and yield strength, making it ideal for load-bearing applications.
- Good Toughness: The steel maintains its toughness even at lower temperatures, reducing the risk of brittle failure.
- Versatile Fabrication: It can be easily welded and machined, allowing for diverse manufacturing processes.
Limitations:
- Corrosion Resistance: Compared to stainless steels, DMR 249A has limited corrosion resistance, necessitating protective coatings in corrosive environments.
- Cost: The alloying elements can increase the cost compared to standard carbon steels.
Historically, DMR 249A has been significant in sectors requiring high-performance materials, contributing to advancements in engineering and manufacturing practices.
Alternative Names, Standards, and Equivalents
| Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
|---|---|---|---|
| UNS | K10420 | USA | Closest equivalent to DMR 249A |
| AISI/SAE | 4130 | USA | Minor compositional differences; lower chromium content |
| ASTM | A829 | USA | General specification for alloy steels |
| EN | 30CrMo4 | Europe | Similar properties; used in similar applications |
| DIN | 1.7220 | Germany | Equivalent with slight variations in composition |
| JIS | SCM430 | Japan | Comparable grade with different mechanical properties |
The differences between these equivalent grades can affect performance in specific applications. For instance, while AISI 4130 is similar, it may not provide the same level of toughness as DMR 249A due to its lower chromium content.
Key Properties
Chemical Composition
| Element (Symbol and Name) | Percentage Range (%) |
|---|---|
| C (Carbon) | 0.28 - 0.34 |
| Mn (Manganese) | 0.60 - 0.90 |
| Cr (Chromium) | 0.80 - 1.10 |
| Ni (Nickel) | 0.40 - 0.70 |
| Mo (Molybdenum) | 0.15 - 0.25 |
| Si (Silicon) | 0.15 - 0.40 |
The primary alloying elements in DMR 249A include:
- Manganese (Mn): Enhances hardenability and strength.
- Chromium (Cr): Improves corrosion resistance and toughness.
- Nickel (Ni): Increases toughness and impact strength at low temperatures.
Mechanical Properties
| Property | Condition/Temper | Test Temperature | Typical Value/Range (Metric) | Typical Value/Range (Imperial) | Reference Standard for Test Method |
|---|---|---|---|---|---|
| Tensile Strength | Annealed | Room Temp | 600 - 700 MPa | 87 - 102 ksi | ASTM E8 |
| Yield Strength (0.2% offset) | Annealed | Room Temp | 350 - 450 MPa | 51 - 65 ksi | ASTM E8 |
| Elongation | Annealed | Room Temp | 20 - 25% | 20 - 25% | ASTM E8 |
| Hardness (Brinell) | Annealed | Room Temp | 170 - 210 HB | 170 - 210 HB | ASTM E10 |
| Impact Strength (Charpy) | Annealed | -20°C | 30 - 50 J | 22 - 37 ft-lbf | ASTM E23 |
The combination of high tensile and yield strength, along with good elongation, makes DMR 249A suitable for applications requiring high mechanical loading and structural integrity. Its toughness at low temperatures is particularly beneficial in environments where impact resistance is critical.
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 | 45 W/m·K | 31.2 BTU·in/h·ft²·°F |
| Specific Heat Capacity | Room Temp | 460 J/kg·K | 0.11 BTU/lb·°F |
| Electrical Resistivity | Room Temp | 0.0000012 Ω·m | 0.0000002 Ω·in |
The density of DMR 249A contributes to its weight and strength, while its thermal conductivity and specific heat capacity are important for applications involving heat transfer. The melting point indicates good thermal stability, allowing for high-temperature applications.
Corrosion Resistance
| Corrosive Agent | Concentration (%) | Temperature (°C/°F) | Resistance Rating | Notes |
|---|---|---|---|---|
| Chlorides | 3-5 | 25°C/77°F | Fair | Risk of pitting |
| Sulfuric Acid | 10-20 | 25°C/77°F | Poor | Not recommended |
| Sea Water | - | 25°C/77°F | Fair | Requires protective coatings |
DMR 249A exhibits moderate resistance to corrosion, particularly in chloride environments, where it may be susceptible to pitting. Compared to stainless steels like 304 or 316, which offer excellent corrosion resistance, DMR 249A requires additional protective measures in corrosive environments. Its performance in acidic conditions is notably poor, making it unsuitable for applications involving strong acids.
Heat Resistance
| Property/Limit | Temperature (°C) | Temperature (°F) | Remarks |
|---|---|---|---|
| Max Continuous Service Temp | 400°C | 752°F | Suitable for prolonged exposure |
| Max Intermittent Service Temp | 500°C | 932°F | Short-term exposure only |
| Scaling Temperature | 600°C | 1112°F | Risk of oxidation beyond this temp |
At elevated temperatures, DMR 249A maintains its mechanical properties up to about 400°C, making it suitable for applications involving heat exposure. However, beyond this temperature, oxidation can occur, leading to degradation of material properties.
Fabrication Properties
Weldability
| Welding Process | Recommended Filler Metal (AWS Classification) | Typical Shielding Gas/Flux | Notes |
|---|---|---|---|
| MIG Welding | ER70S-6 | Argon + CO2 | Good fusion and penetration |
| TIG Welding | ER70S-2 | Argon | Requires preheat for thick sections |
DMR 249A is generally considered weldable, but preheating is recommended to minimize the risk of cracking. Post-weld heat treatment can enhance the toughness of the weldment, ensuring structural integrity.
Machinability
| Machining Parameter | DMR 249A | AISI 1212 | Notes/Tips |
|---|---|---|---|
| Relative Machinability Index | 60% | 100% | Moderate machinability; use carbide tools |
| Typical Cutting Speed (Turning) | 50 m/min | 80 m/min | Adjust based on tooling and conditions |
DMR 249A has moderate machinability, requiring careful selection of cutting speeds and tooling to achieve optimal results. It is advisable to use high-speed steel or carbide tools for machining operations.
Formability
DMR 249A exhibits good formability, allowing for cold and hot forming processes. However, care must be taken to avoid excessive work hardening, which can lead to cracking during bending operations. Recommended bend radii should be adhered to for optimal results.
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 + Tempering | 850 - 900 / 1562 - 1652 | 30 minutes | Oil/Water | Increased hardness and strength |
Heat treatment processes significantly affect the microstructure of DMR 249A, enhancing its hardness and strength while maintaining ductility. Quenching followed by tempering is commonly employed to achieve desired mechanical properties.
Typical Applications and End Uses
| Industry/Sector | Specific Application Example | Key Steel Properties Utilized in this Application | Reason for Selection |
|---|---|---|---|
| Automotive | Chassis components | High strength, toughness | Load-bearing capacity |
| Construction | Structural beams | Ductility, weldability | Ease of fabrication |
| Oil & Gas | Pipeline fittings | Corrosion resistance, strength | Durability under stress |
Other applications include:
- Heavy machinery components
- Aerospace structural parts
- Military equipment
DMR 249A is chosen for these applications due to its ability to withstand high mechanical loads and its versatility in fabrication processes.
Important Considerations, Selection Criteria, and Further Insights
| Feature/Property | DMR 249A | AISI 4130 | EN 30CrMo4 | Brief Pro/Con or Trade-off Note |
|---|---|---|---|---|
| Key Mechanical Property | High Strength | Moderate Strength | High Strength | DMR 249A offers superior toughness |
| Key Corrosion Aspect | Fair | Good | Good | DMR 249A requires coatings for corrosion |
| Weldability | Good | Excellent | Good | Preheating recommended for DMR 249A |
| Machinability | Moderate | High | Moderate | AISI 4130 is easier to machine |
| Formability | Good | Fair | Good | DMR 249A has better cold forming ability |
| Approx. Relative Cost | Moderate | Moderate | Moderate | Costs can vary based on market conditions |
| Typical Availability | Common | Common | Common | Widely available in various forms |
When selecting DMR 249A, considerations include its mechanical properties, cost-effectiveness, and availability. Its moderate corrosion resistance necessitates protective measures in specific environments, while its weldability and machinability make it suitable for various manufacturing processes. Understanding the trade-offs between DMR 249A and alternative grades is crucial for optimizing performance in specific applications.