AISI Type P21 Low carbon Mold Steel Flange (UNS T51621)

1,We Manufacturing processes are primarily classified into four types: 1:Forging, 2:Casting, 3:Cutting, 4:Rolling. 2,We can manufacture in accordance with these standards. Standards: GB Series (Chinese Standards), JB Series (Machinery Standards), HG Series (Chemical Industry Standards), ASME B16.5 (American Standards), BS4504 (British Standards), DIN (German Standards), and JIS (Japanese Standards). Internationally, there are two primary systems of pipe flange standards: the European system, represented by the German DIN standards (including those of the former Soviet Union), and the American system, represented by the US ANSI pipe flange standards. Other common standards include: the Chinese Ministry of Machinery Industry standards (JB series), the Ministry of Chemical Industry standards (HG series), the Chinese National Standard *GB/T 9112–9124-2010 Steel Pipe Flanges*, as well as US standards (ASME B16.5), British standards (BS4504), German standards (DIN), Japanese standards (JIS), and marine standards (CBM), among others. The nominal pressure ratings for the PN series are designated by "PN" and comprise the following nine levels: PN2.5, PN6, PN10, PN16, PN25, PN40, PN63, PN100, and PN160. The nominal pressure ratings for the Class series are designated by "Class" and comprise the following six levels: Class150, Class300, Class600, Class900, Class1500, and Class2500. Flange Classification 1. **According to Chemical Industry Standards:** Flanges are classified as follows: Plate Flat Welding Flange (PL), Necked Flat Welding Flange (SO), Necked Butt Welding Flange (WN), Integral Flange (IF), Socket Welding Flange (SW), Threaded Flange (Th), Butt Welding Ring Loose Flange (PJ/SE), Blind Flange (BL), Flat Welding Ring Loose Flange (PJ/PJ), and Lined Blind Flange (BL(s)). 2. **According to Petrochemical (SH) Industry Standards:** Flanges are classified as follows: Threaded Flange (PL), Butt Welding Flange (WN), Flat Welding Flange (SO), Socket Welding Flange (SW), Loose Flange (LJ), and Blind Flange (no specific designation). 3. **According to Machinery (JB) Industry Standards:** Flanges are classified as follows: Integral Flange, Butt Welding Flange, Plate Flat Welding Flange, Butt Welding Ring Plate Loose Flange, Flat Welding Ring Plate Loose Flange, Lap Joint Ring Plate Loose Flange, and Blind Flange. 4. **According to Connection Method/Type:** Flanges are classified as follows: Plate Flat Welding Flange, Necked Flat Welding Flange, Necked Butt Welding Flange, Socket Welding Flange, Threaded Flange, Blind Flange, Necked Butt Welding Ring Loose Flange, Flat Welding Ring Loose Flange, Ring-Type Joint (RTJ) Flange and Blind Flange, Large-Diameter Plate Flange, Large-Diameter High-Neck Flange, Figure-8 Blind Plate, Butt Welding Ring Loose Flange, etc. 5. **According to the Component Being Connected:** Flanges can be classified into Vessel Flanges and Pipe Flanges. 6. **According to Structural Type:** Flanges include Integral Flanges, Threaded Flanges, Flat Welding Flanges, Butt Welding Flanges, Lap Joint (Loose/Swivel) Flanges, and Blind Flanges. A flange—also referred to as a flange plate or rim—is a component used to connect shafts to one another, or, more commonly, to join the ends of pipes. Flanges are also utilized at the inlet and outlet ports of equipment to facilitate connections between two devices—for instance, the flange on a speed reducer. A "flange connection" or "flanged joint" refers to a detachable joint assembly comprising three interconnected elements—a flange, a gasket, and bolts—that together form a sealed structural unit. In the context of piping systems, a "pipe flange" specifically denotes a flange used for plumbing within the installation; when applied to equipment, it refers to the inlet or outlet flange of that specific device. Flanges feature a series of holes through which bolts are inserted to securely fasten the two flanges together, while a gasket placed between the flanges ensures a leak-proof seal. Flanges are broadly categorized into three types: threaded (screw-in) flanges, welded flanges, and clamp-type flanges. Flanges are invariably used in pairs; threaded flanges are suitable for low-pressure piping applications, whereas welded flanges are required for systems operating at pressures exceeding 4 kilograms per square centimeter. A sealing gasket is inserted between the two flange plates, which are then firmly secured using bolts. The thickness of a flange—as well as the specifications of the bolts used to fasten it—vary depending on the specific pressure rating required for the application. When connecting equipment such as water pumps or valves to piping systems, the corresponding connection points on these devices are often manufactured in the shape of a matching flange; this method of attachment is also referred to as a "flange connection." Generally, any connecting component that utilizes bolts to join and seal the perimeters of two flat surfaces—such as the joints in ventilation ducts—is termed a "flange"; such components may collectively be classified as "flange-type parts." However, since such a connection often constitutes merely a *portion* of a larger device—for instance, the interface between a flange and a water pump—it would be inappropriate to classify the entire water pump itself as a "flange-type part." Conversely, smaller components—such as valves—that feature such flanged interfaces may indeed be appropriately categorized as "flange-type parts." -:- For detailed product information, please contact sales. -: AISI Type P21 Low carbon Mold Steel Flange (UNS T51621) Product Information -:- For detailed product information, please contact sales. -: AISI Type P21 Low carbon Mold Steel Flange (UNS T51621) Synonyms -:- For detailed product information, please contact sales. -:

AISI Type P21 Low carbon Mold Steel (UNS T51621) Product Information -:- For detailed product information, please contact sales. -: # **Product Introduction: AISI Type P21 Low-Carbon Mold Steel (UNS T51621)** ## **Overview** **AISI P21 (UNS T51621)** is a specialized **low-carbon, nickel-aluminum age-hardening (precipitation hardening) mold steel**. Unlike conventional quench-and-tempering steels, P21 achieves its final high strength and hardness through a **low-temperature aging process** after solution annealing and machining. This unique characteristic makes it exceptionally valuable for manufacturing **large, complex plastic injection molds and die-casting dies** where minimal distortion after final heat treatment is absolutely critical. P21 is designed to be machined in a soft, ductile condition and then hardened with negligible dimensional change. ## **1. Chemical Composition (Nominal %)** The composition is designed to facilitate age hardening through the formation of nickel-aluminum (Ni₃Al) intermetallic precipitates. | Element | Content (%) | Primary Function | |---------|------------|------------------| | **Carbon (C)** | 0.18 - 0.22 | **Very low.** Minimizes distortion and ensures excellent machinability and weldability in the annealed state. Does not contribute to martensitic hardening. | | **Nickel (Ni)** | 3.90 - 4.25 | **Key element.** Forms the primary hardening precipitates (Ni₃Al) with aluminum upon aging. Also provides exceptional core toughness. | | **Aluminum (Al)** | 1.05 - 1.25 | **Key element.** Combines with nickel to form the fine, hard Ni₃Al precipitates responsible for age hardening. | | **Manganese (Mn)** | 0.20 - 0.40 | Aids in deoxidation and provides slight solid solution strengthening. | | **Silicon (Si)** | 0.20 - 0.40 | Deoxidizer. | | **Chromium (Cr)** | 0.20 - 0.40 | Provides slight hardenability and improves polishability. | | **Molybdenum (Mo)** | 0.20 - 0.40 | Enhances toughness and provides secondary hardening during aging. | | **Iron (Fe)** | Balance | Base metal. | **Key Chemistry Note:** P21's metallurgy is fundamentally different from other P-series steels (like P20). It is a **maraging-type steel**, where hardening is achieved not by carbon-martensite transformation but by the **precipitation of coherent intermetallic compounds (Ni₃Al)** from a supersaturated low-carbon martensitic or bainitic matrix. This process occurs at relatively low temperatures (~480-540°C / 900-1000°F), causing minimal thermal stress and distortion. ## **2. Physical & Mechanical Properties** Properties depend heavily on the thermal processing cycle (Solution Annealed vs. Aged). | Property | Solution Annealed Condition | Aged (Hardened) Condition | |----------|-----------------------------|----------------------------| | **Hardness** | **~28-32 HRC** (Soft, machinable) | **~40-44 HRC** (Achieved through aging, **not quenching**) | | **Tensile Strength** | ~1000 MPa (145 ksi) | ~1350-1550 MPa (196-225 ksi) | | **Yield Strength (0.2%)** | ~850 MPa (123 ksi) | ~1250-1450 MPa (181-210 ksi) | | **Elongation** | ~15% | ~10-12% | | **Impact Toughness** | **Excellent** | **Very Good** (Superior to through-hardened steels of equivalent hardness) | | **Machinability** | **Excellent** (comparable to pre-hardened P20) | N/A (Machining done before aging) | | **Dimensional Change During Aging** | **Negligible** (< 0.0005 in/in). **The primary advantage.** | | | **Wear Resistance** | Fair | Good (Better than P20, but below high-carbon tool steels) | | **Polishability** | Good (can be pre-polished before aging) | Very Good (aging can slightly improve it) | | **Weldability** | **Excellent** (low carbon content) | Good (but welding should be done in the annealed condition, followed by re-aging) | ## **3. International Standards & Cross-References** P21 is a unique grade with specific equivalents focused on its age-hardening characteristic. | Standard | Designation | Notes | |----------|------------|-------| | **UNS** | T51621 | | | **AISI/ASTM (USA)** | P21 (ASTM A681) | | | **Proprietary/Common Names** | **NAK55, NAK80** (Hitachi Metals, Japan) | **These are the most well-known commercial equivalents.** They are modified P21-type steels, often with added sulfur (NAK55) for even better machinability. | | **DIN (Germany)** | No direct equivalent. Conceptually similar to some low-carbon maraging steels. | | | **JIS (Japan)** | No direct JIS standard. Marketed as proprietary brands (e.g., NAK55, NAK80). | | | **GB (China)** | No direct common equivalent. | | | **Common Description** | **Nickel-Aluminum Age-Hardening Mold Steel, Maraging-Type Mold Steel** | | ## **4. Product Applications** P21 (and its commercial variants like NAK55/80) is the premier choice for **high-precision, long-run production molds** where dimensional accuracy and stability are non-negotiable. **Primary Applications:** * **High-Precision Plastic Injection Molds:** * Molds for **optical components** (lenses, light guides), **connectors, gears**, and other parts with tight tolerances. * **Large automotive exterior body panels** (bumpers, fenders) where minimal post-machining after heat treatment is required. * **Molds for electronic components** (housing, frames). * **Die Casting Dies** for zinc and aluminum for applications requiring high dimensional stability. * **Compression Molds** for critical rubber or composite parts. * **Master Models and Electrodes** for EDM, where stability is key. **Typical Application Process:** 1. **Purchase:** Material is supplied in the **solution annealed condition** (~30 HRC). 2. **Rough Machine:** Bulk removal of material. 3. **Stress Relieve** (optional but recommended for complex cores). 4. **Finish Machine:** Complete all machining, drilling, and tapping to final dimensions. 5. **Polish/Texture:** Perform polishing or texturing in the soft state (easier than in the hardened state). 6. **Aging (Final Hardening):** Heat to **480-540°C (900-1000°F)** for 6-12 hours. **Air cool.** This causes precipitation hardening with near-zero distortion. 7. **Final Assembly:** The mold is ready for service. ## **5. Heat Treatment Process** The entire heat treatment cycle is typically controlled by the steel producer. The mold maker only performs the final **aging** step. * **Solution Annealing (Done by Mill):** * Heated to ~815-845°C (1500-1550°F) and quenched to form a soft, low-carbon martensite/bainite structure. * Supplied in this condition. * **Aging (Done by Mold Maker):** * **Temperature:** **495-525°C (925-975°F)** is typical. * **Time:** 6-12 hours, depending on section size. * **Atmosphere:** Air furnace is sufficient. No special atmosphere required. * **Cooling:** Air cool. No quench. * **Result:** Nickel and aluminum diffuse to form fine, coherent Ni₃Al precipitates, strengthening the matrix and increasing hardness to 40-44 HRC. ## **6. Key Advantages & Limitations** **Advantages:** * **Minimal Distortion:** Aging at low temperature causes negligible size change (<0.05%). This is its **defining advantage**. * **Excellent Machinability and Polishability** in the supplied condition. * **High Dimensional Stability** throughout the mold's life. * **Good Toughness at High Hardness** (40+ HRC), better than through-hardened steels. * **Simple Final Heat Treatment:** Only a low-temperature aging furnace is required, no risk of quench cracking. **Limitations:** * **Higher Material Cost** than standard P20. * **Lower Maximum Hardness** (~44 HRC max) compared to through-hardening tool steels (which can reach >50 HRC). * **Limited Wear Resistance:** Although good, it is not suitable for highly abrasive plastics without coatings. * **No Corrosion Resistance:** Will rust; requires plating for corrosive polymers. * **Not for High-Temperature Applications:** The precipitates will over-age and soften if exposed to temperatures near or above the aging temperature for prolonged periods (e.g., in hot runner systems). --- **Disclaimer:** AISI P21 and its commercial equivalents (NAK55/NAK80) are premium materials for specific, high-value applications where stability outweighs cost. They are not general-purpose replacements for P20. The aging process is straightforward but must be controlled to achieve consistent hardness. Always follow the material producer's specific recommended aging cycle for their grade. For the most demanding wear applications, a through-hardened steel like H13 or a corrosion-resistant grade like 420SS may be more appropriate despite their greater distortion during heat treatment. -:- For detailed product information, please contact sales. -: AISI Type P21 Low carbon Mold Steel (UNS T51621) Specification Dimensions Size： Diameter 20-1000 mm Length <6748 mm Size:We can customized as required Standard： Per your request or drawing We can customized as required Properties（Theoretical） Chemical Composition -:- For detailed product information, please contact sales. -: AISI Type P21 Low carbon Mold Steel (UNS T51621) Properties -:- For detailed product information, please contact sales. -:

Applications of AISI Type P21 Low carbon Mold Steel Flange (UNS T51621) -:- For detailed product information, please contact sales. -: Chemical Identifiers AISI Type P21 Low carbon Mold Steel Flange (UNS T51621) -:- For detailed product information, please contact sales. -:

Packing of AISI Type P21 Low carbon Mold Steel Flange (UNS T51621) -:- For detailed product information, please contact sales. -: Standard Packing: -:- For detailed product information, please contact sales. -: Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and Steel Flange drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 3219 gallon liquid totes Special package is available on request. E FORUs’ is carefully handled to minimize damage during storage and transportation and to preserve the quality of our products in their original condition