The quality standard for 1.2083 round bar in tool steel is primarily defined by the DIN 1.2083 material specification, which is a high-carbon, high-chromium stainless tool steel. This grade is known for its excellent corrosion resistance, high hardness, and good wear resistance, making it ideal for plastic molds, extrusion dies, and cutting tools. The standard ensures that the round bar meets specific chemical composition, hardness, and dimensional tolerances. For example, the chemical composition of 1.2083 typically includes 0.38-0.45% carbon, 12.0-14.0% chromium, 0.4-0.6% manganese, and 0.3-0.5% silicon, with low sulfur and phosphorus (max 0.03% each). The hardness after annealing is usually around 230-255 HB, and after hardening and tempering, it can reach 52-58 HRC. The dimensional tolerances follow the EN 10060 standard for round bars, with diameters from 10 mm to 300 mm and tolerances of ±0.5 mm for smaller sizes. For a reliable supply, you should source from a reputable manufacturer that provides a quality 1.2083 round bar with a mill certificate and traceability.
To get into the specifics, the quality of 1.2083 round bar is not just about meeting a single number; it involves multiple factors that affect performance in real-world applications. The microstructure is critical—after proper heat treatment, the steel should have a fine, uniform distribution of carbides in a martensitic matrix. This ensures high wear resistance and toughness. The purity of the steel is also important, with low inclusion levels (e.g., max 0.02% sulfur) to prevent cracking during polishing or etching. The surface finish of the round bar should be smooth, with a roughness of Ra ≤ 1.6 μm for most applications, especially for mold making. The dimensional accuracy is another key aspect: the round bar must have a straightness tolerance of 0.5 mm per meter, and the diameter should be within ±0.1 mm for precision work. These standards are often verified by the supplier through a material test certificate (MTC) that includes the chemical analysis, mechanical properties, and heat treatment details.
Let’s break down the chemical composition in a table for clarity:
| Element | Percentage (%) |
|---|---|
| Carbon (C) | 0.38 - 0.45 |
| Chromium (Cr) | 12.0 - 14.0 |
| Manganese (Mn) | 0.4 - 0.6 |
| Silicon (Si) | 0.3 - 0.5 |
| Phosphorus (P) | Max 0.03 |
| Sulfur (S) | Max 0.03 |
This composition is what gives the steel its corrosion resistance—the high chromium content forms a passive layer on the surface. The carbon content allows for hardening to high levels, but it also means the steel can be prone to cracking if not handled properly. The hardness after heat treatment is typically specified as 52-58 HRC, but for some applications like plastic molds, a lower hardness of 48-52 HRC might be used to improve toughness. The tensile strength after hardening is around 1,500-2,000 MPa, with a yield strength of 1,200-1,600 MPa. The elongation is usually less than 10%, indicating the steel is brittle but strong.
From a manufacturing perspective, the quality of 1.2083 round bar depends on the production process. The steel is typically made through electric arc furnace (EAF) melting followed by argon oxygen decarburization (AOD) to reduce impurities. It is then cast into ingots and hot-rolled or forged into round bars. The annealing process is crucial: the bar is heated to 800-850°C, held for 2-4 hours, then slowly cooled in the furnace to achieve a soft structure for machining. The hardening process involves heating to 950-1,050°C, quenching in oil or air, and then tempering at 150-200°C for 2 hours to achieve the desired hardness. The tempering temperature affects the final properties: higher tempering temperatures (e.g., 300-400°C) reduce hardness but improve toughness.
Another important standard is the dimensional tolerance for round bars. According to the EN 10060 standard, the tolerances for hot-rolled round bars are as follows:
| Diameter (mm) | Tolerance (mm) |
|---|---|
| 10 - 20 | ±0.3 |
| 20 - 50 | ±0.4 |
| 50 - 100 | ±0.5 |
| 100 - 200 | ±0.6 |
| 200 - 300 | ±0.8 |
For cold-drawn round bars, the tolerances are tighter, typically ±0.1 mm for diameters up to 50 mm. The straightness should be within 0.5 mm per meter for most applications. The surface finish is also specified: for hot-rolled bars, the surface can have a scale layer, but for cold-drawn bars, it should be smooth and free of defects. The inspection of these bars is done through ultrasonic testing to detect internal flaws, and hardness testing to verify the heat treatment.
In terms of application-specific standards, 1.2083 is often used in the plastic molding industry for making molds for corrosive plastics like PVC or ABS. The steel must have a polished surface finish of at least SPI A-2 (Ra 0.05 μm) for high-gloss parts. The etching resistance is also important, as the steel is used for molds that require texture patterns. The wear resistance is measured through pin-on-disc tests, with a wear rate of less than 0.1 mm³ per 1,000 cycles. The toughness is evaluated through Charpy impact tests, with a typical value of 15-20 J at room temperature.
From a supply chain perspective, the quality of 1.2083 round bar can vary between manufacturers. Reputable suppliers like ThyssenKrupp, Böhler, and Uddeholm produce this grade with strict quality control. The mill certificate should include the heat number, chemical analysis, and mechanical properties. The batch traceability is crucial for industries like automotive or medical, where material certification is required. The packaging should protect the bars from rust, especially for stainless grades, with anti-corrosion oil or paper wrapping.
Another angle is the cost vs. quality trade-off. Lower-quality 1.2083 round bars might have higher impurities, leading to inclusions that cause cracking during polishing. The hardness uniformity across the bar diameter is also a concern: for large diameters (e.g., 200 mm), the center might have lower hardness than the surface due to slow cooling. This is addressed by quenching in oil or using vacuum heat treatment to ensure even hardening. The distortion during heat treatment is another issue, with typical shrinkage of 0.1-0.2% for round bars. The stress relieving after rough machining is recommended to reduce warping.
For precision applications like injection molding, the dimensional stability of the steel is critical. The thermal expansion coefficient of 1.2083 is about 11.0 x 10^-6 /°C, which means it expands by 0.011 mm per meter per °C. This must be accounted for in mold design. The thermal conductivity is around 25 W/mK, which is lower than other tool steels, so cooling channels must be designed carefully. The electrical conductivity is low, making it suitable for EDM (electrical discharge machining) without arcing.
In the international standards landscape, 1.2083 is equivalent to AISI 420 in the US, but with a higher carbon content (0.38-0.45% vs. 0.15-0.40% for 420). The JIS equivalent is SUS420J2, and the GB equivalent in China is 4Cr13. The quality standard for these equivalents might differ slightly, but the core properties are similar. The hardness after hardening for AISI 420 is typically 50-55 HRC, while 1.2083 can go higher to 58 HRC due to the higher carbon. The corrosion resistance is similar, but 1.2083 has better wear resistance due to the higher carbon content.
When sourcing a quality 1.2083 round bar, you should look for a supplier that offers third-party inspection and certification. The inspection report should include the chemical composition, hardness, tensile strength, and impact toughness. The ultrasonic test should be done to ASTM A388 standards, with a sensitivity of 1.2 mm diameter flat-bottom hole. The surface inspection should be done visually and with a magnetic particle test for cracks. The dimensional inspection should use a micrometer and caliper for diameter and length, and a straight edge for straightness.
In terms of machinability, 1.2083 is considered fair in the annealed condition, with a machinability rating of 60-70% compared to 1.2311 (P20). The cutting speed for turning is around 150-200 m/min with carbide tools, and the feed rate is 0.1-0.3 mm/rev. The grinding is done with aluminum oxide wheels, with a wheel speed of 30-35 m/s. The polishing is excellent, achieving a mirror finish with diamond paste. The EDM is also possible, but the white layer formed during EDM must be removed by polishing to avoid stress cracking.
Another important factor is the heat treatment response of the bar. The critical temperature for austenitizing is 950-1,050°C, and the quenching medium is oil or air. The tempering curve shows that hardness decreases with increasing tempering temperature: at 150°C, it’s 58 HRC; at 200°C, 56 HRC; at 300°C, 52 HRC; at 400°C, 48 HRC. The secondary hardening effect is minimal, with a slight peak at 500°C. The dimensional change during hardening is about 0.1% expansion in diameter and 0.2% in length. The stress relief after rough machining is done at 600-650°C for 2 hours, followed by slow cooling.
For quality assurance, the supplier should provide a material test certificate (MTC) per EN 10204 type 3.1, which includes the chemical analysis, mechanical properties, and heat treatment details. The batch number should be traceable to the heat number. The packaging should be in bundles with steel straps, and each bar should be marked with the grade, size, and heat number. The storage should be in a dry environment, with a humidity below 60% to prevent rust. The shelf life is indefinite if stored properly, but the steel should be used within 6 months for best performance.
In the market, the price of 1.2083 round bar varies by diameter and quantity. For a 50 mm diameter bar, the price is around $3-5 per kg for standard quality, and $5-8 per kg for high-quality with certification. The lead time is typically 2-4 weeks for standard sizes, and 6-8 weeks for custom sizes. The minimum order quantity is usually 100 kg for standard sizes, and 500 kg for custom sizes. The shipping is done by sea or air, with FOB or CIF terms. The customs clearance requires the MTC and packing list.
To sum up the practical aspects, the quality standard for 1.2083 round bar is a combination of chemical composition, hardness, dimensional tolerances, microstructure, and surface finish. The key standards are DIN 1.2083, EN 10060, and ASTM A388. The verification is done through a mill certificate and third-party inspection. The application in plastic molds requires high polishability and corrosion resistance. The heat treatment must be controlled to achieve the desired hardness without distortion. The supplier must be reliable, with a track record of delivering consistent quality. For a quality 1.2083 round bar, you can check quality 1.2083 round bar from a trusted source that provides full traceability and certification.