H13 ESR Hot Work Tool Steel Bar, H13 Die Steel Round Bars

Product Description

The ESR process acts as a secondary refining stage. A conventional ingot is used as a consumable electrode and remelted through a chemically active pool of molten slag. This yields several critical advantages:

• Extreme Microcleanliness: Non-metallic inclusions (like sulfides and oxides) are almost entirely stripped away.

• Isotropic Properties: Standard tool steels can be weak across their transverse grain (cross-grain). ESR creates a uniform, directional solidification pattern, ensuring that mechanical properties (like impact toughness) are nearly equal in all directions.

• Superior Polishability: Because the steel lacks hard macro-inclusions, ESR bars can be mirror-polished without pitting or "pinholes," making them ideal for high-finish plastic injection or die-casting cavities.

• Minimized Segregation: Solute elements like molybdenum and vanadium stay evenly distributed rather than pooling into brittle networks, giving the bar predictable heat-treat performance.

Technical Comparison: Standard H13 vs. H13 ESR

Heat Treatment Parameters

To fully unlock the potential of an ESR round bar, the heat treatment must be precise to avoid grain growth or retained austenite:

1. Annealed Delivery State: Supplied spheroidized annealed, typically $\le$ 220235 HBW for ideal machining.

2. Preheating: Two-stage preheat is mandatory to minimize thermal shock: first at 540C650C (1000F1200F), then up to 840C870C (1550F1600F).

3. Austenitizing: Elevate to 1020C1050C (1870F1920F). Hold time depends on section thickness but usually ranges from 15 to 30 minutes once equalized.

4. Quenching: High-pressure gas quenching (in vacuum furnaces) or warm oil. The cooling rate must be fast enough to bypass the pearlite nose but slow enough to avoid cracking.

5. Tempering: Minimum of two tempers (three is preferred for ESR tooling) at 550C610C (1022F1130F) to achieve a target hardness of 4652 HRC and relieve retained stresses.

Common Supply Conditions & Dimensions

H13 ESR round bars are typically supplied in either a black forged finish or a bright pre-machined condition (peeled/turned):

• Diameter Range: 20 mm up to 500+ mm (for large forging modules).

• Ultrasonic Testing: Routinely supplied to standard Sep 1921 Class D/d or E/e tolerances to verify zero internal porosity.