Mold Steel Selection & Heat Treatment Specification for Casting Molds – Hardness, Wear Resistance and High Temperature Stability

Mold steel grade and heat treatment directly govern casting mold service life and thermal stability, Xinfeng Mold follows standardized material selection rules for gravity, low pressure and differential pressure casting dies. All mold steel used for casting molds must provide original material certificates, and third-party sampling inspection shall be carried out for 100% of core cavity steel before processing. For gravity casting molds working under 380°C maximum cavity temperature, target hardness after heat treatment is maintained within 40–45 HRC to balance toughness and wear resistance. Low pressure casting mold steel for thin-wall automotive parts reaches 43–48 HRC after quenching and tempering, resisting thermal cycling damage for over 80,000 casting shots. Differential pressure casting molds for high-load chassis castings use reinforced mold steel with final hardness of 45–52 HRC, resisting alternating pressure and thermal fatigue stress. The maximum allowable hardness deviation on one mold cavity surface is ±2 HRC; uneven hardness will cause partial cavity wear and dimensional drift during mass production. Quenching heating temperature shall be controlled within ±15°C of the material specification, and holding time must be calculated according to steel block thickness at 2 minutes per 10 mm thickness. Nitriding surface treatment can increase cavity surface hardness by 20% and reduce aluminum alloy adhesion, extending mold service life by 18% for motorcycle wheel rim molds. Using refurbished or recycled mold steel reduces average mold lifespan by 54%, and these materials often contain internal impurities that lead to early mold cracking. Mold steel selection for shock absorber fork and floating caliper molds must prioritize thermal conductivity; low thermal conductivity steel will enlarge casting deformation risk. Steel material reports, heat treatment curve records and hardness test logs form part of the mold delivery document package and should be filed with mold drawings. Mold base material can adopt medium carbon steel for low-volume gravity molds, while high-cycle differential pressure molds require pre-hardened alloy steel mold base. Heat treatment shall be completed before finish CNC machining; post-finish heat treatment will introduce cavity deformation exceeding 0.04 mm in most large molds. Different casting alloys impose different material requirements; copper alloy casting molds require higher hot hardness than aluminum alloy casting molds. Regular hardness recheck every 3000 casting cycles can detect cavity softening early, preventing unexpected mold failure during mass production.

FAQ

Q1: What is the target hardness range for gravity casting mold steel? A1: Gravity casting mold steel heat treatment hardness is controlled at 40–45 HRC. Q2: What is the maximum hardness deviation allowed on one mold cavity? A2: Hardness variation across a single mold cavity shall not exceed ±2 HRC. Q3: How much service life reduction comes from recycled mold steel? A3: Recycled mold steel reduces average mold service life by 54%. Q4: What is the standard holding time calculation for quenching treatment? A4: 2 minutes holding time for every 10 mm of steel block thickness during quenching. Q5: How often should in-production molds undergo hardness recheck? A5: Hardness recheck is recommended every 3000 continuous casting cycles. Q6: What treatment improves anti-sticking performance of mold cavity surface? A6: Nitriding surface treatment can reduce aluminum sticking and boost wear resistance.

Embedded Keywords: Mold Steel, Heat Treatment, Gravity Casting Mold, Low Pressure Casting Mold, Differential Pressure Casting Mold, Motorcycle Wheel Rim, Shock Absorber Fork, Floating Caliper, Mold Hardness, Aluminum Casting Mold