Wear-Resistant Application Practice of High-Chromium Cast Iron Slurry Pump Impellers in Mine Tailings Transportation

The environment for mine tailings transportation is extremely harsh: the solid particle content in the slurry can reach 40% (e.g., iron concentrate tailings), with particles ≥50μm accounting for over 30%, and it often contains acidic media (pH≤4), leading to severe wear of ordinary pump components. A copper mine application case shows that traditional high-manganese steel impellers have a service life of only 200 hours, while impellers made of high-chromium cast iron (Cr26) through precision casting and composite treatment can exceed 2000 hours of service life, becoming a core solution for wear-resistant pump components in mines.

I. Core Challenges of Mine Slurry Pumps and Material Selection

1. Operating Conditions

·High Abrasiveness: Quartz sand (hardness 7 Mohs) accounts for over 60% of tailings, causing erosive wear on the impeller inlet edge and blade back, with an average monthly wear of 2-3mm.

·High-Load Impact: Coarse particles (≥1mm) generate instantaneous impact stress exceeding 500MPa, easily leading to blade fracture.

·Corrosive Environment: Sulfide ore tailings contain free sulfuric acid (concentration 0.5%-2%), accelerating pitting corrosion on material surfaces.

2. Material Upgrading

High-chromium cast iron Cr26, with excellent abrasion and corrosion resistance, is selected. Its chemical composition includes 2.6%-3.2% C, 24%-28% Cr, and 1.0%-1.5% Mo. In its as-cast structure, M7C3-type carbides (hardness 1300-1800HV) are distributed in a network within the martensitic matrix, providing abrasive wear resistance more than 3 times that of high-manganese steel. By adding 1.2% Ni and 0.8% Cu, the matrix toughness is further improved, increasing impact toughness from 8J/cm² to 15J/cm² and reducing the risk of impact fracture.

II. Optimization of Casting and Heat Treatment Processes

1. Mold Design and Defect Control

·Lost foam casting technology is adopted to avoid sand hole defects in traditional sand casting. The flow channel dimensional accuracy reaches CT8 grade, with blade thickness deviation ≤±0.3mm, ensuring smooth slurry passage.

·Gating and risers are positioned at the thick hub area (25mm thick), combined with exothermic riser sleeves (extending insulation time by 30%), reducing the shrinkage defect rate from 12% to below 2%.

2. Heat Treatment to Strengthen Wear-Resistant Layers

·Quenching + cryogenic treatment: Holding at 1020℃ for 2 hours followed by oil cooling rapidly forms lath martensite. Subsequent -196℃ cryogenic treatment for 4 hours promotes the transformation of retained austenite to twin martensite, increasing hardness from HRC58 to HRC62 and improving carbide distribution uniformity by 40%.

·Surface laser cladding: A tungsten carbide coating (0.5mm thick) is clad on the impeller inlet edge and pressure surface, with microhardness reaching 1500HV, forming a "dual wear-resistant layer" to resist high-speed impact of particles below 5mm.

III. Expansion of Key Application Scenarios

1.Coarse slurry transportation (particles ≤5mm): Impellers adopt a "high-chromium cast iron body + surface ceramic patches" structure, achieving a service life exceeding 3000 hours in iron ore crushing workshops.

2.Acidic tailings ponds (pH=2-3): Impeller substrates undergo aluminum infiltration treatment (50μm thick) combined with a Cr26 high-chromium layer, doubling corrosion resistance and replacing imported nickel-based alloy impellers with a 40% cost reduction.

3.High-concentration tailings backfilling (concentration ≥65%): A large blade thickness design (15mm) is used, paired with dual-phase heat treatment (martensite + bainite), increasing fatigue fracture resistance by 50% to meet the high-frequency start-stop requirements of backfilling pumps.

Through material innovation and process upgrading, high-chromium cast iron slurry pump impellers have achieved a "triple breakthrough" in "erosion resistance, impact resistance, and corrosion resistance" in mine wear-resistant applications. Their technical experience can be replicated in highly abrasive working conditions such as coal washing and non-ferrous metal smelting, providing efficient and reliable equipment support for green mining.