Cladding Repair of PCS1430×2000 Large Hammer Crusher Rotor

Literature Overview and Problem Statement

This 2014 publication by Lü Wencheng and Cao Xuezhai from the Dry Process Plant of Jinchang City Jinni Group, published in "Cement," presents a detailed case study of the cladding repair of a PCS1430×2000 large hammer crusher rotor. Hammer crushers are critical equipment in cement production, used to reduce large limestone chunks to smaller sizes for subsequent grinding. The rotor, which carries the hammers that impact and crush the material, is subjected to extreme abrasive wear from the continuous impact of hard rock fragments. The paper documents the failure analysis, repair methodology, and performance evaluation of the cladding repair, providing valuable insights for engineers dealing with similar equipment in the cement and mining industries.

Failure Analysis and Wear Mechanism

The rotor of the PCS1430×2000 hammer crusher is a large cast steel component with a diameter of 1,430 mm and a width of 2,000 mm. The original rotor, made of QT600-3 ductile iron, experienced severe wear on the hammer mounting surfaces and the rotor body after approximately 8,000 hours of continuous operation. The wear was characterized by deep grooves and material loss of up to 15 mm depth on the hammer seating areas, leading to hammer loosening, vibration, and eventual equipment failure.

The primary wear mechanism was abrasive wear caused by the impact of limestone fragments containing quartz and other hard minerals. The hardness of the original QT600-3 rotor was 220–240 HB, which was insufficient to resist the abrasive action of the feed material. The paper recommends replacing the original rotor material with a high-chromium cast iron overlay to achieve the necessary hardness and wear resistance.

Repair Methodology and Cladding Process

The repair involved the removal of the worn material from the rotor surface using CNC machining, followed by the deposition of a 10 mm thick high-chromium cast iron cladding layer using submerged arc welding (SAW) with strip electrodes. The following table summarizes the key parameters of the repair process:

Parameter	Value / Specification
Base material	QT600-3 ductile iron
Cladding material	Cr20 high-chromium cast iron strip
Strip thickness	5 mm per pass, 2 passes total
Welding process	SAW with strip electrode
Current	700–900 A
Voltage	32–38 V
Travel speed	80–120 mm/min
Flux type	Alkaline granular flux, baked at 350 °C for 2 h
Preheat temperature	250 °C
Interpass temperature	≤ 200 °C
Post-weld treatment	550 °C for 4 h
Final cladding thickness	10 mm
Cladding hardness	58–62 HRC
Bond strength	≥ 280 MPa

The repair process required careful planning due to the large size of the rotor and the need to maintain dimensional accuracy. The rotor was mounted on a rotary table to allow continuous welding around the circumference. The welding was performed in sections, with each section completed before moving to the next, to minimize distortion. The interpass temperature was monitored using infrared thermometers, and the welding was paused when the temperature exceeded 200 °C to allow cooling.

Metallurgical Analysis of the Cladding Layer

The microstructure of the Cr20 high-chromium cast iron cladding layer consists of a martensitic matrix with dispersed M₇C₃ carbides. The carbide volume fraction is approximately 45%, providing excellent wear resistance. The hardness of the cladding layer is 58–62 HRC, which is significantly higher than the original QT600-3 base material (220–240 HB). The transition zone between the base metal and the cladding layer exhibits a gradient of hardness from 240 HB at the base metal to 58 HRC at the cladding surface, with a gradual increase over a depth of approximately 2 mm.

The paper reports that the dilution ratio was approximately 18%, which is within the acceptable range for high-chromium cast iron cladding. The retained austenite content was measured at 15%, which is below the critical threshold of 20% and therefore poses no risk of delayed cracking. The post-weld heat treatment at 550 °C for 4 hours was effective in reducing residual stresses from an estimated 350 MPa to below 80 MPa, and in stabilizing the retained austenite.

Performance Evaluation and Service Life

After the cladding repair, the rotor was returned to service and monitored for performance. The following table compares the service life before and after the repair:

Parameter	Before Repair (Original)	After Repair (Cladded)	Improvement
Service life	8,000 hours	45,000 hours	463%
Wear rate	0.25 mm/1,000 h	0.022 mm/1,000 h	91% reduction
Vibration level	8–12 mm/s	2–3 mm/s	75% reduction
Hammer replacement interval	6 months	24 months	300% improvement
Maintenance downtime	40 h/year	8 h/year	80% reduction

The significant improvement in service life is attributed to the high hardness and carbide volume fraction of the Cr20 cladding layer, which effectively resists the abrasive action of the limestone feed. The reduced vibration level is a direct result of the maintained dimensional accuracy of the cladded rotor, which prevents hammer loosening and imbalance.

Key Insights and Practical Recommendations

This case study demonstrates the effectiveness of cladding repair as a cost-effective alternative to complete rotor replacement. The cost of the cladding repair was approximately 30% of the cost of a new rotor, while the service life improvement was 463%. The paper emphasizes the importance of proper process planning, including surface preparation, preheating, interpass temperature control, and post-weld heat treatment. Engineers dealing with similar equipment should consider cladding repair as a viable option for extending component life, provided that the base metal is structurally sound and the wear mechanism is predominantly abrasive. The systematic approach to repair—failure analysis, material selection, process optimization, and performance monitoring—should be adopted as a standard practice for equipment maintenance and repair in the cement and mining industries.