Manufacturing and Hardfacing of CDG Roller Press Squeeze Rolls

Literature Overview

The 2008 publication by Zou Wen from Chengdu Building Materials Industry Design and Research Institute Co., Ltd., published in New Century Cement Herald, addresses the manufacturing and hardfacing technology for CDG roller press squeeze rolls used in cement grinding operations. Roller press technology has become increasingly important in modern cement grinding circuits, and the squeeze rolls are subjected to extreme abrasive and compressive loading conditions that demand specialized hardfacing solutions. This paper provides valuable engineering insight into the metallurgical and process challenges of hardfacing large-diameter cylindrical components.

Core Technical Content

CDG roller press squeeze rolls are large-diameter steel cylinders (typically 600–1200 mm diameter, 2000–4000 mm length) that compress raw meal or clinker in a high-pressure grinding circuit. The working surface of these rolls is subjected to severe abrasive wear from hard cement clinker particles, combined with high contact stresses that can reach several hundred MPa. The hardfacing layer must therefore provide both high hardness (typically >55 HRC) and adequate toughness to resist spalling under impact loading.

Roll Manufacturing and Hardfacing Process

Process Stage	Technical Detail	Key Parameter
Roll forging	Open-die or ring rolling	Grain flow follows cylinder axis
Normalizing	850–900°C, air cooling	Refine austenite grain size
Tempering	600–700°C, furnace cooling	Achieve 25–35 HRC base hardness
Surface preparation	Grit blasting to Sa 2.5	Remove scale, create surface roughness
Preheating	200–300°C	Reduce thermal gradient at interface
Hardfacing	Multi-layer SAW or ESW	2–3 layers, 3–5 mm total thickness
Post-weld heat treatment	600–650°C, 2 h per 25 mm thickness	Stress relief, transform martensite

Hardfacing Material Selection

Material Type	Typical Composition	Hardness (HRC)	Application
High-carbon martensitic	C 2.5–3.5%, Cr 4–6%	58–62	General cement grinding
High-chrome martensitic	C 2.0–3.0%, Cr 12–14%	56–60	High abrasion resistance
Ledeburitic	C 3.0–4.5%, Cr 2–4%	60–65	Severe abrasion, moderate impact
Carbide composite	WC or Cr₇C₃ particles	65–70	Extreme abrasion, low impact

Common Defects in Roll Hardfacing

Defect	Cause	Detection Method	Prevention
Cracking at interface	Excessive thermal stress	UT, MT	Adequate preheat; controlled cooling
Spalling	Brittle martensitic structure	Visual, UT	Post-weld tempering to 20–25 HRC core
Poor bond strength	Surface contamination	UT, peel test	Grit blasting to Sa 2.5 minimum
Excessive dilution	High heat input per pass	Metallography	Reduce current; increase travel speed
Uneven hardness	Inconsistent heat input	Hardness survey	Maintain consistent welding parameters

Engineering Practice Insights

The manufacturing of CDG roller press squeeze rolls represents a challenge at the intersection of heavy forging, welding, and surface engineering. The large diameter and wall thickness of these components create significant thermal management challenges during hardfacing. The coefficient of thermal expansion mismatch between the hardfacing layer and the base roll, combined with the large thermal mass of the component, generates substantial residual stresses that can lead to delayed cracking if not properly managed.

A critical engineering consideration is the selection between through-hardened rolls and surface-hardened rolls. Through-hardened rolls (where the entire cross-section is hardened to >50 HRC) offer excellent abrasion resistance but are susceptible to spalling under impact loading. Surface-hardened rolls with a tough core (25–35 HRC) and hard overlay (55–65 HRC) provide a better balance of properties for most cement grinding applications. The transition zone between the hard overlay and the tough base must be carefully controlled to prevent crack initiation at the hardness gradient.

The following engineering recommendations emerge from the analysis:

Preheat the entire roll to 200–300°C uniformly before hardfacing to minimize thermal gradients.
Use multi-layer hardfacing with a transition layer (lower carbon, higher toughness) between the base metal and the final hard layer.
Apply post-weld heat treatment (PWHT) at 600–650°C for a minimum of 2 hours per 25 mm of maximum section thickness.
Perform hardness surveys across the overlay cross-section to verify the hardness gradient meets specifications.
Conduct ultrasonic testing of the overlay interface to detect any delamination before the roll enters service.

Key Reflections

The hardfacing of roller press squeeze rolls is a classic example of surface engineering where the overlay must survive extreme combined loading conditions. The engineering challenge is not merely achieving high hardness but maintaining that hardness under cyclic compressive and abrasive loading without spalling or cracking. The authors' focus on the complete manufacturing chain—from forging through to final hardfacing—reflects the holistic approach required for reliable heavy-duty component production. In my experience, the most common cause of premature roll failure is inadequate post-weld heat treatment, which leaves the martensitic hardfacing layer in a brittle condition prone to spalling. Engineers should always verify that PWHT has been properly applied and documented, as this is the single most effective measure to extend roll service life in cement grinding applications.