PTA Bimetallic Screw

Cooperating with a professional Chinese manufacturer of heavy-duty PTA Bimetallic Screw, continuous production lines can avoid expensive unplanned shutdown maintenance. HAPPY PLASTICS adopt precision forged high-strength alloy substrate + automatic PTA plasma surfacing + high-precision CNC thread grinding integrated process. The dual-material structure can withstand strong scraping of crystalline PTA powder, high-temperature shear of molten polyester, and chemical corrosion of trace acidic intermediates such as p-toluic acid.

PTA Working Condition Hazards

Processing raw PTA powder and downstream polyester products faces three severe wear factors: operating temperature higher than 280℃, strong abrasion of hard crystal particles, and acidic volatile corrosion. Ordinary nitrided screws will quickly wear through the hardened surface under such environment, resulting in screw tooth collapse and melt pressure fluctuation.

Our PTA Bimetallic Screw adopts high bonding strength double-layer composite material structure:

• Core substrate: High tensile alloy steel forgings (42CrMo and special die steel), overall quenching and tempering treatment, excellent torsional strength, anti-fatigue crack under high torque continuous operation.

• Wear-resistant surface layer: Automatic plasma welding coats high-density cobalt-based / nickel-based superalloy on screw tooth top and tooth side. Dense pore-free protective layer maintains stable size and hardness under long-term high-load operation.

Superalloy Material Matching Selection Table

We provide multiple bimetallic surfacing alloy grades for different wear and corrosion conditions of polyester production lines:

Optimized Structural Design

Each set of PTA Bimetallic Screw is customized with advanced processing technology to optimize material flow and long-term operation stability:

• Full tooth flank all-round alloy protection: Ordinary manufacturers only surfacing thin alloy on the top of screw teeth. Our PTA plasma technology fully wraps superalloy on tooth crest and both working flanks to protect clearance area from melt backflow abrasion.

• Balanced thermal conductivity: Uniform microstructure of bimetallic coating improves heat conduction inside melt channel, forms stable temperature field, eliminates local hot spots and prevents polyester yellowing & thermal degradation.

• Multi-axis CNC thread precision grinding: After alloy surfacing, the screw profile is finished by multi-axis CNC grinder, inter-tooth dimensional tolerance controlled within ±0.015mm, flow channel mirror finish Ra ≤ 0.2μm.

Full-Set Strict Factory Inspection Standards

• Zero defect commitment: All finished PTA Bimetallic Screw pass complete inspection process before packaging and delivery to guarantee safe operation of high-pressure polycondensation equipment.

• Dye penetrant inspection (DPI): 100% full detection of all surfacing alloy surfaces to check micro-pores, pinholes and thermal cracks, form complete anti-acid corrosion barrier.

• Ultrasonic bonding interface detection: Verify complete metallurgical combination between superalloy layer and steel substrate, ensure no peeling under strong mechanical impact.

• Dynamic balance calibration: Long high-speed screws adopt special dynamic balancing equipment to eliminate rotation vibration, avoid barrel inner wall scratch wear.

FAQ

Q: Why ordinary nitrided screws wear out rapidly when conveying raw PTA crystal powder?

A: Gas nitriding only forms a thin hardened layer of 0.5–0.7mm. Sharp crystalline PTA particles will quickly grind off the thin protective layer in feeding and compression sections. Once the soft base steel is exposed, it will suffer rapid abrasion and organic acid corrosion. Our PTA Bimetallic Screw adopts 1.5–2.5mm thick integrated fused alloy layer, uniform hardness from surface to inner layer, service life several times longer than standard nitrided screws.

Q: Can your factory produce matching replacement screws for large European and American polycondensation reactors?

A: Yes. We build a complete technical database including full-size drawings and drive spline parameters of mainstream global petrochemical and extrusion equipment brands. For old or fully customized non-standard screws, we can provide detailed measurement forms, or produce fully interchangeable direct replacement parts according to your CAD technical drawings.

Q: How does the bimetallic screw avoid polyester degradation in post-condensation extrusion stage?

A: Polyester degradation in later polycondensation is mainly caused by excessive shear heat or material trapped in micro scratches on screw surface. Our PTA Bimetallic Screw adopts smooth optimized transition structure + mirror polishing Ra ≤ 0.2μm, molten polymer flows smoothly without local shear overheating, eliminates material retention and guarantees uniform high-quality melt.