280 Nitriding Steel Double Pelletizer Screw Elements Petrochemical Twin Screw Parts

280 Nitriding Steel Double Pelletizer Screw Elements | Petrochemical Twin Screw Parts

280 Nitriding Steel Double Screw Elements for Petrochemical Pelletizing Lines

The 280 mm size class is where petrochemical pelletizing lines live or die.

At 280 mm nominal screw diameter, a single screw element can weigh tens of kilograms and transmit torque in the thousands of N·m. The elements sit at the very end of a long, expensive production chain — upstream reactors, polymer dryers, devitalization, melt filtration — and any wear or breakage at this point stops the whole line. In petrochemical service that downtime is measured in tonnes of lost output per hour.

That is why the material and the manufacturing sequence matter more here than the price of the part.

Why Nitriding Steel Is the Right Choice for Petrochemical Duty

Petrochemical pelletizing typically processes polyolefins (PE / PP), polystyrene, PET, PBT, nylon and elastomers at elevated temperature and continuous duty. The dominant failure mode is not impact — it is gradual abrasive and adhesive wear on the flight tips and flank surfaces, combined with mild chemical attack from residual catalysts, additives and process residues.

Nitrided steel handles this duty profile well because it delivers a favourable combination:

• Deep, hard case without brittleness. Ion nitriding creates a 0.5–0.8 mm diffusion layer at HV 950–1100, while the core stays tough at HRC 28–32. The element resists surface wear without the risk of catastrophic cracking that a through-hardened tool steel can show under shock loads.
• Corrosion resistance from the nitrided layer provides meaningful protection against mildly corrosive process residues and wash-down environments — better than a plain quench-and-temper steel.
• Dimensional stability. Nitriding is a low-temperature process (typically 500–560 °C) compared with through hardening. Distortion is minimal, which is essential at 280 mm where a few hundredths of a millimetre of runout becomes a sealing problem.
• Cost per unit of production. For non-glass-filled petrochemical grades, nitrided steel delivers a longer cost-effective service interval than premium HIP powder metallurgy alloys, which are better reserved for highly abrasive filled compounds.

Element Types for 280 mm Pelletizers

Built for Stable Die Pressure and Uniform Pellets

Pellet quality at the die face is directly coupled to how evenly the screw delivers melt. Pulse in melt pressure produces uneven strand, irregular pellet geometry, and higher fines content. Our conveying and metering elements are produced with controlled pitch tolerance and post-heat-treatment grinding so that conveying volume stays consistent from element to element — which translates into stable die head pressure, uniform pellet size, and lower fines.

Materials & Heat Treatment

Standard for petrochemical duty (this product):

• 38CrMoAlA (SACM645) nitrided steel — ion nitriding, case depth 0.5–0.8 mm, surface hardness HV 950–1100, core hardness HRC 28–32. The benchmark material for non-abrasive petrochemical pelletizing.

Alternative wear-resistant grades (for filled or highly abrasive service):

• W6Mo5Cr4V2 high-speed tool steel — vacuum quenched and triple tempered, HRC 60–64
• 1.2379 / SKD11 cold work die steel — HRC 58–62, good wear resistance with better toughness than high-speed steel
• HIP powder metallurgy alloys — SAM10 / SAM26 / SAM39, CPM10V / CPM9V, WR5 / WR14 / WR45, homogeneous carbide distribution for extended flight-tip life

Alternative corrosion-resistant grades (for aggressive or halogen-containing service):

• Nickel alloy / Ni-based alloys, 17-4PH, 1.4114, 316L stainless steel for high-corrosion environments
• WR14 / WR45 for combined wear and corrosion resistance

Surface treatments:

• Ion nitriding / gas nitriding (standard for this product)
• Vacuum quenching & tempering
• Sand blasting or mirror polishing, Ra ≤ 0.4 µm
• Hard chrome plating (0.03–0.09 mm) for additional corrosion protection
• Bimetallic hardfacing for extreme local wear

Key Specifications — 280 Size Class

Compatible Co-Rotating Twin Screw Platforms

Our 280 elements are manufactured to OEM-compatible geometry and are fully interchangeable with the original parts on:

Werner & Pfleiderer / Coperion (ZSK series) · Berstorff (ZE series) · Leistritz (ZSE-MICRO) · Theysohn (TSK) · Maris (TM-W) · APV (MP65) · JSW (TEX) · Toshiba (TEM) · SM (TEK-HS) · Feddem (FED-MTS) · Fessia Macross (NRII) · Useon (TDS) · Labtech (LTE) · Shizhou (MTE) · KraussMaffei and other co-rotating twin screw extruder platforms.

Quality Control — Every Element

1. Material verification — all material sourced from domestic or European twin-screw specialty suppliers, verified by elemental analysis and metallurgical inspection
2. In-house heat treatment — nitriding and vacuum quenching performed in our own furnaces, so the process is controlled rather than outsourced
3. Post-heat-treatment finishing — final grinding after nitriding to eliminate deformation and achieve zero-gap assembly
4. Internal spline inspection — checked with spline plug gauges to guarantee interchangeability
5. CNC machining — ensures shape and tolerance consistency element to element
6. Dimensional report — supplied with each shipment
7. Stock availability — common components held in stock; new production typically within 30–60 days

Why Buyers Choose CONLIN

• Competitive cost per unit of production — OEM-equivalent geometry and metallurgy at aftermarket pricing
• Fast turnaround for replacement and refurbishment of worn parts
• Parts available from stock across a wide range of extruder makes and sizes
• Comprehensive pre-dispatch inspection on every part
• Proven quality service with documented material, hardness and dimensional records
• Latest manufacturing techniques and metallurgy for consistent, repeatable performance
• Customized solutions — non-standard geometry, reverse engineering from sample or drawing, and full screw configuration design

Ordering Information

To quote accurately, please provide: extruder brand and model, screw diameter (e.g. 280 mm), Do/Di ratio, element type and pitch or OEM part number, material preference, quantity, and processed polymer plus any filler or additive content. If you only have the worn part, we can reverse-engineer from a sample or a dimensional drawing.

Applications — Petrochemical Industry

• Polyolefin pelletizing — PE / HDPE / LDPE / LLDPE / PP compounding and pelletizing lines
• Engineering resin pelletizing — PET, PBT, PA6 / PA66, POM, PC, PMMA
• Styrenic polymers — PS, ABS, SAN compounding
• Thermoplastic elastomers — TPE, TPV, TPR, TPEE, SEBS
• Hot melt adhesives — EVA, PA, PP, TPU based
• Masterbatch and additive compounding — pigment, antioxidant, UV stabilizer carriers
• Devitalization and reactive extrusion — polymer finishing after reactor train
• Elastomer and rubber compounding — EPDM, EVA, NBR blends
• Post-reactor pelletizing — continuous polymer finishing in petrochemical plants