Screws and barrels melt and homogenize polymers in molding and extrusion. Wear‑resistant steels and specialized screw designs ensure stable melt quality for PE, PP, ABS, PA and filled materials, supporting applications from injection molding to pipe, film, and sheet extrusion.
Screws and barrels in plastifier units are core components in injection molding and extrusion, responsible for melting, homogenizing, and conveying thermoplastic materials. The process begins as polymer pellets enter the feed zone, where the screw transports them forward, generating frictional and heating. In the compression zone, the channel depth decreases, increasing pressure and completing melting. The metering zone ensures consistent melt quality before injection or extrusion. Typical materials processed include PE, PP, ABS, PA, PC, PVC, and filled compounds such as glass‑fiber‑reinforced polymers. Screws are designed as standard three‑zone types or specialized barrier, mixing, and venting screws to improve melt uniformity and are typically manufactured from nitrided steels, bimetallic alloys, or tool steels including advanced powder metallurgical tool steels to ensure wear and corrosion resistance. Barrels are produced from nitrided or bimetallic materials featuring iron‑, nickel‑, or cobalt‑based liners to withstand abrasive fillers like glass fibers and corrosive polymers such as PVC or flame‑retarded compounds. Tooling considerations include heater bands, cooling channels, check valves, and wear sleeves. Applications span injection molding, pipe extrusion, film and sheet production, recycling systems, and compounding lines, where consistent melt preparation is critical for product quality.
BÖHLER K110 is a 12% ledeburitic chromium steel and corresponds to material number 1.2379 (X153CrMoV12, D2). This tool steel combines the advantages of conventional 12% ledeburitic chromium steels with those of advanced tool steels. In the group of 12% ledeburitic chromium steels, BÖHLER K110 offers the best combination of wear resistance, compressive strength and toughness, for which reason it is used in virtually all cold work applications. Its advantageous tempering behavior with a pronounced secondary hardness maximum also enables the use of advanced coatings. This also makes BÖHLER K110 suitable for complex tools requiring a high degree of dimensional stability and shape stability.
Read MoreBÖHLER K294 MICROCLEAN is a cold work tool steel manufactured using powder metallurgy and belongs to the group of 10% vanadium steels. The high content of vanadium carbides makes this steel highly resistant to wear. The toughness is at the same level as conventional 12% chromium steels. BÖHLER K294 MICROCLEAN is used in situations where wear resistance is the decisive factor and toughness is of secondary importance.
Read MoreBÖHLER K360 ISODUR belongs to the group of 8% chromium steels. This tool steel is produced using the electro-slag remelting (ESR) process developed by BÖHLER. This re-melting technology ensures the lowest micro and macro segregation as well as excellent purity and uniformity of the material. The alloy composition with higher molybdenum and vanadium content makes BÖHLER K360 ISODUR even more wear resistant than BÖHLER K340 ISODUR. Compared to tool steels like 1.2379 (D2), this combination of better toughness and wear resistance offers significant advantages for punching and cutting tools.
Read MoreBÖHLER K390 MICROCLEAN is a high-alloyed, high-performance cold work tool steel manufactured using powder metallurgy. This material has the highest alloy content in the group of cold work tool steels with high vanadium content. The high alloy content gives this material outstanding wear resistance. At the same time, the powder metallurgical manufacturing process creates a uniform matrix with finely distributed primary carbides. Among other things, this leads to good material toughness. BÖHLER K390 MICROCLEAN is a problem solver for applications requiring extremely high wear resistance and compressive strength.
Read MoreBÖHLER M310 ISOPLAST is a corrosion-resistant, martensitic chromium steel which, through electroslag remelting and optimization of the chemical composition, has a good homogeneity and a balanced hardness-toughness-corrosion resistance ratio.
Read MoreBÖHLER M390 MICROCLEAN is a corrosion-resistant, martensitic chromium steel produced by powder metallurgy. Due to its alloy design, this steel has very high wear resistance and good corrosion resistance. In addition, BÖHLER M390 MICROCLEAN is approved for food and beverage contact.
Read MoreBÖHLER M398 MICROCLEAN is a corrosion-resistant, martensitic chromium steel produced by powder metallurgy. Due to its alloy design, this steel has good corrosion resistance and higher wear resistance compared to BÖHLER M390 MICROCLEAN.
Read MoreBÖHLER N690 is a corrosion-resistant, martensitic chromium steel with a high carbon content and the addition of cobalt, molybdenum and vanadium. BÖHLER N690 is also approved for food and beverage contact.
Read MoreBÖHLER N695 is a corrosion-resistant, martensitic chromium steel with a high carbon content and added molybdenum.
Read MoreUddeholm Sleipner is a general purpose steel for cold work tooling. It has a mixed-abrasive wear profile and a good resistance to chipping. Furthermore a high hardness (>60 HRC) can be obtained after high temperature tempering. This means that surface treatments such as nitriding or PVD can be made on a high strength substrate. Also, it means that complicated shapes with hardness levels >60 HRC can be wire EDM’d from blocks with relatively thick cross-sections with a much reduced risk of cracking. Uddeholm Sleipner is recommended for medium run tooling applications where a resistance to mixed or abrasive wear and a good resistance to chipping are required. Benefits Very broad property profile Very good steel for all types of surface treatments Extremely versatile conventional tool steel for medium run cold work tooling Suitable upgrade where added chipping or wear resistance is needed over traditional AISI A2 or AISI D2 In East/South East Asian countries served by ASSAB, Uddeholm Sleipner is sold as ASSAB 88.
Read MoreUddeholm Tyrax ESR combines best in class toughness, corrosion and wear resistance. This grade was developed for molding of high performance plastics often filled with glass fiber reinforcements and additives like flame retardants. This matrix- based microstructure is designed to achieve a high-gloss surface by only a few polishing steps, dramatically reducing the tool lead time and enabling production of top quality plastic parts. Uddeholm Tyrax ESR can achieve a high hardness (up to 58 HRC) and is a suitable upgrade from AISI 420 ESR, AISI S7 and AISI 440C. Benefits good dimensional stability at heat treatment and in service even microstructure and small grain size good hardenability Uddeholm Tyrax is also available for Additive Manufacturing, powder for processing Laser Powder Bed Fusion (LPBF) and Laser Metal Deposition (LMD).
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