Screws and barrels melt and homogenize polymers in moulding 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 moulding to pipe, film, and sheet extrusion.
Screws and barrels in plastifier units are core components in injection moulding 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 moulding, 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 K340 ECOSTAR belongs to the group of conventionally produced 8% chromium steels. Compared to conventional 12% chromium steels, this conventionally smelted tool steel has better toughness, hardening response and higher adhesive wear resistance. This combination of high adhesive wear resistance and toughness also offers advantages for industrial knives subject to high stress. This grade is also used for stamping 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 K490 MICROCLEAN is a high-performance cold work tool steel with a balanced property profile, manufactured using powder metallurgy. This powder metallurgical tool steel offers an outstanding combination of high wear resistance, compressive strength, toughness and very good machinability. Thanks to the resulting flexibility, BÖHLER K490 MICROCLEAN is used in virtually all cold work applications, and in many cases this material is the first choice for newly developed tools. The commonly used hardening temperatures of BÖHLER K490 MICROCLEAN also enable shared heat treatment with popular cold work tool steels (1.2379, D2), making it very economical in terms of heat treatment.
Read MoreBÖHLER M303 is a corrosion-resistant, martensitic chromium steel with very good toughness, corrosion resistance, good wear resistance and improved machinability and polishability. Compared to 1.2316, BÖHLER M303 has better homogeneity and is approved for food and beverage contact.
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 M340 ISOPLAST corresponds to a corrosion-resistant, martensitic chromium steel with improved wear resistance. This is ideal for the application area of glass fiber reinforced plastics. In addition, the BÖHLER M340 ISOPLAST is approved for food and beverage contact.
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 W302 ISOBLOC is a 5% chromium steel and corresponds to material number 1.2344 (X40CrMoV5-1). Produced via the electroslag remelting process (ESR), this tool steel has very high hot toughness as well as very high hot hardness and a very good resistance against heat-checkings. The combination of these properties makes it a top performer in closed- and open-die forging as well as in high- and low-pressure die casting. In addition, this material has very good polishability and is therefore also often used as a molding material for plastic injection molds.
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