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1.2316 Injection Mold Steel Selection: A Corrosion-Resistant Solution for Injection Molds

Injection molding is the most common plastic processing method. But corrosive chlorine-containing plastic like PVC and humid working conditions damage mold steel. Many factories pay high repair costs every year. 1.2316 Injection Mold Steel (DIN standard 1.2316, equal to Chinese grade 3Cr17NiMo) uses an alloy mix of 16% chromium plus molybdenum. It balances corrosion resistance and easy cutting for injection mold work. This article looks at real injection molding production conditions. It explains why this steel is a good choice, which jobs fit it, and how to use it without waste.

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1.2316 Injection Mold Steel
1.2316 Injection Mold Steel
DIN 1.2316
DIN 1.2316
1.2316 steel turned bar
1.2316 steel turned bar
1.2316 steel milled surface
1.2316 steel milled surface
1.2316 milling service
1.2316 milling service
1.2316 material milled surface
1.2316 material milled surface

What is 1.2316 Injection Mold Steel?

It is martensitic stainless plastic mold steel marked DIN 1.2316 from Germany, equivalent to Chinese grade 3Cr17NiMo, with core chemical composition of 0.25-0.35% carbon, 16.00-18.00% chromium, 0.60-1.00% nickel and 0.80-1.30% molybdenum; the 16% chromium gives it stainless steel standard corrosion resistance while molybdenum strengthens its pitting resistance, and it is normally delivered pre-hardened at 28-34 HRC so buyers can machine it directly without extra heat treatment.

Four Core Advantages of 1.2316 Injection Mold Steel

  • Great corrosion resistance. PVC, ABS and other plastics release hydrogen chloride gas at high molding temperature, mixing with moisture to create acid surroundings. Ordinary mold steel like P20 and 1.2311 gets pitting corrosion in 3–6 months under wet or chlorine-rich conditions. Its 16% Cr and Mo composition forms stable Cr₂O₃ passive film to greatly prolong mold service life.
  • Suitable hardness. Injection molds do not need 58–62 HRC ultra-hard cold work steel. Its pre-hardened 28–34 HRC resists wear from mold closing and avoids heavy loss of CNC cutters.
  • Excellent polishing performance. Transparent PC, PMMA parts require ultra-smooth mold surfaces. LF and VD refining reduce internal impurities of 1.2316, supporting perfect mirror finish after polishing.
  • Good thermal conductivity. Cooling accounts for 60%–70% of the whole injection cycle. The material’s heat conduction directly affects production speed and efficiency.

Corrosion Resistance Advantages of 1.2316 Injection Mold Steel

The biggest trouble for injection molds is not wear, but corrosion. Once rust spots or pitting pits appear on mold cavities, plastic products will have surface defects, and the whole mold needs repair or has to be discarded. The core protective layer of 1.2316 Injection Mold Steel is Cr₂O₃ passive film. Its 16% chromium content will automatically form a thin chromium oxide layer only a few nanometers thick in air. This film is tight, complete and able to repair itself. Even slight scratches on the cavity surface expose new metal, and fresh passive film will quickly form again with oxygen. Molybdenum at 0.80-1.30% strengthens pitting resistance. Especially in acid liquid with chloride ions, molybdenum stops local breakage of the passive film. In lab salt spray tests, 1.2316 mold steel is 3 to 5 times more resistant to corrosion than P20 (1.2311), and over 10 times better than regular carbon steel.

Balance Between Hardness and Machinability of 1.2316 Injection Mold Steel

People often face a dilemma when picking mold steel. Hard steel is hard to cut, while soft steel wears out quickly. Pre-hardened 1.2316 Injection Mold Steel at 28–34 HRC solves both problems well. The minimum hardness of 28 HRC offers good wear resistance and anti-deformation performance. The maximum hardness of 34 HRC still works well for high-speed CNC machining. It is slightly harder to machine than annealed steel at 20–25 HRC, yet it saves your time and avoids deformation risks from separate quenching and tempering. This hardness range perfectly fits molds with production runs from 100,000 to 500,000 shots. For mass production over 1,000,000 shots, choose ESR remelted grade. Higher purity allows quenching to 40–45 HRC for longer service life.

Four Types of Injection Molding Applications Suitable for 1.2316 Injection Mold Steel

  1. Molding chlorine-containing plastics such as PVC and CPVC. These materials require strong anti-corrosion performance, and mold steel like P20 will rust rapidly.
  2. Molds running in humid production environments. Workshops in southern rainy seasons or coastal areas stay above 70% humidity all year long. Ordinary mold steel grows rust spots after just one night of shutdown.
  3. Transparent or high-gloss plastic parts including PC, PMMA and PET. These products demand ultra-smooth mold surfaces, and 1.2316 delivers mirror polishing effect.
  4. Plastic parts for medical devices and food contact use. The material needs both corrosion resistance and compliance with hygiene safety standards.
On the contrary, if you process non-corrosive plastics like PP, PE and PS with production volume under 500,000 shots, P20 (1.2311) is sufficient. There is no need to spend extra cost on 1.2316 steel.

FAQ:

Q1: What is the difference between 1.2316 Injection Mold Steel and P20 injection mold steel?

A: The chromium content of 1.2316 Injection Mold Steel is over 10 times that of P20 (16% compared with 1.4-2.0%). The main gap lies in corrosion resistance. P20 has no stainless steel feature and will rust under chlorine-rich or humid working conditions. However, P20 costs less and machines more easily. If your molding plastic does not corrode steel, P20 is a more cost-effective choice.

A: Standard stock hot rolled plates can reach 80mm in thickness, which is the limit for hot rolling. Sizes thicker than 80mm adopt forging process, and plates over 400mm thick are available. Five-time upsetting and drawing is required to guarantee core material quality. For large injection molds such as car bumper molds, forged steel with ESR process is recommended to ensure even internal structure for thick cross-sections.

A:The pre-hardened grade at 28-34 HRC works well for most injection molds. You can machine it right after delivery without further heat treatment. If clients require special hardness above 40 HRC for heavy wear conditions, purchase annealed material at 20-25 HRC, and carry out quenching and tempering after machining by yourself.

Conclusion

If you are choosing steel for injection molds, especially when facing corrosion issues from chlorine-containing plastics or humid environments and cannot decide between 1.2316 and P20, you can talk with engineers from Keyspark Steel. We have 20 years of experience supplying mold steel. We can match suitable materials for you, from standard stock sizes to custom forged blocks, so you will not waste money on improper steel.

 

📧 Email: Sales@keysparksteel.com
📱 Mobile/WhatsApp: +86 150 2405 6480

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