1. Introduction
Many mold shops mix-up 1.2085mold steel and 1.2083mold steel. These two martensitic stainless mold steels look similar on material datasheet, but sulfur content creates huge gaps in polishing quality, cycle life and total mold cost. Wrong material selection can cause 20-35% extra rework cost, or even full mold scrapping in corrosive PVC / PET molding projects.
Annual global procurement for these two stainless mold grades exceeds 42,000 tons. Mold designers and purchasers often struggle: Should I pay extra for high-polish 1.2083? Or save machining hours by choosing free-cutting 1.2085?
This article compares them across 5 dimensions: material property, machinability, polishing performance, mold service life and total-lifecycle cost, to give engineers clear data-driven selection rules.
2. Core Material Property Comparison
1.2083 is classic martensitic stainless mold steel without sulfur addition. 1.2085 is modified 1.2083 with 0.05-0.10% sulfur added to improve cutting performance. Sulfur inclusions bring better machinability, meanwhile damage mirror polishing capacity.
| Item | 1.2085 | 1.2083 |
| Pre-hardened hardness | 30-36 HRC | 28-34 HRC |
| Sulfur content | 0.05-0.10 % | ≤0.008 % |
| Cr content | ~15 % | ~14 % |
| Corrosion resistance | Moderate | Good-Excellent |
| Best polish grade | Fine texture / grain etch (Ra0.4-0.8μm) | Mirror finish (Ra0.05-0.1μm) |
| Magnetisable | Yes | Yes |
| Density | 7.65 g/cm³ | 7.70 g/cm³ |
Practical workshop note: Sulfur particles inside 1.2085 will expose after fine polishing, creating tiny pitting marks. Many factories make the costly mistake ordering 1.2085 for mirror-transparent molds, only to find permanent fine speckles after polishing.
2.1 Machinability
1.2085’s sulfur additives greatly lower cutting resistance. Under same tooling condition, milling/drilling speed can increase 20-28% compared with 1.2083. Tool wear reduces around 15%. For large mold plates with massive pocketing and hole work, 1.2085 can cut total CNC machining time by 18-22%.
But sulfur inclusions create more tiny surface cavities after cutting. If you need subsequent high-level polishing, you must leave larger finishing allowance.
1.2083 requires lower cutting speed and consumes more carbide tools. Rough-to-finish cycle takes longer. However its clean inclusion-free microstructure leaves uniform machined surface for subsequent polishing and photo-etching.
2.2 Polishing & Texture Etching
· 1.2085: Suitable for grain texture, normal matt or semi-gloss surface. Not fit for mirror / transparent optical cavity. Sulfur spots cannot be removed even with long-time manual polishing.
· 1.2083: Reaches high-grade mirror finish. Performs stable for fine grain etching, sharp texture replication for cosmetic and transparent plastic parts.
3. Mold Service Life & Working Condition
3.1 Servic-life reference (real-world injection data)
| Working Scenario | 1.2085 Expected Shots | 1.2083 Expected Shots |
| Medium-corrosive plastic (PVC, flame-retardant ABS, non-transparent parts) | 150,000-280,000 | 220,000-400,000 |
| Transparent / high-gloss corrosive plastic | Not recomended | 180,000-350,000 |
| Non-corrosive household appliance parts | 250,000-400,000 | 300,000-450,000 |
1.2085 delivers acceptable anti-corrosion for medium-demand environments. But sulfur inclusion spots become corrosion starting points when facing long-term acidic plastic gas erosion. So under heavy continuous corrosive production, its cavity pitting risk is obviously higher than 1.2083.
Important: Neither 1.2085 nor 1.2083 can avoid rust without daily cleaning, same as S136 mold steel.
4. Cost Analysis (Total Lifecycle Cost)
Raw material price gap: 1.2085 material cost is 8-14% lower than 1.2083. But you need to calculate full cost including CNC hours, polishing labor, repair risk.
· Project A: Non-mirror, heavy-cutting mold, target shots 200k: 1.2085 saves CNC time, total cost can drop 12-18%. Good economic choice.
· Project B: Mirror / fine-texture corrosive mold: If you pick 1.2085 for mirror requirement, polishing rework + scrap risk will offset all raw material saving, total loss can reach 30%. Must choose 1.2083.
5.Quick Selection Guidelines
✅ Choose 1.2085 when:
1. Mold cavity does NOT require mirror finish; grain-texture or semi-gloss surface is acceptable
2. Heavy CNC milling, many holes & pockets, hope to shorten machining cycle
3. Medium-corrosive non-transparent plastic parts, household & packaging industry
4. Mold inserts, back plates, structural components contacting corrosive environment but no high polish demand
❌ Do NOT use 1.2085 for: Transparent parts, mirror cavity, ultra-fine photo-etch texture, long-term non-stop corrosive plastic mass production.
✅ Choose 1.2083 when:
1. Mirror-gloss, transparent plastic molds
2. Fine grain / sharp texture etching requirement
3. Long-run continuous production for corrosive PVC, PET, flame-retardant materials
4. Cosmetic-critical appearance plastic components
❌ Do NOT use 1.2083 when: Large mold plate with huge volume of rough milling and no high-surface requirement, where machining cost saving is top priority.
6.Conclusion
1.2085 and 1.2083 are both pre-hardened stainless mold steel, but sulfur addition completely changes their application boundary.
· 1.2085 is cost-efficient free-cutting option for non-mirror corrosive molds, bringing obvious CNC time saving.
· 1.2083 delivers superior polishability & corrosion resistance for appearance-critical molds, at higher machining cost.
Blindly pursuing cheaper raw material or blindly specifying high-grade steel both create waste. Balance your surface requirement, machining workload, expected shots and tota-lifecycle cost before final steel grade confirmation.
FAQ
Q1: Can 1.2085 reach mirror polishing effect? A1: No. Sulfur inclusions inside material will form tiny speckles on surface after polishing, these defects cannot be eliminated by repeated grinding. Use 1.2083 for mirror requirement.
Q2: Is 1.2085 rust-proof like 1.2083? A2: 1.2085 owns moderate corrosion resistance, but sulfur inclusion points are easy to become pitting source. Under heavy corrosive production, 1.2083 performs much better. Daily cleaning & anti-rust oil are still necessary for both grades.
Q3: Can I replace 1.2083 with 1.2085 to cut cost for grain-textured mold? A3: Yes, if you do not need mirror finish. But confirm texture depth; ultra-fine shallow grain may show uneven replication caused by sulfur inclusions. Do sample etching test before full production.
Q4: What heat-treatment should I use for 1.2085 /1.2083? A4: Both are commonly used under pre-hardened delivery condition. If higher hardness is needed, quench at 820-840℃, oil quench then double tempering. Do not exceed 52 HRC to avoid toughness drop.