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1.2085: Smelting, Forging and Heat Treatment Guide

Do you know how many production steps your 1.2085 goes through before arriving at your factory? Medium frequency furnace → LF refining → VD degassing → ingot casting → forging → annealing → prehardening → inspection, eight major processes in total. Cutting corners on any step will shorten your mold service life. This article breaks down the full production chain from scrap steel to finished steel from a metallurgist’s perspective.

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1.2085
1.2085

1.2085 Melting – EAF & Alloy Mixing

EAF(Electric Arc Furnace)

1.2085 production starts with selected scrap steel instead of iron ore. Factories pick low-phosphorus scrap with few impurities and traceable sources, then melt it above 1600°C inside a electric arc furnace. The liquid steel base is ready, and alloy blocks are added next to adjust chemical composition.
 

Alloy mixing

Mixing workers calculate the weight of ferrochrome, ferrosilicon and ferromanganese to hit target chemical ranges: C 0.28-0.38%, Cr 15-17%, S 0.05-0.10%, Mn ≤1.0%, Si ≤1.0%. Sulfur is the key element of this steel grade. Timing and dosage of sulfur addition are critical: sulfur burns away if added too early, while uneven sulfur distribution occurs if added too late. Sulfur is usually supplemented in the late LF refining stage to lock uniform sulfur content at the ideal 0.06-0.08% range.
 

LF  + VD

LF and VD processes remove solid and gas impurities separately.
 

LF(Ladle Furnace)

LF furnace refining relies on oxidation reactions. Oxidizers such as FeO are poured into liquid steel to oxidize active elements like Al, Si and Mn. These oxidized materials form insoluble slag layers. The high chromium content of X33CrS16 creates a stable chromium oxide layer during melting, and slag floats to the steel surface for removal. Argon gas is blown to stir liquid steel; tiny bubbles carry small impurities up to the surface. This step greatly cuts solid inclusion levels.
 

VD(Vacuum Degassing)

VD vacuum degassing follows LF refining immediately. The steel ladle is placed in a vacuum tank with pressure pulled below 67 Pa. Dissolved hydrogen, oxygen and nitrogen escape under low pressure, just like carbon dioxide bubbles out of an opened soda bottle. VD mainly removes hydrogen gas, which sharply lowers the risk of white spots (hydrogen-induced cracks) during later cooling and forging.
 

Shaping Route of 1.2085 – Casting, ESR & Forging

Casting

Double-cleaned liquid steel moves to shaping. Molten steel is poured into casting molds and solidifies into steel ingots. Cast ingots go into slow cooling pits to avoid cracking of martensitic stainless steel from fast cooling. Skipping this step will drastically raise ingot crack rates.
 

ESR

Electroslag Remelting (ESR) is an upgrade option for ultra-high purity. The cast ingot acts as a consumable electrode, re-melted by electricity inside a slag bath. Liquid steel droplets pass through 1700-1800°C high-temperature slag, which filters out sulfide and oxide impurities. ESR reduces sulfur content from 0.06% down to ≤0.005%, reaching near aerospace cleanliness. It fits mirror-polish molds and high-sanitation medical molds. Many European buyers order grade X33CrS16, referring to this high-purity ESR variant.
 

Forging

1.2085 forging decides final material microstructure. As-cast ingots have large, brittle dendritic crystals similar to frost on winter windows. High heat and heavy forging pressure break and evenly spread these coarse grains. Forging temperature rules: start forging at 1050-1100°C, finish no lower than 850°C. Forging ratio stays at minimum 4, meaning the ingot cross-section is pressed down to 1/4 its original size. Plates thicker than 200mm need 3 upsetting & 3 drawing cycles to fully forge the core section.
 

1.2085 Heat Treatment – Annealing, Prehardening & Hardness Control

Annealing

Forged steel has high hardness and heavy internal stress, which causes broken cutters or cracking during direct machining. Annealing is the first heat treatment step: heat steel to 860-880°C and cool slowly inside the furnace. Annealing removes forging stress and drops hardness below 250 HB for smooth later machining.
 

Prehardening

Quenched:

  1. Heat annealed steel to 1000-1050°C for full austenitization
  2. Fast oil quenching forms hard martensite, reaching 48-50 HRC

Tempered

This hardness is too hard and brittle for machining, so tempering follows right after. Reheat material to 550-650°C to let carbides separate from martensite and release internal stress, finally stabilizing hardness at the ideal 28-34 HRC.

 
This hardness window is carefully calculated: below 28 HRC brings poor wear resistance and quick cavity collapse; above 34 HRC creates tough machining and high cutter costs. 28-34 HRC balances good wear resistance and easy machining perfectly.

Inspection of 1.2085 – Spectrum Test, Hardness & Ultrasonic Test

  1. Ladle spectrum test: Samples taken after melting. Direct reading spectrometers test C, Cr, S, Mn, Si, P and other elements. Material is re-alloyed or discarded if chemical values fall outside standards.
  2. LF & VD endpoint spectrum tests: Samples taken after each refining step to lock stable chemical composition.
  3. Finished hardness test: Every plate and round bar gets hardness checks via the 5-point method – four corners plus the center. All five readings must stay within 28-34 HRC. Deviation over 2 HRC signals uneven heating or cooling during prehardening.
  4. UT ultrasonic flaw detection: Probes scan the steel surface. Internal defects like cracks, shrinkage holes and impurities send abnormal echo signals. Single defect size cannot exceed a Φ2mm flat-bottom hole to pass inspection.
 
Stock passing all four tests is marked with heat number stamps and matched with material test reports before storage and delivery. 
 
For corrosive molding conditions (PVC, flame-retardant ABS), chromium mold steel like 1.2085 is the standard pick. Its 16% chromium content forms a protective chromium oxide passive film to block acid gas erosion, a feature ordinary carbon steel and P20 cannot match.

FAQ

Q1: What are the impacts if 1.2085 skips ESR remelting?

A: Standard non-ESR 1.2085 works fine for most injection molds. ESR only benefits two scenarios: mirror polishing (non-ESR max finish 800#, ESR reaches 1200# and above) and high-sanitation medical/food molds. Regular PVC/ABS injection molds use standard 1.2085 tool steel with no issues; ESR is an optional upgrade, not a must-have.

A: A 4 minimum forging ratio is industry standard. Lower ratios leave unbroken coarse dendritic crystals at the ingot core, cutting finished steel toughness and isotropy. Molds made from under-forged steel only reach 50-60% of normal service life, with failures usually appearing at the cavity bottom core area where original casting defects remain.

A: Only if customers plan to do full heat treatment themselves. Annealed steel below 250 HB has terrible wear resistance for direct injection mold use, with cavity collapse after just tens of thousands of molding shots. Annealed steel is a semi-finished product. It must go through factory prehardening or customer self-run quenching & tempering to hit the stable 28-34 HRC working hardness.

Conclusion

Contact Keyspark Steel engineers if you have questions about mold steel production or quality inspection. We hold 20 years of full-process mold steel manufacturing experience, controlling every step from melting to heat treatment to guarantee stable quality.

 

 

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

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