UGIMA® 4598 – Free-Machining 316L Stainless Steel with Cu & S Addition

Overview

UGIMA® 4598 is an improved-machinability variant of 316L (1.4404) stainless steel. It contains added sulfur (>0.1%) and copper (1.3–1.8%) combined with the proprietary UGIMA® process to deliver outstanding chip breakability and tool life in high-speed turning, drilling, and screw machining – while retaining the corrosion resistance of 316L for most non-acidic, non-marine environments.

Microstructure: Austenitic with elongated sulfides in rolling direction, <1% residual ferrite. Slight ferromagnetism possible from ferrite or strain-induced martensite after heavy cold work.

General Properties

Property	Value
Density	8.0 g/cm³

Mechanical Properties (Solution Annealed, d ≤ 130 mm)

Property	Value	Note
Tensile Strength (R_m)	500 – 700 MPa
Elongation (A)	40 % min
Charpy Impact (V-notch)	100 J min

Elastic Modulus vs. Temperature

Temperature	Modulus (GPa)
20 °C	200
100 °C	194
200 °C	186
300 °C	179
400 °C	172
500 °C	165

Thermal Properties

Property	Value	Range
CTE (20–100 °C)	16.5 × 10⁻⁶ /K
CTE (20–200 °C)	17.3 × 10⁻⁶ /K
CTE (20–300 °C)	17.7 × 10⁻⁶ /K
CTE (20–400 °C)	18.1 × 10⁻⁶ /K
CTE (20–500 °C)	18.4 × 10⁻⁶ /K
Specific Heat	500 J/(kg·K)
Thermal Conductivity	15 W/(m·K)

Electrical Properties

Property	Value
Electrical Resistivity	0.7 nΩ·m (7×10⁻¹⁰ Ω·m)

Chemical Composition (wt%)

Element	Content	Note
Carbon (C)	0.03 max
Chromium (Cr)	16.5 – 18.5
Nickel (Ni)	11.0 – 13.0
Molybdenum (Mo)	2.0 – 2.5
Copper (Cu)	1.3 – 1.8	Added for machinability & corrosion balance
Manganese (Mn)	2.0 max
Silicon (Si)	1.0 max
Phosphorus (P)	0.04 max
Sulfur (S)	0.10 – 0.18	Key for chip breaking

Technological Properties

Property

Details

Typical Applications

Electronics, instrumentation & probes, precision engineering, high-volume screw machining

Cold Forming

Suitable for cold drawing & roll forming. Cold work increases strength, reduces ductility. Solution anneal (1020–1120 °C, rapid cool) restores ductility. Lower strain-induced martensite than 1.4404 (<5% at 95% reduction).

Corrosion Resistance

General Corrosion: In 2M H₂SO₄ at 23 °C, corrosion rate is ~3× that of UGIMA® 4404 (standard 316L). Use in mineral acids requires careful evaluation.
Pitting/Crevice: In drinking water (600 ppm Cl⁻), pitting potential equals UGIMA® 4404. In harsh chloride (30,000 ppm, 35 °C), pitting potential drops below UGIMA® 4404 but matches UGIMA® 4307. Salt spray (ISO 9227, 1000 h) shows equivalent surface condition to UGIMA® 4404. Suitable for food industry; not recommended for marine/splash zones.
Crevice Corrosion: In acidic chloride media (pH 1–4), use is limited. Passive film dissolves below pH 3.5 vs. pH 2.5 for standard 316L.

Machinability (UGITECH R&D Data)

Turning (Hot Bars): ~30% productivity gain vs. UGIMA® 4404HM at equal tool wear; slightly better than UGIMA® 4307HM. Chip breaking: +13 conditions (vs 4404HM) and +11 (vs 4307HM) out of 56 tested.
Drilling (Hot Bars): 50–80% higher max chip flow rate vs. UGIMA® 4404HM.
Screw Machining (Cold Drawn Bars, Tornos Sigma 32): Rough turning: +30% productivity vs. 4404HM. Finish turning: hit machine limit (8000 rpm) → ≥10% gain. Drilling (coated carbide): +45–90% chip flow. Cross-cutting: +100% productivity vs. 4404HM.

Heat Treatment

Solution Annealing: 1020 – 1120 °C, hold, rapid air/water quench. Dissolves carbides, removes work hardening, restores ductility & optimal corrosion resistance.

Hot Forming / Forging

950 – 1250 °C (optimum 1050 – 1250 °C). High deformation forces vs. carbon steels. Air or water cool.

Available Product Forms

Product	Shape	Finish	Tolerance	Dimensions
Hot-rolled descaled bar	Round	–	12–13	22 – 130 mm
Cold-finished bar	Round	Drawn / Turned / Ground	6–11	2 – 130 mm
Cold-finished bar	Hexagonal	Drawn	11	3 – 60 mm (across flats)
Wire	Round	Drawn	–	On request

Other formats: contact supplier.

Welding

Weldable by most arc processes (MIG, TIG, MMA, plasma), laser, resistance, friction, electron beam. High hot-cracking susceptibility – minimize arc energy, avoid laser if possible. Filler: UGIWELD™ 316LM or ER316L/ER316LSi. Shielding gas: Ar + 2–5% CO₂/O₂ (MIG), pure Ar (TIG). He ≤20%, H₂ few % acceptable. Avoid N₂ (increases hot cracking). No PWHT required unless non-magnetic property must be guaranteed (then ferrite reduction anneal in HAZ).

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