Cutting of High Manganese Steel

Overview

High manganese steel is commonly used for wear-resistant parts in engineering machinery, especially under impact or pressure. Although it is difficult to cut, successful machining is possible with the correct approach.

Material Properties

Manganese Content: 11%–18%
Example Grade (ZMn13):
- Mn: 11%–14%
- C: 1%–1.4%
- Si: 0.3%–1%
- P: <0.03%
- S: <0.05%

After Water Toughening Treatment

Heated to 1000–1100°C, then rapidly cooled
Structure: Single-phase austenite
Properties:
- Tensile Strength (σb): 980 MPa
- Yield Strength (σs): 392 MPa
- Hardness: 210 HBW
- Elongation (δ): 80%
- Impact Toughness (ak): 2.94 MJ/m²

Types of High Manganese Steel

Type	Features
High Carbon	Wear-resistant
Medium Carbon	Non-magnetic
Low Carbon	Stainless
Heat-Resistant	High-temperature applications

Cutting Characteristics

Severe Work Hardening
- Hardness increases from 210 HBW to over 500 HBW.
- Hardened layer: 0.1–0.3 mm deep.
- Tool wear increases significantly.
High Cutting Force
- Cutting ZGMn13: 3,800 MPa/mm² (60% higher than 45 steel).
High Cutting Temperature
- Low thermal conductivity (¼ of 45 steel).
- Cutting zone is 200–250°C hotter.
Difficult Chip Breaking
- High toughness and elongation lead to poor chip control.
Low Dimensional Accuracy
- Large thermal expansion (20×10⁻⁶ /°C) causes deformation.

Recommended Cutting Conditions

1. Tool Materials

Tool Type	Recommended Grades
Cemented Carbide	YS2, YS8, YG813, YG643, YW2, TiAlN, TiAlSi
Ceramics	AG2, AT6, T8, SG4, LT35, LT55
High-Speed Steel	W2Mo9Cr4VCo8, W6Mo5Cr4V2Al, etc.

2. Tool Geometry

Parameter	Recommendation
Rake Angle (γ₀)	HSS: 5°–10°, Carbide: 3° to -3°, Ceramic: -5° to -8°
Clearance Angle (α₀)	HSS: 8°–10°, Carbide: 8°–12°, Ceramic: 5°–8°
Main Rake Angle (κr)	30°–45° (fine: 60°–90°)
Inclination Angle (λs)	Rough: -5° to -10°, Finish: 0°–3°
Tip Radius (rε)	Rough: 1.2–1.6 mm, Finish: 0.4–0.8 mm
Negative Chamfer (γ₀1)	Width: 0.2–0.8 mm, Angle: -5° to -15°

3. Cutting Parameters

Tool Type	Cutting Speed (vc)
Cemented Carbide	20–40 m/min
High-Speed Steel	≈6 m/min
Ceramics	50–72 m/min

Depth of Cut (ap): 0.3–5 mm
Feed Rate (f): >0.15 mm/rev
Speed should be 20%–40% of that for 45 steel.

4. Cutting Fluids

Cooling lubricant must be used to reduce cutting temperature and improve tool life.

Drilling Guidelines

Preferred Tools: Carbide drills or indexable shallow-hole drills
HSS Drills: Use modified tip geometry (e.g., 3-point, 7-edge)
Drilling Strategy:
- Use low speed and high feed
- Avoid tool dwell on the surface
- Always apply enough cutting fluid
- Resharpen tools early to avoid excessive wear