Key Specifications
- Hardness Range
- 450–550 BHN (45–55 HRC)
- Charpy Impact Energy
- 15–30 J at 20 C (unnotched 10x10 mm)
- Alloy System
- NiCrMo low-alloy, NiCrMoV medium-alloy
- Heat Treatment
- Austenitise 850–900 C, oil/air quench, temper 180–400 C
- Through-Hardening
- Full martensitic to 200 mm section thickness
- Wear Life vs. Mn Steel
- 1.5–2.5x in abrasive applications
- Applications
- Blow bars, impact plates, hammers, side liners
- Key Advantage
- Rebar and tramp-metal tolerant (recycling, demolition)
Martensitic Grade Comparison
ATF supplies martensitic blow bars in three standard alloy grades, each optimised for a different point on the hardness-toughness curve. The table below compares these grades alongside high-chrome white iron to illustrate the trade-offs. Grade selection depends on the severity of tramp metal contamination versus the abrasiveness of the primary feed material.
| Material | Hardness | Application | Notes |
|---|---|---|---|
| Standard Martensitic (NiCrMo Low-Alloy) | 450 BHN (45 HRC) | Recycling, demolition, C&D waste with frequent rebar and heavy tramp metal | Charpy 25-30 J. Maximum toughness, best tramp metal survival. Preferred for recycling operations. |
| Medium-Alloy Martensitic (NiCrMo+V) | 500 BHN (50 HRC) | Mixed feed operations with moderate contamination and abrasive rock components | Charpy 18-22 J. Balanced grade for operations processing both rock and demolition waste. |
| High-Alloy Martensitic (NiCrMoV High-C) | 550 BHN (55 HRC) | Abrasive limestone, granite, and aggregate with occasional tramp metal risk | Charpy 15-18 J. Approaches chrome iron abrasion resistance while retaining meaningful toughness. |
| High-Chrome White Iron (Cr26-28%) | 600-640 BHN (60-63 HRC) | Clean, abrasive aggregate with no tramp metal contamination | Charpy 2-5 J. Maximum abrasion resistance but shatters on rebar impact. Requires clean feed. |
Standard Martensitic (NiCrMo Low-Alloy)
Medium-Alloy Martensitic (NiCrMo+V)
High-Alloy Martensitic (NiCrMoV High-C)
High-Chrome White Iron (Cr26-28%)
Charpy values are at room temperature (20°C) on standard 10x10 mm unnotched specimens. Actual performance depends on section thickness, heat treatment parameters, and operating temperature.
Martensitic Steel: Balancing Hardness and Impact Toughness in Blow Bars
Martensitic steels are low-alloy NiCrMo and NiCrMoV grades heat-treated to a fully martensitic microstructure through austenitising at 850–900 degrees C, oil or air quenching, and controlled tempering at 180–400 degrees C to deliver hardness in the 450–550 BHN (45–55 HRC) range while retaining meaningful impact toughness of 15–30 J Charpy at room temperature on unnotched 10x10 mm specimens. In blow bar and impact liner applications, this combination fills the critical performance gap between work-hardening manganese steels (high toughness exceeding 100 J but moderate hardness of 200–550 BHN requiring sustained impact to activate) and high-chrome white irons (extreme hardness of 600–700 BHN but brittle under shock loading with Charpy values below 5 J). NiCrMo alloying provides sufficient hardenability for full through-hardening in blow bar cross-sections up to 200 mm, ensuring consistent hardness from surface to core with no soft zones that would wear preferentially.
The defining advantage of martensitic blow bars is their tolerance of mixed and contaminated feed streams—a capability that neither manganese steel nor high-chrome white iron can match as effectively. In recycling, demolition, and construction-and-demolition (C&D) waste processing, rebar, bolts, wire mesh, and other tramp metal are unavoidable realities of the feed material. High-chrome white iron blow bars, with Charpy values typically under 5 J, shatter catastrophically on rebar impact, sending large fragments through the crusher that damage the rotor, housing, conveyor belts, and downstream equipment at a cost that far exceeds the price of the blow bar itself. Martensitic grades, with Charpy impact energy of 15–30 J at room temperature, deform locally—producing a dent or gouge at the impact point—rather than fracturing catastrophically, allowing the blow bar to continue in service. This makes martensitic steel the default material choice for horizontal shaft impact (HSI) crusher blow bars wherever feed contamination with metallic objects is a realistic operational risk.
Key Properties of Martensitic Steel Blow Bars
Controlled Hardness Range (450-550 BHN)
Through-hardened martensitic microstructure provides consistent hardness from surface to core. Unlike manganese steel that requires impact energy to work-harden, martensitic grades deliver full hardness as-supplied, ensuring wear resistance from the first tonne of feed.
Tramp Metal Tolerance
Charpy impact values of 15-30 J at room temperature allow martensitic blow bars to absorb rebar and tramp metal impacts without catastrophic fracture. Local deformation and surface damage occur, but the blow bar remains in service — a critical advantage over high-chrome white iron in contaminated feeds.
Heat Treatment Optimisation
Austenitizing, oil or air quenching, and controlled tempering allow precise tuning of the hardness-toughness balance. Lower tempering temperatures push hardness toward 550 BHN for abrasive feeds; higher tempering temperatures increase toughness toward 30 J for heavy tramp metal exposure.
Uniform Through-Section Properties
NiCrMo alloying provides sufficient hardenability for full through-hardening in blow bar cross-sections up to 200 mm. No soft core or hardness gradient means consistent performance as the blow bar wears through its usable thickness.
Weldable for Field Repair
Unlike high-chrome white iron, martensitic steel can be pre-heated and welded using low-hydrogen electrodes for field repair of localised damage. This extends service life in remote operations where replacement logistics are difficult.
Cost-Effective Wear Life
Martensitic blow bars typically deliver 1.5-2.5x the wear life of manganese in abrasive applications, at a lower unit cost than high-chrome or ceramic composite alternatives. In recycling and demolition operations, the combination of longer life and tramp metal survival produces the lowest cost per tonne.
Need Help Selecting a Martensitic Grade?
Provide your crusher model, feed material, and tramp metal exposure. ATF engineering will recommend the optimal hardness-toughness balance for your operation.
Applications by Duty
Martensitic blow bars are specified across a range of impact crushing applications. The operating environment — particularly tramp metal frequency, feed abrasiveness, and required product shape — determines the optimal grade and hardness target.
Recycling & Demolition
- C&D waste processing with rebar and reinforcing mesh
- Concrete recycling with embedded steel
- Asphalt reclamation with wire and bolt contamination
- Scrap-heavy mixed demolition waste streams
Primary Impact Crushing
- Quarry primary HSI crushing of run-of-mine limestone
- First-stage reduction of blasted rock with drill steel risk
- Portable plant operations with variable feed quality
- High-throughput primary reduction where blow bar life is critical
Limestone & Aggregate
- Cement-grade limestone processing requiring tight gradation
- Aggregate production where product shape is a specification
- Medium-abrasive sedimentary rock with occasional hard inclusions
- Single-pass crushing to finished product in low-abrasion feeds
Mixed Feed Operations
- Transfer stations processing unknown or variable waste streams
- Mining operations with mixed ore and waste rock
- Multi-source aggregate plants with inconsistent feed quality
- Operators switching between clean rock and demolition contracts
Martensitic FAQs
Find answers to common questions about martensitic materials, selection, maintenance, and ordering. Can't find what you're looking for?
Contact Our TeamWhen should I choose martensitic steel over high-chrome white iron blow bars?
How does martensitic steel handle rebar impacts?
What is the cost-per-tonne difference between martensitic and manganese blow bars?
What tempering temperature is used for martensitic blow bars?
Can martensitic blow bars be used in all impact crusher models?
How does wear life of 550 BHN martensitic compare to high-chrome white iron?
Related Materials Technology
High-Chrome White Iron
Maximum abrasion resistance for clean feed applications. 600-640 BHN hardness with 60-63 HRC. Ideal where tramp metal is excluded and pure wear life is the priority.
Learn MoreManganese Steel Alloys
Work-hardening austenitic manganese steels (Mn14-Mn22) for extreme impact applications. Maximum toughness with surface hardening under repeated impact loading.
Learn MoreCeramic Insert Technology
Ceramic-metal composite wear surfaces combining alumina or zirconia inserts with metallic matrices. 2-4x wear life extension in high-abrasion, clean-feed conditions.
Learn MoreTechnical content reviewed by ATF Engineering Team | Metallurgical specifications verified against ASTM/ISO standards
Get a Quote for Martensitic Blow Bars
Specify your crusher model, feed material, and tramp metal exposure. ATF will recommend the right martensitic grade and tempering specification for your operation.
Contact ATF Engineering