Impact plates — the suspended wear plates inside an impact crusher that receive feed rock thrown from the rotor blow bars at 25–40 m/s — control both the crushing action and the product size. The primary impact plate takes the heaviest first-impact load; the secondary plate handles reduced impact but higher sliding-abrasion wear. Matching the wear material to each plate position is critical: high-manganese steel work-hardens under the primary plate’s heavy impact but never reaches effective hardness on the secondary plate’s low-impact sliding duty, where high-chromium cast iron (HRC 58–62) delivers 1.5–2× the wear life. This guide covers the five impact-plate material grades — Mn13Cr2, Mn18Cr2, Cr26/Cr28 high-chromium iron, medium-carbon low-alloy steel and composite casting — their hardness, toughness and selection criteria, as part of our broader mining, crushing and aggregate processing wear-parts program. For the complete range of blow bars, impact plates and liners, see our impact crusher parts catalog.
What Are Impact Plates and Why Material Matters
Impact plates (also called impact bars or reaction plates) are the suspended liners inside the crushing chamber of an impact crusher (PF series). Material is accelerated by the rotor blow bars and flung against the impact-plate surface at 25–40 m/s; the rock fractures on impact, rebounds off the plate, and is struck again by the blow bars — forming an “impact–rebound–re-impact” cycle that repeats until the material exits the chamber at the target size. The impact plate also controls product gradation: by adjusting the gap between the plate and the rotor, the operator changes the crushing ratio and discharge size. Most impact crushers have a primary (first) plate and a secondary (second) plate; some add a tertiary grinding plate. The primary plate absorbs maximum impact and is typically built thicker with high-manganese steel; the secondary plate sees diminished impact but increased sliding wear, making high-chromium iron the better choice. No single material is optimal for both positions — the correct approach is to match material to each plate’s specific impact-and-wear regime.
Impact Plate Material Grades at a Glance
| Grade | Cast / initial hardness | Final hardness | Impact toughness | Typical duty |
|---|---|---|---|---|
| Mn13Cr2 | HB 170–230 | HB 300–450+ (work-hardened) | ≥ 80 J/cm² | 1st plate, limestone / coal |
| Mn18Cr2 | HB 180–260 | HB 450–550+ (work-hardened) | ≥ 120 J/cm² | 1st plate, hard rock |
| Cr26 / Cr28 high-chromium iron | HRC 58–62 | HRC 58–62 (final) | 5–8 J/cm² | 2nd plate, low-impact high-wear |
| Medium-carbon low-alloy steel | HRC 45–55 | HRC 45–55 (tempered) | ≥ 15 J/cm² | Medium impact + high wear |
| Composite casting | HRC 58–62 (face) | HRC 58–62 (face) | Steel-back toughness | Extreme impact + wear |
| Custom alloy | Per specification | Per specification | Per specification | Non-standard duty (on request) |
Impact-plate thickness typically 50–120 mm depending on crusher size and plate position. Single-piece weight 30–300 kg. Mounting: suspended from the crusher main shaft, with adjustable gap to the rotor. Compatible with PF-1007, PF-1010, PF-1210, PF-1214, PF-1315, PF-1320 and PF-1520 impact crushers. Standard: GOST 977-88 (steel castings).
Mn13Cr2: Standard High-Manganese Steel
Mn13Cr2 is the standard high-manganese steel grade for impact plates processing limestone, coal, gypsum and other medium-hardness materials. In the as-cast condition it measures HB 170–230; under impact on the primary plate, the surface work-hardens to HB 300–450+. This is the economical choice for medium-hard feed where impact intensity is sufficient to activate work-hardening: the material self-hardens with use and delivers stable wear life at low cost. Its limitation is the work-hardening ceiling — HB 300–450+ is lower than Mn18Cr2’s HB 450–550+ — and its dependence on impact: on the secondary plate, where impact is diminished, the surface never hardens effectively and wear accelerates. For that position, high-chromium iron is the better choice.
Mn18Cr2: Ultra-High-Manganese for Hard Rock
Mn18Cr2 is the grade for the primary impact plate when the feed is large, hard, blocky rock — granite, iron ore, quartzite. Its cast hardness (HB 180–260) and work-hardening ceiling (HB 450–550+) both exceed Mn13Cr2, but its decisive advantage is impact toughness: ≥ 120 J/cm² versus Mn13Cr2’s ≥ 80 J/cm², a 50% improvement in resistance to impact fracture. The primary plate receives the full first-impact load from the rotor — the heaviest single impact in the crusher — so fracture resistance is the dominant selection criterion. Mn18Cr2 is the correct grade when the primary plate must survive high-impact hard-rock duty without cracking. For medium-hard feed where the impact is lower, Mn13Cr2 is the more economical choice.
Cr26/Cr28 High-Chromium Cast Iron: Secondary-Plate Wear Grade
Cr26/Cr28 high-chromium white cast iron (HRC 58–62, quenched-and-tempered) is the grade for the secondary impact plate and fine-crushing positions where impact is diminished but sliding-abrasion wear is at its highest. As a factory final hardness — no work-hardening required — it delivers 1.5–2× the wear life of Mn13 high-manganese steel in low-impact conditions. This is the rational grade for the secondary plate: the primary plate’s heavy impact is absorbed upstream, so the secondary plate’s dominant failure mode is abrasive wear, not impact fracture. The trade-off is toughness (ak 5–8 J/cm²) — Cr26/Cr28 must not be used in the primary-plate position where high impact would risk fracture. The correct approach is to pair grades: high-manganese on the primary plate, high-chromium iron on the secondary.
Medium-Carbon Low-Alloy Steel: The Middle-Ground Grade
Medium-carbon low-alloy steel (30CrMnSi and similar, tempered to HRC 45–55) occupies the middle ground between high-manganese steel and high-chromium iron. Its initial hardness (HRC 45–55) is higher than high-manganese steel’s as-cast condition (HB 170–230), so it delivers effective wear resistance from the first hour without depending on impact work-hardening. Its impact toughness (ak ≥ 15 J/cm²) is higher than high-chromium iron’s (5–8 J/cm²), so it tolerates moderate impact that would fracture a brittle iron plate. The grade is optimal for medium-impact, high-wear duty — positions where high-manganese steel would not work-harden enough and high-chromium iron would be too brittle. Its tempered microstructure (tempered martensite plus sorbite) provides the hardness-toughness combination.
Composite Casting: Wear Face Plus Tough Back
Composite-casting impact plates combine a high-chromium iron working face (HRC 58–62) with a carbon-steel back, metallurgically bonded through a dual-metal pouring process: the steel back is cast first, then the high-chromium iron face is cast onto it, and the interface bond quality is the critical quality parameter. The working face delivers the same wear life as a solid high-chromium iron plate; the steel back provides near-carbon-steel toughness that absorbs impact a through-hard iron plate could not survive. This is the grade for extreme combined impact-and-wear conditions — large, hard, abrasive rock with high impact energy — where neither a solid iron plate (fracture risk) nor a solid manganese steel plate (wear too fast) is adequate. Composite plates must be custom-manufactured to the specific duty.
Selection Summary by Plate Position and Feed
- Primary plate (limestone / coal, medium impact): Mn13Cr2 — work-hardens to HB 300–450+, economical for medium-hard feed.
- Primary plate (granite / iron ore, high impact): Mn18Cr2 — impact toughness ≥ 120 J/cm², work-hardens to HB 450–550+.
- Secondary plate (low impact, high wear): Cr26/Cr28 — HRC 58–62, 1.5–2× Mn13 wear life in low-impact duty.
- Medium impact + high wear (either position): Medium-carbon low-alloy steel — HRC 45–55, no work-hardening dependence, tougher than iron.
- Extreme impact + extreme wear (combined): Composite casting — hi-Cr face HRC 58–62, steel back for toughness.
- Non-standard duty: Custom alloy — chemistry tailored to specific operating conditions on request.
Heat Treatment and Quality Control
Impact plates are produced by sand casting (for manganese-steel plates) or lost-foam casting (for high-chromium iron plates), with a pouring temperature of 1380–1420°C. Composite-casting plates use a dual-metal pouring process: the carbon-steel back is cast first, then the high-chromium iron working face is cast onto it, and the interface bond quality is the critical parameter. The pre-pour double rule — furnace-front temperature measurement plus sample-block chemistry check — ensures chemical composition meets specification before pouring.
Heat treatment is grade-specific. High-manganese steel plates: water toughening (solution treatment) at 1050–1100°C hold plus water quench, obtaining single austenite structure to ensure the work-hardening characteristic. High-chromium iron plates: quench-and-temper dual process, quenching transforming carbide morphology to the M₇C₃ type, tempering relieving internal stress. Composite plates: staged heat treatment — the high-chromium face is quenched and tempered to HRC 58–62 while the steel back retains toughness. Medium-carbon low-alloy steel plates: quench and temper to a tempered-martensite-plus-sorbite mixed structure, ensuring HRC 45–55 with high toughness.
Quality control includes 100% hardness inspection (3 points per piece, averaged); metallographic analysis confirming the target structure (austenite for Mn steel, M₇C₃ carbide for hi-Cr iron, tempered martensite for alloy steel); composite-plate interface bond quality checked on every piece; dimensional tolerance verification; and suspension-hole precision validation — all fully traceable.
Why Huasuma for Impact Plates
Huasuma’s metal casting capability offers five impact-plate materials — Mn13Cr2, Mn18Cr2, Cr26/Cr28, medium-carbon low-alloy steel and composite casting — each with independent heat-treatment parameters. The primary plate uses Mn18Cr2 for toughness; the secondary plate uses Cr26 for wear resistance; extreme combined duty uses composite casting. Not one alloy for all positions. High-manganese steel water-toughening ensures austenite purity; high-chromium iron quenching transforms carbide from network M₃C to isolated M₇C₃; composite-casting interface bond strength is verified on every piece — the target is a verifiable test result, not an approximation. The primary and secondary plates can be supplied as a paired-material package (primary Mn18 for toughness, secondary Cr26 for wear) — a complete crushing-chamber wear-part solution, not single-piece sales. Pre-pour double rule, 100% hardness inspection, metallographic analysis, dimensional tolerance and suspension-hole precision verification all completed before shipment. Compatible with PF-1007 through PF-1520 impact crushers; plates can be custom-manufactured to shape, thickness and suspension-hole pattern. ISO 9001 throughout; GOST compliance supported; 30 years of casting export experience with multiple batches delivered to Russian, Indian and Australian customers; 24-hour quote response; samples available for in-service validation before bulk orders.
FAQ
What material should the primary impact plate use?
For medium-hard feed (limestone, coal), Mn13Cr2 is the economical choice — work-hardening to HB 300–450+ under the primary plate’s impact. For hard, large, blocky feed (granite, iron ore), Mn18Cr2 is required — its impact toughness of ≥ 120 J/cm² resists fracture and work-hardening reaches HB 450–550+.
Why use different materials for the primary and secondary plates?
The primary plate receives the full first-impact load — high impact, so a tough, work-hardening manganese steel is required. The secondary plate sees diminished impact but increased sliding-abrasion wear, where manganese steel would not work-harden effectively. High-chromium iron (Cr26/Cr28, HRC 58–62) delivers 1.5–2× the wear life of Mn13 in low-impact conditions, making it the correct grade for the secondary plate. Pairing grades by position is the optimal approach.
When should I use composite-casting impact plates?
Composite casting (hi-Cr iron face HRC 58–62 + carbon-steel back) is for extreme combined impact-and-wear conditions — large, hard, abrasive rock with high impact energy — where a solid high-chromium iron plate would fracture and a solid manganese steel plate would wear too fast. The working face provides wear life; the steel back absorbs impact. Composite plates must be custom-manufactured to the specific duty.
What impact crushers are Huasuma plates compatible with?
Huasuma impact plates are compatible with PF-1007, PF-1010, PF-1210, PF-1214, PF-1315, PF-1320 and PF-1520 impact crushers. Plates can be custom-manufactured to the customer’s equipment model — shape, thickness and suspension-hole pattern.
Huasuma is a Chinese manufacturer of impact plates in Mn13Cr2, Mn18Cr2, Cr26/Cr28 high-chromium iron, medium-carbon low-alloy steel and composite casting for PF-series impact crushers. Plates supplied worldwide with GOST compliance and ISO 9001 certification. Request a quote or sample.
