The right jaw plate manganese grade depends on the feed and the impact available to work-harden the surface. A higher manganese percentage is not automatically an upgrade: wear, broken teeth and uneven plates can also point to feed, fit or operating conditions.
Use the tables as starting points for fixed and movable jaw plates. Record the actual wear pattern and operating conditions before asking a foundry to recommend a material.
Why jaw plate duty matters
Jaw plates crush between a fixed surface and a reciprocating movable surface. Austenitic manganese steel can work-harden under impact, but the result depends on the actual duty. Fine, abrasive material and insufficient impact may produce a different wear pattern from large primary feed. For an overview of alloy families, see the crusher wear parts materials guide.
Table A: Jaw plate manganese grade starting points
| Grade | Indicative Mn | As-supplied hardness: typical band | Work-hardened surface | Better starting point when… | Caution |
|---|---|---|---|---|---|
| Mn13 | ~12–14% | ~170–230 HB | Can rise substantially under impact | Softer rock, lower abrasion and manageable primary feed | May wear quickly on highly abrasive hard rock |
| Mn18 | ~17–19% | ~170–230 HB | Can harden strongly under solid impact | Common hard aggregate and quarry duty | Still needs impact; review fine abrasive duty |
| Mn22 | ~21–24% | ~170–230 HB | Potential for deeper hardening under suitable impact | Very hard, abrasive rock, large feed or shock exposure | Low-impact or poorly fed jaws may not develop the expected hardening |
All Mn and hardness bands are indicative starting points, not acceptance limits or guarantees. Actual chemistry, carbon-to-manganese ratio, section size and heat treatment affect the casting. Work-hardened surface hardness varies with duty and location; do not compare it directly with an as-supplied report. See hardness testing when agreeing how a part will be checked.
Table B: Rock and duty to starting grade
| Rock / duty snapshot | Relative impact | Abrasion | Starting grade | What to check |
|---|---|---|---|---|
| Limestone, dolomite or soft shale | Low–moderate | Low–moderate | Mn13; consider Mn18 if wear is excessive | Higher Mn is not an automatic upgrade |
| River gravel or mixed medium-hard feed | Moderate | Moderate | Mn18 | Watch for clay and fines packing |
| Granite, basalt or diabase | High | High | Mn18; consider Mn22 if wear life is short | Review even feed and the site's recommended feed practice |
| Hard abrasive ore with large primary feed | Very high | High | Mn22 is often considered | Confirm section size and heat treatment |
| Contaminated feed with tramp metal risk | Shock events | Variable | A tough manganese family | Review shock exposure and feed control; brittle alternatives can increase breakage risk |
Rock names alone cannot specify a grade. Abrasiveness varies within a rock type, and feed size, moisture, contamination and the machine setup change the duty. Use the matrix to start a discussion, then compare the recommendation with the actual wear record.
Fixed and movable jaw plates
Both plates often use the same manganese family, but they may wear at different rates. Before choosing different grades, check feed distribution, tooth profile, installation and the condition of both plates. If there is a reason to trial different materials, agree the pair and fit requirements with the foundry and review the results together.
Send clear photos of both plates, their part numbers and installation positions. You can browse jaw crusher liners by part number or model match.
Table C: Read the wear pattern
| Observed pattern | Possible drivers | What to gather for the RFQ |
|---|---|---|
| Fast uniform thinning | High abrasion for the grade or insufficient work-hardening | Rock type, CSS / opening, hours or tonnes, current grade |
| Deep peening or plastic flow | High impact or surface condition | Photos, feed size and observations of the work-hardened surface |
| Corner or tooth breakage | Shock, tramp metal, or casting / heat-treatment issues | Photos, tramp history and any hardness report |
| Uneven left / right or fixed / movable wear | Feed bias, alignment or mismatched pair | Both plate part numbers and installation photos |
| Wear concentrated in the belly | Chamber or feed gradation mismatch | Opening settings and feed size distribution notes |
A wear pattern is a clue, not a diagnosis. Check feed, installation and settings alongside the material before changing grade.
Verify the material and fit
Ask for the agreed chemistry and inspection records for the supplied heat, and specify where and how hardness is to be checked. If the proposed grade has a different name, compare its requirements using the cast steel grade equivalents guide. Agree fit-critical checks using the dimensional tolerances guide.
If the part number is missing, a drawing or sample can help with model matching and reverse engineering; worn areas may need additional evidence of the original shape.
Table D: Jaw plate mini RFQ
| Field | Send |
|---|---|
| Identity | Fixed or movable jaw plate and part number if known |
| Machine | Model / series designation for model match |
| Pair | Whether both plates are needed; thickness and tooth profile notes |
| Duty | Rock, feed size and opening / CSS practice |
| Evidence | Photos, worn sample or drawing |
| Preference | Mn13, Mn18, Mn22 or “recommend” |
| Quantity and port | Quantity, ship-to destination and urgency |
Send the checklist to info@gubtcasting.com or use the contact form. Include the wear history if you want GUBT to discuss a starting grade.
FAQ
Does Mn22 always last longer than Mn18?
No. Actual performance depends on impact, abrasion, feed and the casting itself. In low-impact duty, a higher-Mn plate may not work-harden as expected.
Can fixed and movable plates use different grades?
They can be considered separately when the duty and wear evidence justify it. First check the fit, feed distribution and tooth profiles, then agree the proposed pair with the foundry.
What if I only have a part number?
Send it with the plate position and machine designation if available. Photos and a drawing can help confirm the configuration; the foundry may need more evidence before manufacturing.
Soft rock is wearing the plates quickly. Should I change grade?
Not immediately. Check whether the feed contains abrasive fines, how evenly it enters the chamber, and how much material is being processed. Share photos and operating records before choosing a new trial grade.
What causes broken jaw plate teeth?
Shock or tramp metal, installation and material condition are possible contributors. Photograph the fracture and installation, record the feed history, and ask the foundry to review the evidence.
What affects lead time?
Stock, pattern availability, quantity, casting, heat treatment and the agreed inspections all matter. See the casting MOQ and lead-time guide and request a quote for your part number and quantity.
