Welding NM Wear Plate for Chute Liners: Heat Affected Zone, Preheat and Fixing Notes
NM wear plate can be weldable and still require a material-specific welding procedure. Preheat, interpass temperature, heat input and consumable cannot be selected from the grade label alone. Plate thickness, actual chemistry, joint restraint, ambient condition, hydrogen control and the steel producer’s current recommendations all matter.
This guide helps buyers define welded chute-liner RFQs and inspection evidence. It is not a welding procedure specification and does not authorize field hot work.
First decide whether welding is necessary
| Attachment route | Potential reason | Review before selection |
|---|---|---|
| Direct welded edge/detail | Approved permanent attachment with suitable access. | Heat input, removal, shell effect, joint restraint and inspection. |
| Plug-weld opening | Drawing-controlled attachment through the liner. | Hole geometry, backing contact, weld procedure and removal plan. |
| Stud-backed liner | Smooth wear face with attachment from the shell side. | Stud process, qualification, position, access and shell holes. |
| Bolt-on/countersunk | Replaceable fixing with reduced site welding. | Rear access, head exposure, hole pattern, torque and shell condition. |
If frequent replacement is expected, a bolted or studded system may reduce uncontrolled site cutting and repair. Compare the bolted versus welded liner guide and plug-weld chute liner plates.
Identify the actual material before writing a WPS
Record standard, grade, suffix, producer, thickness, heat or plate number and certificate chemistry. The official Chinese database lists GB/T 24186-2022 as current for high-strength abrasion-resistant steel plate, sheet and strip for construction machinery. The contract may instead specify a proprietary product.
Nominal NM400, NM450 and NM500 labels do not provide enough information to calculate welding controls. Use the certificate and the producer’s instructions for the supplied product form and thickness.
Understand the heat-affected zone
Welding creates a heat-affected zone (HAZ) adjacent to the weld metal. Its microstructure and properties depend on peak temperature and cooling history. Excessive heat input can widen the affected region and increase distortion, while an unsuitable low-heat approach can create its own risks. The approved procedure must balance cracking control, toughness, strength and wear performance.
Preheat is not one universal temperature
Required preheat may depend on combined thickness, carbon-equivalent information, hydrogen level, heat input, restraint and ambient temperature. Do not copy a number from another grade, thickness or manufacturer. Measure temperature using the method and location stated by the procedure and control interpass temperature as well as the initial preheat.
SSAB’s current Welding of Hardox wear plate guide provides brand-specific recommendations for preheating, interpass temperature, heat input and consumables. It is a useful example of the variables a producer controls, but it is not a generic NM welding table.
Control heat input and sequence
| Welding control | Record in WPS/work instruction | Risk if uncontrolled |
|---|---|---|
| Process and parameters | Current, voltage, travel speed, polarity and process. | Unexpected heat input, penetration or discontinuities. |
| Preheat/interpass | Minimum/maximum, measurement location and instrument. | Hydrogen cracking risk or excessive thermal exposure. |
| Sequence | Run order, restraint, back-step or balanced sequence where approved. | Distortion, high residual stress or poor fit. |
| Consumable | Classification, strength level, hydrogen control and storage. | Incompatible weld metal or hydrogen pickup. |
| Cleaning | Surface condition and inter-run cleaning. | Porosity, inclusions or contamination. |
Qualify the procedure and personnel
ISO 15614-1:2017 specifies how a preliminary welding procedure is qualified by procedure tests for applicable arc and gas welding of steels. ISO 9606-1:2012, confirmed in 2023 and currently expected to be replaced in the future, specifies qualification testing of welders for fusion welding of steels. The contract or applicable construction standard determines what qualification is required.
ISO 3834-2:2021 defines comprehensive quality requirements for fusion welding in workshops and at field installation sites. Referencing a standard is not enough; the project must define scope, acceptance and records.
Consumable and hydrogen control
Consumable selection considers base material, required joint properties, restraint, service and the approved procedure. Storage and handling must preserve the specified hydrogen condition. Clean moisture, oil, paint, scale and cutting residue from the joint area as required by the procedure. Do not weld over unknown contamination or packed material behind an installed liner.
Keep critical welds away from peak wear when possible
A weld toe, start/stop or protrusion in the primary material path can become a local wear or impact feature. Coordinate joint location with the wear map, flow direction and panel removal plan. Where a weld is intentionally exposed, the drawing should define its finished contour and inspection.
Control fit-up and restraint
Forcing a misfitting liner into position increases restraint and residual stress. Verify shell datums, gaps, backing contact and tack sequence before completing the joint. Worn or patched shells may require an approved repair or shim plan; a weld should not be used to hide dimensional mismatch.
Welding near holes, bends and edges
Holes, countersinks, bend lines and flame-cut edges can concentrate stress or alter heat flow. Maintain the drawing-approved distance between weld and functional features. If welding after bending or machining is required, the manufacturing sequence should be reviewed for distortion and inspectability.
Inspection and records
| Stage | Evidence | Acceptance basis |
|---|---|---|
| Before welding | Material identity, joint preparation, fit-up, consumable and equipment checks. | Drawing, WPS and work instruction. |
| During welding | Preheat/interpass readings, parameters, sequence and welder identity. | Approved procedure and project ITP. |
| Visual examination | Weld size/length, contour, starts/stops and visible discontinuities. | Specified acceptance standard. |
| NDT when ordered | Method, area, procedure, personnel and report. | Contractual code and acceptance criteria. |
| Final dimensional check | Profile, distortion, holes and mating interfaces. | Approved drawing tolerance. |
Field welding and hot-work safety
Field work adds fire, fume, access, stored-energy and falling-object hazards. In U.S. general-industry contexts, OSHA 29 CFR 1910.252 addresses welding, cutting and brazing precautions, ventilation and protection. The site’s jurisdiction and procedures govern actual work.
Before hot work, isolate the equipment, remove or control combustible material, clean the chute, assess coatings and residues, establish ventilation and fire watch as required, and control released liner mass. Never weld into a chute containing unknown material or residual energy.
RFQ checklist
- base material standard, grade, producer, thickness and certificate;
- joint drawing, location, restraint and backing/shell material;
- welding process, site or shop location and applicable code;
- required WPS/PQR and welder qualification;
- preheat, interpass, heat-input and consumable requirements;
- fit-up, sequence, distortion and dimensional controls;
- visual/NDT acceptance and documentation;
- removal, repair, coating and hot-work constraints.
Related resources: stud-backed chute liners, bolt-on chute liners and quality documents for custom liners.
Technical review boundary
This article is not a WPS, hot-work permit or structural calculation. Welding must be approved and supervised by qualified personnel under the applicable procedure and site safety system. Updated by the EB China engineering-content team against the cited current ISO, OSHA and manufacturer sources.