C-Cr-Mo Cast Steel Chemical Composition: AS2074 L2A, L2B and L2C Casting Guide

Composition table: the practical starting point

Public EB group capability tables list the following nominal mass-percent ranges. They are useful for comparing quotations, but they should not be represented as a verbatim reproduction of the standard. AS2074 has multiple editions, and third-party tables can differ in residual limits or notation.

Write the invoked standard edition into the purchase documents. If the order uses a modified grade, list every modification and define whether acceptance is by heat analysis, product analysis or another agreed sample. The row name alone is not enough.

What the AS2074 reference does and does not mean

AS2074 is an Australian standard for steel castings for general engineering purposes, with historical and current editions. Material requirements do not automatically define every manufacturing, dimensional, NDT, repair, documentation or service-life requirement for a finished chute liner.

A buyer should specify the material grade and standard edition, then add the casting drawing, delivery condition, hardness or mechanical properties, test methods, acceptance criteria, marking and traceability. Where another casting standard governs supplementary requirements, state it explicitly rather than assuming the grade name imports every condition.

Why carbon separates L2A, L2B and L2C

Carbon rises across the three public screening families. That increases maximum attainable hardness and changes the transformation and tempering response. It can also reduce weldability and usable toughness if heat treatment or geometry is not matched to the composition.

The highest-carbon option is not automatically the longest-lasting liner. A bolt recess, unsupported lip or sudden section change may make fracture control more valuable than indentation hardness. Select carbon range around the real load and required section response.

Chromium: hardenability rather than a high-chrome label

The L2 families use roughly one to two percent chromium in public tables. Chromium delays transformation and supports hardening to useful depth, depending on carbon, molybdenum, section and quench. It can also influence carbide formation and tempering behavior.

These percentages are far below many high-chromium white irons. Calling L2C “high chrome” can mislead buyers into expecting a carbide-dominant white-iron structure. It is better described as abrasion-resistant low-alloy cast steel under the invoked standard.

Molybdenum: why L2B and L2C differ from L2A

Public supplier tables list 0.2-0.4% Mo for L2B and L2C, while L2A has no specified Mo entry in that comparison. Molybdenum can increase hardenability and help resist softening during tempering, which is useful when a casting must develop properties below the surface.

Mo does not guarantee through-hardness by itself. A heavy boss still cools more slowly than a thin wall; austenitizing, transfer and quenchant remain decisive. The certificate should confirm Mo when the ordered grade requires it.

Hardness versus hardenability

Hardness is a local indentation result. Hardenability is the ability to form the intended hardened structure to depth under a defined cooling condition. A surface can meet a hardness target while the center of a heavy section transforms differently.

For chute liners, state measurement scale, prepared locations, number of readings and acceptable range. If through-section response matters, define a depth criterion or representative block. Do not infer hardenability from one HRC value on an accessible edge.

Cast steel versus white cast iron

Cast steel generally contains less carbon than cast iron and is designed around a steel matrix. High-Cr white iron uses much higher C and Cr to establish a large fraction of hard carbides. The two families require different fracture, support, machining and application assumptions.

A procurement page that mixes AS2074 L2 steel and ASTM A532 or AS2027 white iron in one unlabeled table creates technical risk. Keep standards, composition families and delivery structures separated, then compare them by service mechanism.

Melting and chemistry control

Induction melting can produce alloy steel castings when charge, furnace practice, deoxidation and sampling are controlled. Recovery and residuals depend on raw material and process. The heat analysis must identify the melt and report the elements required by the purchase specification.

Chemistry creates potential but cannot reveal shrinkage, inclusions or final microstructure. Laboratory analysis, traceable heat identity and controlled pouring work with casting-process and heat-treatment records as one evidence chain.

Sand molding and liner geometry

Resin-sand or sodium-silicate-sand processes may be used for custom liner shapes. Pattern allowance, draft, cores, gating, risers and chills need to reflect the alloy and geometry. Thick bolt bosses and abrupt junctions can create hot spots and feeding difficulties.

The buyer should identify critical faces, datums, holes, ribs, joint direction and bearing interfaces. A casting drawing should not copy every worn contour from a failed sample. Restore the intended geometry and improve unsupported edges before repeating production.

Austenitizing before quenching

Austenitizing prepares the matrix for transformation. Temperature and hold must suit grade, prior structure and section without causing excessive grain growth, oxidation or decarburization. Furnace load, uniformity and part spacing influence the result.

A public Blog should not prescribe one universal temperature for L2A, L2B and L2C. Carbon and alloy levels differ, as do casting sections and foundry practices. The approved heat-treatment procedure and final verification should control the order.

Quench selection and section effect

Cooling medium, agitation, temperature, transfer delay and geometry determine the quench severity experienced by the casting. L2B and L2C molybdenum additions may support useful depth, but they cannot make a heavy section behave like a thin coupon.

Overly severe cooling can drive cracking or distortion; insufficient cooling can leave an unintended soft structure. Handling fixtures and lifting plans should support dimensional stability and safe transfer. Record the production lot and required thermal evidence.

Tempering for a usable hardness-toughness balance

Freshly transformed steel can contain high stress and excessive brittleness. Tempering adjusts hardness, toughness and stability. Carbon, chromium and molybdenum influence how the steel softens and how carbides evolve during tempering.

The correct endpoint is an application-specific range, not the maximum possible HRC. Verify after the final thermal cycle. If machining is needed, agree whether it occurs before or after hardening and protect the approved final condition.

Pearlitic, bainitic and martensitic delivery concepts

Public market descriptions sometimes label Cr-Mo liners as pearlitic or martensitic. Those words must be supported by the specified grade, thermal route and sampled microstructure. A mixed structure may occur through a variable section if cooling is not uniform.

Use metallographic terms only with an agreed sample location, preparation and acceptance description. One polished coupon cannot prove the entire casting. When structure is critical, link metallography to hardness and mechanical evidence.

Mechanical testing and representation

Hardness, impact and tensile results are meaningful only when specimen geometry, orientation, temperature and sample relationship are defined. Separately cast test bars may be required but can cool differently from the actual liner.

For a new heavy section, consider an attached block, representative keel block or sacrificial casting by agreement. The report should state what was tested and how it represents production. Do not compare impact joules from different notch types or specimen sizes as if identical.

Where L2A may be evaluated

The lower-carbon L2A screening family can be considered where a buyer values cast geometry and a moderate abrasion-strength balance with more toughness margin than a higher-carbon condition may offer. Actual suitability depends on heat treatment and duty.

It should not be chosen merely because it is first in the table. If the failure is rapid fine-particle cutting with little impact, a carbide-bearing material may be more appropriate. If the failure is edge fracture, geometry and support may dominate the chemistry.

Where L2B may be evaluated

L2B adds carbon relative to L2A and includes a published Mo range, creating a commonly discussed Cr-Mo wear-casting family. It can be evaluated for combined impact and abrasion when a heat-treated cast-steel matrix is desirable.

Buyers should focus on section response, tempering and actual failure mode. A modified L2B is not automatically equivalent to the base grade; write modifications, properties and acceptance evidence into the purchase package.

Where L2C may be evaluated

L2C carries the highest published carbon and chromium ranges among these three and includes molybdenum. This gives substantial hardness and hardenability potential but also increases the importance of crack control, tempering, section transition and fixing design.

Use an application and first-article review rather than a “higher grade is better” assumption. Unsupported impact edges or loose bolts can defeat a hard alloy. Field monitoring should confirm whether wear—not premature fracture—sets replacement life.

Chute zoning before material selection

A transfer chute can contain a receiving impact zone, accelerating bed, curved transition, sidewall and discharge interface. Impact, gouging and sliding severity differ across these positions. One grade across the whole chute may waste toughness in one area and wear too fast in another.

Map the trajectory, contact footprint and previous thickness loss. Compare L2 cast steel with manganese steel, high-Cr white iron, Ni-Hard and rolled wear plate by zone. Material selection becomes clearer when the failure mechanism is localized.

Fixing and backing can overwhelm alloy choice

A hard casting that rocks on an uneven backing experiences bending it was not selected to carry. Exposed flow-facing joints receive localized blows. Insufficient ligament around a countersunk hole concentrates stress. These installation effects can make a correct chemistry look unsuccessful.

Specify bearing condition, allowed finish, shim or backing practice, bolt property and tightening method, joint direction, gap and edge profile. Record installation condition during a trial so field evidence separates alloy behavior from fixing failure.

Chemistry certificate and PMI limitations

A useful certificate reports C, Si, Mn, Cr, Mo, P and S with heat identity and the ordered grade. Required residuals should also be stated. Check units, decimal points and whether the result is a generic target or an actual heat analysis.

Portable XRF can screen chromium and molybdenum but does not directly quantify carbon, and surface condition affects results. Use a suitable laboratory method for full grade verification. Treat field PMI as evidence within an investigation, not a complete acceptance method unless contractually defined.

Inspection and traceability

Part marking should link each liner to the heat, thermal lot, drawing revision and inspection documents. Dimensional inspection needs critical datums, holes, recesses, profile and bearing surfaces. Visual examination and NDT require written methods, locations and acceptance criteria.

Generic “100% NDT” is incomplete. Method capability depends on geometry and structure. Agree hold and witness points before manufacturing, then release the casting against the same approved plan used for the quotation.

Field trial and wear-life evidence

Before installation, record part ID, baseline thickness, hardness locations, mass where practical, support and photographs. During service, track tonnes or hours, feed size, throughput, abnormal impact events, fixing condition and thickness on a numbered grid.

At removal, classify uniform wear, gouging, cracking, deformation, bolt damage or support failure. Compare cost per processed tonne and maintenance exposure, not only calendar months. A fair trial holds duty and position as constant as possible.

Common specification mistakes

Frequent errors include ordering “AS2074” without grade or edition, calling all Cr-Mo castings identical, treating L2C as an automatic upgrade, comparing cast steel with white iron by hardness alone, and omitting heat-treatment condition. Others are copying a worn sample, ignoring section effects, specifying NDT without criteria and accepting generic chemistry instead of heat analysis.

The correction is a linked evidence chain: duty, drawing, chemistry, casting route, thermal condition, properties, inspection, installation and field monitoring.

RFQ checklist

Provide the standard and edition, L2A/L2B/L2C or approved modification, chemistry limits, heat-treatment condition, hardness and required mechanical evidence. Send 2D/3D drawings, revision, liner map, mass, sections, fixing, datums and machining.

Describe material handled, maximum lump, impact/drop, abrasion, throughput, moisture, temperature, current grade, wear map and failure mode. Define chemistry report, thermal record, dimension plan, NDT, marking, packing and witness points.

Decision summary

L2A, L2B and L2C should be read as different C-Cr-Mo design spaces, not a simple good-better-best ladder. Carbon raises hardness potential; chromium and molybdenum support hardenability and tempering response; geometry and heat treatment determine whether that potential reaches the real section.

Select the family that matches the failure mechanism and required toughness, then verify it with traceable production evidence. When sliding abrasion dominates and impact is controlled, compare carbide-bearing iron. When high contact stress can work harden austenite, compare manganese steel.

Sources and engineering boundary

Technical basis includes public EB group AS2074 capability tables, official standards catalog information for AS2074 editions, general cast-steel and heat-treatment guidance from the American Foundry Society, NIST/NBS and ASM. Verify current standards from authorized full text before contractual use.

Final grade, geometry, structure, support, fixing and installation require customer and qualified-engineer approval. No chemistry table guarantees wear life. Isolation, stored-energy control, lifting and site safe-work procedures always apply.

• AS 2074-2003 standards catalog record.
• American Foundry Society Casting Source: Steel 101.
• NBS/NIST: Heat Treatment and Properties of Iron and Steel.
• ASM Handbook: Heat Treating of Low-Alloy Steels.