Recycled Steel Raw Materials Inspection: Standards, Testing Items, and Methods

Recycled steel raw materials inspection is a critical quality assurance process that verifies whether recovered ferrous scrap meets the stringent chemical, radioactive, and physical requirements set out in standards such as GB/T 39733-2020 and international scrap specifications. This article explains the technical framework, sampling procedures, key testing items, laboratory methods, and practical applications of recycled steel raw material inspection for steelmakers, traders, and importers who need to demonstrate compliance and avoid solid waste classification. Read on to understand how accredited third-party laboratories evaluate radioactivity, residual elements, non-metallic inclusions, and prohibited substances in recycled steel consignments.

Technical Overview

Recycled steel raw materials refer to recovered iron and steel products that have been collected, sorted, sheared, shredded, baled, or otherwise processed into a clean, furnace-ready charge material. Unlike unprocessed scrap, which may be regulated as solid waste in many jurisdictions, properly processed recycled steel raw materials are recognized as a legitimate metallurgical raw material and a valuable feedstock for electric arc furnace (EAF) steelmaking, basic oxygen furnace (BOF) cooling charge, and foundry melting.

In China, the governing product standard is GB/T 39733-2020, which establishes classification codes, technical requirements, test methods, and inspection rules for recycled steel raw materials. The standard was developed specifically to distinguish high-quality processed ferrous scrap from prohibited solid waste imports, making third-party inspection a decisive factor in customs clearance. Internationally, trade is guided by recognized scrap classification systems such as the ferrous scrap specifications published by industry associations, while the transboundary movement of metal scrap falls under the Basel Convention framework. Accredited third-party laboratories perform inspections against these standards to verify safety, cleanliness, and chemical suitability.

The core objectives of inspection are fourfold:

• To confirm that radioactivity levels are within regulatory limits and that no radioactive contamination is present.
• To verify chemical composition, including control of residual and tramp elements that degrade steel quality.
• To quantify non-metallic foreign matter, oil, moisture, and non-ferrous contamination.
• To exclude prohibited and dangerous items such as explosives, sealed pressure vessels, and military materials.

Testing Samples

Heavy and Medium Scrap Steel

Heavy and medium grades consist of clean steel sections, plates, rails, structural shapes, and machinery parts above defined thickness and size thresholds. Inspection focuses on dimensional conformity, freedom from excessive oxidation and corrosion, and absence of attached non-steel components such as concrete, brick, or machined bearing assemblies.

Crushed (Shredded) Steel

Shredded material produced from end-of-life vehicles and light gauge scrap is inspected for bulk density, non-ferrous metal carryover, and residual fluff, plastics, rubber, and glass generated during the shredding process. Post-shredder eddy current and air separation efficiency is verified through manual sorting analysis.

Baled and Compacted Material

Bales and briquettes of light steel scrap are checked for density, binding integrity, and internal concealed contamination. Because non-metallic materials and liquids can be hidden inside bales, inspection typically involves destructing a statistically determined number of bales for full sorting and weighing.

Steel Turnings and Borings

Machining swarf is highly susceptible to oil and moisture contamination and may conceal alloy segregation. Sampling programs target oil content, moisture, and verification that turnings are free from cast iron, non-ferrous alloys, and dangerous elongated spirals that can tangle in charging equipment.

Cast Iron and Alloy Steel Scrap

These higher-value streams require careful chemical verification because alloying elements such as chromium, nickel, molybdenum, and manganese significantly affect melting economics and heat chemistry calculations. Laboratory melt samples are used to obtain representative analytical specimens.

Laboratory Analytical Samples

For chemical analysis, increments collected across the consignment are melted in a laboratory induction furnace under argon or nitrogen to produce a homogeneous button, which is then sectioned, ground, and polished for instrumental analysis. Alternatively, drillings and millings from thick sections may be composited, subject to the limitations imposed by segregation and coatings.

Testing Items

Inspection scope is defined by the product standard and the trade contract. The principal testing items are listed below.

• Radioactive dose rate screening at the consignment surface and surrounding environment, compared against natural background limits.
• Surface contamination measurement for alpha and beta emitting radionuclides.
• Gamma spectrometric identification of radionuclides in any suspected source or contaminated item.
• Chemical composition: carbon, silicon, manganese, phosphorus, and sulfur as the base elements.
• Residual and tramp element control: copper, tin, arsenic, antimony, bismuth, and lead, which cause hot shortness and embrittlement in finished steel.
• Alloying element determination: chromium, nickel, molybdenum, vanadium, and tungsten where alloy scrap is declared.
• Non-metallic inclusions and foreign materials content, including slag, sand, refractory, glass, rubber, plastics, textiles, wood, and paper.
• Non-ferrous metal content such as copper wire, brass fittings, aluminum, and zinc-coated components.
• Oil, grease, and moisture content, particularly in turnings and crushed material.
• Bulk density and unit weight verification against grade requirements.
• Prohibited items inspection: explosives, munitions, sealed pressurized containers, gas cylinders, fuel tanks, and containers holding liquids or powders.
• Category conformity, including morphology, size, and freedom from heavily corroded or burnt material.

The standard sets maximum permissible limits for non-metallic foreign matter and requires that radioactive detection, chemical composition, and cleanliness all conform before a consignment can be certified as recycled steel raw material rather than solid waste.

Testing Methods

Radioactivity Testing

Initial screening is performed using radiation portal monitors or handheld scintillation detectors that measure the ambient gamma dose equivalent rate around the load, vehicle, or stockpile. Measured values are compared with local natural background, and any anomaly triggers closer investigation with a portable gamma spectrometer to identify the responsible radionuclide. Surface contamination is assessed by wipe testing and direct measurement using alpha-beta probes, evaluated against contamination limits referenced from radiation protection standards such as GB 18871 and international transport regulations. Suspected orphan sources are located, shielded, and referred to competent radiation safety authorities.

Chemical Composition Analysis

Spark discharge optical emission spectrometry (OES) in accordance with GB/T 4336 and ASTM E415 is the primary method for simultaneous multi-element analysis of melt buttons and solid specimens. Carbon and sulfur are determined precisely by high-frequency combustion infrared absorption (GB/T 20123 or ASTM E1019). X-ray fluorescence spectrometry (ASTM E1621 and related methods) provides rapid screening of residual elements, while inductively coupled plasma optical emission spectrometry (ICP-OES) serves as the reference method for trace elements such as bismuth, antimony, arsenic, and tin at low concentration levels. Classical wet chemical methods in the GB/T 223 series remain available for arbitration analysis.

Sampling for Chemical Analysis

Sampling follows the principles of GB/T 20066 and ISO 14284 for the sampling and preparation of samples for chemical analysis. Because scrap is heterogeneous, a sufficient number of increments is drawn from different locations, lots, and depths of the stockpile or cargo. Increments are degreased, cleaned of surface scale, and remelted to eliminate segregation effects before analysis. The number of samples and analytical frequency are defined by the lot size and the inspection level agreed in the contract.

Foreign Matter and Cleanliness Determination

Non-metallic and non-ferrous contamination is quantified by manual sorting of representative subsamples. Each constituent category is separated magnetically and manually, then weighed, and results are reported as a mass percentage of the total sample. For bales, a predetermined quantity is opened and fully dismantled for sorting. The measured foreign matter content is compared with the maximum limits in the applicable grade specification.

Physical and Ancillary Tests

Moisture is determined by drying representative samples to constant mass at 105 degrees Celsius. Oil and grease content is measured by solvent extraction and gravimetric determination. Bulk density is determined by filling a calibrated container of known volume, weighing the contents, and computing the mass per unit volume, with results evaluated against grade minimums. Visual and manual inspection by experienced surveyors complements laboratory work for prohibited items and overall category conformity.

Inspection Rules and Certification

Conformity assessment follows the inspection rules of the product standard, including lot definition, sampling plans, and permitted tolerance for re-testing of borderline results. Accredited third-party laboratories issue inspection reports and certificates covering radiation monitoring records, chemical analysis certificates, cleanliness determination, and visual findings, which support customs declaration and contractual settlement.

Applications

• Import and export compliance: verifying that consignments of recycled steel raw materials meet GB/T 39733 and the importing country's requirements, supporting customs clearance and preventing rejection or solid waste enforcement action.
• EAF steelmaking procurement: assuring steelmakers that purchased scrap delivers predictable chemistry, low residual elements, and acceptable cleanliness for charge calculations and quality planning.
• Foundry charge qualification: confirming cast iron and alloy steel scrap suitability for melting operations where tramp elements and contamination directly affect casting integrity.
• Trade settlement and pricing: providing independent determination of grade, density, foreign matter content, and yield that underpins contract pricing, penalties, and bonuses.
• Radiation safety management: protecting ports, scrap yards, and mills from orphan radioactive sources concealed in recycled material streams.
• Environmental and waste regulation compliance: documenting that material has been processed to raw material status and does not constitute controlled solid waste under national environmental regulations or the Basel Convention framework.
• Supplier qualification and ongoing surveillance: auditing recycling and processing facilities to confirm consistent sorting, depollution, and quality control capability.

FAQ

What is the difference between recycled steel raw material and solid waste scrap?

Recycled steel raw material has been sorted, processed, and cleaned to the point where it is a directly usable furnace charge meeting defined quality standards, whereas unsorted, contaminated, or unprocessed scrap may be classified and controlled as solid waste. Inspection against GB/T 39733-2020 provides the technical evidence for this distinction.

Which standards govern recycled steel raw materials inspection in China?

GB/T 39733-2020 is the core product standard covering classification, requirements, test methods, and inspection rules. Supporting methods include GB/T 4336 for spark OES, GB/T 20066 for sampling, GB/T 20123 for carbon and sulfur, and radiation protection requirements referenced from GB 18871.

How is radioactivity in scrap cargo actually checked?

Radiation portal monitors or handheld detectors measure gamma dose rate around the cargo and compare it with natural background. If an elevated reading is found, gamma spectrometry identifies the radionuclide, and wipe tests or direct probe measurements assess surface contamination. Consignments exceeding limits must not be imported and require reporting to regulatory authorities.

Why are residual elements such as copper and tin controlled?

Copper, tin, arsenic, antimony, bismuth, and lead cannot be removed in the steelmaking process and accumulate with each melting cycle. Above certain levels they cause surface hot shortness, temper embrittlement, and reduced ductility, so their content in scrap feedstock must be quantified and controlled.

How are bales inspected for hidden contamination?

Because contamination can be concealed inside compacted bales, inspection standards require random destructive opening of a defined number of bales per lot, followed by complete manual sorting and weighing of all non-metallic and non-ferrous materials found within.

How long does a typical inspection take?

Radiation screening and visual surveying can be completed during loading or discharge within hours, while full chemical analysis of melt samples, cleanliness sorting, and report issuance typically requires several working days depending on lot size and the number of samples.