The batch has to remain visible at the bundle
Check the physical bundle against its packing entry and material record before the stock is mixed or charged.
Select an image to open the full-size original and inspect its labels.
Key takeaways
- A steel heat, a heat-treatment lot and a delivery are different identifiers.
- Match the actual rods to the ordered specification and the results that represent them.
- Compare individual readings at consistent locations; a matching average can hide a different spread.
- Keep retests and process changes visible through to the mill record.
One delivery can contain more than one batch
Grinding rod batch consistency starts with a clear definition of the material being compared. The same grade name and a familiar HRC range are not enough. Record the steel heat, the relevant processing and heat-treatment lots, the finished dimensions and the test positions represented by each result.
A heat number identifies the steelmaking heat. Rods from that heat may pass through different treatment runs; one delivery may contain several heats and treatment lots. Keep those relationships visible rather than compressing them into a single shipment number.
The inspection document belongs in this chain. ISO 10474 defines inspection-document types for steel products; the order still has to identify the required tests, acceptance criteria and material represented. [2]
| Stage | Keep this link |
|---|---|
| Steel heat | Heat number → grade, chemistry and relevant upstream records |
| Processing / heat treatment | Heat and bar identity → treatment run or defined process lot |
| Inspection | Sample and test location → actual results → represented lot |
| Packing and receiving | Bundle mark → packing entry → quantity and document set |
| Mill charging | Received lot → charge date, mill and quantity added |
Read the numbers, not just the certificate heading
The public record below is a real, redacted 40Cr material example. It is useful for showing how actual results are presented. A grinding-rod delivery needs its own linked inspection record. [1]
Inside a real material test record
Read the column units before transcribing the values. The five mechanical-result rows below are document rows, not five identified grinding-rod batches.
Select an image to open the full-size original and inspect its labels.
| Document row | Rp0.2 (MPa) | Rm (MPa) | A (%) | Z (%) |
|---|---|---|---|---|
| 1 | 615 | 795 | 21.0 | 67 |
| 2 | 613 | 791 | 21.5 | 66 |
| 3 | 576 | 756 | 24.0 | 69 |
| 4 | 576 | 756 | 24.0 | 69 |
| 5 | 588 | 769 | 22.0 | 68 |
The visible proof-strength results run from 576 to 615 MPa; tensile results run from 756 to 795 MPa. Those are observations from this record, not purchasing limits. Whether each result meets an order depends on the specified grade, section, condition and test requirements.
For an actual delivery, make the same check with the unredacted document: which heat, which treatment lot and which sample produced each row? The public crop deliberately omits identity fields, so it cannot perform that matching step.
A receiving check that follows the rods
Start before unloading stock into a shared storage position. Match the bundle identity and quantity with the packing list, then check that the document set refers to the ordered grade, diameter, length and treatment condition. Record damage or missing marks while the delivery is still identifiable.
| Check | What to record | When something does not match |
|---|---|---|
| Bundle and documents | Marking, heat/treatment-lot links, packing line and quantity | Keep the bundle segregated until the identity is resolved |
| Dimensions and ends | Actual diameter, length, straightness setup and end condition | Record the measured deviation against the order requirement |
| Surface and handling | Visible damage, corrosion, bent rods, damaged restraints and photographs | Identify affected material and notify the responsible supplier/site contact |
| Hardness and ordered tests | Sample location, method, individual values and represented lot | Follow the agreed retest and release procedure; preserve the first results |
| Release to storage or use | Decision, approver, date and any accepted deviation | Keep held stock separate from released stock |
The same average can conceal a wider spread
Keep the individual readings. In the simple example below, both sets average 60 HRC. Their ranges are very different. The figures are invented to demonstrate the arithmetic, not taken from a production lot.
| Set | Five readings (HRC) | Mean (HRC) | Range (HRC) |
|---|---|---|---|
| A | 59, 60, 60, 60, 61 | 60 | 2 |
| B | 56, 58, 60, 62, 64 | 60 | 8 |
Neither set can be passed or rejected without the order limits and sampling plan. The example shows why reporting only the mean loses information. Also keep surface, subsurface, centre and end readings in their own groups; an intentional hardness gradient should not be mistaken for random scatter.
Keep the test position with the reading
Use a repeatable position, preparation and method for comparison. Equipment identity and calibration status belong with the result.
Select an image to open the full-size original and inspect its labels.
ASTM E18 covers Rockwell testing, including equipment and test procedures. In a delivery comparison, the method and specimen condition must travel with the reported number. [3]
Once a stable measurement routine and a useful history exist, plot results in production order. NIST describes control charts as a way to detect unusual process behaviour. Control limits come from that process history; purchase-specification limits come from the agreed requirement. [5]
Use the hardness-profile guide for the radial map and the testing guide for the inspection method. This page is about carrying those results consistently from delivery to delivery.
Repeat the route as well as the grade
After a successful qualification, record the route that produced it: material specification, section, delivered condition, treatment and straightening sequence, inspection plan and agreed reporting. Identify which changes need review before the next batch is released.
Production identity has to survive the next operation
The upstream heat record and the downstream processing record serve different purposes. Preserve the link when material changes hands or operations.
Select an image to open the full-size original and inspect its labels.
ISO 20431 provides a framework for heat-treatment quality, facility inspection and specification discussions. For an order, translate that into the records and controls relevant to the agreed process. Ask which facility performs each operation and who reviews the resulting lot record. [4]
In a JOTAIN order review, separate the upstream mill’s steelmaking documents from the processing and final inspection records. Name the responsible operation and release point. The buyer should be able to follow the material without having to infer responsibility from a factory photograph.
Where mechanical testing is ordered, keep the specimen and test conditions with the values. ASTM A370 is a testing reference; it does not replace the product specification or the buyer’s acceptance schedule. [8]
Keep batch identity after the delivery is accepted
A well-documented delivery can still become untraceable at the mill. Carry the lot identity into the charging log with date, mill, rod size and mass added. Keep mixed-charge periods visible when old and new rods overlap.
For each comparison period, put gross kg/t beside product size, dry throughput, energy, damaged removals and the operating conditions. Record ore changes, liner work and charge changes before attributing a difference to the latest delivery.
The wear-rate and consumption guide explains the mass balance. The breakage investigation guide covers preserved samples and incident evidence. Both records should point back to the same lot register.
Put the repeat-order requirement in writing
A useful order brief says what has to remain consistent, what may change with approval and what evidence accompanies each delivery. Keep it short enough for receiving and production teams to use.
- Identify grade, standard/edition, rod dimensions and delivered treatment condition.
- Define the heat and treatment-lot relationships and the physical marking method.
- Attach the sampling plan, test positions, methods and acceptance requirements.
- Request individual results, original retest records and approved deviations.
- Agree process-change notification, release responsibility and the lot-to-charge feedback record.
Send JOTAIN the specification and the inspection format used by your receiving team. We can review the proposed material, processing and reporting route against the repeat-delivery requirement.
Questions buyers ask
Is a heat number the same as a grinding rod batch number?
No. A heat number identifies a steelmaking heat. A heat-treatment lot identifies material processed under a defined treatment run or lot rule. A shipment may contain several of each. Keep the links between them and the bundle identity.
Can two rod batches have the same average hardness but different consistency?
Yes. The average can match while the individual values have different spreads. Compare results at equivalent locations and with the same method; keep an intentional radial or axial hardness profile separate from random variation.
What should we check when grinding rods arrive?
Match physical identity, packing records and inspection documents; check dimensions, straightness, ends, surface condition and ordered test results. Record discrepancies and the release decision before material is mixed with other stock or charged.
How many rods should be hardness tested from each lot?
Use the sampling plan agreed for the defined lot, characteristic and purchasing risk. Specify the test positions, method, acceptance criteria and retest rules. A fixed sample count without those inputs does not define an inspection plan.
Does a material test certificate establish mill performance?
It records the identified material and the inspection results represented by the document. Mill performance comes from a separate operating record that follows those rods into the charge and compares consumption, removals and process duty.
RFQ checklist
- Grade, standard, diameter, length and delivered condition.
- Heat → treatment lot → sample/result → bundle → mill-charge identity.
- Sampling plan, test positions, individual readings and acceptance criteria.
- Receiving discrepancies, retests, process changes and approved deviations.
- Release responsibility, retained samples and repeat-delivery feedback.
References
- Redacted 40Cr material test record — technical fields
- ISO 10474:2013 Steel and steel products — Inspection documents
- ASTM E18-25 Standard Test Methods for Rockwell Hardness of Metallic Materials
- ISO 20431:2023 Heat treatment — Control of quality
- What are Control Charts?
- ISO 3951-1:2022 Sampling procedures for inspection by variables — Part 1: Specification for single sampling plans indexed by acceptance quality limit (AQL) for lot-by-lot inspection for a single quality characteristic and a single AQL
- ISO 2859-1:2026 Sampling procedures for inspection by attributes — Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection
- ASTM A370-26 Standard Test Methods and Definitions for Mechanical Testing of Steel Products
Inquiry support
Working from a part drawing?
For this review, send the heat and treatment-lot identity, the required inspection-document content, the radial hardness measurements, and the receiving inspection results. For a quotation, also include the quantity and destination.