Key takeaways
- Start with the approved component drawing, manufacturing route, critical sections, and buyer validation plan before naming a bar grade.
- Keep bar-product evidence separate from forging, machining, heat treatment, surface processing, NDT, and finished-component acceptance.
- Define tensile, impact, and UT requirements by representation, method, location, lot, acceptance, and record.
- Require route changes and alternatives to receive written engineering approval before commitment.
Treat the part route as critical context
For crankshaft, connecting rod, eccentric shaft, or similar heavy-duty routes, the RFQ should describe the intended part and operating context in careful terms. The supplier can then review whether the bar route, condition, and inspection scope are suitable for quotation discussion.
Review section size and condition together
Large section size, rough machining allowance, and heat-treatment condition can affect the review. Buyers should state diameter, length, rough size, final drawing size, required condition, and whether later machining or heat treatment is planned.
Link fatigue and toughness to inspection
If fatigue, toughness, impact, or internal soundness matters, the RFQ should state the requirement and expected evidence, such as mechanical testing, hardness check, UT, heat-number traceability, MTC, or third-party inspection.
Avoid ambiguous equivalent-grade wording
When grades such as 42CrMo4 / 4140 or 34CrNiMo6 / 4340 are under review, buyers should identify the controlling standard and acceptable equivalents. Certificate scope should match the order wording.
Review the full component route before the bar RFQ
Crankshafts and connecting rods combine geometry, section transitions, manufacturing history, and cyclic duty. A bar supplier cannot infer those design inputs from the component name. The buyer should provide the controlled drawing, supplied and finished envelopes, critical zones, forging or machining route, heat-treatment responsibility, surface operations, NDT stage, and component validation owner. Procurement then specifies only the bar evidence needed at the contractual supply boundary.
ISO 683-2 provides product and condition context for covered alloy steels, but it does not qualify a finished crankshaft or connecting rod. Avoid claims that a grade guarantees fatigue resistance, toughness, or service life. Where tensile or impact evidence is justified, link the ordered values to the approved product or project specification and define exactly which production material and process lot the specimen represents.
Assign evidence to the correct production stage
Use the matrix to stop bar tests, NDT, and finished-component validation from being treated as interchangeable proof.
| Decision | RFQ input | Evidence to return | Acceptance owner |
|---|---|---|---|
| Bar identity and state | Grade, product standard, edition, section, condition, surface, and process boundary | Inspection document, actual ordered results, heat and lot map | Material engineering accepts the incoming bar route |
| Mechanical representation | Tensile and impact methods, values, specimen geometry, orientation, location, temperature, frequency, and retest | Reports linked to represented heat, section, and treatment lot | Engineering and quality approve representation and judgment |
| Internal inspection | Applicable UT method, product state, coverage, reference basis, acceptance, end zones, personnel, and report | Approved procedure, personnel evidence, and identity-linked report | Buyer confirms bar-method applicability and indication disposition |
| Downstream component | Forging or machining, treatment, surface operations, final NDT, geometry, assembly, and validation plan | Records purchased under the downstream scope | Component owner retains finished-part acceptance |
Freeze the supply boundary, specimen representation, NDT applicability, downstream controls, and approval owners in the reviewed drawing package. Only accepted order terms define the requirements for a specific supply.
Control specimen representation and UT applicability
For tensile and Charpy testing, state specimen geometry, orientation, radial and longitudinal location, represented section, material state, treatment-lot link, frequency, and retest disposition. ISO 6892-1 and ISO 148-1 are test methods; they do not select component values or prove performance. A separately prepared coupon or near-surface specimen should represent production material only when the accepted product route and sampling schedule authorize it.
Worked RFQ example for a bounded bar supply
This example keeps bar conformity distinct from downstream component qualification. Expand the scope only when those operations are purchased.
Any alternative material or inspection route should show technical, cost, and schedule effects before written approval.
Item: Alloy-steel bars for [crankshaft or connecting-rod drawing and revision], [size and quantity]
Supply boundary: [bar or prepared blank]; downstream forging, machining, treatment, surface processing, final NDT, and validation by [party]
Material: [grade] to [product standard and edition], [section, condition, and surface]; alternatives quoted separately
Mechanical evidence: Approved tensile and Charpy requirements with methods, specimens, orientations, locations, temperature, represented lot, and retest
UT: Bar examination only to the applicable approved procedure, with state, coverage, reference basis, acceptance, end zones, personnel, and report fields
Documents: Actual results and heat-to-process-lot-to-bar map, deviations, subcontract reports, and inspection index
Approval and release: Written acceptance of alternatives and closure of the named hold point before dispatch
Only accepted order terms define the requirements for a specific supply.Steel bar RFQ review for crankshaft and connecting rod routes buyer questions
What should a crankshaft steel bar RFQ include?
A crankshaft steel bar RFQ should include part route, controlling grade standard, diameter, length, rough and final sizes, delivery condition, heat-treatment expectation, drawing revision, inspection scope, certificate requirement, quantity, packing, and destination.
Which steel grades are often reviewed for heavy-duty rotating parts?
Buyers often review alloy steel routes such as 42CrMo4 / 4140, 42CrMo, and 34CrNiMo6 / 4340 depending on section size, toughness, fatigue, heat treatment, and inspection requirements.
Why should drawing and inspection details be sent with the inquiry?
Drawing and inspection details help align rough size, machining allowance, heat-treatment condition, UT or mechanical testing, certificate scope, and shipment documents before the supplier prepares a quotation.
Steel bar RFQ review for crankshaft and connecting rod routes RFQ checklist
- Part route such as crankshaft, connecting rod, eccentric shaft, heavy shaft, or reciprocating component blank
- Controlling grade standard and acceptable equivalent-grade wording if alternatives are allowed
- Diameter, length, rough bar size, final drawing size, machining allowance, and section-size concerns
- Delivery condition, heat-treatment route, hardness target, or mechanical property requirement
- Fatigue, toughness, impact, internal soundness, or load-bearing requirement if specified
- Drawing revision, controlled dimensions, special notes, and document hierarchy
- Inspection scope such as UT, hardness, mechanical testing, MTC, heat number, and third-party witness
- Packing, marking, traceability, destination, and shipment document requirements
- Component drawing revision, critical sections, duty concern, and supplied boundary
- Grade, product standard, edition, section, delivered condition, and surface route
- Forging, machining, treatment, surface work, NDT, assembly, and validation owners
- Tensile and impact methods, specimens, locations, orientation, temperature, lot, and retest
- UT applicability, state, coverage, reference basis, acceptance, personnel, and reports
- Alternative approval, heat and process-lot traceability, deviations, dossier, and release
References
- ISO 683-2:2016 Alloy steels for quenching and tempering
Supports: Provides official product, condition, and size-bounded delivery context for covered alloy steels used in bar routes.
Limitation: It does not qualify a crankshaft or connecting rod, predict fatigue life, or validate downstream forging, machining, and treatment.
- ISO 6892-1:2019 Metallic materials — Tensile testing at room temperature
Supports: Defines the room-temperature tensile-test method used when an accepted product or project route requires tensile evidence.
Limitation: The method does not select values, specimen representation, lot frequency, retest, or finished-component acceptance.
- ISO 148-1:2016 Metallic materials — Charpy pendulum impact test
Supports: Defines the Charpy pendulum impact method used when the approved bar route requires toughness-related test evidence.
Limitation: The method does not select temperature, specimen, location, values, averaging, lot frequency, or component performance.
- BS EN 10308:2002 Ultrasonic testing of steel bars
Supports: Provides official standards-body scope for ultrasonic examination of steel bars and agreement on certain technique choices.
Limitation: It does not define order-specific coverage, acceptance, finished-forging applicability, personnel, report fields, or component suitability.
Revision note: Expanded the RFQ review into a stage-bounded bar evidence plan, including mechanical-test representation, UT applicability, a decision table, two context figures, and a worked component-route example.
Inquiry support
Send part route, grade, condition, inspection needs, and destination.
JOTAIN can review the stated grade, size, delivery condition, processing route, inspection requirements, and export details against the project requirement.