Guide for Purchasing Copper Tubes for Continuous Casting Mould

The core replacement standard is “prevention first, condition priority.” Purchasers should know two types of standards: planned replacement (Ni-Co-Cu copper tubes last about 5,000–10,000 tons of steel, or 120–150 hours) and condition-based mandatory replacement (taper >1.2% or negative taper, corner radius >1.5–2 times design value, scratches >0.5–1.0 mm, hot cracks >10% of wall thickness, coating peeling >10 cm², or any water leakage).

Purchasers should judge comprehensively using over-steel volume data, precise measurement, surface condition and production performance. Even if the over-steel volume does not reach the upper limit, replace the copper tube once condition data exceeds the standard.

We recommend putting these indicators into the purchasing technical agreement, arrival acceptance specifications and quality claim clauses, and establishing a safety stock and supplier evaluation mechanism to control costs, ensure production and prevent leakage steel.

Key words: continuous casting billet crystallizer copper tube, copper tube replacement standard, copper tube purchasing, over-steel volume life, cone angle standard, corner radius wear, coating peeling, leakage warning, purchasing acceptance specifications

Guide for Purchasing Copper Tubes for Continuous Casting Slab Mold: How to Scientifically Set Replacement Standards, Control Costs, and Ensure Production

From a procurement perspective, transform the question of “when to replace” into a decision-making basis of “when to buy, how much to buy, and how to inspect”.

I. Core Pain Points for Purchasers

Copper tubes are replaced too early, resulting in waste; replaced too late, leading to accidents.

In continuous casting production, the crystallizer copper tubes are one of the core spare parts with the fastest consumption and the highest unit price. The purchasing department often faces a dilemma:

Replacing too early: The copper tubes still have remaining lifespan, and the procurement cost increases unnecessarily.

Replacing too late: The pulling resistance increases, the risk of leakage steel rises, and batch occurrences of longitudinal cracks at the corner of the cast slab occur, and the shutdown losses are far higher than the value of the copper tubes themselves.

Therefore, what purchasers need is not a “technical parameter table”, but a set of executable, verifiable, and negotiable replacement standards, converting technical language into procurement decision language.

The “planned replacement” data that purchasers must master

Used to determine the purchase quantity and inventory

Planned replacement is the basis for procurement budget and inventory management. The following are the reference life indicators that should be clearly specified in the purchasing contract:

Procurement Suggestions: In the supplier contract, require the provision of a life calculation report based on the factory’s operating conditions, rather than general sample data. Also, agree on a quality accountability clause stating that “the product is considered invalid if the steel content does not reach the lower limit.”

Mandatory Replacement Criteria for Condition

Technical Basis for Procurement Inspection and Claims

Mandatory replacement based on condition is the red line of “must be replaced immediately”. The purchaser should incorporate these criteria into the inspection and quality objection clauses of the goods receipt specifications to avoid suppliers using the “already used” excuse to shirk responsibility.

Excessive wear of inner cavity dimensions (detected during arrival or use)

Taper change: Normal taper is 0.4% to 0.9%; over 1.2% or negative taper must be replaced.

Corner radius wear: You should replace the copper tube when the corner radius exceeds the design value by 1.5 to 2 times (e.g., if the design is R8mm and the actual measurement is R12 to 16mm).

Procurement Action: Require the supplier to provide a taper inspection report; the factory conducts random inspections using taper gauges or three-dimensional scanners. Non-conforming products should be returned or claimed.

Surface damage and defects (key point during unpacking inspection)

Severe scratches/grooves: Longitudinal scratches with an inner wall depth >0.5 to 1.0mm – rejected or downgraded for use.

Thermal cracks (cracking): You must replace the copper tube when cracks are deeper than 10% of the wall thickness or visible to the naked eye.

Chromium/nickel-based alloy copper tube coating peeling: Large-scale (e.g., >10cm²) peeling or wearing away of the coating exposing the copper – immediate replacement.

Procurement Action: Write these quantitative indicators into the procurement technical agreement as hard evidence for inspection and claims.

Water Cooling System Related

Severe water seam scaling: Blockage of more than 10% and poor condition after cleaning – consider replacement.

Copper tube leakage/infiltration: Any perforation, cracking, or leakage – strictly prohibit from going online and directly scrap.

Procurement Action: Require the supplier to ensure the smoothness of water seams and uniformity of wall thickness; conduct water pressure tests upon arrival.

Production Performance and Quality Correlation Standards (Feedback during use)

When the following abnormalities occur and other factors are ruled out, the copper tube should be checked and considered for replacement:

• Increasing resistance during drawing (higher current/hydraulic pressure).
• Frequent warning of leakage (increased abnormal alarms of adhesion, cracking).
• Continuous increase in the incidence and severity of longitudinal cracks at the corner of the casting billet.
• Disordered surface wave marks, too deep.
• Increased misshaping defect.

Uneven billet shell thickness, abnormal fluctuations of the thickness measuring instrument.

Procurement Action: Establish a “copper tube usage performance ledger”, link these abnormalities with the supplier’s product quality, and use it as the basis for annual supplier evaluation and negotiation.

Procurement Decision Process Suggestions

Transform Technical Standards into Procurement Systems

Regular measurement: The purchasing team must measure the taper and corner radius offline every certain number of castings or cycles, and archive the data to predict the timing of procurement.

Online monitoring: Drawing current, vibration current, leakage warning, surface quality of the casting billet – trigger inspection upon any anomaly.

Abnormal response: Check production performance or monitoring anomalies, immediately arrange offline inspection, and notify procurement to prepare spare parts simultaneously.

Comprehensive judgment: Overhead steel content + measurement data + surface condition + production performance. Even if the over-steel volume does not reach the upper limit, the purchasing team must replace the copper tube once the status data exceeds the limit.

Procurement System Suggestions:

Agree with the supplier on a joint confirmation mechanism for “exceeding condition standards requires replacement”;

Establish safety stock: Prepare based on the longest delivery period + the amount for one replacement cycle;

For copper tubes from three consecutive hot replacements, mandatory offline inspection, and procurement to simultaneously initiate the next batch of orders.

Conclusion

Prevention first, priority given to condition – Procurement is not about “buying cheap”, but about “buying at the right time”

For purchasers, the copper tube replacement standards are essentially a tool for balancing costs and risks:

Use planned standards for budgeting and inventory;

Use status-based standards for acceptance and claims;

Use production performance for supplier evaluation and negotiation.

Remember this one sentence: Do not simply rely on the quantity of steel; you must combine it with precise measurement and the actual production status. You must replace the copper tubes in time before their performance deteriorates to the point where it can cause accidents or batch quality defects — this is how you truly reduce costs and improve efficiency.

E-mail: cykc@cykcgroup.com.cn