Casting Process Reconciliation: Melt Loss, Rejection and Auto-Component Material Accounting

An aluminium HPDC supplier in the Toyota Kirloskar (TKM) supplier cluster near Bidadi runs four 800-tonne HPDC machines producing transmission housings for the TKM Innova Hycross and Camry programs. The shop floor is built around two melting furnaces (one electric, one gas-fired) running A380 and A413 alloys, four HPDC machines with cycle times of 75-95 seconds, trim presses, shot-blast lines and machining cells for the housing’s mating-face and bore. Ingot arrives from Hindalco and Vedanta on the supplier’s own purchase ledger — typically 95 metric tonnes a month — with LME-linked RMPV against TKM monthly. Around 38 percent of the metal poured into the dies returns to the furnace as gates, runners and rejects, recycled in-house. By the end of the month, the reconciliation must close the metal balance per furnace, account for around 3.2 tonnes of dross skim, raise the LME-linked RMPV claim, post die-amortisation on three HPDC die sets, and reconcile the conversion-charge billing through the correct Section 393(1)(a) payment-code lineage. This is casting melt loss rejection reconciliation auto component India — closed-loop metal accounting where the structural losses are recycled but the energy and time cost is not.

Quick reference

What does the casting shop actually do?

A modern auto-component casting line is a six-stage operation:

1. Charging — virgin aluminium ingot (LM2, LM6, LM24, A380 or A413 grade) plus return-melt scrap (gates, runners, rejects) is fed into the melting furnace. The charge ratio is typically 60-70% virgin ingot and 30-40% return-melt at steady state.
2. Melting — the charge is melted in an electric resistance, electric induction or gas-fired reverberatory furnace at around 700 degrees Celsius for aluminium. Cast-iron and copper-alloy castings use higher temperatures (1,200-1,500 degrees) but the structural process is identical.
3. Holding and degassing — the melt is transferred to a holding furnace and refined by argon or nitrogen lancing to remove dissolved hydrogen and floated oxide. Grain refiner and modifier are added. This stage is the slowest in setting metal quality.
4. Pouring — for HPDC, the metal is ladled into the shot sleeve and injected into the die at high pressure (40-100 MPa). For GDC, the metal is gravity-poured into a permanent-mould die. For sand casting, the metal is gravity-poured into a sand mould that is destroyed after each pour. Each technology has different cycle times, die costs, finish quality and yield profiles.
5. Trimming — the casting is removed from the die, gates and runners are sheared off in a trim press, drops fall into a return-melt bin.
6. Finishing and machining — shot blast removes surface oxide, fettling removes parting-line flash, and machining cells finish mating faces, bores and threaded features. Machining swarf is collected separately because it can be sold externally if not contaminated with cutting fluid.

The metal balance closes:

Ingot purchased + return-melt charged − (good casting weight × good piece count + dross skimmed + finishing fines + permitted process loss) = closing molten + closing return-melt stock − opening molten − opening return-melt stock

Over a month, the return-melt cycle is in approximate balance — what is generated this month as trim and rejects roughly equals what is charged from the return-melt stock — so the period equation simplifies to: virgin ingot consumption equals good casting weight plus dross plus finishing fines plus permitted process loss.

Why melt loss is 2 to 4 percent and structural

Aluminium reacts strongly with oxygen at melt temperature. The surface of the molten bath in the furnace continuously forms an aluminium-oxide skin that floats up trapping liquid aluminium underneath as a dross layer. The dross has to be skimmed periodically — typically every 30-90 minutes on a steady-state melting furnace — and disposed.

The dross layer carries:

• Aluminium oxide (the actual oxidation product) — useful only as scrap-grade dross.
• Liquid aluminium trapped beneath the oxide film — economically recoverable through external dross-processing.
• Salt flux residues (where used) — process additives that promote dross separation.

Even at mature aluminium foundries with covered furnaces, controlled flux additions, minimal turbulence and gentle furnace agitation, dross loss runs 2-4% of charged metal. The variation depends on:

• Charge ratio (more return-melt with high surface area drives more dross).
• Furnace technology (induction is cleaner than gas-fired).
• Holding time (longer holding drives more dross).
• Alloy (magnesium-rich grades oxidise faster).

Dross is sold externally to a specialised dross-processor who recovers the trapped aluminium and returns ingot or pays cash. The supplier is the legal seller — Section 394 TCS code 1071 at 1% of the gross sale value applies, collected from the dross-processor at debit or receipt, whichever is earlier.

Rejection rate and the return-melt cycle

Casting rejection is structural at typical bands:

Defects include porosity (hydrogen or shrinkage), cold-shut, mis-run, sink marks, dimensional deviation, surface roughness, and (for housings) pressure-test leak failure. Reject castings are not separately written off — they go back into the next furnace charge as return-melt and the metal value is recovered.

The real cost of rejection is the conversion cost of the rejected pieces: the energy, die-cycle time, machine occupation, labour and die wear consumed in producing a piece that becomes return-melt. If rejection ages above the contracted norm, the supplier’s per-good-piece conversion cost rises proportionally. The reconciliation must:

• Track the rejection rate per shift per die against contracted norm.
• Surface aging above norm as a conversion-cost erosion signal.
• Drive root-cause analysis (die maintenance, holding time, melt chemistry, machine condition).
• Tie the return-melt cycle into the metal balance so the period closing makes sense.

LME-linked RMPV on aluminium ingot

Auto-grade aluminium ingot is benchmarked against the London Metal Exchange aluminium price plus a regional premium and grade-specific alloy adjustment. Indian auto-component contracts typically reference:

• The LME aluminium 3-month closing on a specified day of the prior month (often the last business day).
• Plus the published Indian premium for the month, capturing freight, regional supply-demand and importer margin.
• Plus a grade-specific alloy adjustment — A380 carries higher silicon and copper than LM6; the alloy adjustment captures the alloying-element cost differential against pure aluminium.

The RMPV claim is calculated as:

RMPV claim = (Contractual reference price − Actual landed ingot cost) × Consumed tonnage at contracted yield

Aluminium price has high volatility — LME swings of 10-25 percent inside a year are routine — and a robust RMPV mechanism is essential. The mechanics are covered in RMPV calculation formula for auto components. Where the supplier sells the finished casting as a goods sale (rather than as a job-work conversion service), the RMPV is built into the finished-casting price rather than invoiced separately, but the same index reference applies.

Ind AS 16 die capitalisation and the cycle counter

A casting die is a tool-steel block, machined to the inverted geometry of the part, hardened, and operating under high cyclic thermal and pressure stress. HPDC die life is dominated by:

• Aluminium operating temperature (around 700°C molten injected at 40-100 MPa).
• Thermal cycling (the die heats and cools every shot).
• Part complexity (sharp features, thin walls, undercuts shorten life).
• Casting alloy (more aggressive alloys, like copper-rich A380, wear faster than silicon-rich LM6).

Typical HPDC die life:

Under Ind AS 16, the die is capitalised at fabrication cost and depreciated over expected die-cycle life. Depreciation per cycle = die capital cost ÷ expected cycle life; cumulative depreciation flows into the conversion-rate build-up. The discipline mirrors the forging die and the injection-mould amortisation — covered together in tooling cost recovery and amortisation in auto components.

TDS payment code: 393(1)(a) versus 194Q

Two structurally different commercial arrangements drive different TDS treatments:

• Conversion-service billing on free-issue or principal-supplied ingot. The supplier is rendering a job-work service under Section 143 / Schedule II — the casting is the OEM’s. The conversion charge is the supplier’s revenue, GST at 18% under HSN 9988. The OEM’s TDS deduction on payment to the supplier falls under Section 393(1)(a) of the Income Tax Act 2025 with payment code 1002 (the new payment-code rail operative 1 April 2026 onwards, replacing legacy Section 194C section-code lineage). Rate: 1% individual / HUF, 2% other entity, on the conversion charge net of GST. Captured in Form 26Q quarterly, Form 16A issued to the supplier, credit flows through Form 26AS.

• Casting sold as a finished good. The supplier owns the ingot, sells the finished casting as a goods supply at the relevant chapter-76 GST rate (typically 18%). The OEM’s TDS deduction on payment for the goods purchase falls under Section 194Q (purchase-side TDS at 0.1% on annual purchase from a single seller above ₹50 lakh). Different code series, different TRACES section, different reconciliation against Form 26AS.

The supplier’s reconciliation must keep the two streams on separate payment-code maps because they hit different lines on Form 26AS for the OEM, and a misclassification can produce TDS short-deduction notices on the supplier-side or excess-deduction credit-mismatch on the OEM-side. The new payment-code rail and cross-era treatment is in the TDS 2026 migration cluster.

Worked example — Toyota Kirloskar HPDC supplier, 95 MT/month aluminium

The Bidadi HPDC Tier-1 introduced at the top runs the following monthly profile for Toyota Kirloskar:

• Virgin aluminium ingot purchased: 95 MT (60 MT A380 for housings, 35 MT A413 for smaller cast assemblies), supplier-owned, on supplier purchase ledger.
• Return-melt charged: 36 MT (trim, runners and rejects from the month and from prior carry).
• Total furnace charge: 131 MT.
• HPDC die mix: four dies in production, three at mature cycle life, one in ramp-up with elevated rejection.
• Rejection norms: contracted 4.5% on mature dies, 7.0% on ramp-up die.

Metal balance

The metal balance closes inside the contracted melt-loss band (3.2 of 131 = 2.4%, within the 2-4% norm). The return-melt cycle accumulates 42.1 MT generated against 36.0 MT consumed — net 6.1 MT increase in return-melt stock, carried into next month.

Conversion invoice and TDS

The conversion invoice — only on the portion of production that is contractually structured as conversion service on TKM-supplied or pre-nominated ingot — runs at the contracted HPDC rate per kilogram of good casting. For the substantial finished-goods-sale portion (the bulk of TKM business), the supplier raises a goods invoice for finished housings at the contracted finished-piece price including embedded ingot value. The mixed-stream TDS treatment:

• Conversion-service stream: Section 393(1)(a) code 1002, deducted at 2% on conversion charge net of GST.
• Finished-goods sale stream: Section 194Q, deducted at 0.1% on annual purchase above ₹50 lakh.

LME-linked RMPV

LME aluminium 3-month closing on the last business day of May 2026 (the contractual reference for June): USD 2,460/MT. India premium for June: USD 215/MT. A380 alloy adjustment: USD 380/MT. Contractual reference USD 3,055/MT converted at the contracted INR-USD rate. Actual landed cost: ₹275/kg blended (A380 and A413). Differential moved in the supplier’s favour — RMPV claim raised on consumed tonnage of 95 MT against the contracted band, approximately ₹6.8 lakh.

Die amortisation and external scrap

Die amortisation under Ind AS 16: three mature dies and one ramp-up die, cycles run aggregated to 41,200 for the month, blended depreciation rate ₹18.50 per cycle, ₹7.62 lakh into conversion-cost build-up.

External scrap: 3.2 MT dross sold to a Bangalore-region dross-processor at ₹52,000/MT = ₹16.64 lakh. Section 394 TCS code 1071 at 1% = ₹16,640 collected from the processor and remitted on the next monthly challan. Finishing fines sold at scrap-grade aluminium price to a separate dealer — separate TCS lineage.

How casting reconciliation ties into the wider auto stack

Casting reconciliation is one rail inside automotive component manufacturing reconciliation. The LME-linked RMPV machinery is in RMPV calculation formula. The die-amortisation discipline is set out in tooling cost recovery and amortisation. The Section 394 TCS rail on dross and swarf is in Section 394 TCS scrap sale. For the ACMA framework on casting yield norms, melt-loss benchmarks and rejection-rate bands see the Automotive Component Manufacturers Association of India (ACMA).

What automated reconciliation changes

Manual casting reconciliation across multiple furnaces, four dies, three alloy grades and a return-melt cycle is a metal-balance discipline that breaks under volume — and where rejection drift, melt-loss creep and LME-RMPV miscalculation typically only surface at the quarterly review. Purpose-built auto-component reconciliation software India closes the metal balance per furnace per month, tracks rejection rate per shift per die against contracted norm, runs the LME-linked RMPV claim engine with reference-day publication tracking, posts die-amortisation under Ind AS 16 with cycle-counter alerts, maps conversion-service Section 393(1)(a) code 1002 versus finished-goods-sale Section 194Q on the right payment-code series, and ties dross and swarf external sales to the Section 394 TCS code 1071 register. TransactIG carries 24+ industry presets including casting shop-floor configurations for return-melt accounting, rejection-norm tracking, LME-linked RMPV and die-cycle amortisation. Customer outcomes include match-rate improvement from 51% to 88%. Build is two-to-four weeks on AWS Mumbai (ISO 27001:2022). For the inbound match discipline across ingot GRN, conversion invoice and dross-sale settlement see three-way matching software India.

Continue reading in the automotive components cluster

• Automotive component manufacturing reconciliation in India (sub-pillar)
• RMPV calculation formula for auto components
• Tooling cost recovery and amortisation in auto components
• Section 394 TCS on scrap sale (payment code 1071)
• Section 143 deemed supply for auto components