Casting – Advantages, Disadvantages and Product Classification

By Nico Yin · Qingdao Zhaoyuqi Machinery Co., Ltd.

Casting is the shortest route from a drawing to a complex metal shape: a molten alloy fills a cavity, takes its form, and comes out as a part that needs little or no machining. That is why castings still carry 40–70% of the weight in agricultural machinery and 70–80% in machine tools, decades after forging, stamping and additive manufacturing started competing for the same parts. This page sets out where casting wins, where it does not, and how the main casting families are classified.

Advantages of Casting

1. Complex shapes with internal cavities. A sand core can leave a water jacket, oil gallery or valve passage that would otherwise need three separate parts welded or bolted together.

2. Wide material range. Grey iron, ductile iron, malleable iron, carbon and low-alloy steel, stainless steel, aluminium and copper alloys can all be cast. Part weight runs from a few grams to several hundred tonnes; our own foundry covers 0.5–200 kg per piece.

3. Low raw material cost. Returns, process scrap and machining swarf go straight back into the melt, so the charge cost stays well below wrought bar stock.

4. Near-net shape. Sand casting holds ISO 8062 CT8–CT10 on typical dimensions, which leaves 2–5 mm of machining allowance instead of cutting a part out of solid block.

5. Established supply base. Foundries, pattern shops, heat treaters and machine shops already work to the same standards, so a casting programme does not need a new supply chain built from scratch.

Disadvantages — and How They Are Managed

1. Mechanical properties sit below a forging of the same alloy. This is handled by grade selection and heat treatment: a ductile iron to EN-GJS-500-7 reaches 500 MPa tensile with 7% elongation, and normalising or quenching and tempering closes most of the remaining gap.

2. Jobbing sand casting is labour intensive for single pieces and small batches, because every mould is made and broken by hand.

3. Quality is less predictable than in a machining process: many variables act at once, and porosity, shrinkage, sand inclusion or cold shut can appear if the process window is not held.

4. Tooling is needed before the first part. A pattern and core box must be paid for up front, which is why casting economics improve sharply with volume.

Product Classification of Casting

Commonly Used Cast Ferrous Metals

1. Grey cast iron — excellent damping and machinability, used for housings, bases and brake discs.

2. Ductile iron (nodular cast iron) — graphite in nodular form gives strength and elongation close to steel; the standard choice for pipe fittings, brackets and suspension parts.

3. Malleable cast iron — white iron cast, then annealed; still specified for thin-section hardware.

4. Cast steel — carbon, low-alloy and stainless grades for higher strength or corrosion resistance.

Commonly Used Cast Non-Ferrous Metals

1. Brass and bronze — bearings, valves and pump components.

2. Aluminium alloys — weight-sensitive housings and covers, usually die cast or gravity cast.

3. Zinc and magnesium alloys — smaller, high-volume die cast parts.

What Decides Casting Cost and Lead Time

Four variables drive almost every quotation. Pattern and core box cost sets the fixed investment and is amortised over the order quantity; a 100-piece order carries a very different unit price from a 10,000-piece release of the same part. Material grade moves the price through charge cost and melting practice. Part weight and wall section decide which process fits — thin walls favour shell mould or investment casting, heavy sections favour sand. Finally, machining allowance, heat treatment and inspection level add cost only where the drawing actually calls for them.

Controlling the Defects That Matter

Most rejections in iron castings come from four causes: shrinkage porosity where feeding was insufficient, gas porosity from damp sand or high pouring temperature, sand inclusion from a weak mould surface, and dimensional drift from pattern wear. Each has a known countermeasure — riser and chill design, controlled pouring temperature, better sand compaction, and pattern maintenance on a fixed cycle. We keep the full list of failure modes and their fixes in casting defects and how to prevent them, and the allowance side — shrinkage, draft, machining — in the five pattern allowances.

If you are still deciding between processes, the comparison in green sand casting on an automatic line explains where a DISA line beats jobbing moulding, and ductile iron castings covers the grade and inspection side.

Get a Quote

Send your casting requirement — material grade (EN-GJS-500-7 / ASTM A536 65-45-12), drawing, annual volume and target price — through our RFQ form. A foundry engineer replies within one business day with a quotation, material certificate draft and production lead time.