Principles of Metal Casting Starter Cards

If sand in the PUNB (Phenolic Urethane No-Bake) process has high ADV (Acid Demand Value), what are the effects?

Alkaline sand speeds up the reaction → shorter work and strip time.

If sand in the PUNB (Phenolic Urethane No-Bake) process has low ADV (Acid Demand Value), meaning acidic sand, what are the effects?

The reaction slows → longer work and strip time.

If sand in the FNB (Furan No-Bake) process has high ADV (Acid Demand Value), what are the effects?

The alkaline sand neutralizes the acid catalyst before curing → slow or incomplete cure and lower strength. Catalyst must be adjusted; monitor ADV.

If sand in the PUCB (Phenolic Urethane Cold Box) process has high ADV (Acid Demand Value), what are the effects?

Bench life of the coated sand gets shorter; tensile strength drops off quickly with bench time.

If moisture rises in FNB (Furan No-Bake) sand, what happens?

Water dilutes the acid catalyst and slows the cure rate.

If moisture rises in PUNB (Phenolic Urethane No-Bake) or PUCB (Phenolic Urethane Cold Box) sand, what happens?

Water reacts with Part II (isocyanate) to form a crystalline substance → less binder for bonding, lower strength, shorter bench life.

How does high humidity affect the FNB (Furan No-Bake) process?

Slows evaporation of the water given off by the cure, slowing the cure.

If PUNB (Phenolic Urethane No-Bake) sand drops from 70 °F to 52 °F, what happens?

Reaction speed roughly halves (10 °C / 18 °F rule) and resin viscosity rises → longer work/strip time, poorer coating, lower strength.

If PUNB (Phenolic Urethane No-Bake) sand rises from 70 °F to 88 °F, what happens to strip time?

Roughly halves (reaction about twice as fast).

Why is it better to control sand temperature than catalyst in the FNB (Furan No-Bake) process?

Sand temperature is easier to control than catalyst level.

If a PUNB (Phenolic Urethane No-Bake) line switches to a finer sand with more than 1% on the 140 screen, what happens?

More surface area → more binder needed; lower permeability → more gas defects. Extra binder adds Part II nitrogen and carbon → more pinholes and lustrous carbon in iron.

Why does round-grain sand help the FNB (Furan No-Bake) process, and what is the risk?

Coats better, more uniform properties, higher compaction density. Risk: veining defects.

Why do angular grains need more binder than rounded grains?

Angular grains have more surface area to coat.

How does silica expansion cause defects in resin-bonded cores?

Silica's sudden quartz-inversion expansion near 1063 °F cracks the mold surface → veining (also buckles, rat tails).

What sand additive fights veining in PUCB (Phenolic Urethane Cold Box) cores, and how much?

Clay or iron oxide, 1–2%.

What sand additive fights expansion and metal penetration in PUCB (Phenolic Urethane Cold Box) cores, and how much?

Gypsum-based additive, 5–10%.

What three factors limit bench life in the PUCB (Phenolic Urethane Cold Box) process?

Sand temperature, ADV, and moisture content (blown air and dew point).

How does sand segregation hurt resin-bonded processes?

It upsets binder coating and core blowing because grain size and shape are no longer uniform.

How does hot sand affect green sand vs some resin systems?

Green sand: rapid moisture loss, properties degrade. Some resins: interferes with the bonding mechanism.

How is furan resin graded?

By nitrogen (0–11%) and water (0–30%) content; lower = higher grade.

What are the effects of more furfuryl alcohol in furan resin?

Better environmental, casting and process performance, but higher cost.

What are the three functions of the acid catalyst in the FNB (Furan No-Bake) process?

1) Neutralize alkaline contaminants 2) Initiate cross-linking 3) Sustain the condensation cure.

In which direction does the furan condensation cure progress?

From the outside inward (a slow cure).

Why use a concentrated acid catalyst in the FNB (Furan No-Bake) process?

To optimize cure rate and get 'deep-set' properties.

List the FNB (Furan No-Bake) acid catalysts from least to most reactive.

75% phosphoric, 85% phosphoric, toluene sulfonic, xylene sulfonic, benzene sulfonic.

Why is resin added slowly in the FNB (Furan No-Bake) process?

Concentrated areas of resin create a rapid, uneven cure.

What is the resin level in the FNB (Furan No-Bake) process (BOS)?

0.9–2.0% based on sand weight.

What is the catalyst level in the FNB (Furan No-Bake) process (BOR)?

30–50% based on resin weight.

What is FNB (Furan No-Bake) work time as a percent of strip time?

50–60%.

What percent of FNB (Furan No-Bake) properties are developed in three hours?

70–90%.

When should a refractory coating be applied to an FNB (Furan No-Bake) mold?

Only after deep-set properties have developed; earlier gives incomplete cure.

Which sands work for most FNB (Furan No-Bake) applications?

Most silica, zircon and chromite.

Which two sands can neutralize FNB (Furan No-Bake) catalyst?

Some silica sands and olivine (high ADV).

What indicates that FNB (Furan No-Bake) sand is curing?

A color change.

What are the advantages of the FNB (Furan No-Bake) process?

Lower smoke and odor, wider binder ranges, color change shows cure, excellent flowability, made from agricultural by-products.

What are the disadvantages of the FNB (Furan No-Bake) process?

Nitrogen and sulfur residues, raw material shortages, acidic grain surface, mechanical reclamation only.

Besides no-bake, what other method can make furan cores?

Warm box.

In the ester-cured alkaline phenolic process, what replaces hydrogen in the alcohol radical?

Sodium or potassium.

What are the resin and co-reactant levels for ester-cured alkaline phenolic?

Resin 1.0–1.5% BOS; ester 20–25% BOR.

What are the advantages of ester-cured alkaline phenolic?

Lower smoke and odor, easy stripping, good finish, low veining, minimal erosion, excellent hot strength, water-based resin.

What are the disadvantages of ester-cured alkaline phenolic?

High resin viscosity, poor flowability and compaction, low mold/core strength, limited storage life, poor reclamation, shakeout problems.

Shell hot coat: at what temperature is the resin added?

320 °F.

Shell hot coat: at what temperature are quench water and hexa added?

275 °F.

Shell hot coat: at what temperature does the sand 'break'?

200 °F.

Shell hot coat: at what temperature is the sand aerated and discharged?

160 °F.

When curing shell resin coated sand, what happens in Phase 1?

Thermoplastic: heat and melt (melt viscosity drops).

When curing shell resin coated sand, what happens in Phase 2?

Transitional: flow and cure; gel begins to harden.

When curing shell resin coated sand, what happens in Phase 3?

Thermoset: fused solid, postcure.

What happens if shell resin is overheated?

Overbake: the resin decomposes.

What are the five steps of the Shell (Croning) process?

1) Dump/blow coated sand into heated box 2) Build shell thickness 3) Rotate to drain unreacted sand 4) Dwell to cure through 5) Strip or eject.

What shell thickness is typical in the Shell (Croning) process?

1/8 to 1/2 inch.

What is the die temperature range for the Shell (Croning) process?

450–525 °F.

How is uniform die temperature achieved in the Shell (Croning) process?

Strategically positioned gas burners.

Which shell additive is used for magnesium castings?

Potassium fluoroborate.

Which shell additive eliminates orange peel on steel castings?

Kaolinite clay (also improves hot strength and provides chill).

What does iron oxide do as a shell resin additive?

Reduces thermal cracking, provides chill, minimizes gas defects.

What do plasticizers do as a shell resin additive?

Reduce thermal cracking.

What is Part I of the PUNB (Phenolic Urethane No-Bake) binder?

Phenolic polyol dissolved in organic solvents.

What is Part II of the PUNB (Phenolic Urethane No-Bake) binder?

Polymeric MDI-type isocyanate dissolved in solvent.

What is Part III of the PUNB (Phenolic Urethane No-Bake) binder?

Amine-type catalyst.

Is the PUNB (Phenolic Urethane No-Bake) catalyst consumed in the reaction?

No. It initiates the reaction and is not consumed.

What is the typical PUNB (Phenolic Urethane No-Bake) binder level?

0.8–1.75%.

What is the typical PUNB (Phenolic Urethane No-Bake) catalyst level?

2–9%, depending on the catalyst and the desired work/strip time.

Where do VOCs (Volatile Organic Compounds) come from in the PUNB (Phenolic Urethane No-Bake) process?

The catalyst and the solvents.

Which part of the PU (Phenolic Urethane) binder contains all the nitrogen?

Part II (isocyanate). It also has more carbon than Part I.

Why do foundries run PU (Phenolic Urethane) binder at 55:45 instead of 50:50?

Part II carries all the nitrogen and more carbon, which cause nitrogen pinholes in iron and lustrous carbon defects. Favoring Part I reduces them.

What is the trade-off of running PU (Phenolic Urethane) binder at 55:45?

Lower ultimate strength.

What happens if PUNB (Phenolic Urethane No-Bake) catalyst is not distributed evenly?

Hot spots and soft areas.

In batch PUNB (Phenolic Urethane No-Bake) production, when is the catalyst added?

After mixing with Parts I and II, or blended into Part II.

What forms when water reacts with PU (Phenolic Urethane) Part II?

A diisocyanate crystalline substance.

What are three ways to address humidity in the PUNB (Phenolic Urethane No-Bake) process?

Heat the sand, warm or dry the pattern, put a drier on Part II.

Should you paint a pattern used for PUNB (Phenolic Urethane No-Bake) molds?

No. Use organic-based release agents, spray and wipe down, and clean tooling periodically.

What red iron oxide addition is used in PUNB (Phenolic Urethane No-Bake), and how much?

Hematite, 0.25–3%.

What black iron oxide addition is used in PUNB (Phenolic Urethane No-Bake), and how much?

Magnetite, 1–6%.

Why do iron oxide additions in PUNB (Phenolic Urethane No-Bake) require more binder?

They add surface area.

What casting improvements do PUNB (Phenolic Urethane No-Bake) defect-prevention additives give?

Minimize gas defects, control sand expansion defects, improve surface finish.

What are the three levels of no-bake systems?

Simple no-bake loop, semi-automated loop, fully automated high-speed line.

Strip and Work Time chart: what does a high-speed PUNB (Phenolic Urethane No-Bake) catalyst do?

Moves both work time and strip time earlier.

Effect of Temperature chart (1.25% PU (Phenolic Urethane)): at what sand temperature is tensile strength highest?

Around 80–100 °F.

Effect of Temperature chart (1.25% PU (Phenolic Urethane)): what happens to tensile at 50 °F and at 130 °F?

Both are low (~75 psi): too cold = slow and viscous; too hot = reaction too fast.

What happens during the PUCB (Phenolic Urethane Cold Box) blow cycle?

Coated sand is blown with dry air into the core box.

What happens during the PUCB (Phenolic Urethane Cold Box) gassing cycle?

Tertiary amine gas is introduced; exhaust ports and vents let it pass through.

What happens during the PUCB (Phenolic Urethane Cold Box) purging cycle?

Dry air flushes the core to distribute and complete the cure and remove the amine gas.

What is the PUCB (Phenolic Urethane Cold Box) sand blow pressure?

35–65 psi.

What are the PUCB (Phenolic Urethane Cold Box) gas and purge pressures?

Amine gas at low pressure, 5–20 psi; dry-air purge at high pressure, 20–60 psi.

Does a longer PUCB (Phenolic Urethane Cold Box) blow cycle increase core density?

No. It causes extra resin wipe-off, parting-line blowout and sticking to the core box.

What is the amine concentration in the PUCB (Phenolic Urethane Cold Box) carrier gas?

6–12%.

What happens with too little or too much amine in the PUCB (Phenolic Urethane Cold Box) process?

Too little → under-cured cores. Too much → higher cost and odor.

What three things does PUCB (Phenolic Urethane Cold Box) amine concentration depend on?

Catalyst type, operating pressure, temperature ranges.

What is the vapor pressure of DMEA (Dimethylethylamine) vs TEA (Triethylamine)?

DMEA 435 mm vs TEA 54 mm (liquid at 20 °C).

How much more carrier gas does TEA (Triethylamine) need than DMEA (Dimethylethylamine)?

7.8 times as much to deliver the same amount of amine.

How should a water-based coating be applied to PUCB (Phenolic Urethane Cold Box) cores?

As soon as possible (it interrupts curing), then dried immediately at 250 °F in a convection oven.

What are six ways to reduce lustrous carbon in PUCB (Phenolic Urethane Cold Box) cores?

Offset ratio to 55:45, lower resin content, higher pour temperature, shorter pour time, venting, 1–3% iron oxide.

What does bio-diesel (dimethyl ester) do in PUCB (Phenolic Urethane Cold Box) resin?

Improves shakeout.

What do PUCB (Phenolic Urethane Cold Box) resin additives improve?

Casting properties, release, moisture resistance, bench life, and lower VOCs.

High Alkaline Impurities chart: rank low ADV (Acid Demand Value), lake sand and high ADV by bench life.

Low ADV holds strength longest, lake sand in between, high ADV loses strength fastest (~1.5 h).

Effect of Moisture on Bench Life chart: how long is bench life at 0–1% vs 5% moisture?

About 2 hours at 0–1%; about 0.3 hours at 5% (30% tensile loss criterion).

What are the causes of process variation in resin-bonded sands?

Sand type, segregation, transport, temperature (patterns, reaction rate, resin blending), sticking, cycle times, moisture, humidity, sand additives, refractory coating (high moisture).

What does a good molding aggregate need? (list)

Thermal/dimensional stability, suitable size and shape, chemically stable and non-wetting with metal, economical, doesn't degrade in volatile gases, uniform and pure, right chemistry, compatible with binder.

Why do fine grains need disproportionately more binder?

Their surface area is about 20× greater than coarse grains.