The latest development in coatings for heavy iron and steel castings

Tim BirchInternational Marketing Manager – Foseco International Ltd

Introduction

Product development for heavy iron and steel castings Fast dry water-based coatings Duplex Coating Single-layer flow coat application

The need for control Automatic control of density Effective mixing and coating homogenisation

Content

Introduction to Total Coatings Management

Identifying the needs of the market

Investment in R&D to fulfil the needs of the foundry customer: Increase capability to produce complex, defect-free castings Improve productivity and reduced re-work Reduce overall costs

Specialised testing equipmente.g Rheometry,

Molten metal facilities,SEM

£4.5 million investment in new Foundry R&D Facility (2014)

Total Coating Management

End-to-end process control

Delivering Quality & Consistency at all process stages…..

…To ensure optimum performance at our Customers.

R&D - Delivering new products for heavy iron and steel castings

• Fast dry water-based coatings• Duplex Coating• Single-layer flow coat application

New Products

New Process TechnologyNew Raw Materials

• Automated control• Improved mixing

Fast Dry Water-Based Coating – Northern Europe Case Study

Drying of Larger Components

For larger sized components the coating is applied by flow application

• Historically alcohol based systems are used and flamed-off for quick drying

• Health and Safety Issues arise

Release of VOC’s into the environment Respiratory issues relating to solvents Restrictions on storage and use of flammable products ATEX or equivalent certification for associated equipment

Solvents – Health, Safety and Environmental Issues

Ref: European Chemical Agency Website

Improved environmental benefits through elimination of solvents Reduced surface cracking of mould due to heat generated in flame-off Reduced burn-out of coating binder

BUT : air drying is significantly longer

Benefits of water-based products

SEMCO FDC - a new range of water-based coatings for flow coating High solids content, with significantly less water to be evaporated off New rheological system allows excellent flow coating at higher solids

Layer build equivalent to a traditional coating (zircon, al-silicate or olivine fillers) Elimination of runs and drips Excellent casting performance

Faster drying water-based products

3 hour (75% solids)

5 hour (65% solids)

Drying time at 25oC (RH=60%)

When used in combination with drying oven fast drying water-based coatings deliver: Improved productivity Reduction in drying energy requirements

SEMCO FDC – improved productivity and energy saving

Oven temperature set to 61oCSEMCO FDCWLT 275 – 300μ

StandardWLT 325 – 350μ

Equivalent dry layer thickness

SEMCO FDC – improved productivity and energy saving

Surface Temperature / Moisture ContentTime in Oven Standard Coating SEMCO FDC0 minutes 25°C / 3.9% 25°C / 3.1%3 minutes 29°C / 3.7% 36°C / 0.7%6 minutes 40°C / 0.8% 48°C / 0.0%9 minutes 46°C / 0.4%12 minutes 48°C / 0.1% DRY

DRYResults50% reduction in drying time50% reduction in energy

SEMCO FDC – improved productivity and energy saving

Duplex Coating – North American Case Study

Duplex Coating System

For the prevention of metal penetration and burn-on Specifically hot spot areas Undercuts where sand compaction is not optimum

Examples of burn-on and severe metal penetration

Duplex Coating System

Prone areas pre-treated with penetration coating Fine zircon flour based coating (water or solvent based) Penetrates into surface of mould (3-5mm) Minimal surface layer build-up Completely fills all voids between sand grains

Mould then coated with traditional coating (water or solvent-based) Flow coated Brushed etc…

If there is a failure of the surface coating layer in critical areas: Mould beneath completely sealed No voids between sand grains for metal to penetrate High refractory material prevents interaction with silica sand

Duplex Coating System

Case Study 1: NORAM – Iron Jobbing Foundry

Significant problem with burn-on and metal penetration on large floor moulds.

Severe metal penetration and burn-on

WithHOLCOTE Z-Primer

(SEMCO 9223)

Clean casting

Note: Top coat is HOLCOTE 950(al-silicate coating)

Case Study 1: NORAM – Iron Jobbing Foundry

Case Study 2: NORAM – Steel Foundry

Problem – significant metal penetration in flange area

Solution – ISOMOL Z-primer (TENO ZKPX)• Brushed in critical areas• Penetration 3-5mm

Top coat - ISOMOL 578-85 (brushed) 2 layers (zircon based coating) Flame Dried between layers

Casting Results Dramatic improvement in casting finish Metal penetration and burn-on eliminated

Converted floor molding coatings to the duplex coating technology

Case Study 2: NORAM – Steel Foundry

Single Layer Flow Coating for Jobbing Foundries

For larger moulds and cores Need to apply multiple coating layers to build-up required layer

thickness (>300um)

Productivity issues arise: Time for multiple applications Availability of crane Time to use crane (multiple times)

Casting quality issues: If done incorrectly the coating layers may de-laminate Brushing leads to inconsistency in layer and brush-marks

Single Layer Flow Coating for Jobbing Foundries

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New rheological system allows for: Thick layer (>700um) to be applied in one application Consistent layer build from top-to-bottom of mould surface No slumping No runs and drips No cracking on drying

Casting performance equivalent to that achieved with multiple-layer application

Single Layer Flow Coating for Jobbing Foundries

2/03/2017 Footnote

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Flow tests

A wide variety of flow characteristics can be obtained by modifying the formulation

Applied wet layer: 1000 μm

Example – dry layer achieved on furan cores

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Dry layer≈ 1050 μm

Dry layer≈ 830 μm

Hexagon Block – Steel Casting

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• Casting weight: ≈ 125 kg• Six different coatings

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Casting Comparison

bottom (ingate) top

R962Single layer thick coating

top layer: ≈ 850 μm

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SemcoCoat 9223 +SemcoZir 7300B (1x)

top layer: ≈ 450 μmpenetration ≈ 5mm

In-house casting trials with steel

Casting design (severe conditions)• Cast weight approx. 210 kg• Increased core length

Magma simulation• Longer solidification times (≈ 53 min – 65 min)

#1

#4

#3

#20,0

20,0

40,0

60,0

80,0

100,0

1400,0

1440,0

1480,0

1520,0

1560,0

1600,0

0,0 10,0 20,0 30,0 40,0 50,0 60,0 70,0 80,0

Degree of solidificatio

n [%]

Temp

erat

ure

[⁰C]

Time [min]

Simulation of hexagon test casting: solidification and core temperature

Core #1 Core #2

Core #3 Core #4

maximum T steel around core#1 maximum T steel around core#3

Degree of solidification [%]

Tliquidus≈ 1520 ⁰C

Tsolidus ≈ 1470 ⁰C

Awaiting casting results

Effective Mixing and Coating Control

The effectiveness of a specific coating is controlled by the applied dry layer thickness

Too thin and the coating is not effective Too thick and material is wasted, plus risk of: Dimensional issues Scabbing Excessive runs and drips etc…

Wet layer thickness is a good proxy for dry layer

Measurement of dilution and adjustment

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Traditionally the application parameters for foundry coatings are defined by Baume or Flow Cup viscosity – related to applied layer

Both methods open to operator interpretation Measurement technique Supplier of measurement device (specifically Baume) Local standards (DIN, Ford, ISO etc..)

Baume vs. Flow Cup

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Lowest actual Baume = 24 275um Highest actual Baume = 30 440um

Layer Thickness variation

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Lowest actual Viscosity = 13.5 sec 260um Highest actual Viscosity = 16.5 sec 410um

Baume Flow Viscosity

These measurements attempt to measure the combined influence of Solids Content (or dilution) Rheological effect of the gel For Baume – termed “Body” For Flow Cup – the viscosity

If we eliminate the need to measure rheology…. Batch-to-batch consistency from supplier Correct homogenisation of product

….An improved measurement technique can be adopted.

The Limitations of Baume and Flow Viscosity

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Flow cup and Baume incorporate the coating rheology into the measurement

If we have consistency of rheology from the supplier Density becomes the most effective measurement

Density measurement variations

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Density measurement of a coating

Density measured in range of +/- 0.004 g/ml

With variation of +/- 0.004 g/ml Variation in applied layer of +/- 10um

Automatic Density Measurement Proven method of continuous density measurement Provides coating density measurement to 3 decimal places Complete homogenisation of the prepared coating

Continuous Density Measurement

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Coating density versus time Courtesy: Atlantis Foundry (Halberg), S.Africa

Minimise scrap and re-work in the most cost effective manner

Ensure the coating you use is rheologically stable with time Apply most protection where it is needed – Z-Primer Improve your productivity

Fast drying water-based products Single layer flow coating to high layer thickness

Reduce your energy consumption Fast drying water-based products

Ensure you apply a sufficient protective layer every time Automated density control and coating homogenisation

Conclusions

2/03/2017 Footnote

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Questions

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Thank-you for your attention

Acknowledgements: Christoph Genzler Europe - Product Manager (Coatings)Bruce Lundeen North American - Product Manager (Mould & Core)Martien Haanepen R&D Scientist