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25. October 2017

ASK - That certain something in the casting process

ASK - That certain something in the casting process

New hybrid additive for more effectiveness and efficiency in casting production

Verena Sander, Manager Global Marketing Communications; Ismail Yilmaz, Technical Product Manager Additives and Coated Sands Europe

Missed out on an order again? The competitor tendered a cheaper bid again? Who hasn´t experienced that?

The major challenges in the foundry industry are pronounced cost pressure and strong competition for the technological leading-edge. In order to master these developments successfully, now more than ever,  it is important that foundries are concerned with questions of effectiveness, i.e. quality and efficacy of target achievement, and efficiency - i.e. the cost-benefit ratio - in the production area.

What exactly is meant by this? Effectiveness highlights the question of whether the right things are being done to achieve the desired goal. A fire can be extinguished with water or also with champagne. Both achieve the goal: the fire is extinguished. But does the choice of champagne as an extinguishing agent justify the cost-benefit ratio, i.e. its efficiency?

This article provides an overview of how the use of hybrid additives can increase both effectiveness and efficiency in casting production.

Depending on the requirements, additives essentially do the following: they are used to reduce or avoid casting defects that usually result in rejects or rework. This is already common practice and can be regarded as standard procedure in the foundry industry. In addition, new additive technologies open up the possibility to expand and re-evaluate casting technology limits. In this case, each specific process must be examined and evaluated for the new options and their feasibility. Experience shows that new hybrid additives can be an alternative to partially replace the coating process or to avoid deploying or replace expensive specialty sands.

Classification of additives

Different types of core sand additives are available to foundrymen. The classification is based on the origin of the material; namely organic, inorganic and hybrid additives. These three types each have specific properties. Consideration of the advantages and disadvantages must not be carried out in isolation, but must take place in the context of the complete requirements profile.

Organic additives

This class generally consists of hardwood or plant extracts and is usually dosed at 0.5% to 4%. These additives are often used in the core production of cold-box processes in order to avoid sand expansion defects.

Inorganic additives

Inorganic additive ingredients include, for example, iron oxides, ceramics or minerals. As a rule, due to their composition, no gas development arises.

Inorganic additives are particularly suitable for coating-free casting, but they require a high additive rate of 4% to 10% and result in high raw material costs.

Hybrid additives

A relatively new generation of additives are hybrid additives. They combine the advantages of the aforementioned additive systems. They are very effective against veining. They can also be used for coating-free casting. Hybrid additives of the latest generation are also used to replace expensive specialty sands.

Hybrid additives for uncoated castings

In the field of cold-box production, additives offer great economic potential, because casting defects are avoided on the one hand and, on the other hand, process costs can be saved by the elimination of the coating process. The foundry saves investment in peripheral equipment required for the coating process. Thus, for instance, expensive drying equipment such as convection ovens or microwave ovens, coating basins or the provision of storage space are not necessary. Thus, in the case of upcoming reinvestments, the use of addives has particularly to be reconsidered and is an interesting way to save cost.

Particularly in cost-intensive West and North European foundry markets, the savings in the production steps considerably increases the efficiency of the production process: the process of coating and subsequent drying takes time and personnel, so that productivity is improved through its elimination. Elimination of the coating process is accompanied by a reduction in energy costs, since the energy-intensive drying of coated cores is no longer required. If the foundry works with alcohol coatings, the switch to a coating-free process also represents a boost for safety in the workplace.

It is indisputable that coating contributes significantly to improvements in cast surfaces. It must not be forgotten, however, that coating can also be a potential source of defects in the process chain.

Converting to coating-free casting eliminates this risk. Coating-specific casting defects such as gas defects or surface imperfections can therefore be prevented by means of additives. It is true that surface finishes from coating-free casting cannot always be measured with those of coated workpieces but the crucial questions remain: what is the goal and which is the right means to achieve it? And... what is the appropriate cost-benefit relationship?

If the application and requirements of the casting allow it, it is worthwhile to consider the coating-free casting approach. It is advisable to speak with the supplier and to use their expertise in the transition to a coating-free process.

The following case study shows the potential that a conversion to a coating-free process offers.

The example in figure 2 shows the cost consideration for the production of a core in a Western European automotive foundry. The elimination of the coating process and the use of VEINO ULTRATM resulted in a cost saving of 36% per core and thus a significant increase in efficiency.

The latest addition to the "VEINO  ULTRATM" family, VEINO ULTRATM 3010, has been developed specifically for use in the coating-free process and for substitution of specialty sands. VEINO ULTRATM 3010 demonstrates high thermal stability and dimensional stability

Hybrid additives for substitution of special sands

Specialty sands are natural mineral sands, sintered or melted products and mixtures thereof. The granular mould is produced, if necessary, through crushing, classification and screening processes or also through other physico-chemical processes. Specialty sands differ from quartz sand in particular due to their low thermal expansion behaviour in the temperature range from 20°C to 600°C. Foundries use specialty sands mainly due to the associated high efficiency against casting defects such as, e.g. veining or metal penetration. Specialty sands typically demonstrate little to no gas emissions. [2] Before deploying specialty sands, an accurate cost assessment should be performed. Typical addition quantities of 30% to 100% as well as the factors of availability, reclamation, transport, storage and waste disposal clearly demonstrate the high cost of using these raw materials. Moreover, it has to be considered that specialty sands, like all natural products, are subject to quality fluctuations which can impair process reliability.

In contrast are the hybrid additives of the latest generation, such as VEINO ULTRATM 3010. These products allow either to partially or completely abandon the use of cost-intensive specialty sands, resulting in the same or even better casting quality.

This is illustrated by two examples: Figure 4 shows the improvement of the surface quality and Figure 5 the possible material cost savings that can be achieved by using VEINO ULTRATM.

New hybrid additives such as VEINO ULTRATM 3010 are ideal for resolving casting defects and optimising casting quality. Comparing the cost of quartz sand in combination with VEINO ULTRATM 3010 with the cost when using specialty sands, the moulding material mixture with additive demonstrates a significantly better cost-benefit ratio.

Summary

New innovative hybrid additives demonstrate the highest efficiency when it comes to implementing sophisticated, coating-free casting or replacing expensive specialty sands.

Components produced with hybrid additives are not yet standard practice. However, due to the high competitive pressure in the foundry industry, the use of these substances can become a competitive advantage. The aforementioned examples reflect the application experience in product implementation. Hybrid additives are an effective way for foundries to produce high-quality castings and to utilise materials and processes with maximum efficiency.

ASK Chemicals develops and manufactures additives in Germany, providing foundries with new ways to meet the challenges described above by implementing new hybrid additives to (completely or partially) substitute expensive special sands and to improve the total cost-benefit ratio with equal or higher casting quality. The use of hybrid additives for uncoated castings offers a very interesting potential for foundries in high wage countries to reduce their process costs while improving process reliability. ASK Chemicals always supplies additive solutions specifically tailored to customer processes.

Sources:
[1] ASK Chemicals; Technical Data Sheet VEINO ULTRATM 3010
[2] Recknagel, U.; GIESSEREI RUNDSCHAU 56 (2009); p. 6 ff. (Foundry Review, in German)

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