CPT International 04/2014

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global foundry industry – Das führende Fachmagazin für die
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Authors: Xu Peng Cheng, Zhang Lei, Zhang Zhouqin, Toshiba Hydro Power Co., Ltd., Hang Zhou, China

First understand, then optimize!

Toshiba uses Magma 5 to reduce inclusions in its steel castings

Inclusions on the outer surface after machining (Photos: Toshiba Hydro Power)

With increasing quality demands on

steel castings, steel carrier rings used in

thermal power units are manufactured

under very strict quality specifications.

Toshiba Hydro Power in Hang Zhou,

China, has been producing these ringshaped

castings for over se ven years for

its parent company. One of their most

significant challenges has been the presence

of inclusions on the outer ring surface,

which accounts for over 40 % of

the total defects.

Due to the high quality requirements,

these inclusions had to be removed by

polishing and subsequent welding. The

cost for the welding electrodes alone

was extremely high. The welding took

roughly 12,142 total hours per year and

about 2,600 kg of weld rods were used

to achieve high quality castings for four

projects during 2011 ( Figure 1). In order

to find a solution that would decrease

or eliminate this problem, a number of

measures had been investigated over the

years.

By mastering Magmasoft by Magma

Gießereitechnologie GmbH, Aachen,

Germany, the abilities and skills in understanding

process knowledge were

constantly enhanced and the foundry’s

experts were convinced that they

had to first identify the root causes of

the problem in order to solve it. Before

purchasing Magmasoft, many different

factors were suspected to be the cause

of the inclusions, such as melt quality,

molding materials and inclusion formation

due to reoxidation. However, it had

always been guesswork to predict which

factor might have contributed most to

the problem.

With the purchase and implementation

of Magma 5 in 2012, the foundry

simulated their current casting layout

using the “inclusion” criterion. The

simulation clearly showed the potential

endangered areas (Figure 2). The filling

process was also evaluated in detail. It

was determined that excessive turbulence

at two main ingate areas resulted

in an enlargement of the melt free

Casting Plant & Technology 4/2014 35

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