Case Studies



Capital Refractories are now able to offer an extensive series of gas diffuser products  for the treatment of melts across a range hot metal industries.

Experience at an Investment Foundry

Capital has converted an investment foundry from chrome-alumina crucibles to Coral SMC fitted with a gas diffuser. Before conversion the crucible would last one day (18-20 heats) before erosion necessitated its replacement. The photographs here show the Coral SMC lining after a day. The lining surface is very clean and overall life much extended. The life expectancy of the furnace is now about 1 week between re-lines.

mckenna mckenna

More Gas Diffuser Success

Capital Refractories has again demonstrated the huge benefits that can be achieved by employing a gas diffusers within an induction furnace. Capital recently worked in conjunction with Weaver Materiel, their distributor in the State of Pennsylvania. The foundry manufacture steel castings for the oil and refining industry, and were looking for a way in which they could de-gas the whole melt rather than having to adopt the SPAL method (i.e. spraying liquid argon onto the top of the melt), therefore reducing their costs and achieving a better surface finish on their castings.

Weaver Materiel installed Capital’s Coral SMC lining along with a standard 3 inch gas diffuser (model 7126). They were on site for the full 2 day trial, instructing all melters and supervisors on the procedures involved with the simple installation and running of the plug. In line with Capital’s policy, all distributors offer ongoing support to their customers if needed.

Benefits reported:

  • Huge financial and environmental savings in the gas used.
  • Improved surface finish on the castings due to the ability to de-gas through the whole melt.
  • Hardly any wear on the Capital lining.
  • Easier to pour metal into the moulds – cleaner metal means that pouring can be done faster through the pouring cups and filters.
  • Scrap rate reduced.

This Pennsylvanian foundry has since reported a substantial financial saving along with an improvement in the quality of their castings, and have already placed further orders for Capital’s combined lining and gas diffuser product.

Capital Refractories' Gas Diffusers – New trials show benefits

Case Study A

 A particularly large foundry was one of the first to take advantage of our highly developed gas diffusers for their induction furnace.

Whilst it is well known that gas diffusers can greatly improve metal quality and reduce gases within the melt, it took a lining problem for this company to further investigate this gas treatment solution.

The problem was zonal overheating of the linings, in particular the lower side wall. The brick lining was being heated beyond its capability thereby causing severe wear on the bricks and potentially disastrous fusion of the backing powder.

We introduced our gas diffuser and began passing argon through the melt which caused a stirring effect. This displaced the superheated metal into the remainder of the melt on a continuous basis and therefore homogenised the temperature throughout the bulk of the melt. By eliminating this superheated zone the condition of the bricks at this location improved dramatically with a consequent substantial improvement in lining life. The company now use 8 plugs a month from us.

We are continuing to work with this induction furnace team to improve their production and are looking to install a gas diffuser in the base of the casting ladle shortly.

    A reduced bath temperature
    Reduction of “elephant’s foot”
    Even wear of refractory lining
    Increased life of consumables

Case Study B

A steel foundry was experiencing quality problems with a high scrap and reclamation rate. Defects in the metal were particularly apparent on the top face. It was thought to be due to dissolved nitrogen coming out of the solution which could be reduced by flushing with argon.

A Capital plug was introduced in the base of the foundry’s 300 kg furnace and there was a large improvement in the casting quality of the metals. With over 70 casts undertaken, there was found to be only a slight deterioration of the plug with no wearing of the lining.

Our gas diffuser is being used successfully with argon at the foundry. Reports suggest that the castings being taken are the foundry’s best quality in history, and the use of our plugs is now standard practice in the Induction Furnace.

    Reduced scrap rate
    Reduced nitrogen levels
    Improvement in cast quality

Case Study C

 A large foundry has recently installed a gas diffuser with a specific aim.

The foundry wished to become more economical due to the high scrap rate produced from the 600 kg furnace. Ring castings were also pin-holed and these issues were thought to be due to high levels of nitrogen.

Our plug was installed to be utilised with argon. Use of the plug led to a large reduction in nitrogen levels and the scrapping of castings being halved. Deterioration of linings is also reduced with the use of a gas diffuser. The company are now looking to put plugs in all furnaces which will reduce lining wear, reduce scrap and increase the metal quality.

Metal quality has been hugely improved and the foundry expect glowing reports from their customers about this.

    Reduced Nitrogen levels from 0.42%
to 0.22%
    Reduced scrap levels

Case Study D

A company that produce engineering castings for the offshore industry have become yet another satisfied Capital Refractories customer.

This Dutch foundry has recently installed a gas diffuser in their 500 kg furnace. This furnace is used for producing steel castings.

The metal quality is markedly improved and appears far cleaner. There has also been a 30% improvement on the mechanical properties of the metal during low temperature impact testing. Obviously this is significant for the industry for which they cater .

Reports suggest that the company are delighted with our impact on their production, and are looking to install another plug on a furnace used to produce other steel grades shortly.

    Although gas levels remained constant, the impact strength increased as the gas diffuser removed other contaminants (such as sand and refractory inclusions).
    Scrap levels have been drastically reduced.
    Quality of the metal has been vastly improved due to a stainless steel alloy being purged with the gas diffuser.

For more on Capital's range of gas diffusers click here.