Porosity in Cast Bronze Bar Stock: What it is, and How to Eliminate it

Porosity in bronze may be one of the most consistent and common complaint of cast bronze users.  Porosity in cast bronze contributes directly to customers concerns about reliability and quality.  Controlling porosity depends on understanding its sources and causes.  Here at National Bronze Mfg. Co. we have developed a few techniques to help you control and even eliminate any porosity issues.

What Causes Porosity?

Porosity in castings is due to air bubbles being trapped during the solidification process.  Porosity sources include entrapped air during filling, centerline shrinkage, blowholes, reactions at the mold wall, dissolved gasses from melting and dross or slag containing gas porosity.

bronze porosity

bronze porosity


National Bronze Manufacturing Solutions:


We have found that the single most effective way to reduce porosity in cast bronze bar stock is to use the continuous casting process when casting bronze bar.  Continuous Cast Bronze Bar Stock is less likely to produce porosity than any other methods used for manufacturing this product.  The continuous casting process produces an extremely fine grain microstructure and promotes excellent dispersion of alloying elements.


For this reason over 95% of our inventory is of continuous cast bronze bar.  An even higher percentage of our machined products are machined from continuous cast bar stock.

Continuous Cast Bronze Tubes


Often certain requirements do not allow for the continuous cast bronze to be used.  Other casting methods must be used for these situations.  Another way to eliminate porosity issues is to have us rough machine the castings.  Supplying you with semi machined blanks.  As both a metal service center and a full production machine shop we offer you this unique advantage.

While porosity may not be visible from the rough skin of the bar stock, a semi machined blank can expose irregularities and save you the hassle.  Our machined blanks are also a great way to shorten your additional machining time and eliminate down time from porous material.

cast bronze blank

Using these two strategies can help you control and even eliminate porosity in your cast bronze bar stock, so you can devote more of your time doing what you do best.

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