Synapse: While EAF/AOD melting is cheap, it cannot handle the extreme loads required for US process improvement. Premium melt grades are used to ensure higher quality products for demanding applications.
In the early days of melting, Electric Arc Furnace (1878) and Vacuum Induction Melting (1927) were leaps ahead in quality compared to the Bessemer and Open Hearth technologies. Argon Oxygen Decarburization (1965) and later came Vacuum Arc Remelting (1970s).
Electroslag Remelting was introduced in the late 1970s and is now preferred over the vacuum technologies when possible. It creates an ingot directionally solidified, and results in even lower inclusions than the vacuum grades.
Some of our products had been developed with the EAF/AOD process, and while it worked for many structural applications, it simply could not remove linear defects caused at the time of pouring the ingot. Lamellar defects such as banding and segregation could not be avoided using the standard chemistry. In high pressure environments, these defects would be found through leak down or outright failure.
To combat these types of defects, the ESR process was implemented after the EAF/AOD process to create a more homogenous and extremely low inclusion product. While it does add to the overall cost of the processing, the yield improvements and much lower rate of customer reports makes a difference overall.
Instances of linear defects reported in these revamped products have dropped, and the sales force has become more comfortable in recommending these higher quality products for high pressure service again. In many cases, we supply the higher quality product without it having been specified or asked to do so. If you want to be sure that your product is High Performance, make sure it will hold up to the pressures with a higher quality melt process such as ESR.
Originally posted on LinkedIn by Jeff Kirchner, COO, Manufacturing Director at High Performance Alloys, Inc. >