
(from the article `steel`) In order to convert wrought iron into steelthat is, increase the carbon contenta carburization process was used. Iron billets were heated with ...
Found on
http://www.britannica.com/eb/a-z/b/78

Blister-steel is iron bars which, when converted into steel, have their surface covered with blisters, probably from the expansion of minute bubbles of air. Steel is used in the blister state for welding to iron for certain pieces of mechanism, but is not employed for making edge-tools. It requires for this purpose to be converted into cast or shea...
Found on
http://www.probertencyclopaedia.com/browse/GB.HTM

High-carbon steel produced by carburizing wrought iron. The bar, originally smooth, is covered with small blisters when removed from the cementation (carburizing) furnace.
Found on
https://steelforge.com/literature/steelog-the-5000-word-metals-glossary/

First type of steel that was commercially produced. Process took place in a Cementation Furnace and produced a bar that had a high carbon content on the surface and a low Carbon content in the centre. Process resulted in a blistered appearance to the bars, thus the name. Not much use in this form until processed into Crucible Steel or Shear Steel.
...
Found on
https://www.encyclo.co.uk/local/20483

steel produced from wrought iron by cementation in covered pots, having a blistered appearance because of the gases generated during the process.
Found on
https://www.infoplease.com/dictionary/blister-steel

High-carbon steel produced by carburizing wrought iron. The bar, originally smooth, is covered with small blisters when removed from the cementation
Found on
https://www.unifiedalloys.com/resources/glossary/
No exact match found.