When subtracting two numbers, regrouping means starting at the ones column and borrowing a value from the next column as one moves to the left until the subtraction is completed. Regrouping and borrowing are words that mean the same thing when subtracting.
The Bessemer process was the first inexpensive industrial process for the mass-production of steel from molten pig iron prior to the open hearth furnace. The key principle is removal of impurities from the iron by oxidation with air being blown through the molten iron.
The Bessemer process revolutionized steel manufacture by decreasing its cost, from Â£40 per long ton to Â£6â7 per long ton, along with greatly increasing the scale and speed of production of this vital raw material.