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US RE28,719 EGranted
Method of making flat steel files
AssigneeUnited States Steel Corporation
InventorJohn G. Cutton
Life of this patent
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Abstract
A process for making flat steel files wherein a highcarbon steel is hot rolled on a wide strip mill and coiled. The coil is given a spheroidizing anneal and slit into bar and cut into flat bar stock. File blanks are cut from the flat bar stock and ground to remove a pure iron surface caused by the anneal. Thereafter, the file teeth or grooves are cut and the file hardened.
Claims5
A method of making high-carbon steel flat bar stock, the steps comprising:
- a. hot rolling a high-carbon steel slab at a temperature within the range 1,600.degree. to 2,200.degree.F on a strip mill to form a strip having a thickness as desired for the final flat bar stock,
- b. coiling said strip at a temperature above 1,000.degree. F,
- c. annealing said coiled strip in a reducing atmosphere at a temperature above the A.sub.1 critical temperature for at least 2 hours to austenitize the steel microstructure,
- d. maintaining the reducing annealing atmosphere at a dewpoint of less than +15.degree. F at least at temperatures above about 1,100.degree. F,
- e. furnace cooling the annealed coiled strip at a rate of about 20.degree. to 40.degree. F per hour to a temperature of about 1,250.degree. F while maintaining the reducing atmosphere at a dewpoint of less than +15.degree. F to form spheroidized carbide precipitates, and then furnace cooling the coiled strip to a temperature below about 400.degree. F while maintaining the reducing atmosphere to avoid surface oxidation, and
- f. uncoiling [ and slitting] the strip [into bars of the desired width] and cutting bars of the desired size therefrom.
3 more elements
A method of making steel files, the steps comprising:
- a. hot rolling a high-carbon steel slab at a temperature within the range 1,600.degree. to 2,200.degree.F on a strip mill to form a strip having a thickness as desired for the final flat bar stock.
- b. coiling said strip at a temperature above 1,000.degree.F.
- c. annealing said coiled strip in a reducing atmosphere at a temperature above the A.sub.1 critical temperature for at least 2 hours to austenitize the steel microstructure,
- d. maintaining the reducing annealing atmosphere at a dewpoint of less than +15.degree.F at least at temperatures above about 1,100.degree.F,
- e. furnace cooling the annealed coiled strip at a rate of about 20.degree. to 40.degree.F per hour to a temperature of about 1,250.degree.F while maintaining the reducing atmosphere at a dewpoint of less than +15.degree.F to form spheroidized carbide precipitates, and then furnace cooling the coiled strip to a temperature below about 400.degree.F while maintaining the reducing atmosphere to avoid surface oxidation,
- f. uncoiling and slitting the strip into bars of the desired width,
- g. cutting the bars to the desired length, and cutting the bar lengths into file blanks,
- h. grinding the surface of the file blanks to remove a pure iron surface layer caused by the anneal and expose a high-carbon subsurface,
- i. cutting file grooves into the file blanks, and
- j. hardening the file blanks.
7 more elements
Dependencies are inferred from the claim text.