In-line heat treatment of hot-rolled rod
AssigneeUnited States Steel Corporation
InventorRaymond A. Grange
Life of this patent
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Abstract
Hot rolled steel rod, containing less than 0.4% C, is cooled by a prescribed, interrupted-cooling procedure for producing rod with enhanced ability to receive cold work. In cooling from the austenite range, the rod is held within a specified, narrow temperature range for a period of at least about 2 minutes. The particular holding range is shown to be a function of carbon content, whereby low carbon steels (<0.28% C) are held at a prescribed temperature above 1,450.degree.F, while medium carbon steels are held at a temperature of about 1,250.degree.F.
Claims24
In the commercial production of extended lengths of low alloy steel rod having a carbon content below about 0.4%, wherein said rod is cooled from the A.sub.3 temperature thereof to a temperature below 1,200.degree.F in a constrained time period, said period being within the range of 2.5 to 15 minutes;
- an interrupted cooling procedure for enhancing the ability of said rod to receive subsequent cold-work, said procedure comprising,
- a. cooling said rod from said A.sub.3 temperature to a temprature within the range of T.sub.p .+-. 35.degree.F and holding the rod within said temperature range for a duration of at least 2 minutes, wherein T.sub.p is a function of carbon content as given by:
- (C <
- 0.28%) T.sub.p = 1,585 - 500 .sup.. %C
- (C >
- 0.20%) T.sub.p = A.sub.1 - 70
- b. thereafter cooling said rod to about room temperature.
An in-line process for the production of extended lengths of low alloy steel rod which comprises,
- a. forming said rod by hot-roling a steel billet having a carbon content below about 0.4%, the resultant hot-rolled rod exiting from the finishing stand at a temperature in excess of about 1,750.degree.F,
- b. cooling said rod, and then depositing said cooled rod in the form of offset rings, onto a conveyor;
- whereby said rod is carried on said conveyor in the form of spirals,
- c. retarding the cooling of said rod spirals to a degree sufficient to maintain the rod within a prescribed temperature range of T.sub.p .+-. 35.degree.F for a duration of 2 to 10 minutes, wherein T.sub.p is a function of carbon content, as given by:
- (C <
- 0.28%) T.sub.p = 1,585 - 500 .sup.. %C
- (C >
- 0.20%) T.sub.p = A.sub.1 - 70
- d. cooling said rod to reforming temperature, and reforming said rod spirals into a rod bundle,
- e. cooling the resultant rod bundle to about room temperature.
Dependencies are inferred from the claim text.