Method and apparatus for reducing and sizing hot rolled ferrous products

• US 6,546,777 B2
• Filed: 08/10/2001
• Issued: 04/15/2003
• Est. Priority Date: 09/08/2000
• Status: Expired due to Term

• Current Assignee: Primetals Technologies USA LLC (Mitsubishi Heavy Industries, Ltd.)
• Original Assignee: Morgan Construction Company (Siemens AG)
• Inventors: Kiefer, Bruce V., Keyzer, Pieter L., Shore, T. Michael
• Primary Examiner(s): Ostrager, Allen
• Assistant Examiner(s): Goetz, John S
• Application Number:
  US09/927,660
• Publication Number:
  US 20020046590A1
• Time in Patent Office: 613 Days
• Field of Search: 722/00, 722/01, 723/62, 723/64, 723/652, 723/662
• US Class Current: 72/235
• CPC Class Codes: B21B 1/18 in a continuous process

Abstract

A method of continuously rolling a ferrous workpiece into a finished round, comprising rolling the workpiece in successive first and second roll passes at an elevated temperature of between about 650 to 1000° C., the first and second roll passes each being defined by two work rolls and being dimensioned to effect a combined reduction in the cross sectional area of the workpiece of at least about 20-55%, with an accompanying effective strain pattern dominated by a concentration of maximum effective strain at a central region of the cross sectional area; and while the effective strain pattern remains dominated by a concentration of maximum effective strain at a central region of the cross section, continuing to roll the workpiece in at least third and fourth consecutive roll passes, each of the third and fourth roll passes being defined by at least three rolls and being sized to effect a combined reduction in the cross sectional area of the workpiece of not more than about 4-25 %.

Claims

1. A method of continuously rolling a ferrous workpiece into a finished round, comprising:

rolling said workpiece in an oval first roll pass and a round second roll pass at an elevated temperature of between about 650 to 1000°

C., said first and second roll passes each being defined by two work rolls and being dimensioned to effect a combined reduction in the cross sectional area of said workpiece of at least about 20-55%, with an accompanying effective strain pattern dominated by a concentration of maximum effective strain at a central region of said cross sectional area; and

while said effective strain pattern remains dominated by a concentration of maximum effective strain at a central region of said cross section, continuing to roll said workpiece in at least third and fourth consecutive round roll passes, each of said third and fourth roll passes being defined by at least three rolls and being sized to effect a combined reduction in the cross sectional area of said workpiece of not more than about 4-25%.

2. The method of claim 1 wherein rolling continues in said third and fourth roll passes prior to the occurrence of microstructural changes due to recrystalization and recovery.

3. The method of claim 1 or 2 wherein the workpiece emerges from the last of said at least third and fourth roll passes as a finished round having no more than ±

0.1 mm diameter tolerance and 0.1 mm ovality.

4. The method of claim 1 wherein after cooling to a state of thermal equilibrium, said workpiece has a grain size variation across its cross section of not more than about 2 ASTM grain size numbers.

5. A method of continuously rolling a round ferrous workpiece, comprising:

rolling said workpiece in successive first and second roll passes at an elevated temperature of between about 650 to 1000°

C., said first and second roll passes each being defined by two work rolls and being configured respectively to impart progressively reduced oval and round cross sections to said workpiece and to effect a combined reduction in the cross sectional area of said workpiece of at least about 20-55%, with an accompanying effective strain pattern dominated by a concentration of maximum effective strain at a central region of said cross sectional area; and

prior to the occurrence of microstructural changes due to recrystalization and recovery, while said effective strain pattern remains dominated by a concentration of maximum effective strain at a central region of said cross section, continuing to roll said workpiece in at least third and fourth consecutive round roll passes into a finished round, each of said third and fourth roll passes being defined by at least three rolls and being sized to effect a combined reduction in the cross sectional area of said workpiece of not more than about 4-25%, with said finished round having no more than ±

0.1 mm diameter tolerance and 0.01 mm ovality.