Method of Production of High-Strength Hollow Bodies from Multiphase Martensitic Steels

• US 20120273095A1
• Filed: 02/01/2012
• Published: 11/01/2012
• Est. Priority Date: 02/18/2011
• Status: Active Grant

• Current Assignee: Zapadoceska Univerzita V Plzni (Urad Vlady Cr)
• Original Assignee: Zapadoceska Univerzita V Plzni (Urad Vlady Cr)
• Inventors: Masek, Bohuslav, Jirková, Hana, Hronek, Pavel, Stádler, Ctibor, Urbánek, Miroslav
• Granted Patent: US 8,852,367 B2
• Time in Patent Office: Days
• US Class Current: 148/654
• CPC Class Codes: C21D 2211/008 Martensite
• CPC Class Codes: C21D 8/10 during manufacturing of tubular bodies
• CPC Class Codes: C21D 8/105 of ferrous alloys
• CPC Class Codes: C21D 9/08 for tubular bodies or pipes
• CPC Class Codes: C21D 9/085 Cooling or quenching

Abstract

A method of production of high-strength hollow bodies from multiphase martensitic steels includes a heating process, a forming process and a cooling process. A heating device heats hollow steel stock to the austenitic temperature of the material from which the stock is made. The stock is then converted by deformation in a forming device into a hollow body having the final shape. A cooling device thereafter cools the hollow body such that the material with the original austenite microstructure refined by deformation during the forming process cools to a temperature at which incomplete transformation of austenite to martensite occurs. The retained austenite stabilization is performed in an annealing device by diffusion-based carbon partitioning within the material from which the hollow body is made. The hollow body is cooled in a cooling device to ambient temperature after stabilization.

Claims

1. A method of producing high-strength hollow bodies from multiphase martensitic steels, where the production includes a heating process, a forming process and a cooling process, comprising the steps of:

heating a body of hollow steel stock to about an austenitic temperature of the material from which the stock body is made;

converting the stock by deformation of the hollow steel stock body in a forming device into a hollow body having a final shape;

initially cooling the hollow body having the final shape in an initial cooling device after the forming step in such a way that the material comprising the hollow body having a final shape and having an original austenite microstructure refined by deformation introduced during the forming step is initially cooled down to a temperature at which incomplete transformation of austenite to martensite takes place;

annealing the initially cooled hollow body having a final shape in an annealing device whereby retained austenite stabilization is performed in the annealing device by diffusion-based carbon partitioning within the material from which the hollow body having a final shape was manufactured; and

finally cooling the hollow body having a final shape to ambient temperature in a final cooling device after the annealing step has substantially finished the retained austenite stabilization.

2. The method of production of high-strength hollow bodies from multiphase martensitic steels of claim 1, wherein the converting step in the forming device is carried out using an explosive, and wherein the explosive is placed by means of the holder of explosive inside a cavity of the hollow stock steel body which is located inside a die of the forming device 3.

3. The method of production of high-strength hollow bodies from multiphase martensitic steels of claim 1 wherein the final cooling device is a cooling conveyor.

4. The method of production of high-strength hollow bodies from multiphase martensitic steels of claim 1 wherein the initial cooling step is performed immediately after the completion of the converting step.

5. The method of production of high-strength hollow bodies from multiphase martensitic steels of claim 1 wherein the annealing step is performed immediately after the completion of the initial cooling step.

6. The method of production of high-strength hollow bodies from multiphase martensitic steels of claim 1, wherein the initial cooling step is carried out in the initial cooling device which is a different device than the final cooling device.

7. The method of production of high-strength hollow bodies from multiphase martensitic steels of claim 2, wherein the final cooling device is a cooling conveyor.