System and method for producing a hardened and tempered structural member
System and methods relating to in-line heat-treating, hardening and tempering of material, such as for example, coiled steel into a roll-formed, hardened and tempered structural member having uniform or different targeted properties in selected zones of the structural member. The different targeted properties may be achieved by heating and/or cooling the material subject to certain parameters.
1. A method for producing a hardened and tempered structural member comprising the steps of:
providing a coiled ferrous continuous work piece of selected composition;
roll forming said coiled ferrous continuous work piece into a desired profile;
rapidly heating said ferrous continuous work piece in an induction heating device within a range of about 850° C. to 1000° C. within about 300 seconds to produce austenite substantially throughout the profile of said continuous work piece;
rapidly cooling said austenitized continuous work piece with a cooling medium to below about 350° C. within 10 seconds or less to convert said austenite to martensite substantially throughout said continuous work piece, resulting in a hardened work piece;
tempering said continuous workpiece by rapidly heating said hardened work piece in a second induction heating device to about 450° 600° C. within 40 seconds or less, providing a hardened and tempered work piece of a desired hardness;
wherein at least one of said heating, said cooling, or said tempering is asymmetrical at selected zones of said work piece;
cooling said hardened and tempered continuous work piece to a desired cutting temperature; and,
cutting said hardened and tempered continuous work piece to a desired length.
2. The method of claim 1 further comprising the step of powder coating said hardened and tempered work piece.
3. The method of claim 1 wherein said selected composition of said continuous work piece is SAE 15B27 steel.
4. The method of claim 1 wherein said continuous work piece is subjected to at least one of substantially symmetric heating and symmetric cooling, wherein distortions resulting from different heating or cooling rates is substantially minimized.
5. The method of claim 1 wherein said asymmetrical tempering at one or more zones of said work piece results in said hardened and tempered continuous work piece of said desired profile having at least a first zone having a first hardness and a second zone having a second hardness different from said first hardness.
6. The method of claim 5 wherein said first zone includes a web.
7. The method of claim 5 wherein said second zone includes at least one flange.
8. The method of claim 1 wherein each step occurs substantially continuous and in-line in a straight line.
9. The method of claim 1 wherein distortions are measured by an optical measuring device.
10. The method of claim 9 wherein said optical measuring device includes a laser.
11. The method of claim 9 wherein said optical measuring device continuously provides measurement information to a computer, and said computer determines if there is distortion above an acceptable amount, wherein said computer activates a calibration device if distortion is above said acceptable amount.
12. The method of claim 11 wherein said method further comprises the step of further roll forming said hardened and tempered continuous work piece resulting from activation of said calibration device, and wherein said acceptable amount is less than about 1 mm/m.