Method for producing a corrosion-resistant, workable sheet metal with full-surface coating of the joined, thermally treated steel sheets

Abstract

The invention relates to a method of producing corrosion-resistant and workable sheet metal consisting of uncoated steel sheets ( 1, 1′ ), comprising the following steps: —placing the steel sheets ( 1, 1′ ) in abutting relationship, —welding the or each joint groove ( 14 ) by butt joint welding by means of a welding beam ( 13 ) for forming a weld ( 2 ) along the respective joint groove ( 4 ), —thermal treatment of the or each weld ( 2 ) directly after or even during the forming of the weld ( 2 ) by means of an annealing beam ( 15 ), —full-surface coating of the joined steel sheets ( 1, 1′ ), including the or each weld ( 2 ), after cooling the welds ( 2 ), with a metallic coating.

1 . Method for producing corrosion-resistant and workable sheet metal consisting of uncoated steel sheets comprising the following steps:
 placing the steel sheets in abutting relationship   welding the or each joint groove by butt-joint welding by means of a welding beam for forming a weld along the respective joint groove,   thermal treatment of the or each weld directly after or even during the forming of weld by means of an annealing beam, wherein, during cooling after welding, the temperature of weld is held in a temperature range between 800° C. and 500° C. by the annealing beam for a time period of 1 to 3 seconds in order to prevent martensite formation in the region of weld.   full-surface coating of the joined steel sheets, including the or each weld, after cooling the welds, with a metallic coating.   
     
     
         2 . Method for producing corrosion-resistant and workable sheet metal consisting of the steel sheets coated with a metallic coating comprising the following steps:
 placing the coated steel sheets in abutting relationship   welding the or each joint groove by butt-joint welding by means of a welding beam for forming a weld along the respective joint groove,   thermal treatment of the or each weld directly after or even during the forming of weld by means of an annealing beam, wherein, during cooling after welding, the temperature of weld is held in a temperature range between 800° C. and 500° C. by the annealing beam for a time period of 1 to 3 seconds in order to prevent martensite formation in the region of weld.   applying a strip-shaped metallic coating onto each weld after cooling the weld.   
     
     
         3 . Method according to  claim 1 , wherein the coating of the steel sheets takes place by electrodeposition, especially by galvanic tinning, zinc coating or galvanic chrome-plating. 
     
     
         4 . Method according to  claim 1  wherein the annealing beam follows the welding beam in the welding direction. 
     
     
         5 . Method according to  claim 1 , wherein the annealing beam is incident on the weld as a line focus. 
     
     
         6 . Method according to  claim 1 , wherein the temperature of weld is held in a temperature range between 800° C. and 500° C. during cooling after welding for a time period of 1.5 to 2 seconds by means of an annealing beam. 
     
     
         7 . Method according to  claim 2 , wherein the coating of weld is effected by electrodeposition on weld. 
     
     
         8 . Method according to  claim 7 , wherein an electrical voltage is applied on the steel sheets referenced to an anode which runs along the weld at a distance from it for electrodeposition on weld, and an electrolyte is simultaneously applied onto the weld. 
     
     
         9 . Method according to  claim 7 , wherein the coated steel sheets can be tin-plated or special chrome-plated steel sheets, and in that the electrolyte contains dissolved tin cations or chromium cations. 
     
     
         10 . Method according to  claim 8  wherein the electrolyte has an electrical conductivity of 50-500 mS/cm. 
     
     
         11 . Method according to  claim 8 , wherein the electrolyte is applied onto the weld via a pad; this pad contacts the weld and is made from electrically nonconductive open-cell material. 
     
     
         12 . Method according to  claim 11 , wherein the pad contacts the surface of weld at a prescribed pressure and covers it completely. 
     
     
         13 . Method according to  claim 8 , wherein the electrolyte is sprayed onto the weld via a tube provided with at least one spray opening or spray nozzle. 
     
     
         14 . Method according to  claim 7 , wherein the steel sheets are held mostly flat in one plane during the electrodeposition on weld by means of clamping elements in the region around the weld. 
     
     
         15 . Method according to  claim 8 , wherein the steel sheets are cleaned of electrolyte residues that remain on the surface after electrodeposition on weld at least in the region around the weld. 
     
     
         16 . Method according to  claim 1 , wherein the cooling time of weld is prolonged by the annealing beam such that the cooling rate with which the weld cools is held below the cooling rate at which martensite formation could have taken place in the region of the weld without the effect of annealing beam. 
     
     
         17 . Method according to  claim 2  wherein the annealing beam follows the welding beam in the welding direction. 
     
     
         18 . Method according to  claim 2 , wherein the annealing beam is incident on the weld as a line focus. 
     
     
         19 . Method according to  claim 1 , wherein the temperature of weld is held in a temperature range between 800° C. and 500° C. during cooling after welding for a time period of 1.5 to 2 seconds by means of an annealing beam.