Annealing installation with m-shaped strip treatment tunnel

Abstract

An annealing installation for the continuous annealing of metal strip guided through the installation, includes an entrance chute 2, a first top roller chamber 3, a heating station 4, 5, 6, a cooling station 7, 8, a second top roller chamber 9 and a discharge chute 10 together delimiting an M-shaped meandering tunnel with four legs connected with each other via the two top roller chambers and a lower turning section. The entrance chute extends along the first one of the legs, the heating and the cooling stations extend along the second one of the legs, the lower turning section and the third one of the legs, and the discharge chute extends along the fourth one of the legs. Strip feeding and discharging means are provided for continuously guiding the strip as a free-hanging loop between the two top roller chambers through the heating and cooling stations during a process of annealing.

1 . An annealing installation for the continuous annealing of metal strip guided through the installation, comprising:
 an entrance chute;   a heating station with heating means;   a cooling station with cooling means;   wherein the entrance chute, the heating station and the cooling station being positioned one after the other and being connected to each other substantially gastight such that they delimit a longitudinal meandering substantially gastight strip treatment tunnel which is to be filled with a shielding gas and which has vertically directed tunnel parts connected to each other by means of a top roller chamber having at least one roller for guiding the strip from the one to the other vertically directed tunnel part,   wherein the tunnel having a strip inlet and a strip outlet at its respective outer ends which are both provided with shielding gas closures,   wherein the installation further comprises a discharge chute downstream of the cooling station and being connected substantially gastight thereto,   wherein the entrance chute, a first one of the top roller chambers, the heating station, the cooling station, a second one of the top roller chambers and the discharge chute together delimiting an M-shaped meandering tunnel with four legs connected with each other via the two top roller chambers and a lower turning section, wherein:   the entrance chute extends along the first one of the legs;   the heating and the cooling stations extend along the second one of the legs, the lower turning section and the third one of the legs; and   the discharge chute extends along the fourth one of the legs,   wherein strip feeding means and strip discharging means are provided for continuously guiding the strip as a free-hanging loop between the two top roller chambers through the heating and cooling stations extending along the second leg, the lower turning section and the third leg during a process of annealing.   
     
     
         2 . The annealing installation according to  claim 1 , wherein the heating station extends at least along part of the second leg, and wherein the cooling station extends at least along part of the third leg. 
     
     
         3 . The annealing installation according to  claim 2 , wherein the heating station further extends along the lower turning section. 
     
     
         4 . The annealing station according to  claim 1 , wherein the cooling station extends along substantially the entire third leg. 
     
     
         5 . The annealing installation according to  claim 3 , wherein the heating station further extends along a lower part of the third leg, and wherein the cooling station extends along an upper part of the third leg. 
     
     
         6 . The annealing installation according to  claim 3 , wherein the heating station comprises at least two separate heating chambers:
 a first chamber extending along the second leg, and   a second chamber extending along the lower turning section,   wherein the chambers being separated from each other by means of substantially gastight flexible connections.   
     
     
         7 . The annealing installation according to  claim 5 , wherein the heating station further comprises:
 a third chamber connecting to the second chamber and extending along the lower part of the third leg.   
     
     
         8 . The annealing installation according to  claim 6 , wherein the heating chambers are separated from each other by means of substantially gastight flexible bellows. 
     
     
         9 . The annealing installation according to  claim 6 , wherein the second heating chamber is of the refractory type with the heating means directly radiating heat towards the strip during a process of annealing. 
     
     
         10 . The annealing installation according to  claim 1 , further comprising:
 a pre-heating station extending along an upper part of the first and/or an upper part of the second leg.   
     
     
         11 . The annealing installation according to  claim 1 , wherein an upper part of the entrance chute is provided with a further shielding gas gate such that together with the shielding gas closure near the strip inlet at the lower part of the entrance chute, a sluice for shielding gas is formed. 
     
     
         12 . The annealing installation according to  claim 1 , wherein an upper part of the discharge chute is provided with a further shielding gas gate such that together with the shielding gas closure near the strip outlet at the lower part of the discharge chute, a sluice for shielding gas is formed. 
     
     
         13 . The annealing installation according to  claim 1 , wherein the entrance chute extending along the first leg in its upper part comprises a pre-heating station. 
     
     
         14 . The annealing installation according to  claim 13 , wherein the entrance chute is provided with shielding gas gates upstream and downstream of the pre-heating station. 
     
     
         15 . The annealing installation according to  claim 1 , wherein the discharge chute extending along the fourth leg in its upper part comprises an after-cooling station. 
     
     
         16 . The annealing installation according to  claim 15 , wherein the discharge chute is provided with a shielding gas gate downstream of the after-cooling station. 
     
     
         17 . The annealing installation according to  claim 1 , wherein the part of the heating station extending along the lower turning section is provided with a lock door. 
     
     
         18 . A method for continuous annealing of a metal strip, comprising:
 providing the annealing installation according to  claim 1  for the annealing of the metal strip;   filling the M-shaped meandering tunnel with a protective shielding gas; and   annealing metal strip by guiding it through the M-shaped tunnel while having it heated in the heating station and then having it cooled in the cooling station.   
     
     
         19 . The method according to  claim 18  for the bright-annealing of stainless steel strip, wherein the shielding gas contains at least 50% H2, and wherein the heating station is heated to a temperature of at least 850 degrees Celsius in order to heat the stainless steel strip therein to a temperature of at least 700 degrees Celsius. 
     
     
         20 . The method according to  claim 18 , wherein a low H2 percentage shielding gas is present in the first and fourth leg, separated from a high H2 percentage shield gas in the second and third legs.