Steel shell for a suction roll and a method of producing a steel product

Abstract

A suction roll shell having a plurality of through holes is made of a stainless ferrite-austenite steel having a micro-structure essentially consisting of 35-65% by volume of ferrite and 35-65% by volume of austenite. The steel has a composition containing, among other things, 0.005-0.07 C and 0.15-0.30 N, in % by weight.

1 - 19 . (canceled) 
     
     
         20 . A suction roll shell with a plurality of drilled through holes, wherein the shell is formed of a plurality of segments united by circular joints and subjected to a working by turning and cutting in order to have through holes in the shell, and the shell is made of a stainless ferrite-austenite steel having a microstructure essentially consisting of 35-65% by volume of ferrite and 35-65% by volume of austenite, and having a chemical composition containing 0.005-0.07 C, 0.1-2.0 Si, 3-8 Mn, 19-23 Cr, 0.5-1.7 Ni, 0.15-0.30 N, in % by weight, and wherein the steel does not contain additives for improving cuttability. 
     
     
         21 . A suction roll shell according to  claim 20 , wherein the steel contains up to 1.0 (Mo+W/2) and up to 1.0 Cu, balance being iron and impurities, and for the chromium and nickel equivalents
   20<Creq<24.5,     10<Nieq,     where Creq=Cr+1.5 Si+Mo+2 Ti+0.5 Nb,     and Nieq=Ni+0.5 Mn+30(C+N)+0.5 (Cu+Co)   
       and wherein the steel contain no sulphur as an additive for improving cuttability. 
     
     
         22 . A suction roll shell according to  claim 20 , wherein the steel contains 0.02-0.05 C. 
     
     
         23 . A suction roll shell according to  claim 20 , wherein the steel contains 0.18-0.26 N. 
     
     
         24 . A suction roll shell according to  claim 20 , wherein the steel contains 20-23 Cr. 
     
     
         25 . A suction roll shell according to  claim 20 , wherein the steel contains 0.8-1.70 Ni. 
     
     
         26 . A suction roll shell according to  claim 25 , wherein the steel contains 1.35-1.7 Ni. 
     
     
         27 . A suction roll shell according to  claim 20 , wherein the steel contains 0.22 N, 21.5 Cr, 1.5 Ni, 0.3 Mo, 5 Mn, no more than 0.04 C. 
     
     
         28 . A suction roll, comprising a suction roll shell according to  claim 20 . 
     
     
         29 . A suction roll shell according to  claim 20 , wherein the steel contains 0.3 Cu and 0.7 Si. 
     
     
         30 . A suction roll shell according to  claim 20 , wherein the drilled through holes can be drilled with an uncoated high-speed twist drill for a drilled length of 1000 m at a cutting speed of 36 m/min with tool failure.