Cold work die steel, die, and method for production of cold work die steel

Abstract

The invention relates to a cold work die steel containing, by mass %, C: 0.20 to 0.60%, Si: 0.5 to 2.00%, Mn: 0.1 to 2%, Cr: 3.00 to 9.00%, Al: 0.3 to 2.0%, Cu: 1.00 to 5%, Ni: 1.00 to 5%, Mo: 0.5 to 3% and/or W: 2% or less (including 0%), S: 0.10% or less (not including 0%), in which the following requirements (1) to (3) are satisfied {wherein each square bracket [ ] means a content (%) of each element}: [Cr]×[C]≦3.00,  (1) [Cu]/[Ni]:0.5 to 2.2,  (2) [Mo]+0.5×[W]:0.5 to 3.0%,  (3) with the remainder being iron and unavoidable impurities; and to a die obtained by the using the same. The invention also relates to a production method for a cold work die steel.

1 . A cold work die steel comprising, by mass %,
 C: 0.20 to 0.60%,   Si: 0.5 to 2.00%,   Mn: 0.1 to 2%,   Cr: 3.00 to 9.00%,   Al: 0.3 to 2.0%,   Cu: 1.00 to 5%,   Ni: 1.00 to 5%,   at least one of Mo: 0.5 to 3%, and W: 2% or less (including 0%),   S: 0.10% or less (not including 0%),   wherein the following requirements (1) to (3) are satisfied in which each square bracket [ ] means a % content of each element:
   [Cr]×[C]≦3.00,  (1) 
   [Cu]/N11:0.5 to 2.2,  (2) 
   [Mo]+0.5×[W]:0.5 to 3.0%,  (3) 
   with the remainder being iron and unavoidable impurities.   
   
   
       2 . The cold work die steel according to  claim 1 , which further comprises V: 0.5% or less (not including 0%). 
   
   
       3 . The cold work die steel according to  claim 1 , which further comprises at least one element selected from the group consisting of Ti, Zr, Hf, Ta and Nb in a total amount of 0.5% or less (not including 0%). 
   
   
       4 . The cold work die steel according to  claim 1 , which further comprises Co: 10% or less (not including 0%). 
   
   
       5 . The cold work die steel according to  claim 1 , which has a martensite transformation point (Ms point) of 170° C. or higher represented by the following formula:
     Ms  point=550−361×[C]−39×[Mn]−35×[V]−20×[Cr]     − 17 ×[Ni]−10×[Cu]−5×([Mo]+[W])+     15×[Co]+30×[Al]   wherein each square bracket [ ] means a % content of each element.   
   
   
       6 . A die comprising the cold work die steel according to  claim 1 . 
   
   
       7 . A method for producing a cold work die steel, comprising:
 preparing a steel satisfying the composition according to  claim 1  and further satisfying the following requirement (4) wherein each square bracket [ ] means a % content of each element:
   [Cu]/[C]:4.0 to 15;  (4) 
   and subjecting the steel to a solution treatment and an aging treatment under the condition satisfying the following formula (5):
     TA− 10≦T2≦TA+10  (5) 
   wherein,
     TA= 0.29 ×T 1-2.63×[Cu]/[C]+225, 
   T1 means a solution treatment temperature (° C.), and   T2 means an aging temperature (° C.).   
   
   
       8 . The production method according to  claim 7 , wherein the steel further comprises V: 0.5% or less (not including 0%). 
   
   
       9 . The production method according to  claim 7 , wherein the steel further comprises at least one element selected from the group consisting of Ti, Zr, Hf, Ta and Nb in a total amount of 0.5% or less (not including 0%). 
   
   
       10 . The production method according to  claim 7 , wherein the steel further comprises Co: 10% or less (not including 0%). 
   
   
       11 . The production method according to  claim 7 , wherein the steel has a martensite transformation point (Ms point) of 170° C. or higher represented by the following formula:
     Ms  point=550−361×[C]−39×[Mn]−35×[V]−20×[Cr]     − 17 ×[Ni]−10×[Cu]−5×([Mo]+[W])+     15×[Co]+30×[Al]   wherein each square bracket [ ] means a % content of each element,   of 170° C. or higher.   
   
   
       12 . A die obtained in accordance with the production method according to  claim 7 .