Induction hardened blade
A method of manufacturing a blade including heating and quenching a coil of strip steel material to harden the material, heating the strip steel material to temper the material, grinding a first angle along an edge of the material, and subsequent to the grinding, re-hardening, for example by induction heating, the edge of the material.
1. A method of manufacturing a utility knife blade comprising:
heating and quenching a coil of strip steel material to harden the strip steel material and to form a martensitic microstructure substantially throughout the coil of strip steel material, the coil of strip steel material comprising a cutting edge portion along one edge and a remaining portion;
tempering the hardened strip steel material by reheating the hardened strip steel material to form a tempered martensitic microstructure substantially throughout the coil strip steel material having a first hardness; and
subsequent to said tempering, re-hardening the strip steel material locally at the cutting edge portion by reheating and quenching the strip steel material locally at said cutting edge portion such that the microstructure of the strip steel material substantially throughout said cutting edge portion is untempered martensite having a second hardness that is greater than the first hardness, while the tempered martensite microstructure having the first hardness remains the microstructure substantially throughout the remaining portion.
2. The method according to claim 1 , wherein said reheating of the re-hardening operation is performed at a temperature between about 800° C. and 900° C.
3. The method according to claim 1 , further comprising grinding an angle along the cutting edge portion.
4. The method according to claim 1 , wherein said reheating of the re-hardening operation comprises induction heating the cutting edge portion of the material.
5. The method according to claim 4 , wherein said induction heating is performed by applying an induction frequency between about 26 and 30 MHz.
6. The method according to claim 1 , wherein said re-hardening forms a heat affected zone between the cutting edge portion and the remaining portion, the heat affected zone being softer than each of the cutting edge portion and the remaining portion.
7. The method according to claim 1 , wherein said cutting edge portion that is re-hardened is a region of the blade between approximately 0.3 mm to 0.5 mm wide.
8. The method according to claim 1 , wherein quenching said cutting edge portion of the strip of steel material subsequent to reheating said cutting edge portion of the strip of steel material during the re-hardening operation comprises cooling said cutting edge portion of the material faster than a critical rate.
9. A method of manufacturing a utility knife blade comprising:
heating and quenching a coil of strip steel material to harden the strip steel material and to form a martensitic microstructure substantially throughout the coil of strip steel material, the coil of strip steel material comprising a cutting edge portion along one edge and a remaining portion;
tempering the hardened strip steel material by reheating the hardened strip steel material to form a tempered martensitic microstructure substantially throughout the coil strip steel material having a first hardness; and
subsequent to said tempering, re-hardening the strip steel material locally at said cutting edge portion by reheating and quenching the strip steel material locally at said cutting edge portion such that the microstructure of the strip steel material substantially throughout said cutting edge portion is untempered martensite having a second hardness that is over 30 HV greater than the first hardness, while the tempered martensite microstructure having the first hardness remains the microstructure substantially throughout the remaining portion.
10. The method according to claim 9 , wherein said reheating of the re-hardening operation is performed at a temperature between about 800° C. and 900° C.
11. The method according to claim 9 , further comprising grinding an angle along the cutting edge portion.
12. The method according to claim 9 , wherein said reheating of the re-hardening operation comprises induction heating the cutting edge portion of the material.
13. The method according to claim 12 , wherein said induction heating is performed by applying an induction frequency between about 26 and 30 MHz,
14. The method according to claim 9 , wherein said re-hardening forms a heat affected zone between the cutting edge portion and the remaining portion, the heat affected zone being softer than each of the cutting edge portion and the remaining portion.
15. The method according to claim 9 , wherein said cutting edge portion that is re-hardened is a region of the blade between approximately 0.3 mm to 0.5 mm wide.
16. The method according to claim 9 , wherein quenching said cutting edge portion of the strip of steel material subsequent to reheating said cutting edge portion of the strip of steel material during the re-hardening operation comprises cooling said cutting edge portion of the material faster than a critical rate.
17. A method of manufacturing a plurality of utility knife blades, the method comprising:
scoring a coil of strip steel material such that the scoring defines a plurality of trapezoidal shaped utility knife blades in the strip steel material, the coil of strip steel material comprising a cutting edge portion along one edge and a remaining portion;
subsequent to the scoring, heating and quenching the coil of strip steel material to harden the strip steel material and to form a martensitic microstructure substantially throughout the coil of strip steel material;
tempering the hardened strip steel material by reheating the hardened strip steel material to form a tempered martensitic microstructure substantially throughout the coil strip steel material having a first hardness;
subsequent to said tempering, re-hardening the strip steel material locally at said cutting edge portion by reheating and quenching the strip steel material locally at said cutting edge portion such that the microstructure of the strip steel material substantially throughout said cutting edge portion is untempered martensite having a second hardness that is greater than the first hardness, while the tempered martensite microstructure having the first hardness remains the microstructure substantially throughout the remaining portion; and
subsequent to the re-hardening, forming plurality of utility knife blades by separating the utility knife blades along the scores.
18. The method according to claim 17 , wherein said reheating of the re-hardening operation is performed at a temperature between about 800° C. and 900° C.
19. The method according to claim 17 , further comprising grinding an angle along the cutting edge portion.
20. The method according to claim 17 , wherein said reheating of the re-hardening operation comprises induction heating the cutting edge portion of the material.
21. The method according to claim 20 , wherein said induction heating is performed by applying an induction frequency between about 26 and 30 MHz.
22. The method according to claim 17 , wherein said re-hardening forms a heat affected zone between the cutting edge portion and the remaining portion, the heat affected zone being softer than each of the cutting edge portion and the remaining portion.
23. The method according to claim 17 , wherein said cutting edge portion that is re-hardened is a region of the blade between approximately 0.3 mm to 0.5 mm wide.
24. The method according to claim 17 , wherein quenching said cutting edge portion of the strip of steel material subsequent to reheating said cutting edge portion of the strip of steel material during the re-hardening operation comprises cooling said cutting edge portion of the material faster than a critical rate.