Spreaders for die casting and methods of making the same

Abstract

A spreader configured to be implemented in a die of a die casting system is disclosed. The spreader includes: a substrate; a hardening layer and an oxide layer. The hardening layer includes: a nitride and carbide layer disposed on the substrate and increasing hardness; and a white layer disposed on the nitride and carbide layer. The oxide layer includes: an inner transition layer disposed on the white layer and increasing resistance to oxidation; and an outer iron oxide layer disposed on the inner transition layer and increasing resistance to soldering during die casting of a part in the die casting system.

1 . A spreader configured to be implemented in a die for a die casting system, the spreader comprising:
 a substrate;   a hardening layer comprising
 a nitride and carbide layer disposed on the substrate and increasing hardness, and 
 a white layer disposed on the nitride and carbide layer, wherein the white layer has been transformed into pearlite comprising alternating layers of ferrite and cementite; and 
   an oxide layer comprising
 an inner transition layer disposed on the white layer and increasing resistance to oxidation and enriched with at least one of nickel and copper, and 
 an outer iron oxide layer disposed on the inner transition layer and increasing resistance to soldering during die casting of a part in the die casting system, wherein the outer iron oxide layer comprises at least one external guide surface i) upstream from the die in which a part is formed, and ii) guides molten metal from a sprue bush into a gate system area of the die. 
   
     
     
         2 . The spreader of  claim 1 , wherein the substrate comprises at least one of martensite, bainite, and ferrite. 
     
     
         3 . The spreader of  claim 1 , wherein the substrate comprises nanoprecipitation having size less than 50 nm. 
     
     
         4 . The spreader of  claim 1 , wherein thermal conductivity of the substrate is greater than 38 W/mK. 
     
     
         5 . The spreader of  claim 1 , wherein the hardening layer has a hardness of greater than or equal to 65 HRC. 
     
     
         6 . The spreader of  claim 1 , wherein the spreader comprises a body comprising:
 a first disc;   a second disc; and   a channel cut into the first disc and the second disc,   wherein the channel comprises a guide surface for guiding molten metal during a die casting process of the part.   
     
     
         7 . The spreader of  claim 1 , wherein a thickness of the outer iron oxide layer is 0.5-10.0 μm. 
     
     
         8 . The spreader of  claim 1 , wherein a thickness of the inner transition layer is 0.1-5.0 μm. 
     
     
         9 . The spreader of  claim 1 , wherein the outer iron oxide layer mainly comprises by weight 70-74% iron, 25-30% oxygen, and 1-5% aluminum. 
     
     
         10 . (canceled) 
     
     
         11 . The spreader of  claim 1 , wherein metal in the inner transition layer comprises by weight 4-20% nickel and 1-5% copper. 
     
     
         12 . The spreader of  claim 1 , wherein:
 a thickness of the white layer is 0.5-2.0 μm; and   a thickness of the nitride and carbide layer is 80-300 μm.   
     
     
         13 . The spreader of  claim 1 , wherein a chemical composition of the substrate comprises by mass 0-0.2% carbon, 0.2-6% copper, 3-10% nickel, 0.5-3% aluminum, 0.2-1.5% manganese, 0-1.5% chromium, 0-2.5% molybdenum, 0-1.5% tungsten, and 0-0.2% vanadium. 
     
     
         14 . The spreader of  claim 1 , wherein the inner transition layer comprises a sawtooth structure. 
     
     
         15 . A die casting system comprising:
 the spreader of  claim 1 ; and   the die comprising a first half and a second half,   wherein the spreader is attached to the first half and guides molten metal from a sprue bush into a gate system area and a cavity of the die during a die casting process.   
     
     
         16 . A method of forming a spreader for a die casting system, the method comprising:
 providing a forged block of tool steel;   machining the block of tool steel to form a preliminary spreader;   austenitizing the preliminary spreader;   subsequent to austenitizing preliminary spreader, cooling the preliminary spreader to room temperature;   subsequent to cooling the preliminary spreader, machining the preliminary spreader to form a final spreader; and   subsequent to machining the preliminary spreader, form a hardening layer and an oxide layer by i) nitrocarburizing the spreader and oxidizing the nitrocarburized spreader or ii) oxy-nitrocarburizing the spreader,   wherein the hardening layer comprises
 a nitride and carbide layer disposed on a substrate, and 
 a white layer disposed on the nitride and carbide layer, and 
   wherein the oxide layer comprises
 an inner transition layer disposed on the white layer, 
 an outer iron oxide layer disposed on the inner transition layer, and 
 at least one external guide surface i) upstream from a die in which a part is formed, and ii) guides molten metal from a sprue bush into a gate system area of the die. 
   
     
     
         17 . The method of  claim 16 , further comprising, subsequent to machining, nitrocarburizing the preliminary spreader and oxidizing the nitrocarburized spreader to form the hardening layer and the oxide layer. 
     
     
         18 . The method of  claim 16 , further comprising, subsequent to machining, oxy-nitrocarburizing the preliminary spreader to form the hardening layer and the oxide layer. 
     
     
         19 . The method of  claim 16 , further comprising, subsequent to forming the oxide layer, machining the final spreader. 
     
     
         20 . The method of  claim 16 , wherein a chemical composition of the block of tool steel comprises by mass 0-0.2% carbon, 0.2-6% copper, 3-10% nickel, 0.5-3% aluminum, 0.2-1.5% manganese, 0-1.5% chromium, 0-2.5% molybdenum, 0-1.5% tungsten, and 0-0.2% vanadium. 
     
     
         21 . The spreader of  claim 1 , wherein the spreader comprises:
 a first disc;   a second disc disposed on the first disc, having a smaller outer diameter than the first disc, and having a notched side to provide the at least one external guide surface;   the at least one external guide surface comprises a plurality of adjacent planar guide surfaces that are recessed in the second disc; and   a plurality of side surfaces extending inward from an outer surface of the second disc to the plurality of adjacent planar guide surfaces.