US2008073006A1PendingUtilityA1

Low alloy steel plastic injection mold base plate, method of manufacture and use thereof

38
Individually held — no corporate assignee on recordPriority: Sep 27, 2006Filed: Sep 27, 2006Published: Mar 27, 2008
Est. expirySep 27, 2026(~0.2 yrs left)· nominal 20-yr term from priority
Inventors:Eric D. HennRobert J. FriedrichMichael A. GuscottTerry O. Henn
B29C 45/37C22C 38/02C22C 38/04C22C 38/18
38
PatentIndex Score
0
Cited by
0
References
0
Claims

Abstract

A hot worked low alloy tool steel plate can be machined into mold base parts useful for holding tooling used in plastic injection molding. The tool steel alloy preferably exhibits desired strength, toughness, ductility, weldability, uniform hardness and dimensional stability. A process for manufacture of the steel plate includes hot working, hot roller leveling, air cooling and tempering to desired hardness.

Claims

exact text as granted — not AI-modified
1 . A mold base plate useful as plastic injection mold base parts formed of a hot worked boron-free tool steel alloy plate which has been manufactured by hot working, hot leveling after the hot working, air cooling after the hot leveling until complete transformation of the microstructure occurs, and tempering after the air cooling to lower hardness of the plate to below about 320 BHN, the tool steel alloy comprising: about 0.21 percent to about 0.28 percent by weight carbon; about 0.6 percent to about 0.9 percent by weight manganese; a maximum of 0.02 percent by weight phosphorous; from about 0.02 to about 0.1 percent by weight sulfur; from about 0.25 percent to about 0.5 percent by weight silicon; from about 1.7 percent to about 2.2 percent by weight chromium; a maximum of 0.35 percent by weight nickel; a maximum of 0.4 percent by weight copper; up to about 0.2 percent by weight molybdenum; from about 0.015 percent to about 0.05 percent by weight aluminum; and the balance being iron with up to 0.5 percent by weight total of other elements. 
     
     
         2 . The mold base plate of  claim 1  wherein the alloy has a hardness within the range of from about 277 to about 311 BHN. 
     
     
         3 . A hot worked and tempered mold base plate of a boron-free tool steel alloy, the tool steel alloy being comprised of from about 0.21 percent to about 0.28 percent by weight carbon, from about 0.6 percent to about 0.9 percent by weight manganese, a maximum of 0.02 percent by weight phosphorous, from about 0.02 to about 0.1 percent by weight sulfur, from about 0.25 percent to about 0.45 percent by weight silicon, from about 1.7 percent to about 2.2 percent by weight chromium, a maximum of 0.35 percent by weight nickel, a maximum of 0.4 percent by weight copper, up to about 0.2 percent by weight molybdenum, from about 0.015 percent to about 0.05 percent by weight aluminum and the balance being iron with up to 0.5 percent by weight total of other elements wherein the alloy has a hardness within the range of from about 270 to about 320 BHN. 
     
     
         4 . The mold base plate of  claim 3  wherein the carbon is in a range of from about 0.21 to about 0.25 percent by weight. 
     
     
         5 . The mold base plate of  claim 4  wherein the carbon is about 0.22 to 0.24 percent by weight. 
     
     
         6 . The mold base plate of  claim 3  wherein the manganese is in a range of from about 0.7 to about 0.8 percent by weight. 
     
     
         7 . The mold base plate of  claim 6  wherein the molybdenum is about 0.1 to 0.2 percent by weight. 
     
     
         8 . The mold base plate of  claim 3  wherein the silicon is in a range of from about 0.3 to about 0.4 percent by weight. 
     
     
         9 . The mold base plate of  claim 8  wherein the nickel is about 0.1 to 0.35 percent by weight. 
     
     
         10 . The mold base plate of  claim 3  wherein the chromium is in a range of from about 1.8 to about 2.2 percent by weight. 
     
     
         11 . The mold base plate of  claim 10  wherein the chromium is about 2.0 percent by weight and the sulfur is about 0.03 percent by weight. 
     
     
         12 . A mold base part made from the plate of  claim 3 , the mold base part comprising at least one of a top support, bottom support, core plate, cavity block or rail. 
     
     
         13 . A hot worked and tempered mold base plate of a boron-free tool steel alloy, the tool steel alloy consisting essentially of from about 0.21 percent to about 0.28 percent by weight carbon, from about 0.6 percent to about 0.9 percent by weight manganese, a maximum of 0.02 percent by weight phosphorous, from about 0.02 to about 0.1 percent by weight sulfur, from about 0.25 percent to about 0.5 percent by weight silicon, from about 1.7 percent to about 2.2 percent by weight chromium, a maximum of 0.35 percent by weight nickel, a maximum of 0.4 percent by weight copper, up to about 0.2 percent by weight molybdenum, from about 0.015 percent to about 0.05 percent by weight aluminum and the balance being iron with up to 0.5 percent by weight total of other elements wherein the alloy has a hardness within the range of from about 270 to about 320 BHN. 
     
     
         14 . The mold base plate of  claim 13  wherein the carbon in a range of from about 0.21 to about 0.25 percent by weight. 
     
     
         15 . The mold base plate of  claim 13  wherein the manganese is in a range of from about 0.7 to about 0.8 percent by weight. 
     
     
         16 . The mold base plate of  claim 13  wherein the silicon is in a range of from about 0.3 to about 0.4 percent by weight. 
     
     
         17 . The mold base plate of  claim 13  wherein the chromium is in a range of from about 1.8 to about 2.2 percent by weight. 
     
     
         18 . The mold base plate of  claim 13  wherein the molybdenum is about 0.1 to about 0.2 percent by weight. 
     
     
         19 . A process for manufacturing the mold base plate according to  claim 1 , the process comprising the steps of: shaping the tool steel alloy by hot rolling or hot forging into a hot worked plate using a hot rolling mill or hot forging mill; hot leveling the hot worked plate while the hot worked plate is still on the hot rolling mill or forging mill; cooling the hot leveled plate by free air cooling to a temperature below about 600° F.; and tempering the air cooled plate to a hardness in the range of from about 270 to about 320 BHN and forming the tempered air cooled plate into a mold base plate. 
     
     
         20 . The process of  claim 19 , comprising preparing a material charge, melting the material charge in an electric furnace, ladle refining the melted material to remove impurities and homogenize the melted material, removing gases from the melted material by vacuum degassing, argon shield pouring the melted material into a mold and shaping the cast tool steel alloy in a hot rolling or hot forging mill using an argon shield, hot leveling the tool steel alloy after rolling or forging, cooling the tool steel alloy by free air cooling to a temperature below about 600° F., and tempering the tool steel alloy to a hardness in the range of from about 277 to about 311 BHN. 
     
     
         21 . The process of  claim 19 , wherein the tool steel includes about 0.1 to about 0.2 percent by weight molybdenum. 
     
     
         22 . The process of  claim 19 , wherein the air cooled plate has a hardness higher than that desired for the mold base part and the tempering lowers the hardness to the desired hardness for a mold base part made from the plate. 
     
     
         23 . The process of  claim 19 , wherein the tool steel is melted and cast into a mold, cooled and reheated prior to the hot rolling or hot forging step. 
     
     
         24 . The process of  claim 19 , wherein the tool steel is formed into a plate having parallel top and bottom surfaces, parallel left and right surfaces and parallel front and back surfaces by milling the tempered air cooled plate and the milled plate is formed into a finished mold base plate having pockets, pins and/or alignment holes. 
     
     
         25 . The process of  claim 19 , wherein the free air cooling comprises cooling the hot leveled plate on a rigid cooling table so as to obtain a flat and wrinkle free plate which is not moved or lifted until the hot leveled plate is cooled below 600° F., the hot leveling and free air cooling thereby producing an air cooled plate free of residual bending stresses associated with low temperature leveling and flattening operations. 
     
     
         26 . A method of forming plastic injected parts using plastic mold tooling comprising mold base plates connected to a manifold wherein each of the mold base plates comprise the mold base plate of  claim 1 , the method comprising mating the mold base plates to form a mold cavity and injecting molten plastic through the manifold and into the mold cavity. 
     
     
         27 . The method of  claim 26 , further comprising machining pockets in the mold base plates.

Join the waitlist — get patent alerts

Track US2008073006A1 — get alerts on status changes and closely related new filings.

We store only your email — no account needed. See our privacy policy.