Method of manufacturing cooling block for hot stamping mold using three-dimensional metal printer

Abstract

The present disclosure relates to a method of manufacturing a cooling block for a hot stamping mold using a three-dimensional (3D) metal printer, and more particularly, to a method of manufacturing a cooling block for a hot stamping mold using a 3D metal printer including a process of first step for forming a plurality of semicircular channels through which a fluid passes on a lower block, and a process of second step for forming an upper block to form channels using a 3D metal printer respectively on the plurality of semicircular channels formed in the lower block along the plurality of semicircular channels.

Claims

1. A method of manufacturing a cooling block for a hot stamping mold using a three-dimensional (3D) metal printer, the method comprising: a process of first step for forming a plurality of semicircular channels through which a fluid passes on a lower block; and a process of second step for forming an upper block to form a shape of circular channels using a 3D metal printer respectively on the plurality of semicircular channels formed in the lower block along the plurality of semicircular channels, wherein the process of second step comprises forming circular channels by assembling a coupon having semicircular grooves on the semicircular channels formed in the lower block, and forming an upper block by depositing metal powder using a 3D metal printer on perimeter of the coupon, wherein the metal powder contains 8-10% of Cr, 1.8-2.5% of Si, 0.25-0.35% of C, 2-3% of Mn, and a remainder of Fe, in weight %.

2. The method of manufacturing a cooling block for a hot stamping mold using a 3D metal printer of claim 1, wherein the coupon has a slope surface with a decrease in width towards an upper surface from a lower surface where the semicircular grooves are formed.

3. The method of manufacturing a cooling block for a hot stamping mold using a 3D metal printer of claim 1, wherein the process of second step comprises installing copper pipes in the semicircular channels formed in the lower block, and forming an upper block by depositing metal powder using a 3D metal printer on perimeter of the copper pipes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of a general hot stamping mold.

(2) FIG. 2 is a perspective view of a cooling block of a general hot stamping mold.

(3) FIG. 3 is a partial perspective view of a cooling block of a general hot stamping mold.

(4) FIG. 4 is a diagram showing a process of manufacturing a cooling block for a hot stamping mold according to the present disclosure.

(5) FIG. 5 is a schematic diagram of a cooling block of a hot stamping mold according to the present disclosure.

(6) FIG. 6 is a schematic diagram of another embodiment of a cooling block of a hot stamping mold according to the present disclosure.

(7) FIG. 7 is a diagram showing a process of preparing metal powder for a three-dimensional (3D) metal printer.

(8) FIG. 8 is a diagram showing another process of preparing metal powder for a 3D metal printer.

(9) FIG. 9 shows a test apparatus of a shear mold to which metal powder for a 3D metal printer is applied.

(10) FIG. 10 is a detailed enlarged view of section A of FIG. 9.

(11) FIG. 11 shows a surface photographic image after a shear operation of a shear mold to which metal powder for a 3D metal printer is applied.

(12) FIG. 12 shows a comparison table of amounts of burrs occurred after a shear operation of a shear mold to which metal powder for a 3D metal printer is applied.

(13) FIG. 13 shows a hardness comparison table of metal powder for a 3D metal printer.

MODE FOR CARRYING OUT THE INVENTION

(14) A method of manufacturing a cooling block for a hot stamping mold using a three-dimensional (3D) metal printer according to the present disclosure includes a process of first step for forming a plurality of semicircular channels C through which a fluid passes on a lower block 212, and a process of second step for forming an upper block 211a to form a shape of circular channels C using a 3D metal printer respectively on the plurality of semicircular channels C formed in the lower block 212 along the plurality of semicircular channels C.

(15) The process of second step may include forming the circular channels C by assembling a coupon 213 having semicircular grooves on the semicircular channels C formed in the lower block 212, and forming the upper block 211a by depositing metal powder as a 3D metal printer on the perimeter of the coupon 213.

(16) The coupon 213 may have a slope surface with a decrease in width towards an upper surface from a lower surface where the semicircular grooves are formed.

(17) The process of second step may include installing copper pipes 214 in the semicircular channels C formed in the lower block 212, and forming an upper block 211 by depositing metal powder as a 3D metal printer on the perimeter of the copper pipes 214.

(18) The metal powder may include SKD61 species.

(19) The metal powder may consist of 8-10% of Cr, 1.8-2.5% of Si, 0.25-0.35% of C, 2-3% of Mn, and a remainder of Fe, in weight %.

(20) Hereinafter, a detailed description of the method of manufacturing a cooling block for a hot stamping mold using a 3D metal printer according to the present disclosure is provided below with reference to the accompanying drawings.

(21) FIG. 1 is a perspective view of a general hot stamping mold, FIG. 2 is a perspective view of a cooling block of the general hot stamping mold, and FIG. 3 is a partial perspective view of the cooling block of the general hot stamping mold.

(22) For reference, a machine which prints a 3D object using metal powder as a toner is referred to as a 3D metal printer.

(23) As shown in FIGS. 1 through 3, the hot stamping mold includes upper and lower molds 100 and 200, and in the hot stamping mold, a cooling block 200 is provided to cool a material molded by pressing within the upper and lower molds 100 and 200.

(24) Generally, the upper and lower molds 100 and 200 are manufactured by casting.

(25) The cooling block 200 has channels C inside as a passage through which cooling water moves, and generally, copper pipes 214 are installed and used as the channels C.

(26) Thus, when cooling water flows through the copper pipes 214, heat is transferred by the cooling water, and the material and the upper and lower molds 100 and 200 are thus cooled.

(27) However, because the copper pipes 214 are made of an expensive metal, it costs so much to manufacture the cooling block 200 having the plurality of channels C.

(28) FIG. 4 is a diagram showing a process of manufacturing a cooling block for a hot stamping mold according to the present disclosure, and FIG. 5 is a schematic diagram of a cooling block of a hot stamping mold according to the present disclosure.

(29) As shown in FIG. 4, the method of manufacturing a cooling block for a hot stamping mold according to the present disclosure includes a process of first step for forming a plurality of semicircular channels C through which a fluid passes on the lower block 212, and a process of second step for forming the upper block 211 to form a shape of circular channels C using a 3D metal printer respectively on the plurality of semicircular channels C formed in the lower block 212 along the plurality of semicircular channels C.

(30) That is, the cooling block 200 is composed of the upper block 211 and the lower block 212, and the process of first step includes forming semicircular channels C through which a fluid passes on the lower block 212.

(31) The process of second step includes forming the upper block 211 to form a shape of circular channels C using a 3D metal printer respectively on the plurality of semicircular channels C formed in the lower block 212 along the plurality of semicircular channels C.

(32) The channels C are concave grooves in cross section, and may be formed in various shapes based on the shape of a material to be manufactured.

(33) FIG. 6 is a schematic diagram of another embodiment of the cooling block of the hot stamping mold according to the present disclosure.

(34) As shown in FIG. 6, the process of second step includes assembling the coupon 213 having semicircular grooves on the semicircular channels C formed in the lower block 212 to form circular channels C, and depositing metal powder as a 3D metal printer on the perimeter of the coupon 213 to make the upper block 211a.

(35) In this instance, due to a size of an inlet through which molten metal powder is fed into the 3D metal printer, the coupon 213 has a slope surface with a decrease in width towards an upper surface from a lower surface where the semicircular grooves are formed, to prevent the interference between adjacent coupons 213.

(36) That is, on the channels C, the coupon 213 having a vertical cross-sectional shape of ‘’ is coupled, and on the coupon 213, the upper block 211a having a vertical cross-sectional shape of ‘’ is coupled.

(37) Particularly, the metal powder used to make the upper block 211a is from materials with high thermal conductivity.

(38) The process of second step may include installing copper pipes 214 in the semicircular channels C formed in the lower block 212, and forming the upper block 211 by depositing metal powder as a 3D metal printer on the perimeter of the copper pipes 214.

(39) In the present disclosure, the metal powder for a 3D metal printer may include SKD61 species, or otherwise metal powder of the following composition.

(40) The metal powder for a 3D metal printer according to the present disclosure may consist of 8-10% of Cr, 1.8-2.5% of Si, 0.25-0.35% of C, 2-3% of Mn, and a remainder of Fe, in weight %.

(41) Cr is a metal which is excellent in corrosion resistance and mechanical properties, and when less than 8% of Cr is present, the effect of Cr in the composition is insignificant, and when more than 10% of Cr is present, the effect obtained by Cr is insignificant as compared to an increase in content, so the cost effectiveness reduces.

(42) For reference, a steel alloy containing 12% or more of Cr is known as stainless steel.

(43) C is an element which changes the properties of steel such as strength and hardness based on the content, and most carbon steels with the carbon content of 0.1-1.5% can be heat treated, and the metal powder of the present disclosure contains 0.25-0.35% of C.

(44) Mn is an element which is hard, and is necessary to increase corrosion resistance and mechanical properties in metal alloying, and when less than 2% of Mn is present, its effect is insignificant, and when more than 3% of Mn is present, the effect obtained relative to an increase in content is low.

(45) Si is an element which causes little chemical reaction and is grown on surfaces of other metals, and when less than 1.8% of Si is present, its effect is insignificant, and when more than 2.5% of Si is present, the effect obtained relative to the content fed is low.

(46) Particularly, Mn and Si are an element necessary as a deoxidizer in steel making.

(47) To improve the function of a metal product, the metal powder may further include 0.01-0.05% of P, 0.05-1.0% of Ni, 0.01-0.05% of Mo, 0.001-0.005% of Ti, 0.01-0.05% of V, 0.004-0.01% of Nb, 0.02-0.05% of W, 0.01-0.05% of Co, 0.004-0.01% of Zr, and 0.002-0.005% of B, in weight percent.

(48) The P, Ni, Mo, Ti, V, Nb, W, Co, Zr, and B may be present singly or in combination.

(49) P (phosphorus) is an extremely flammable element which spontaneously ignites in air, and when the content of P is less than 0.01%, ignitability is insignificant, less affecting the melting of the metal powder, and when the content of P is more than 0.05%, strong ignitability leads to ignition of all the other metals and brings the metal powder into too soft liquid state, making deposition difficult during a printing operation.

(50) Ni (nickel) is an element which can forge and forge weld, is rich in ductility and flexibility, and is less prone to oxidization than iron, and it is used as a catalyst or for iron plating. When the content of Ni is less than 0.05%, its effect relative to Ni feeding is insignificant, and when the content is 1.0% or more, the effect obtained relative to the amount of Ni present is low.

(51) Mo (molybdenum) is so mechanically strong over a wide temperature range, does not dissolve in ordinary acid, and does not erode in concentrated nitric acid. Molybdenum steel made by alloying with iron is used for a cutting tool. When the content of Mo is less than 0.01%, the effect obtained is insignificant, and when the content is more than 0.05%, the effect obtained relative to the content is reduced.

(52) Ti (titanium) is an element which has high strength, ductility and flexibility, and forms an oxide film on surfaces and is less susceptible to corrosion in acid or sea water, and when the content is less than 0.001%, the effect from Ti inclusion is insignificant, and when the content is more than 0.005%, it costs so much in comparison to the effect obtained.

(53) V (vanadium) forms alloys with steel or iron for use in high speed tool steel and steel for a high strength structure, and when less than 1% is present in steel, steel has a fine surface structure, and it reacts with carbon into carbide. When the content of V is less than 0.01%, the effect from V inclusion is insignificant, and when the content is more than 0.05%, the effect relative to cost is low.

(54) Nb (niobium) is an element which does not erode in oxygen or strong acid and is added to provide heat resistance of stainless alloys. When the content of Nb is less than 0.004%, the effect from Nb inclusion is insignificant, and when the content is more than 0.01%, the effect is low as compared to the amount of Nb present.

(55) W (tungsten) is used in high speed steel, permanent magnet steel, and heat resistant and anticorrosive alloys, and tungsten carbide is used in a tool. Because it is expensive, when less than 0.02% of W is present, the effect from W inclusion is insignificant, and when the content is more than 0.05%, the effect obtained is low as compared to the amount of W present.

(56) Co (cobalt) is a shiny metal similar to iron and has strong magnetic property. It is less prone to melting when heated, and it rusts on surfaces but is less prone to corrosion in air, and is excellent in oxidization resistance, wear resistance, and mechanical properties. When less than 0.01% is present, the effect from Co feeding is low, and when 0.05% or more is present, the effect is low as compared to the amount of Co present.

(57) Zr (zirconium) has high corrosion resistance in high temperature water. Zr is an element which forms an oxide film when exposed to air, exhibiting strong corrosion resistance, and powdered zirconium ignites in air, and when less than 0.004% is present, it ignites in air, causing no reaction, and when 0.01% or more is present, the effect is low as compared to the amount of Zr present, imposing an economic burden.

(58) B (boron) has low reactivity but forms a compound with oxygen or nitrogen, and is used as a degasser in metal smelting, and a compound with C (carbon), B4C, is one of the hardest artificial materials, and when less than 0.002% is present, reactivity is weak, and when more than 0.005% is present, the effect obtained is low as compared to the amount introduced

(59) FIG. 7 is a diagram showing a process of preparing metal powder for a 3D metal printer.

(60) As shown in FIG. 7, the process of preparing metal powder for a 3D metal printer according to the present disclosure includes a process of first step for preparing constituent metal materials of metal powder, and mixing the metal materials at a designated weight ratio.

(61) The metal materials mixed at the process of first step undergo a process of second step for pulverizing into metal powder using a pulverizer.

(62) As a process of third step, the metal powder produced at the second step is sieved through a sieving machine to separate metal powder with designated particles, impurities, and metal powder with larger particles.

(63) FIG. 8 is a diagram showing another process of preparing metal powder for a 3D metal printer.

(64) The process of preparing metal powder for a 3D metal printer according to the present disclosure includes a process of first step for preparing each of constituent metal materials of metal powder.

(65) Each of the prepared metal materials undergoes a process of second step for pulverizing into metal powder using a pulverizer.

(66) Each metal powder produced at the second step undergoes a process third step for sieving through a sieving machine to separate metal powder with a designated particle size, and finally, as a process of fourth step, each metal powder separated at the third step is mixed at a designated weight ratio.

(67) The following is a test to which the metal powder is applied.

(68) FIG. 10 shows a test apparatus for a shear mold to which metal powder for a 3D metal printer is applied, and FIG. 11 is a detailed enlarged view of section A of FIG. 10.

(69) As shown in FIGS. 10 and 11, based on 23F85 metal material, a shear mold is manufactured through welding, deposition, and flame heat treatment, respectively, applied to upper and lower notched parts which come into direct contact with a material during a shear operation.

(70) A shear operation is performed using the shear molds manufactured as above.

(71) FIG. 12 shows a surface photographic image after a shear operation of a shear mold to which metal powder for a 3D metal printer according to the present disclosure is applied.

(72) As shown in FIG. 12, it can be seen that a shear mold made by welding or deposition has more smooth and clean surfaces than that of flame heat treatment.

(73) FIG. 13 shows a comparison table of amounts of burrs occurred after a shear operation of a shear mold to which metal powder for a 3D metal printer according to the present disclosure is applied.

(74) It shows deposition stability as a result of depositing metal powder of a different material according to the present disclosure on a basic material of a shear mold 23F5 cast steel, and it can be seen that after deposition, an amount of scratches occurred on the steel surface after a 12,000-stroke shear operation is smaller than those of welding and raw material heat treatment conditions.

(75) FIG. 14 shows a hardness comparison table of metal powder for a 3D metal printer.

(76) As metal powder generally has similar constituents to a welding rod by the present disclosure, a comparison was conducted by depositing the constituent materials of the welding rod, SKD11 powder and SKD61 powder, and as shown in FIG. 14, according to the test, it can be seen that the shear mold manufactured by the metal powder of the present disclosure has highest hardness.

(77) On the other hand, the metal powder may be used singly or in combination with either SKD11 or SKD61, or both.

(78) The method of manufacturing a cooling block for a hot stamping mold using a 3D metal printer according to the present disclosure makes a cooling block from a less expensive material, and forms only a contact part between a lower mold and an upper mold from an expensive material with high thermal conductivity via 3D deposition processing, thereby curtailing material costs and maximizing the cooling performance, leading to remarkable effects of economical and procedural efficiency improvements.