JP4200486B2 - Manufacturing method of mold with hardness gradient by partial heat treatment using fluidized bed furnace - Google Patents

Description

  The present invention relates to a mold which is manufactured by performing partial heat treatment such as partial quenching and partial tempering using a fluidized bed furnace as means for manufacturing a mold having a hardness gradient.

  Conventionally, many processes using a salt bath heat treatment using a salt bath furnace have been widely used for producing molds.

  However, the salt bath furnaces used in the past are highly corrosive due to the use of salt, and further require a water washing treatment, etc., which is very time consuming and requires salt bath evaporative gas, factory effluent, and salt bath industry. There are problems such as measures against pollution such as waste.

  Therefore, the present invention is a method of producing a mold using a fluidized bed heat treatment furnace that is less deliquescent than a salt bath furnace and is environmentally friendly, and is a furnace in which one side of the mold is maintained at a quenching temperature. A mold having a hardness gradient from one side of the mold to the other side is provided by partial immersion in the fluidized bed, quenching after holding for a predetermined time, and then tempering the whole. It is for the purpose.

In order to solve the above-mentioned problems, the present invention provides a rough-processed mold 2 in a fluidized bed heat treatment furnace 4 having a fluidized bed temperature of 850 ° C. with the bottom surface 2a of the mold 2 facing up and the top surface 2b facing down. Then, it is suspended directly above the fluidized bed 4b so as to be preheated 5 and the upper surface 2b side of the mold 2 is partially immersed 6 in the fluidized bed 4b and held for 2 hours, and then the temperature is raised to 1030 ° C. By maintaining 7 for 2 hours, a gradient is applied to the quenching temperature, and after the partial quenching 8 is performed on the mold 2, the whole is tempered 9 to provide a hardness gradient from one side to the other side. When the hardness of the bottom surface 2a of the mold 2 is too high, the partial tempering process 13 is performed again in the fluidized bed heat treatment furnace 12 to control the hardness, and the mold 2 is finished as the product 15 and finished 14 By partial heat treatment using a fluidized bed furnace. We had a hardness gradient was a method for manufacturing a mold according to claim.

  The present invention has the following effects. First, by using a fluidized bed heat treatment furnace, each processing step can be performed efficiently and environmental issues can be taken into consideration.

  Second, by performing a tempering treatment after partial quenching, a concentration gradient of the martensite phase is formed in the thickness direction of the mold by the first partial quenching, and the martensite phase is subsequently tempered. Since the treatment strongly affects hardness and toughness, a mold having a hardness gradient from one side of the mold to the other side can be produced.

  By using a fluidized bed heat treatment furnace that does not have deliquescence and is environmentally friendly, we have created a mold with a hardness gradient.

  Below, based on an accompanying drawing, the metal mold | die with the hardness gradient by the partial heat processing using the fluidized bed furnace which is this invention is demonstrated in detail. FIG. 1 is a flowchart showing a manufacturing process of a mold having a hardness gradient by partial heat treatment using a fluidized bed furnace according to the present invention. 2 to 5 are diagrams showing processing states in each process during the manufacturing process.

  FIG. 1 is a flowchart showing a manufacturing process of a mold having a hardness gradient by partial heat treatment using a fluidized bed furnace according to the present invention. As shown in FIG. 1, in the mold manufacturing process 1, a rough-processed mold 2 is placed in an atmospheric furnace 3, and preheat treatment 5, partial immersion preheating 6, partial immersion quenching temperature holding 7 is performed in a fluidized bed heat treatment furnace 4. Then, the partial quenching 8 and the tempering process 9 are performed, and the pass mold 10 having the low bottom hardness is subjected to the finishing process 14 as it is to become the product 15. After each process in the fluidized bed heat treatment furnace 4, the bottom hardness The mold 11 that is too high is subjected to a partial tempering process 13 again in the fluidized bed heat treatment furnace 12 and then a finishing process 14 to become a product 15.

  2 to 5 are diagrams showing processing states in each step of the mold manufacturing process 1 shown in FIG. 2 is a diagram showing a treatment state in the pre-heat treatment step, FIG. 3 is a diagram showing a treatment state in the partial immersion preheating step, FIG. 4 is a diagram showing a treatment state in the partial immersion quenching temperature holding step, FIG. 5 is a diagram showing a processing state in the partial tempering process. In the following, each step of the mold manufacturing process 1 shown in FIG. 1 will be described together with the processing state diagrams shown in FIGS.

  In the manufacturing process 1 of a mold having a hardness gradient by partial heat treatment using a fluidized bed furnace according to the present invention, first, a rough-processed mold 2 is manufactured in an atmospheric furnace 3. At this time, the rough-processed mold 2 is a mold having a size in which a portion that is cut by each finishing process is added as a finishing allowance.

  The atmospheric furnace 3 used here becomes the atmospheric furnace 3 by blowing air from the bottom of the fluidized bed furnace. Moreover, the furnace used for producing the rough-processed mold 2 may be a nitrogen gas atmosphere furnace instead of the atmospheric furnace 3. Similarly to the atmospheric furnace 3, the nitrogen gas atmosphere furnace also becomes a nitrogen gas atmosphere furnace by blowing up nitrogen gas from the bottom of the fluidized bed furnace.

  The die 2 roughly processed in the atmospheric furnace 3 is then subjected to each treatment in the fluidized bed heat treatment furnace 4. The first treatment in the fluidized bed heat treatment furnace 4 is a preheat treatment 5. The pre-heat treatment 5 will be described with reference to a diagram showing a treatment state in the pre-heat treatment of FIG.

  As shown in FIG. 2, in the preheat treatment 5, the rough-processed mold 2 is placed on the base 16 c of the mold suspension jig 16 so that the bottom surface 2 a is up and the top surface 2 b is down. The die suspension jig 16 hangs a hanging portion 16a provided on the upper portion of the support portion 16b on a crane and is suspended in the direction of arrow 17 by the crane.

  The temperature of the fluidized bed 4b surrounded by the furnace inner wall 4a of the fluidized bed heat treatment furnace 4 when the preheat treatment 5 is performed is 850 degrees. When the pre-heat treatment 5 is performed, the rough-processed mold 2 placed on the pedestal 16c of the mold suspension jig 16 is suspended and held immediately above the fluidized bed 4b so as not to be immersed in the fluidized bed 4b.

  The process performed after the preheating 5 is a process of partial immersion preheating 6. The partial immersion preheating 6 will be described with reference to the drawing showing the processing state in the partial immersion preheating of FIG.

  As shown in FIG. 3, in the partial immersion preheating 6, the rough-processed mold 2 is partially immersed in the fluidized bed 4 b preheated to 850 degrees by the preheat treatment 5. That is, the mold suspension jig 16 adjusts so that it is immersed in the fluidized bed 4b to almost half the height of the rough-processed mold 2 placed on the base 16c of the mold suspension jig 16 so that the upper surface 2b faces down. Then, the upper surface 2b side of the rough-processed mold 2 is partially immersed in the fluidized bed 4b.

  The temperature of the fluidized bed 4b in the partial immersion preheating 6 is 850 ° C., and the preheating at 850 ° C. is maintained for about 2 hours while the upper surface 2b side of the rough-processed mold 2 is partially immersed in the fluidized bed 4b.

  The processing step after the partial immersion preheating 6 is a step of partial immersion quenching temperature holding 7. The partial immersion quenching temperature holding 7 will be described with reference to FIG. 4 showing the treatment state in the partial immersion quenching temperature holding.

  In the process of partial immersion quenching temperature holding 7, the furnace temperature is increased while the upper surface 2b side of the rough-processed mold 2 held for 2 hours in the partial immersion preheating 6 process is partially immersed in the fluidized bed 4b. The temperature of the fluidized bed 4b is set to 1030 degrees which is the quenching temperature.

  As shown in FIG. 4, the partial immersion quenching temperature maintaining step 7 raises the temperature of the furnace while maintaining the partial immersion preheating 6, so that rough machining placed on the pedestal 16 c of the mold suspension jig 16 is performed. The finished mold 2 is baked into the mold by raising the temperature of the furnace with the upper surface 2b side partially immersed in the fluidized bed 4b, raising the temperature of the fluidized bed 4b to 1030 degrees, and holding it for 2 hours. Put a temperature gradient.

  The process after partial immersion quenching temperature holding 7 is a process of partial quenching 8. The partial quenching 8 is a step of performing oil quenching after holding the partial immersion for 2 hours in the fluidized bed 4b raised to 1030 degrees by the partial immersion quenching temperature maintenance 7.

  After the partial quenching 8 process, a tempering process 9 for tempering the entire mold is performed. In the tempering process 9, the entire mold is tempered at a predetermined temperature and time, thereby producing a mold having a hardness gradient from one side of the mold to the other side. Can do.

  In this way, the entire tempering process 9 is performed after the partial quenching 8 by first performing the partial quenching 8 process, so that the concentration gradient of the martensite phase is increased in the thickness direction of the mold. This is because the martensite phase strongly affects hardness and toughness by the subsequent tempering treatment.

  By using the fluidized bed heat treatment furnace 4, pre-heat treatment 5, partial immersion preheating 6, partial immersion quenching temperature holding 7, partial quenching 8, and tempering treatment 9 are performed. When the mold 10 can be manufactured, the finishing process 14 is performed as it is, and the product 15 is obtained.

  Further, when each processing step in the fluidized bed heat treatment furnace 4 is performed and the mold 11 has a bottom surface hardness that is too high, processing for finer hardness control is performed. That is, the partial tempering process 13 by the fluidized bed heat treatment furnace 12 is performed to control the hardness.

  FIG. 5 is a diagram showing a processing state in the partial tempering process. As a result of preheating 5 in the fluidized bed heat treatment furnace 4, partial immersion preheating 6, partial immersion quenching temperature holding 7, partial quenching 8, and tempering treatment 9, the mold 11 having a too high bottom hardness is In order to control the hardness, the partial tempering process 13 is again performed in the fluidized bed heat treatment furnace 12.

  As shown in FIG. 5, in the step of the partial tempering process 13, the base of the mold suspending jig 16 is arranged so that the upper surface 11b is on the upper surface 11b and the lower surface 11a is on the lower surface hardness of the mold 11. Place on 16c. The mold suspension jig 16 is moved up and down using a crane, and the bottom surface 11a side of the mold 11 having a too high bottom surface hardness is partially immersed in the fluidized bed 12b. Reference numeral 12a represents the furnace inner wall.

  The temperature of the fluidized bed 12b of the fluidized bed heat treatment furnace 12 used for the partial tempering process 13 is adjusted between about 650 degrees and 730 degrees as necessary. In this way, fine hardness control of the mold bottom surface can be performed by partially immersing the bottom surface 11a side and performing the partial tempering process 13.

  By applying a partial tempering process 13 by a fluidized bed heat treatment furnace 12 to the mold 11 whose bottom surface hardness is too high and finely controlling the hardness of the mold bottom surface, To product 15.

  As described above, by performing each processing step of the mold manufacturing process 1 shown in FIG. 1, a mold having a hardness gradient by partial heat treatment using a fluidized bed furnace can be manufactured.

  6 is a plan view of a mold used in a mold having a hardness gradient by partial heat treatment using a fluidized bed furnace according to the present invention, FIG. 7 is a sectional view of the mold, and FIG. 8 is a diagram of the mold. It is a perspective view.

  As shown in FIGS. 6 to 8, the mold 18 is a receiving material for high-temperature tool steel (DH31) made of two cylinders having different diameters, and the diameter of the upper part 18b is larger than the diameter of the cylinder of the lower part 18a. Is smaller.

  As shown in FIG. 7, the diameter of the hole 18d drilled in the center of the lower portion 18a is smaller than the diameter of the hole 18c drilled in the center of the lower portion 18b. It is connected and is provided through the center of the mold 18.

  Suspension screw holes 18f and 18f are formed on the lower surface side of the lower part 18a so as to correspond to the suspension screw holes 18e and 18e formed in the upper part 18b.

  FIG. 9 is a vertical cross-sectional hardness distribution diagram showing the experimental results of a mold having a hardness gradient by partial heat treatment using a fluidized bed furnace according to the present invention.

  The conditions of the experiment shown in FIG. 9 are such that a high-temperature tool steel (DH31) receiving material is used for the mold 18, and it is not immersed in the fluidized bed 19 up to 40 mm from the bottom of the mold 18 in the fluidized bed heat treatment furnace. This part is immersed in a fluidized bed and partially quenched at a temperature of 1030 ° C. for 1 hour. The bottom surface temperature at that time is 750 ° C. and oil-quenched. Was made twice. In addition, the code | symbol 19a represents the fluidized bed immersion position.

  FIG. 9 shows a result obtained by performing an experiment on the mold 18 under the above conditions. As shown in FIG. 9, a mold having a hardness gradient is obtained by the partial quenching / entire tempering process of the mold 18, and it is understood that partial quenching is effective for producing a mold having a hardness gradient. .

  FIG. 10 is a graph showing the influence of the quenching temperature on the tempering hardness of the mold showing the experimental results of the mold having a hardness gradient by partial heat treatment using the fluidized bed furnace according to the present invention.

  The vertical axis of the graph 20 represents the quenching / tempering hardness (HRC) 20a, and the horizontal axis represents the quenching temperature 20b. A small square material of 14 × 14 × 16 mm was used as an experimental material, and the quenching temperature was measured from 600 ° C. to 950 ° C. at intervals of 50 ° C. and nine temperatures of 1030 ° C., held at each temperature for 2 hours, Quenching was performed.

  Thereafter, the process of tempering at 550 ° C. for 3 hours and air cooling was repeated twice to measure the hardness.

  As shown in FIG. 10, at a quenching temperature of 800 ° C. or lower, there is no increase in hardness due to the subsequent tempering treatment, and the low hardness of the experimental material is maintained, but when measured at 800 ° C. or higher, a high hardness is obtained. keeping.

  From this, it can be seen that effective partial quenching to obtain a mold having a hardness gradient is to keep the temperature of the opposite surface (bottom surface) immersed in the quenching temperature at 800 to 850 ° C.

It is a flowchart which shows the manufacturing process of the metal mold | die with the hardness gradient by the partial heat processing using the fluidized bed furnace which is this invention. It is a figure which shows the process state in a pre-heat treatment process during the manufacturing process of the metal mold | die with the hardness gradient by the partial heat processing using the fluidized-bed furnace which is this invention. It is a figure which shows the process state in a partial immersion preheating process in the manufacturing process of the metal mold | die with the hardness gradient by the partial heat processing using the fluidized bed furnace which is this invention. It is a figure which shows the process state in the partial immersion quenching temperature maintenance process in the preparation process of the metal mold | die with the hardness gradient by the partial heat processing using the fluidized bed furnace which is this invention. It is a figure which shows the process state in a partial tempering process process in the preparation process of the metal mold | die with the hardness gradient by the partial heat processing using the fluidized bed furnace which is this invention. It is a top view of the metal mold | die used with the metal mold | die with the hardness gradient by the partial heat processing using the fluidized bed furnace which is this invention. It is sectional drawing of the metal mold | die used with the metal mold | die with the hardness gradient by the partial heat processing using the fluidized bed furnace which is this invention. It is a perspective view of the metal mold | die used with the metal mold | die with the hardness gradient by the partial heat processing using the fluidized bed furnace which is this invention. It is a longitudinal section hardness distribution figure of a metallic mold showing an experimental result of a metallic mold with a hardness gradient by partial heat treatment using a fluidized bed furnace which is the present invention. It is a graph showing the influence of the quenching temperature on the tempering hardness to a metal mold | die which shows the experimental result of the metal mold | die with the hardness gradient by the partial heat processing using the fluidized-bed furnace which is this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold production process 2 Roughly processed mold 2a Bottom surface 2b Top surface 3 Atmospheric furnace 4 Fluidized bed heat treatment furnace 4a Furnace inner wall 4b Fluidized bed 5 Preheat treatment 6 Partial immersion preheating 7 Partial immersion quenching temperature maintenance 8 Partial quenching 9 Baking Return processing 10 Die with low bottom hardness 11 Die with too high bottom hardness 11a Bottom surface 11b Top surface 12 Fluidized bed heat treatment furnace 12a Furnace inner wall 12b Fluidized bed 13 Partial tempering treatment 14 Finishing 15 Product 16 Mold suspension Jig 16a Suspension part 16b Support part 16c Pedestal 17-17c Arrow 18 Mold 18a Lower 18b Upper 18c Hole 18d Hole 18e Suspension screw hole 18f Suspension screw hole 19 Fluidized bed 19a Fluidized bed immersion position 20 Graph 20a Quenching / tempering Hardness (HRC)
20b Quenching temperature

Claims (1)

In a fluidized bed heat treatment furnace in which the temperature of the fluidized bed is 850 ° C., the roughened mold is suspended on the pedestal of the mold suspension jig with the bottom face of the mold up and the top face down, and the fluidized bed. Pre-heat treatment by hanging directly above so as not to immerse in the mold, adjust the height with a tool for suspending the mold, and partially immerse the upper surface of the mold in the fluidized bed and hold for 2 hours, then the temperature of the fluidized bed heat treatment furnace To increase the temperature of the fluidized bed to 1030 ° C. and hold it for 2 hours to make a gradient in the quenching temperature, and after partially quenching the mold, the whole is tempered and the other side is Give a hardness gradient along the surface side, and if the hardness of the bottom surface of the mold is too high , partial tempering treatment by adjusting the temperature of the fluidized bed by partially immersing the bottom surface side again in a fluidized bed heat treatment furnace controlling the hardness of the bottom performed, the mold as a product Method for producing a mold, characterized in that with a hardness gradient by partial heat treatment using a fluidized bed furnace, characterized in that the raised processing.

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