Method and apparatus manufacturing hot press formed parts for multi-step process

Abstract

Provided are a method and apparatus for manufacturing hot press formed parts for a multi-step process, the method comprising: a heating step for heating a strip material; a transferring step for transferring the heated strip material to a processing apparatus having mounted on a press a plurality of molds comprising a notching mold and/or a blanking mold, a forming mold, and a trimming mold; a notching step, for obtaining a notched material connected to the strip by means of a web portion by cutting a part of the material by means of the notching mold, and/or a blanking step for obtaining a blanked material separated from the strip by cutting a part of the material by means of the blanking mold; a forming step of transferring and positioning the material which has gone through the notching step and/or the blanking step near the forming mold, and then forming the material by means of the forming mold; and a trimming step for removing, by means of the trimming mold, an outer edge portion of the material which is unnecessary for a final product shape.

1 . A method for manufacturing a hot press formed member for a multistage process, the method comprising:
 a heating step of heating a strip material;   a transfer step of transferring the heated strip material to a processing apparatus in which a plurality of molds including one or more molds of a notching mold and a blanking mold; a forming mold; and a trimming mold; are mounted on one press;   one or more steps of a notching step of obtaining a notched material connected to the strip by a web portion by cutting a part of the material using the notching mold and a blanking step of obtaining a blank material separated from the strip by cutting a part of the material using the blanking mold;   a forming step of transferring the material subjected to one or more steps of the notching step and the blanking step and positioning the material in the vicinity of the forming mold, and then forming the material using the forming mold; and   a trimming step of removing an unnecessary outer edge portion of the material from a final product shape using the trimming mold.   
     
     
         2 . The method for manufacturing a hot press formed member for a multistage process of  claim 1 , wherein in the transfer step, the heated strip material is transferred in a thermal insulation chamber, and the thermal insulation chamber is maintained within a temperature range of Ts−200° C. or higher and Ts+50° C. or lower based on a surface temperature (Ts) of the strip material supplied to the thermal insulation chamber. 
     
     
         3 . The method for manufacturing a hot press formed member for a multistage process of  claim 1 , wherein in the one press, the molds are arranged to be spaced apart from each other by a designed pitch amount between two molds adjacent to each other in a transfer direction of the material, and
 after each stroke is performed according to a pressing motion, the material is transferred by the designed pitch amount in the transfer direction of the material.   
     
     
         4 . The method for manufacturing a hot press formed member for a multistage process of  claim 1 , wherein an initial temperature of the notching mold and an initial temperature of the blanking mold are 400° C. or higher. 
     
     
         5 . The method for manufacturing a hot press formed member for a multistage process of  claim 1 , wherein one or more of one or more steps of the notching step and the blanking step; the forming step; and the trimming step are performed in a multistage process by being divided into two or more steps. 
     
     
         6 . The method for manufacturing a hot press formed member for a multistage process of  claim 1 , wherein in the notching step and the blanking step, the strip material put into the processing apparatus is controlled so that the strip material is lowered to a pressing bottom dead center from a transfer height level of the strip material in a non-contact state with an upper mold of a mold, and then comes into contact with an upper mold surface and a lower mold surface of the mold only in a cutting process. 
     
     
         7 . The method for manufacturing a hot press formed member for a multistage process of  claim 1 , wherein in a pressing motion of the processing apparatus, a percentage of a holding time in the vicinity of a bottom dead center in one stroke is 4 to 30%, and
 the percentage of the holding time in the vicinity of the bottom dead center is a percentage of a time for the press to stay to a point corresponding to 1 mm from a pressing bottom dead center in an upward direction.   
     
     
         8 . The method for manufacturing a hot press formed member for a multistage process of  claim 1 , further comprising, between the forming step and the trimming step, one or more steps of a piercing step of removing an unnecessary hole portion from a formed material and a flanging step of forming a flange portion in the formed material. 
     
     
         9 . The method for manufacturing a hot press formed member for a multistage process of  claim 1 , wherein the multistage process is performed with the number of processes equal to or greater than a minimum number of processes calculated by the following Relational Expression 1:
     N =ROUNDUP{ T /[(60/SPM)×( f/ 100)]}  [Relational Expression 1]
   in Relational Expression 1, N represents a minimum required number of processes from the forming step except for the notching step and the blanking step,   SPM represents the number of strokes per minute (SPM) of the press,   f represents a percentage (%) of a holding time in the vicinity of a bottom dead center in one stroke,   T represents a value calculated from the following Relational Expression 2 when 0.8≤t≤1.5, and represents a value calculated from the following Relational Expression 3 when 1.5≤t, and   ROUNDUP represents a value obtained by rounding up the number below the decimal point of the calculated value within { },
     T=t   [Relational Expression 2]
 
     T= 5× t −6  [Relational Expression 3]
 
   in Relational Expressions 2 and 3, t is a thickness of the material, and a unit thereof is mm.   
     
     
         10 . The method for manufacturing a hot press formed member for a multistage process of  claim 9 , wherein f satisfies the following Relational Expression 4 when 0.8≤t≤1.5 is satisfied, and satisfies the following Relational Expression 5 when 1.5≤t is satisfied:
   0.8× t+ 2.6≤ f   [Relational Expression 4]
 
   4.4× t− 2.8≤ f   [Relational Expression 5]
 
 in Relational Expressions 4 and 5, t is a thickness of the material, and a unit thereof is mm. 
 
     
     
         11 . The method for manufacturing a hot press formed member for a multistage process of  claim 1 , wherein when the material is put into the processing apparatus, a pressing slide is lowered to a pressing bottom dead center to process the material, the material stays in the vicinity of the pressing bottom dead center during lifting of the pressing slide, and then, when the pressing slide reaches a point that does not interfere with the transfer of the material, the material positioned in the vicinity of the pressing bottom dead center is lifted utilizing position information of the pressing slide. 
     
     
         12 . The method for manufacturing a hot press formed member for a multistage process of  claim 1 , wherein the method includes a blanking step of obtaining a blank material separated from the strip by cutting a part of the heated strip material put into the processing apparatus using the blanking mold, and
 a tongs-shaped transfer unit is used when the material is transferred from a mold in a previous step to the vicinity of a mold in a subsequent step based on two molds adjacent to each other in a transfer direction of the material in the one press.   
     
     
         13 . An apparatus for manufacturing a hot press formed member for a multistage process, the apparatus comprising:
 a supply unit for continuously supplying a strip material;   a heating unit for heating the strip material;   a processing unit including a processing apparatus in which a plurality of molds including one or more molds of a notching mold and a blanking mold, a forming mold, and a trimming mold are mounted on one press; and   a transfer unit for transferring the strip material heated in the heating unit to the processing unit.   
     
     
         14 . The apparatus for manufacturing a hot press formed member for a multistage process of  claim 13 , wherein the processing apparatus further includes a temperature control unit for controlling an initial temperature of one or more molds of the notching mold and the blanking mold to 400° C. or higher, and
 the temperature control unit is provided between the one or more molds of the notching mold and the blanking mold and the press. 
 
     
     
         15 . The apparatus for manufacturing a hot press formed member for a multistage process of  claim 13 , wherein a push bar operated by a spring is provided as a structure protruding from a surface of an upper mold of one or more molds of the notching mold and the blanking mold in contact with the strip material. 
     
     
         16 . The apparatus for manufacturing a hot press formed member for a multistage process of  claim 13 , wherein the one press includes a pressing slide and a press bolster, and
 a material position control unit in the form of a cylinder is provided on a surface on which the mold on the press bolster is provided.   
     
     
         17 . A hot press formed member manufactured by the method for manufacturing a hot press formed member for a multistage process of  claim 1 , wherein the hot press formed member has an under-cut shape, and a tensile strength of the hot press formed member is 1,300 MPa or more.