Roller Forging Process for Heart Rail Blank

Abstract

The present invention relates to the technical field of heart rail production process, and in particular to a heart rail blank roll die forging forming process, which includes three steps: roll forging, segmented die forging and trimming; the roll forging is to heat a steel section heated to a predetermined temperature, and then roll it through 1-4 roll forging dies to perform metal pre-distribution to obtain a preform; the segmented die forging is to forge the preform on an open split forging die, first forging the left section, and then forging the right section, and the forged left section and right section are both greater than half the length of the preform, so as to obtain the heart rail; the trimming is to cut off the flash of the forged heart rail on the die. The present invention heats the steel section once, and through the composite process of roll forging and segmented die forging, a one-piece heart rail forging with high precision can be quickly obtained. Because the segmented die forging is adopted, the tonnage requirement of the die forging equipment is greatly reduced, and the formed heart rail is the same as the finished product, but with very little machining allowance in size, which greatly improves the material utilization rate.

Description

Technical Field

[0001] The invention relates to the technical field of heart rail production technology, in particular to a heart rail blank roller die forging forming process. Background Art

[0002] Rod-type workpieces with a large aspect ratio, especially complex workpieces with changing cross-sectional shape and area along the length direction, often have poor working conditions in practical applications; for example, the heart rail (such as the heart rail, an important component for railway train track change) Figure 1 The intermediate workpiece shown in the figure) not only bears heavy pressure when the train changes track, but also bears the head-on impact force and lateral thrust during the track change. These forces change continuously along the length direction of the heart rail, causing the heart rail to bear alternating loads such as compression, tension and bending.

[0003] The length of the heart rail is usually greater than 2 meters. Due to the complex structure, it is very difficult to forge such workpieces, and the scrap rate is high. They have always been manufactured by casting, free forging and then machining, or separate forging and then welding. These manufacturing methods all have unavoidable defects. For example, casting is difficult to improve the strength even after subsequent heat treatment; free forging and then machining is complicated, and a large number of anvils are required during machining, resulting in serious material loss and a long time. In addition, machining cuts off the streamline of the free forging in the metal, and the finished product is difficult to adapt to high-strength and alternating loads in all directions; separate forging and then welding is difficult to control the accuracy, and the subsequent processing is complicated, and there are also lesions in the welding area.

[0004] As the country's requirements for heavy-duty railways become increasingly stringent, the strength and service life of the heart rails manufactured by the above methods are difficult to meet the requirements, prompting people to turn their attention back to one-piece forging. As we all know, forging heart rails, which are large-length-diameter-ratio and complex-structured variable-section rods, have the following problems: First, the forging size is large, and the changes in each section along the axial direction are complex, requiring a large forming tonnage to complete the local and overall metal distribution; Second, variable-section long rods are prone to sectionally suspended in the mold, and the mass distribution of each section is very different, and the forming method may be completely different. During forging, the metal flow and distribution are difficult to control, the workpiece is easy to be bent, or even misaligned, and in severe cases, the side thrust generated by the forging tonnage may even break the mold.

[0005] In summary, research and development of a heart rail forging process with low forming difficulty, high machining precision, high efficiency and strong adaptability has important practical value and application prospects for the heart rail and such workpieces. Summary of the invention

[0006] The purpose of the present invention is to provide a heart rail blank roller forging forming process to address the deficiencies of the prior art. The process adopts a composite process of multi-pass roll forging to open the blank and distribute the metal, and then segmented die forging to obtain a high-quality one-piece heart rail forging. The finished product has high precision, high production efficiency, and low requirements on equipment.

[0007] The technical solution adopted by the present invention to solve its technical problems is: a heart rail blank roller die forging forming process, including three steps of roller forging, segmented die forging and trimming; the roller forging is to heat a steel section heated to a predetermined temperature, and then pass 1-4 roller forging die rolling to perform metal pre-distribution to obtain a preform; the segmented die forging is to forge the preform on an open split forging die, first forging the left section, and then forging the right section, and the forged left section and right section are both greater than half the length of the preform, so as to obtain the heart rail; the trimming is to cut off the flash of the forged heart rail on the die.

[0008] Furthermore, the roll forging is to heat the round steel segment to above 1150°C using a medium frequency furnace, then clamp one end and sequentially send it into three roll forging dies for rolling, so that the metal of the round steel segment is distributed axially. The obtained preform is an axially superimposed structure of multiple coaxial rectangular columns, and adjacent rectangular columns are smoothly transitioned by conical surfaces.

[0009] Furthermore, the cross section of the preform is a rectangle with rounded corners and arc-shaped protrusions formed outwards in the middle of the upper and lower sides.

[0010] Furthermore, the central angle corresponding to the roller forging die is ≤250°.

[0011] Furthermore, the open split forging die includes a first cavity for the left section of the forged preform, and a second cavity for the right section of the forged preform, the first cavity and the second cavity are formed into a product heart rail and have a processing allowance, the right end of the first cavity and the left end of the second cavity extend to the edge of the die to form an opening, and the lengths of the first cavity and the second cavity are both greater than half the length of the heart rail to be forged; the left and right side surfaces of the first cavity close to the right end of the die are inclined surfaces with gradually decreasing spacing to prevent the forgings from jumping out, and the upper and lower surfaces of the second cavity close to the left end of the die are formed with slopes to prevent the forgings from jumping out.

[0012] Furthermore, the part of the preform used for clamping during roll forging is the clamping section. During die forging, the end of the preform not including the clamping section is first placed in the first cavity for forging, and then the end of the preform including the clamping section is placed in the second cavity for forging.

[0013] Furthermore, the first cavity and the second cavity can be co-molded, or respectively arranged in two molds.

[0014] Furthermore, intermediate bin-type flash grooves are provided on both sides of the first cavity and the second cavity.

[0015] Furthermore, the forming tonnage of the segmented die forging is less than 15,000 tons.

[0016] Furthermore, it also includes heat treatment after cooling inspection.

[0017] The beneficial effects of the present invention are as follows: the heart rail blank roll die forging forming process includes three steps: roll forging, segmented die forging and trimming; the roll forging heats the steel section to a predetermined temperature, and rolls it through 1-4 roll forging dies to perform metal pre-distribution to obtain a preform; the segmented die forging forges the preform on an open split forging die, first forging the left section, then forging the right section, and the forged left section and right section are both greater than half the length of the preform, thus obtaining the heart rail; the trimming trims the flash of the forged heart rail on the die. The present invention heats the steel section once, and through the composite process of roll forging and segmented die forging, a one-piece heart rail forging with high precision can be quickly obtained. Because the segmented die forging is used, the tonnage requirement of the die forging equipment is greatly reduced. The heart rail after forming has the same shape and structure as the finished product, but only a small amount of machining allowance is left in the size, which greatly improves the material utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of the installation of the center rail of the present invention in use;

[0019] Figure 2 is a three-dimensional diagram of the heart rail forging of the present invention;

[0020] Figure 3 is a die plan view of the roll forging die;

[0021] Figure 4 is a plan view of the second die of the roll forging die;

[0022] Figure 5 is a three-die plan view of the roll forging die;

[0023] Figure 6 is a schematic cross-sectional view of a preform after roll forging;

[0024] Figure 7 is a schematic diagram of the posture of the open split forging die during forging of the center rail;

[0025] Figure 8 is a left side view of the open split forging die;

[0026] Fig. 9 It is a stereoscopic view of the lower die of the open split forging die.

[0027] Description of reference numerals:

[0028] 1——first cavity, 11——inclined surface, 2——second cavity, 21——slope surface, 3——flash groove. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, but the implementation scope of the present invention is not limited thereto.

[0030] like Figure 2-9 As shown, the roller die forging forming process of the heart rail blank of this embodiment includes three steps: roll forging, segmented die forging and trimming. The raw material for making the heart rail forging is steel segment. In order to reduce costs and increase efficiency, round steel, square steel or hexagonal steel and other steel sections can be selected. This embodiment takes round steel as an example for explanation. First, the round steel is cut into round steel segments of predetermined length on a sawing machine, and then placed in a medium frequency furnace and heated to above 1150°C. During roll forging, the auxiliary clamp next to the roll forging equipment is used to clamp one end of the heated round steel segment, and keep the round steel segment horizontal, and the height is the middle of the upper and lower roll forging dies; here, the longer the length of the round steel segment and the higher the temperature, the longer the length of the clamped round steel segment. Taking the 2.5-meter-long heart rail of this embodiment as an example, the length of the clamped round steel segment is 120-140mm. The movable auxiliary clamp feeds the round steel segment into the space between the two upper and lower roller forging dies. The center angle of the roller forging die is ≤250°. This embodiment adopts 245°, which is less than 360°, that is, there is a section without the roller forging die on the circumference of the roller. In order to smoothly feed the round steel segment and make the rolling of the round steel segment obtain the desired predetermined shape and structure, the round steel segment should be fed into the section without the roller forging die, and then stop at the position where the front end of the round steel can just be engaged by the upper and lower roller forging dies. During roller forging, the horizontal moving speed of the auxiliary clamp matches the roller forging speed of the roller forging die. In addition, the roller forging die can be integral or spliced. This embodiment adopts the spliced ​​type for easy installation, that is, the roller forging die is assembled by two die forgings with a center angle less than 180°. At the same time, the material of the roller forging die in this embodiment can be 5CrNiMo.

[0031] The length of the center rail in this embodiment is 2.5 meters, and three roller forging dies are used. In actual production, the number of roller forging dies used can be appropriately adjusted according to the length of the center rail, thereby reducing the tonnage requirement of the pressure equipment and reducing the deformation ratio of the blank during each roller forging, preventing defects such as tearing of the blank. The roller forging process is completed by the roller forging die. During production, the blank is rolled through the three roller forging dies in sequence, so that the metal of the blank is pre-distributed along the axial direction. The final preform obtained is an axially superimposed structure of multiple coaxial rectangular columns, and the adjacent rectangular columns are smoothly transitioned by conical surfaces; in order to better guide the blank in the roller forging die and position it in the subsequent open split forging die, the cross-section of the preform obtained after the roller forging is a rectangle with rounded corners and an arc-shaped bulge in the middle of the upper and lower sides.

[0032] Because the metal pre-distribution of the blank is completed by the roll forging die, the efficiency is high and the time consumption is short, and the heat dissipation and temperature drop of the roll-forged preform is not much, so it does not need to be heated again and can be directly die-forged; in order to reduce the tonnage demand of the die forging equipment, the present invention adopts a segmented die forging process, that is, the preform is die-forged from both ends successively on an open segmented forging die; for example, the tonnage of the die forging press in this embodiment is 16,000 tons, and the tonnage used in normal production is only 12,000 tons by adopting the segmented die forging process.

[0033] The specific process of the segmented die forging is as follows: Figure 7 The posture of the heart rail during forging shown in the figure is designed with a parting surface, and the open split forging die is designed. The open split forging die forms a first cavity 1 and a second cavity 2 after the mold is closed. The first cavity 1 and the second cavity 2 are formed with the finished heart rail and have a processing allowance. The right end of the first cavity 1 and the left end of the second cavity 2 extend to the edge of the mold to form an opening, and the lengths of the first cavity 1 and the second cavity 2 are both greater than half the length of the heart rail to be forged; the left and right side surfaces of the first cavity 1 close to the right end of the mold are inclined surfaces 11 with gradually decreasing spacing to prevent the forgings from jumping out, and the upper and lower surfaces of the second cavity 2 close to the left end of the mold are formed with slopes 21 to prevent the forgings from jumping out.

[0034] In this embodiment, the first cavity 1 and the second cavity 2 are arranged in the same mold. Fig. 9 As shown; in actual production, the first cavity 1 and the second cavity 2 can also be divided into two molds, so that the segmented die forging process is divided into two forging positions to further improve production efficiency.

[0035] During operation, the part of the preform used for clamping during roll forging is the clamping section. During die forging, the end of the preform that does not include the clamping section is first placed in the first cavity 1 for forging, and then the end of the preform that includes the clamping section is placed in the second cavity 2 for forging; because the lengths of the first cavity 1 and the second cavity 2 are both greater than half the length of the heart rail to be forged, the full section forging of the heart rail can be completed in two forgings. The opening directions of the first cavity 1 and the second cavity 2 are opposite and follow the forging order of the heart rail. During forging, the forging only needs to be translated to place the two ends of the forging into the cavity.

[0036] In addition, for the convenience of explanation, the die used in this embodiment first forges the dovetail end of the heart rail and then forges the pointed end of the heart rail. In actual production, the order of forging the two ends of the heart rail can also be adjusted as needed, and the corresponding open split forging die can be designed. That is, the open split forging die used in this embodiment is for the convenience of explaining the present invention and cannot be used as a limitation of the present invention such as the die.

[0037] In order to fully fill the mold during die forging, the area of ​​each cross section of the preform after roll forging should be larger than the area of ​​each cross section of the first cavity 1 and the second cavity 2, and in order for the metal of the preform to flow well along the inner wall of the cavity and fill the cavity during die forging, the difference in the metal margin left in each cross section of the preform should be as small as possible, and the vertical surfaces of the first cavity 1 and the second cavity 2 are both provided with draft angles; in addition, the shape and structure of the heart rail forging after die forging are exactly the same as the finished product, except that there is a small amount of machining margin in size, which greatly improves the material utilization rate and reduces the amount of subsequent processing. Because the forging cannot move axially during die forging, and it is difficult for metal to flow axially, an intermediate bin-type flash groove 3 is provided between the first cavity 1 and the second cavity 2, and on the outside of the two cavities to accommodate excess metal, and objectively produce a pressure relief effect, further reducing the tonnage demand of the die forging equipment.

[0038] Excess metal forms flash in the flash groove 3, and finally the flash is cut off by a whole-section die to obtain an integrated heart rail forging; then it is left to cool naturally, or air cooling is added to speed up the cooling speed. After the heart rail forging is inspected and qualified, it is subjected to quenching and tempering treatment to obtain a finished heart rail forging.

[0039] This embodiment takes the heart rail as an example to illustrate the roller forging composite process of the present invention. In actual production, the roller forging + segmented die forging composite process of the present invention is not limited to the heart rail, and can also be used for other rod or shaft workpieces with large aspect ratio and complex axial changes in each cross section.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, and for the convenience of describing the technical solution, the front, back, left, right, top, middle, bottom and other directions are set based on the drawings, rather than limiting the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. The heart rail blank roller forging process is characterized by: The process includes three steps: roll forging, segmented die forging and trimming. The roll forging process is to heat the steel segment to a predetermined temperature, and then roll the steel segment through 1 to 4 roll forging dies to pre-distribute the metal and obtain a preform. The segmented die forging process is to forge the left section of the preform on an open split forging die, and then forge the right section. The forged left section and right section are both greater than half the length of the preform, so as to obtain a heart rail. The trimming process is to cut off the flash of the forged heart rail on the die. The roll forging is to heat the round steel segment to above 1150°C in a medium frequency furnace, then clamp one end and sequentially send it into three roll forging dies for rolling, so that the metal of the round steel segment is distributed axially. The obtained preform is an axially superimposed structure of multiple coaxial rectangular columns, and adjacent rectangular columns are smoothly transitioned by conical surfaces; The cross section of the preform is a rectangle with rounded corners and arc-shaped convexities formed outwards in the middle of the upper and lower sides; The open split forging die comprises a first die cavity (1) for forging a left section of the preform, and a second die cavity (2) for forging a right section of the preform, the first die cavity (1) and the second die cavity (2) are formed into a finished product heart rail and have a processing allowance, the right end of the first die cavity (1) and the left end of the second die cavity (2) extend to the edge of the die to form an opening, and the lengths of the first die cavity (1) and the second die cavity (2) are both greater than half the length of the heart rail to be forged; the left and right side surfaces of the first die cavity (1) close to the right end of the die are inclined surfaces (11) with a gradually decreasing spacing to prevent the forging from jumping out, and the upper and lower sides of the second die cavity (2) close to the left end of the die are formed with slope surfaces (21) to prevent the forging from jumping out; The part of the preform used for clamping during roll forging is the clamping section. During die forging, the end of the preform not including the clamping section is first placed in the first cavity (1) for forging, and then the end of the preform including the clamping section is placed in the second cavity (2) for forging.

2. The roller die forging process for the center rail blank according to claim 1 is characterized in that: The central angle corresponding to the roller forging die is ≤250°.

3. The roller die forging process for the center rail blank according to claim 1 is characterized in that: The first cavity (1) and the second cavity (2) can be co-moulded, or respectively arranged in two moulds.

4. The roller die forging process for the center rail blank according to claim 1 is characterized in that: Intermediate bin-type flash grooves (3) are provided on both sides of the first cavity (1) and the second cavity (2).

5. The roller die forging process for the center rail blank according to claim 1 is characterized in that: The forming tonnage of the segmented die forging is less than 15,000 tons.

6. The roller die forging process for the center rail blank according to claim 1 is characterized in that: It also includes tempering treatment after cooling inspection.

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