A method for forming small-size square-like forgings from large-size bars

Abstract

The application discloses a method for forming small-size square forgings by using large-size bars, and first, a ring piece is obtained by rolling through a ring rolling machine device according to the size of the square forging. The height size of the ring piece is equal to the width size of the square block, and the thickness size of the ring piece is slightly larger than the height size of the square block. Then, the arc segment size is determined on the ring piece according to the length size requirement of the square block. The sawing method is adopted to cut the required arc segment on the ring piece, the arc segment is heated, and the square forging with qualified size is obtained after the furnace forging and the arch height and the two end faces of the arc segment are flattened. The method has the advantages that the forming problem of the square forgings of high-temperature alloy and titanium alloy materials which are poor in plasticity and sensitive to temperature and deformation is solved, the ring rolling technology and the free forging elongation technology are combined, most of the forming process is transferred to the automatic rolling stage, the elongation is only used for finishing, the traditional elongation multi-pass and large-deformation characteristics are changed, the production efficiency is improved, and the cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of forging manufacturing, in particular to a square forging which is formed by using large-size bar material and has small size and poor material plasticity. Background Art

[0002] Parts such as brackets, balancing weights and straightening blades used in the aerospace field have high requirements for microstructure and performance, and most of them use rough materials made of difficult-to-deform materials such as high-temperature alloys and titanium alloys. During the research and development stage, in order to speed up the development progress and reduce tooling costs, square forgings that can accommodate the entire part outline are mostly used. The free forging method is formed on a forging hammer, which is easy to operate and flexible in turning the force-bearing surface, and has been widely used. Use suitable bar stock, place the bar stock between the upper and lower hammer anvils, so that the bar stock axis is perpendicular to the striking direction, and finally obtain forgings with qualified size and microstructure and performance through upsetting, drawing, squaring and other steps. However, for square forgings with poor plasticity and sensitive materials, they are often scrapped due to alternating stress on the core and improper process control. Patent CN106391961A discloses a free forging method for TA12A block forgings, which first beats the blank into a cube, then forges it into a 14-hedron, and finally forges it into a tetrahedron to avoid the generation of free forging cracks. Patent CN201510817994 discloses a process for eliminating low-magnification crystallinity during hammer forging of titanium alloy forgings. By strictly controlling the deformation speed and multiple small deformations, and following the process steps of strike-flip 90°-strike-flip 90°, the batch scrapping loss of forgings can be reduced.

[0003] To obtain qualified forgings, the aforementioned method is complex in process control and difficult to operate, making it difficult to achieve stable mass production. Furthermore, forming square forgings requires the use of appropriate bar stock dimensions. Specifically, the round cross-section of the bar stock must meet the requirements for a square cross-section, adhering to the round-to-square forming principle outlined in forging manuals and experience. Furthermore, the bar stock length must be greater than the diameter to facilitate widening during upsetting. However, for military forgings in the development phase, it is difficult to quickly procure round bar stock of varying specifications and high quality requirements, especially the 50mm to 90mm diameter bar stock required for small-sized forgings. Summary of the Invention

[0004] In order to solve the above problems, the present invention discloses a method for forming small-sized square forgings using large-sized bar stock.

[0005] The specific technical solution includes the following steps:

[0006] 1. A method for forming small-sized square forgings from large-sized bar stock, comprising the following steps:

[0007] 1) Based on the material characteristics that are prone to defects during drawing, the forming process route of square forgings is determined. The main processes include forging bar blanking, billet making, rolling, arc cutting, drawing, heat treatment, physical and chemical testing, and auxiliary processes include grinding, cleaning and inspection. The billet making process includes upsetting, punching and horse bar reaming or pre-rolling to provide suitable ring-shaped blanks for the rolling process;

[0008] 2) Determine the arc size using the square forgings. Calculate the arc length at the mid-diameter position based on the principle of equal metal volume. For square forgings with streamline requirements, the arc direction must be the streamline direction of the forging. Use the method described above for forming small square forgings using large-gauge bar stock.

[0009] 3) Determine the size of the ring rolled piece; determine the size of the ring rolled piece's pitch diameter and the size of the arc angle according to the arch height of the ring rolled piece's pitch diameter; in order to reduce the damage factor when the arc segment is flattened, the smaller the arch height, the better. According to the plastic deformation characteristics of different materials at the shaping temperature, the calculated pitch diameter and angle are optimized. The product of the angle and the number of arc segments cut from a single ring is equal to 360°. To avoid material waste, the following formula is used for calculation: the outer diameter and inner diameter of the ring are determined by the pitch diameter and the wall thickness of the arc segment;

[0010]

[0011]

[0012]

[0013] The outer diameter of the ring rolled piece D = 2R + t;

[0014] The inner diameter of the ring rolled piece d = 2R-t;

[0015] ⌒ is the median diameter of the arc segment, unit: mm; n is the number of arc segments, R is the median arc length, unit: mm; h is the arch height, unit: mm;

[0016] 4) Determine the blanking size. Based on the ring rolled piece size and the material core size, taking into account 1-2% fire loss, calculate the required blanking section volume. Calculate the diameter and height of the section based on the ring rolled piece size and the material core size. Generally, the height is 1.25-2.5 times the diameter.

[0017] The square forging has a hexahedron shape, generally a cuboid, with the streamline direction being the length direction, the length dimension being greater than the width dimension, the width dimension being greater than the height dimension, the height dimension of the arc segment being approximately equal to the width dimension of the block, and the thickness dimension of the arc segment being slightly greater than the height dimension of the block.

[0018] The method for forming small-sized square forgings using large-sized bar stock comprises the following steps:

[0019] 1) Blanking: Heat the bar material in step 4) to 1020-1040℃ and keep it warm for 75-140 minutes.

[0020] 2) Upsetting and punching: After coming out of the furnace, the bar is subjected to upsetting and punching steps on the forging hammer, and then the bar is expanded or pre-rolled to obtain the ring blank size;

[0021] 3) Rolling: The ring blank described in step 3) is heated to 1020-1040° C. and held at this temperature for 25-60 minutes. After being taken out of the furnace, the ring blank is rolled into a ring-rolled product of the required size on a ring rolling mill. Finally, the ring blank is sawed and drawn to obtain a forging of the required size. The forging is then subjected to solution treatment and aging treatment to obtain a product with qualified microstructure and properties.

[0022] The advantages of the present invention are: in view of the phenomenon that the stress state of square forgings is complex, difficult to control, and prone to defects and waste during the free forging and drawing process, the method provided by the present invention effectively solves the problem of forming square forgings made of high-temperature alloys and titanium alloys with poor forging plasticity and sensitive to temperature and deformation. The present invention combines ring rolling technology with free forging and drawing technology, transfers most of the forming process to the automated rolling stage, and drawing is only used for finishing, which changes the characteristics of traditional drawing with multiple passes and large deformation. Since the price of small-sized bar stock is higher than that of large-sized bar stock, the product qualification rate and drawing production efficiency are greatly improved, and the material cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the production method and common defects of conventional square forgings;

[0024] Figure 2 for Figure 2 The process route designed for this patent;

[0025] a) Blanking, b) Blanking, c) Rolling, d) Arc Cutting, e) Lengthening

[0026] 1-upper anvil 2-arc section 3-lower anvil;

[0027] Figure 3 It is a schematic diagram of the shape and size of square forgings and arc segments;

[0028] Figure 4 This is a schematic diagram for calculating the median diameter of an arc segment; DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0030] Example 1:

[0031] against Figure 3 Square forging 4, made of GH4169 high temperature alloy, forging size × (50 ± 3) × (45 ± 3) unit: mm, using Figure 1 Conventional process requires a bar diameter of Φ70mm, and cracks will appear during the process of forging from a circular section to a rectangular section on a free forging hammer. Figure 2 The process method comprises the following steps:

[0032] Step 1: Determine Figure 3 The size of the middle arc segment 5.

[0033] refer to Figure 3 、 Figure 4 ,in Figure 4 In the equation, CD is the height h of arc segment AB, O is the center of the circle, and θ is the central angle of arc segment AB (expressed in degrees). The arc's height B1 is approximately equal to the square's width B, and its thickness t is slightly greater than the square's height H. Based on the principle of equal metal volume, calculate the arc length ⌒ at the mid-diameter of the arc segment.

[0034] B1=55,t=50,mid-diameter arc length ⌒=127

[0035] Step 2: Determine Figure 4 The arc segment diameter and ring rolled product size.

[0036] The number of arc segments n is 16, and the central angle θ is 360 / 16 = 22.5°.

[0037] The median diameter of the arc segment R = 127 × 180 / θ / π = 323;

[0038] Arch height h = 323-323*cos(11.25°) = 6.2

[0039] The outer diameter of the ring rolled piece D = 2R + t = 2*323 + 50 = 696;

[0040] The inner diameter of the ring rolled piece is d = 2R-t = 2*323-50 = 596;

[0041] Step 3: Determine the cutting size.

[0042] The required blank volume is equal to the volume of the ring rolled piece plus the volume of the core. Considering 2% burnout, the result is 6419431mm3. The blank diameter is Φ180mm and the height is 252mm. The height-to-diameter ratio of the material section is 1.4.

[0043] Step 4: Process route for forming square forgings using large-size bars ( Figure 2 )as follows:

[0044] a) Cutting size Φ180×252, b) Blanking size Φ468×Φ300×55, c) Rolling out rings with a size of Φ696×Φ596×55, d) Sawing out arc segments with a 22.5° angle, e) Drawing out: Heat the arc segment to (1000±10)℃, keep it warm for (20~50)min, and then take it out of the furnace and forge it into block size.

[0045] The bar is first heated to (1020-1040)°C and kept warm for (75-140) minutes. After being taken out of the furnace, it is subjected to upsetting and punching steps on a forging hammer. The punched blank is Φ130×55, and then the bar is expanded or pre-rolled to obtain the ring blank size.

[0046] The ring blank is heated to 1020-1040°C and held at this temperature for 25-60 minutes. After exiting the furnace, it is rolled into the required ring size on a ring rolling mill. Finally, the required forging size is achieved through sawing and drawing. The forging undergoes solution treatment and aging treatment to obtain a product with acceptable microstructure and properties.

[0047] Example 2:

[0048] against Figure 3 Square forging 4, made of GH708 high temperature alloy, forging size ××(65±2). Figure 1 Conventional process requires a bar diameter of Φ90mm, and cracks will occur during the process of forging from a circular section to a rectangular section on a free forging hammer. Figure 2 The process method comprises the following steps:

[0049] Step 1: Determine Figure 3 The size of the middle arc segment 5.

[0050] The arc segment's height dimension B1 is approximately equal to the block's width dimension B, and the arc segment's thickness dimension t is slightly larger than the block's height dimension H. Based on the principle of equal metal volume, the arc length ⌒ at the mid-diameter position of the arc segment is calculated.

[0051] B1=82,t=72,mid-diameter arc length ⌒=163

[0052] Step 2: Determine Figure 4 The arc segment diameter and ring rolled product size.

[0053] The number of arc segments n is 12, and the central angle θ is 360 / 12 = 30°.

[0054] The median diameter of the arc segment R = 163 × 180 / θ / π = 312;

[0055] Arch height h = 312 - 312 * cos (15°) = 10.6;

[0056] The outer diameter of the ring rolled piece D = 2R + t = 2*312 + 72 = 696;

[0057] The inner diameter of the ring rolled piece is d = 2R-t = 2*312-72 = 552;

[0058] Step 3: Determine the cutting size.

[0059] The required blank volume is equal to the volume of the ring rolled piece plus the volume of the core. Considering 2% burnout, the result is 12874000mm3. The blank diameter is Φ200mm and the height is 410mm. The height-to-diameter ratio of the material section is 2.05.

[0060] Step 4: Process route for forming square forgings using large-size bars ( Figure 2 )as follows:

[0061] a) Cutting size Φ200×410, b) Blanking size Φ519×Φ300×82, c) Rolling out rings with a size of Φ696×Φ552×82, d) Sawing out 30° arc segments, e) Drawing out: Heat the arc segment to (1000±10)℃, keep it warm for (30~60)min, and then take it out of the furnace and forge it into block size.

[0062] The bar is first heated to (1100-1150)°C and kept warm for (80-160) minutes. After being taken out of the furnace, it is subjected to upsetting and punching steps on a forging hammer. The punched bottom sheet is Φ130×82, and then the bar is expanded or pre-rolled to obtain the ring blank size.

[0063] The ring blank is heated to 1100-1150°C and held at this temperature for 30-60 minutes. After exiting the furnace, it is rolled into the required ring size on a ring rolling mill. Finally, the required forging size is achieved through sawing and drawing. The forging undergoes solution treatment and aging treatment to obtain a product with acceptable microstructure and properties.

Claims

1. A method for forming small-sized square forgings from large-sized bars, characterized in that: The steps include: 1) Based on the material characteristics that are prone to defects during drawing, the forming process route of square forgings is determined. The processes include blanking, billet making, rolling, arc cutting, drawing, heat treatment, physical and chemical testing. Auxiliary processes include grinding, cleaning and inspection. The billet making process includes upsetting, punching and horse bar reaming or pre-rolling to provide suitable ring blanks for the rolling process. 2) Determine the arc size using the square forging and calculate the arc length at the mid-diameter position of the arc based on the principle of equal metal volume; 3) Determine the size of the ring rolled piece; determine the size of the ring rolled piece's median diameter and the size of the arc angle based on the arch height of the median diameter; in order to reduce the damage factor when the arc segment is flattened, the smaller the arch height, the better. According to the plastic deformation characteristics of different materials at the shaping temperature, the calculated median diameter and the size of the angle are optimized. The product of the angle and the number of arc segments cut from a single ring is equal to 360°. To avoid material waste, the following formula is used for calculation: the outer diameter and inner diameter of the ring are determined by the median diameter and the wall thickness of the arc segment; ； ； ， ； Where, ⌒ is the median diameter of the arc segment, unit: mm; n is the number of arc segments, R is the median arc length, unit: mm; h is the arch height, unit: mm; 4) Determine the blanking size. Based on the ring rolled piece size and the core size, taking into account 1-2% fire loss, calculate the required blanking section volume. Based on the ring rolled piece size and the core size, calculate the diameter and height of the section. The height is 1.25-2.5 times the diameter.

2. The method for forming small-sized square forgings using large-sized bar stock according to claim 1, characterized in that: The square forging has a hexahedral shape, a streamline direction is a length direction, a length dimension is greater than a width dimension, and a width dimension is greater than a height dimension.

3. The method for forming small-sized square forgings using large-sized bar stock according to claim 1, characterized in that: The steps include: Cutting: Heat the bar material in step 4) to 1020-1040℃ and keep it warm for 75-140 minutes. Upsetting and punching: After coming out of the furnace, the bar is subjected to upsetting and punching on the forging hammer, and then the bar is expanded or pre-rolled to obtain the ring blank size; Rolling: The ring blank described in step 3) is heated to 1020-1040°C and kept at this temperature for 25-60 minutes. After being taken out of the furnace, the ring blank is rolled into a ring-rolled product of the required size on a ring rolling mill. Finally, the ring blank is sawed and drawn to obtain a forging of the required size. The forging is then subjected to solution treatment and aging treatment to obtain a product with qualified microstructure and properties.

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