A free forging method for large stainless steel curved step forgings

Abstract

This invention belongs to the field of injection valves and relates to a free forging method for large stainless steel arc-shaped stepped forgings. The method includes the following steps: Step 1) Blanking a steel billet; Step 2) Heating and holding the steel billet at that temperature; Step 3) Repeatedly upsetting and then drawing the heated steel billet under high pressure; Step 4) Upsetting the steel billet from Step 3) and then drawing it into a rectangular thick plate billet; Step 5) Heating and holding the steel billet from Step 4); Step 6) Drawing the billet into a stepped steel billet with wings at both ends; Step 7) Heating and holding the steel billet from Step 6); Step 8) Drawing the boss portion of the steel billet from Step 7) into a stepped slab; Step 9) Heating and holding the stepped slab; Step 10) Bending the side of the stepped slab segment by segment into a stainless steel arc-shaped stepped forging. The beneficial effects of using this method are: the large stainless steel arc-shaped stepped forging formed by free forging has dimensions and shape consistent with the target part, and requires less subsequent machining.

Description

Technical Field

[0001] This invention belongs to the field of forging forming technology, specifically, it relates to a free forging forming method for a large stainless steel arc-shaped step forging. Background Technology

[0002] like Figure 1 and Figure 2 As shown, a large stainless steel arc-shaped stepped forging has a length L≥3000mm, L1≥1500mm, B≥700mm, T1≥600mm, T2≥200mm, a forging weight m≥6.5T, and a forging grain size requirement ≥2. It is forged using a large free forging press.

[0003] Current conventional forging methods involve forging slabs into large, multi-step straight slab forgings, such as... Figure 3 and Figure 4 As shown, using this forging method, the forging weight m' can reach 1.5m, resulting in a large amount of forging residue and subsequent machining. Furthermore, the boss portion of the forging shows no deformation when the wings are extended after forging, leading to coarse and mixed grain size. Additionally, the flow lines of the forging structure are inconsistent with the arc direction of the part, affecting the uniformity of the forging quality. Therefore, improvement is necessary. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a free forging method for large stainless steel arc-shaped stepped forgings, which ensures that the size and shape of the forging are consistent with the target, and that the forging flow lines are uniform and continuous.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] As one aspect of the present invention, a free forging forming method for large stainless steel arc-shaped stepped forgings is proposed, which includes the following steps:

[0007] Step 1) Cut a steel billet with a diameter of D0 and a length of L0;

[0008] Step 2) Heat the steel billet to 1180-1230℃ and hold for 8-10 hours to ensure uniform internal temperature of the billet;

[0009] Step 3) Repeat the upsetting and drawing process on the heated steel billet multiple times to ensure that the upsetting ratio and drawing ratio are ≥2 each time, and fully compact the steel billet; after each drawing process, keep the steel billet at 1200±20℃ for 8~10h.

[0010] Step 4) Upset the steel billet from step 3) to a diameter of [diameter missing].

[0011] d n+1 =1.26 * 0.996 n+1 *D02 / 3 *L0 1 / 3 The length is l n+1 =0.63 * 0.996 n+1 *D0 2 / 3 *L0 1 / 3 n is the nth upsetting step 3);

[0012] The blank is then drawn into a rectangular thick plate with dimensions: width B. m Thickness T m Length L m , of which: B m =1.2~1.3B, T m =1.2~1.3T1,L m =0.785 * 0.99 n+1 *D0 2 *L0 / (B m *T m ), where n is the nth forced stretching in step 3);

[0013] Step 5) Heat the steel billet from Step 4) to 1000-1100℃ and hold for 2-3 hours to give the steel billet sufficient plasticity while reducing the rate of grain growth and slowing down grain coarsening.

[0014] Step 6) Divide the billet at lengths of 0.8L2*T2 / T1 at both ends, and elongate the billet into a stepped billet with a thickness of T2, a width of B, and a length of L2 at both ends. The deformation of the flanged portion at both ends should be ≥70%, and sufficient dynamic recrystallization should occur in the flanged portion of the billet, resulting in sufficiently refined grains; the middle length is L m The boss portion of -1.6L2*T2 / T1 retains the deformation amount and is not forged in this step;

[0015] Step 7) Heat the steel billet from Step 6) to 1000-1050℃ and hold for 3-4 hours. At this temperature, the steel billet has the plasticity required to complete the boss forming in Step 8), while the grain growth rate of the steel billet is very slow, and heating will not cause the grains to coarsen.

[0016] Step 8) Lengthen the boss portion of the billet from Step 7) to a stepped slab with cross-sectional dimensions of width B, thickness T1, and length L1. During forging, the boss portion has a deformation of 30% to 40%, which allows for sufficient dynamic recrystallization and refinement of the boss grains.

[0017] Step 9) Heat the stepped slab to 1000-1100℃ and hold for 2-3 hours. At this temperature, the billet has the plasticity required to bend the stepped slab in step 10), while the grain growth rate of the billet is very slow and heating will not cause the grains to coarsen.

[0018] Step 10) Using an arc anvil, the side of the stepped slab is bent segment by segment into a stainless steel arc-shaped stepped forging with an inner diameter of R1 and an outer diameter of R2.

[0019] Alternatively, in step 1),

[0020] Wherein, D0 and L0 must satisfy the following formulas respectively:

[0021] D0 is 0.85~0.91[B*(L1*T1+2L2*T2)] 1 / 3 ,

[0022] L0 is 1.7 to 1.9[B*(L1*T1+2L2*T2)] 1 / 3 ,

[0023] Wherein, B is the width of the target large stainless steel arc-shaped step forging, L is the total arc length of the target large stainless steel arc-shaped step forging, L1 is the arc length of the boss portion of the target large stainless steel arc-shaped step forging, L2 is the arc length of one side of the target large stainless steel arc-shaped step forging excluding the boss portion, T1 is the total thickness of the target large stainless steel arc-shaped step forging, T2 is the thickness of the target large stainless steel arc-shaped step forging excluding the boss portion, R1 is the inner diameter of the target large stainless steel arc-shaped step forging, and R2 is the outer diameter of the target large stainless steel arc-shaped step forging.

[0024] Alternatively, in step 3),

[0025] The upset steel billet needs to meet the following formula:

[0026] d n =1.26 * 0.996 n *D0 2 / 3 *L01 / 3 ,l n =0.63 * 0.996 n *D0 2 / 3 *L0 1 / 3 ,

[0027] The drawn steel billet needs to meet the following formula:

[0028] D n =0.996 n *D0,L n =0.996 n *L0 ensures that the deformation amount during each upsetting and high-pressure drawing is ≥50%, fully compacting the stainless steel billet, breaking the internal columnar crystals, and refining the grains;

[0029] n refers to the nth upsetting and high-pressure drawing operation, n = 1.5 * m 0.2[n is an integer]. The value of n should be chosen to increase with the weight of the forging, but not exceed 4. m is the weight of the steel billet.

[0030] Optionally, the width H of the arc anvil is controlled within L / 6 ≤ H ≤ L / 4, and the amount of feed P per anvil during bending is controlled within H / 2 ≤ P ≤ 2H / 3, to ensure smooth connection of the curves of each arc segment of the forging during bending.

[0031] The free forging method for large stainless steel arc-shaped step forgings of the present invention has the following advantages: the size and shape of the large stainless steel arc-shaped step forging formed by free forging and contour forging are consistent with the target part, the subsequent processing amount is small, the flow lines of the forging structure are uniform and continuous and consistent with the direction of the part, the grain size of the forging can reach level 3 to 4, saving raw materials and reducing production costs. Attached Figure Description

[0032] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0033] Figure 1 The main structural view of a large stainless steel arc-shaped stepped forging;

[0034] Figure 2 Top view of a large stainless steel arc-shaped stepped forging;

[0035] Figure 3 The main structural view of an existing forging scheme for a large stainless steel arc-shaped step forging;

[0036] Figure 4 A structural side view of an existing forging scheme for a large stainless steel arc-shaped stepped forging;

[0037] Figure 5 This is a schematic diagram of the billet blanking dimensions for the free forging forming method of the large stainless steel arc-shaped stepped forging of the present invention.

[0038] Figure 6 This is a schematic diagram of billet upsetting in the free forging forming method of the large stainless steel arc-shaped stepped forging of the present invention.

[0039] Figure 7 This is a schematic diagram of the billet strong pressure drawing of the free forging forming method of the large stainless steel arc-shaped stepped forging of the present invention.

[0040] Figure 8 This is a front view of a rectangular thick slab for the free forging forming method of the large stainless steel arc-shaped stepped forging of the present invention.

[0041] Figure 9A side view of a rectangular thick slab for the free forging forming method of the large stainless steel arc-shaped stepped forging of the present invention.

[0042] Figure 10 This is a front view of the stepped slab of the free forging forming method for the large stainless steel arc-shaped stepped forging of the present invention.

[0043] Figure 11 A top view of the stepped slab in the free forging forming method of the large stainless steel arc-shaped stepped forging of the present invention;

[0044] Figure 12 This is a schematic diagram of the bending forming method of the free forging forming method of the large stainless steel arc-shaped step forging of the present invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0046] One embodiment of this application discloses a free forging forming method for a large stainless steel arc-shaped stepped forging, which includes the following steps:

[0047] Step 1) Cut a steel billet with a diameter of D0 and a length of L0, such as... Figure 3 As shown,

[0048] Wherein, D0 and L0 must satisfy the following formulas respectively:

[0049] D0 is 0.85~0.91[B*(L1*T1+2L2*T2)] 1 / 3 ,

[0050] L0 is 1.7 to 1.9[B*(L1*T1+2L2*T2)] 1 / 3 ,

[0051] Where B is the width of the target large stainless steel curved step forging, L is the total arc length of the target large stainless steel curved step forging, L1 is the arc length of the boss portion of the target large stainless steel curved step forging, L2 is the arc length of one side of the target large stainless steel curved step forging excluding the boss portion, T1 is the total thickness of the target large stainless steel curved step forging, T2 is the thickness of the target large stainless steel curved step forging excluding the boss portion, R1 is the inner diameter of the target large stainless steel curved step forging, and R2 is the outer diameter of the target large stainless steel curved step forging. Figure 1 and Figure 2 As shown;

[0052] Step 2) Heat the steel billet to 1180-1230℃ and hold for 8-10 hours to ensure uniform internal temperature of the billet;

[0053] Step 3) Repeat the upsetting and then high-pressure drawing process on the heated steel billet multiple times, ensuring that the upsetting ratio and drawing ratio are ≥2 each time, to fully compact the steel billet; Figure 6 and Figure 7 As shown,

[0054] The upset steel billet needs to meet the following formula:

[0055] d n =1.26 * 0.996 n *D0 2 / 3 *L0 1 / 3 ,l n =0.63 * 0.996 n *D0 2 / 3 *L0 1 / 3 ,

[0056] The drawn steel billet needs to meet the following formula:

[0057] D n =0.996 n *D0,L n =0.996 n *L0 ensures that the deformation amount during each upsetting and high-pressure drawing is ≥50%, fully compacting the stainless steel billet, breaking the internal columnar crystals, and refining the grains;

[0058] n refers to the nth upsetting and high-pressure drawing operation, n = 1.5 * m 0.2 [n is an integer], the value of n should be increased with the weight of the forging, but not exceeding 4, m is the weight of the steel billet; after each drawing, the steel billet is kept at 1200±20℃ for 8~10h;

[0059] Step 4) Upset the steel billet from step 3) to a diameter of [diameter missing].

[0060] d n+1 =1.26 * 0.996 n+1 *D0 2 / 3 *L0 1 / 3 The length is l n+1 =0.63 * 0.996 n+1 *D0 2 / 3 *L01 / 3 n is the nth upsetting step 3);

[0061] The blank is then drawn into a rectangular thick plate with dimensions: width B.m Thickness T m Length L m , of which: B m =1.2~1.3B, T m =1.2~1.3T1,L m =0.785 * 0.99 n+1 *D0 2 *L0 / (B m *T m ), where n is the nth forced stretching in step 3), such as Figure 8 and Figure 9 As shown; this ensures that after the forging of both wings in step 6), the boss portion still has 30% to 40% deformation, ensuring that the boss portion has sufficient deformation during the subsequent forging deformation in step 8) to allow for sufficient dynamic recrystallization and refinement of the boss grains.

[0062] Step 5) Heat the steel billet from step 4) to 1100-1150℃ and hold for 4-5 hours to give the steel billet sufficient plasticity while reducing the rate of grain growth and slowing down grain coarsening.

[0063] Step 6) Divide the billet at lengths of 0.8L2*T2 / T1 at both ends, and elongate the billet into a stepped billet with a thickness of T2, a width of B, and a length of L2 at both ends. The deformation of the flanged portion at both ends should be ≥70%, and sufficient dynamic recrystallization should occur in the flanged portion of the billet, resulting in sufficiently refined grains; the middle length is L m The boss portion of -1.6L2*T2 / T1 retains the deformation amount and is not forged in this step. Figures 8-11 As shown;

[0064] Step 7) Heat the steel billet from Step 6) to 1000-1050℃ and hold for 3-4 hours. At this temperature, the steel billet has the plasticity required to complete the boss forming in Step 8), while the grain growth rate of the steel billet is very slow, and heating will not cause the grains to coarsen.

[0065] Step 8) Lengthen the boss portion of the billet from Step 7) to a stepped slab with a cross-sectional dimension of width B, thickness T1, and length L1. During forging, the boss portion has a deformation of 30% to 40%, which allows for sufficient dynamic recrystallization and refinement of the boss grains.

[0066] Step 9) Heat the stepped slab to 1000-1100℃ and hold for 2-3 hours. At this temperature, the billet has the plasticity required to bend the stepped slab in step 10), while the grain growth rate of the billet is very slow and heating will not cause the grains to coarsen.

[0067] Step 10) Using an arc anvil, the side of the stepped slab is bent segment by segment into a stainless steel arc-shaped stepped forging with an inner diameter of R1 and an outer diameter of R2, such as... Figure 12 As shown; the width H of the arc anvil is controlled within L / 6≤H≤L / 4, and the amount of feed P of each anvil during bending is controlled within H / 2≤P≤2H / 3 to ensure smooth connection of the curves of each arc segment of the forging during bending.

[0068] Example 1

[0069] like Figure 1 and Figure 2 As shown, the large stainless steel arc-shaped stepped forging for the BEST coil box is made of 316LN, with a width B of 735mm, a thickness T1 of 671mm, a thickness T2 of 218mm, an arc length L1 of 1677mm, an arc length L2 of 929mm, an arc length L of 3534mm, an inner diameter R1 of 3695mm, and an outer diameter R2 of 4430mm. The forging method for this large stainless steel arc-shaped stepped forging uses the following steps:

[0070] Step 1) Cut a steel billet with a diameter of Φ920mm and a length of 1870mm.

[0071] Step 2) Heat the steel billet to 1200±20℃ and hold for 9 hours to ensure uniform internal temperature of the billet;

[0072] Step 3.1) Perform the first upsetting and high-pressure drawing on the steel billet. First, upset the billet to a diameter of Φ1460mm and a height of 730mm, then draw it to a diameter of Φ915mm and a length of 1865mm. The upsetting ratio is 2.6, and the drawing ratio is 2.5. The upsetting deformation is 61%, and the drawing deformation is 61%. After drawing, hold the billet at 1200±20℃ for 9 hours.

[0073] Step 3.2) Perform a second upsetting and high-pressure drawing on the steel billet. First, upset the steel billet to a diameter of Φ1455mm and a height of 725mm, then draw it to a diameter of Φ910mm and a length of 1855mm. The upsetting ratio is 2.6, and the drawing ratio is 2.6. The upsetting deformation is 61%, and the drawing deformation is 61%. After drawing, hold the steel billet at 1200±20℃ for 9 hours.

[0074] Step 4) Upset the steel billet to a diameter of Φ1450mm and a height of 725mm, then draw it into a rectangular thick plate billet with a width of 900mm, a thickness of 810mm, and a length of 1650mm. This ensures that after forging both sides of the flange in Step 6), the boss portion still has 30% to 40% deformation, ensuring that the boss portion has sufficient deformation during the subsequent forging deformation in Step 8) to allow for sufficient dynamic recrystallization and refinement of the boss grains.

[0075] Step 5) Heat the steel billet to 1120±20℃ and hold for 4.5h to give the steel billet sufficient plasticity while reducing the rate of grain growth and slowing down grain coarsening.

[0076] Step 6) Divide the billet at 245mm lengths at both ends and draw it into a stepped billet with a thickness of 218mm, a width of 735mm, and a length of 929mm at both ends. The deformation of the flanged portion at both ends is 78%, and sufficient dynamic recrystallization occurs in the flanged portion of the billet, resulting in fully refined grains. The deformation of the boss portion in the middle with a length of 1160mm is retained, and it is not forged in this step.

[0077] Step 7) Heat the billet to 1020±20℃ and hold for 3.5h. At this temperature and holding time, the billet has the plasticity required to complete the boss forming in step 8), while the grain growth rate of the billet is very slow, and heating will not coarsen the grains.

[0078] Step 8) Lengthen the boss portion of the billet to a stepped slab with a cross-sectional dimension of 735mm width, 671mm thickness and 1677mm length. During forging, the boss portion has a deformation of 32%, which allows for sufficient dynamic recrystallization and refinement of the boss grains.

[0079] Step 9) Heat the stepped slab to 1020±20℃ and hold for 2.5h. At this temperature and holding time, the billet has the plasticity required to bend the stepped slab in step 10), while the grain growth rate of the billet is very slow and heating will not coarsen the grains.

[0080] Step 10) Using an 800mm wide arc anvil, the side of the stepped slab is bent segment by segment into a stainless steel arc-shaped stepped forging with an inner diameter of 3695mm and an outer diameter of 4430mm. During the bending process, the anvil advance is 300±20mm to ensure smooth connection of the curves of each arc segment of the forging during the bending process.

[0081] In this embodiment, the large stainless steel arc-shaped step forging formed by free forging and contour forging has the same size and shape as the target part, requires less subsequent processing, and has a uniform and continuous flow line in the microstructure that is consistent with the direction of the part. The grain size of the forging can reach level 3 to 4.

[0082] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0083] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0084] In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0085] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0086] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this application.

[0087] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0088] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A free forging forming method for a large stainless steel arc-shaped stepped forging, characterized in that, It includes the following steps: Step 1) Cut a steel billet with a diameter of D0 and a length of L0; Step 2) Heat the steel billet to 1180~1230℃ and hold for 8~10 hours to make the internal temperature of the billet uniform; Step 3) After heating, the steel billet is subjected to repeated upsetting followed by high-pressure drawing to ensure that the upsetting ratio and drawing ratio are ≥2 each time, and the steel billet is fully compacted; after each drawing, the steel billet is kept at 1200±20℃ for 8~10h. Step 4) Upset the steel billet from Step 3) to a diameter of d. n+1 =1.26*0.996 n+1 *D0 2 / 3 *L0 1 / 3 The length is l n+1 =0.63*0.996 n+1 *D0 2 / 3 *L0 1 / 3 n is the number of upsetting operations in step 3); The blank is then drawn into a rectangular thick plate with dimensions: width B. m Thickness T m Length L m , of which: B m =1.2~1.3B, T m =1.2~1.3T1, L m =0.785*0.99 n+1 *D0 2 *L0 / (B m *T m ), where n is the number of times the force is stretched in step 3); Step 5) Heat the steel billet from Step 4) to 1000~1100℃ and hold for 2~3 hours to give the steel billet sufficient plasticity while reducing the rate of grain growth within the steel billet and slowing down grain coarsening. Step 6) Divide the billet at lengths of 0.8L2*T2 / T1 at both ends, and elongate the billet into a stepped billet with a thickness of T2, a width of B, and a length of L2 at both ends. The deformation of the flanged portion at both ends should be ≥70%, and sufficient dynamic recrystallization should occur in the flanged portion of the billet, resulting in sufficiently refined grains; the middle length is L m The boss portion of -1.6L2*T2 / T1 retains the deformation amount and is not forged in this step; Step 7) Heat the steel billet from Step 6) to 1000~1050℃ and hold for 3~4 hours. At this temperature, the steel billet has the plasticity required to complete the boss forming in Step 8) while the grain growth rate of the steel billet is very slow, and heating will not cause the grains to coarsen. Step 8) The boss portion of the billet from Step 7) is drawn out to a stepped slab with a cross-sectional dimension of width B, thickness T1, and length L1. During forging, the boss portion has a deformation of 30% to 40%, which allows for sufficient dynamic recrystallization and refinement of the boss grains. Step 9) Heat the stepped slab to 1000~1100℃ and hold for 2~3 hours. At this temperature, the billet has the plasticity required to bend the stepped slab in step 10), while the grain growth rate of the billet is very slow and heating will not cause the grains to coarsen. Step 10) Using an arc anvil, the side of the stepped slab is bent segment by segment into a stainless steel arc-shaped stepped forging with an inner diameter of R1 and an outer diameter of R2. In step 1), Wherein, D0 and L0 must satisfy the following formulas respectively: D0 is 0.85~0.91[B*(L1*T1+2L2*T2)] 1 / 3 , L0 is 1.7~1.9[B*(L1*T1+2L2*T2)] 1 / 3 , Wherein, B is the width of the target large stainless steel arc-shaped step forging, L is the total arc length of the target large stainless steel arc-shaped step forging, L1 is the arc length of the boss portion of the target large stainless steel arc-shaped step forging, L2 is the arc length of one side of the target large stainless steel arc-shaped step forging excluding the boss portion, T1 is the total thickness of the target large stainless steel arc-shaped step forging, T2 is the thickness of the target large stainless steel arc-shaped step forging excluding the boss portion, R1 is the inner diameter of the target large stainless steel arc-shaped step forging, and R2 is the outer diameter of the target large stainless steel arc-shaped step forging.

2. The free forging forming method for large stainless steel arc-shaped stepped forgings as described in claim 1, characterized in that, In step 3), The upset steel billet needs to meet the following formula: d n =1.26*0.996 n *0 2 / 3 *L0 1 / 3 ,L n =0.63*0.996 n *0 2 / 3 *L0 1 / 3 , The drawn steel billet needs to meet the following formula: D n =0.996 n *D0,L n =0.996 n *L0 ensures that the deformation amount during each upsetting and high-pressure drawing is ≥50%, fully compacting the stainless steel billet, breaking the internal columnar crystals, and refining the grains. n refers to the number of upsetting and high-pressure drawing operations in step 3), n=2.

3. The free forging forming method for large stainless steel arc-shaped stepped forgings as described in claim 1, characterized in that, The width H of the arc anvil is controlled within L / 6≤H≤L / 4, and the amount of feed P per anvil during bending is controlled within H / 2≤P≤2H / 3 to ensure smooth connection of the curves of each arc segment of the forging during bending.

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