Free forging forming method of large stainless steel arc-shaped step forge piece

Abstract

The invention belongs to the field of liquid injection valves, and relates to a free forging forming method of a large stainless steel arc-shaped step forge piece, which comprises the following steps of: 1) blanking a steel billet, and 2) heating and preserving heat of the steel billet; (3) the heated steel billet is subjected to multiple times of repeated upsetting firstly and then strong pressing and drawing-out; (4) upsetting the steel billet in the step (3), and then drawing the steel billet into a rectangular thick plate blank; (5) heating the steel billet in the step (4), and preserving heat; (6) the blank is drawn out to form a step steel billet with the two wingspans at the two ends; (7) heating the steel billet in the step (6), and preserving heat; (8) the boss part of the steel billet in the step (7) is drawn out to form a step plate blank; (9) the step plate blank is heated and subjected to heat preservation; and (10) the side face of the step plate blank is bent section by section to form the stainless steel arc-shaped step forge piece. After the method is adopted, the method has the beneficial effects that the size and the shape of the large stainless steel arc-shaped step forge piece formed through free forging profiling forging are consistent with those of a part target, and the follow-up machining amount is small.

Description

Technical Field

[0001] The invention belongs to the technical field of forging forming, and in particular relates to a free forging forming method for a large stainless steel arc-shaped step forging. Background Art

[0002] like Figure 1 and Figure 2 As shown, large stainless steel arc step forgings have a length of L ≥ 3000mm, L1 ≥ 1500mm, B ≥ 700mm, T1 ≥ 600mm, T2 ≥ 200mm, forging weight m ≥ 6.5T, forging grain size requirement ≥ level 2, and are forged using a large free forging press.

[0003] The conventional forging method is to forge a large multi-step straight slab forging from a slab, such as Figure 3 and Figure 4 As shown, with this forging method, the weight of the forging m' can reach 1.5m, the forging has many excess pieces, the subsequent processing is large, the boss part has no deformation when the forging is completed on both sides of the wings, the forging grain size is easy to be coarse and mixed, and the forging organization streamline is inconsistent with the arc direction of the part, which affects the uniformity of the forging quality. Therefore, it is necessary to make improvements. Summary of the invention

[0004] In order to solve the above problems in the prior art, the present invention provides a free forging method for large stainless steel arc-shaped step forgings, so that the size and shape of the forgings are consistent with the target, and the streamlines of the forgings are uniform, continuous and consistent.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] As one aspect of the present invention, a free forging method for a large stainless steel arc-shaped step forging is provided, which comprises the following steps:

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

[0008] Step 2) heating the steel billet to 1180-1230°C and keeping it warm for 8-10 hours to make the temperature inside the billet uniform;

[0009] Step 3) The heated steel billet is repeatedly subjected to upsetting followed by strong pressing and stretching, ensuring that the upsetting ratio and the stretching ratio are both ≥ 2 each time, and the steel billet is fully compacted; after each stretching, the steel billet is heated to 1200±20℃ and kept warm for 8-10h;

[0010] Step 4) The steel billet of step 3) is first upset to a diameter of

[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 in step 3);

[0012] Then draw it into a rectangular thick plate blank, the blank size: width is B m , thickness is T m , length is L m , where: 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 strong pressure extension in step 3);

[0013] Step 5) heating the steel billet of step 4) to 1000-1100° C. and keeping the temperature for 2-3 hours, so that the steel billet has sufficient plasticity, while reducing the growth rate of grains in the steel billet and slowing down grain coarsening;

[0014] Step 6) The billet is divided at the length of 0.8L2*T2 / T1 at both ends, and the billet is stretched to a step billet with a span of thickness T2, width B, and length L2 at both ends. The deformation of the span part at both ends is ≥70%, and the billet in the span part undergoes sufficient dynamic recrystallization and the grains are fully refined; the middle length is L m -1.6 The boss part of L2*T2 / T1 retains the deformation and is not forged in this step;

[0015] Step 7) heating the steel billet of step 6) to 1000-1050°C and keeping the temperature for 3-4 hours. At this temperature, the steel billet has the plasticity required for the boss forming in step 8), and the grain growth rate of the steel billet is very slow, and heating will not coarsen the grains;

[0016] Step 8), the boss portion of the steel billet in step 7) is stretched to a step slab with a cross-sectional size of width B, thickness T1, and length L1. During forging, the boss portion has a deformation amount of 30% to 40%, which allows sufficient dynamic recrystallization to occur and fully refine the boss grains;

[0017] Step 9) heating the step slab to 1000-1100° C. and keeping the temperature for 2-3 hours. At this temperature, the steel billet has the plasticity required for bending the step slab in step 10), and the grain growth rate of the steel billet is very slow, and heating will not coarsen the grains.

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

[0019] As an option, in step 1),

[0020] Among them, D0 and L0 need to 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] Among them, B is the width of the target large stainless steel arc step forging, L is the total arc length of the target large stainless steel arc step forging; L1 is the arc length of the boss part of the target large stainless steel arc step forging, L2 is the arc length of one side of the target large stainless steel arc step forging excluding the boss part, T1 is the total thickness of the target large stainless steel arc step forging, T2 is the thickness of the target large stainless steel arc step forging excluding the boss part, R1 is the inner diameter of the target large stainless steel arc step forging, and R2 is the outer diameter of the target large stainless steel arc step forging.

[0024] As an option, in step 3),

[0025] Among them, the billet after upsetting needs to satisfy 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 billet needs to satisfy the following formula:

[0028] D n =0.996 n *D0,L n =0.996 n *L0, which can ensure that the deformation of each upsetting and each strong pressing and 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 strong stretching performed, n = 1.5*m 0.2[n is an integer], the value of n should be selected as the weight of the forging increases, but not exceeding 4, and m is the weight of the billet.

[0030] Optionally, the arc anvil width H is controlled within L / 6≤H≤L / 4, and the anvil advance amount P of each anvil during the bending process is controlled within H / 2≤P≤2H / 3, ensuring that the curves of each arc segment of the forging are smoothly connected during the bending process.

[0031] The free forging forming method of the large stainless steel arc-shaped step forging of the present invention has the beneficial effects that the size and shape of the large stainless steel arc-shaped step forging formed by free forging conforming forging are consistent with the target part, the subsequent processing amount is small, the forging organization streamline is uniform and continuous and consistent with the part direction, the forging grain size grade can reach 3 to 4 levels, raw materials are saved, and production costs are reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings in the specification, which constitute a part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0033] Figure 1 This is the structural front view of a large stainless steel curved step forging;

[0034] Figure 2 This is a top view of the structure of a large stainless steel curved step forging;

[0035] Figure 3 It is a structural front view of an existing forging scheme for a large stainless steel curved step forging;

[0036] Figure 4 It is a structural side view of an existing forging scheme for a large stainless steel curved step forging;

[0037] Figure 5 It is a schematic diagram of the blanking dimensions of the steel billet in the free forging method of the large stainless steel arc-shaped step forging of the present invention;

[0038] Figure 6 It is a schematic diagram of steel billet upsetting in the free forging method of the large stainless steel arc-shaped step forging of the present invention;

[0039] Figure 7 It is a schematic diagram of the steel billet strong pressing and drawing of the free forging method of the large stainless steel arc-shaped step forging of the present invention;

[0040] Figure 8 It is a front view of a rectangular thick plate blank of the free forging method of the large stainless steel arc-shaped step forging of the present invention;

[0041] Fig. 9A side view of a rectangular thick plate blank of the free forging method of the large stainless steel arc-shaped step forging of the present invention;

[0042] Fig.10 It is a front view of a step slab of the free forging method for forming a large stainless steel arc-shaped step forging of the present invention;

[0043] Fig.11 A top view of a step slab of the free forging method for forming a large stainless steel arc-shaped step forging of the present invention;

[0044] Fig.12 It is a schematic diagram of bending forming of the free forging method of the large stainless steel arc-shaped step forging of the present invention. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0046] A free forging method for a large stainless steel arc-shaped step forging according to an embodiment of the present application comprises 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] Among them, D0 and L0 need to 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] Wherein, B is the width of the target large stainless steel arc step forging, L is the total arc length of the target large stainless steel arc step forging; L1 is the arc length of the boss part of the target large stainless steel arc step forging, L2 is the arc length of one side of the target large stainless steel arc step forging excluding the boss part, T1 is the total thickness of the target large stainless steel arc step forging, T2 is the thickness of the target large stainless steel arc step forging excluding the boss part, R1 is the inner diameter of the target large stainless steel arc step forging, and R2 is the outer diameter of the target large stainless steel arc step forging. Figure 1 and Figure 2 As shown;

[0052] Step 2) heating the steel billet to 1180-1230°C and keeping it warm for 8-10 hours to make the temperature inside the billet uniform;

[0053] Step 3) The heated steel billet is repeatedly subjected to upsetting followed by strong pressing and drawing to ensure that the upsetting ratio and drawing ratio are ≥ 2 each time and the steel billet is fully compacted; Figure 6 and Figure 7 As shown,

[0054] Among them, the billet after upsetting needs to satisfy 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 billet needs to satisfy the following formula:

[0057] D n =0.996 n *D0,L n =0.996 n *L0, which can ensure that the deformation of each upsetting and each strong pressing and 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 strong stretching performed, n = 1.5*m 0.2 [n is an integer], the value of n should increase with the weight of the forging, but not exceed 4, m is the weight of the billet; after each drawing, the billet is kept at 1200±20℃ for 8~10h;

[0059] Step 4) The steel billet of step 3) is first upset to a diameter of

[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 in step 3);

[0061] Then draw it into a rectangular thick plate blank, the blank size: width is Bm , thickness is T m , length is L m , where: 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 strong pressure extension in step 3), such as Figure 8 and Fig. 9 As shown; this ensures that after the forging of the two side spans in step 6), the boss part still has a deformation of 30% to 40%, ensuring that the boss part has sufficient deformation during the subsequent forging deformation in step 8), sufficient dynamic recrystallization can occur, and the boss grains can be fully refined;

[0062] Step 5) heating the steel billet of step 4) to 1100-1150° C. and keeping the temperature for 4-5 hours, so that the steel billet has sufficient plasticity, while reducing the growth rate of grains in the steel billet and slowing down grain coarsening;

[0063] Step 6) The billet is divided at the length of 0.8L2*T2 / T1 at both ends, and the billet is stretched to a step billet with a span of thickness T2, width B, and length L2 at both ends. The deformation of the span part at both ends is ≥70%, and the billet in the span part undergoes sufficient dynamic recrystallization and the grains are fully refined; the middle length is L m -1.6L2*T2 / T1 The boss part retains the deformation and is not forged in this step. Figure 8-Figure 11 As shown;

[0064] Step 7) heating the steel billet of step 6) to 1000-1050°C and keeping the temperature for 3-4 hours. At this temperature, the steel billet has the plasticity required for the boss forming in step 8), and the grain growth rate of the steel billet is very slow, and heating will not coarsen the grains;

[0065] Step 8), the boss portion of the steel billet in step 7) is stretched to a step slab with a cross-sectional size of width B, thickness T1, and length L1. During forging, the boss portion has a deformation amount of 30% to 40%, which allows sufficient dynamic recrystallization to occur and fully refine the boss grains;

[0066] Step 9) heating the step slab to 1000-1100° C. and keeping the temperature for 2-3 hours. At this temperature, the steel billet has the plasticity required for bending the step slab in step 10), and the grain growth rate of the steel billet is very slow, and heating will not coarsen the grains.

[0067] Step 10) Using an arc anvil, bend the side of the step slab section by section into a stainless steel arc step forging with an inner diameter of R1 and an outer diameter of R2, such as Fig.12 As shown; the arc anvil width H is controlled within L / 6≤H≤L / 4, and the anvil advance amount P of each anvil during the bending process is controlled within H / 2≤P≤2H / 3, ensuring that the curves of each arc segment of the forging are smoothly connected during the bending process.

[0068] Example 1

[0069] like Figure 1 and Figure 2 As shown, the large stainless steel arc step forging in 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 large stainless steel arc step forging is forged by the following steps:

[0070] Step 1) Cutting a steel billet with a diameter of Φ920 mm and a length of 1870 mm.

[0071] Step 2) heating the steel billet to 1200±20°C and keeping it warm for 9 hours to make the temperature inside the billet uniform;

[0072] Step 3.1) The steel billet is subjected to the first upsetting and forced stretching. The steel billet is first upset to a diameter of Φ1460mm and a height of 730mm, and then forced stretched to a diameter of Φ915mm and a length of 1865mm; the upsetting ratio is 2.6, and the stretching ratio is 2.5; the upsetting deformation is 61%, and the stretching deformation is 61%. After the stretching is completed, the steel billet is kept at 1200±20℃ for 9 hours;

[0073] Step 3.2) The steel billet is subjected to a second upsetting and forced stretching, wherein the steel billet is first upset to a diameter of Φ1455 mm and a height of 725 mm, and then forced stretched to a diameter of Φ910 mm and a length of 1855 mm; the upsetting ratio is 2.6, and the stretching ratio is 2.6; the upsetting deformation is 61%, and the stretching deformation is 61%; after the stretching is completed, the steel billet is kept at 1200±20°C for 9 hours;

[0074] Step 4) upsetting the steel billet to a diameter of Φ1450 mm and a height of 725 mm, and then stretching it to a rectangular thick plate billet with a size of 900 mm in width, 810 mm in thickness, and 1650 mm in length; this ensures that after the forging of both sides of the wings in step 6), the boss part still has a deformation of 30% to 40%, ensuring that the boss part has sufficient deformation during the subsequent forging deformation in step 8), sufficient dynamic recrystallization can occur, and the boss grains can be fully refined;

[0075] Step 5) heating the steel billet to 1120±20° C. and keeping the temperature for 4.5 hours, so that the steel billet has sufficient plasticity, while reducing the growth rate of grains in the steel billet and slowing down grain coarsening;

[0076] Step 6) The billet is divided at the length of 245mm at both ends, and the billet is stretched to a step billet with a span of 218mm, a width of 735mm, and a length of 929mm at both ends. The deformation of the span parts at both ends is 78%, and the billet in the span part undergoes sufficient dynamic recrystallization, and the grains are fully refined; the boss part with a length of 1160mm in the middle retains the deformation, and no forging is performed in this step;

[0077] Step 7) heat the steel billet to 1020±20°C and keep it warm for 3.5 hours. At this temperature and holding time, the steel billet has the plasticity required for the boss forming in step 8), while the grain growth rate of the steel billet is very slow, and heating will not coarsen the grains.

[0078] Step 8) The boss portion of the billet is stretched to a cross-sectional size of a step slab with a width of 735 mm, a thickness of 671 mm, and a length of 1677 mm. During forging, the boss portion has a deformation amount of 32%, which allows sufficient dynamic recrystallization to occur and fully refine the boss grains;

[0079] Step 9) heating the step slab to 1020±20°C and keeping it warm for 2.5h. At this temperature and holding time, the steel billet has the plasticity required for bending the step slab in step 10), while the grain growth rate of the steel billet is very slow, and heating will not coarsen the grains;

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

[0081] The size and shape of the large stainless steel arc-shaped step forging formed by free forging copy forging in this embodiment are consistent with the target part, the subsequent processing amount is small, the forging organization streamline is uniform and continuous, consistent with the part direction, and the forging grain size grade can reach 3 to 4 levels.

[0082] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0083] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. Meanwhile, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0084] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

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

[0086] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0087] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" 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 it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0088] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A free forging method for large stainless steel arc-shaped step forgings, characterized in that: It includes the following steps: Step 1) Cutting a steel billet with a diameter of D0 and a length of L0; Step 2) heating the steel billet to 1180-1230°C and keeping it warm for 8-10 hours to make the temperature inside the billet uniform; Step 3) The heated steel billet is repeatedly subjected to upsetting followed by strong pressing and stretching, ensuring that the upsetting ratio and the stretching ratio are both ≥ 2 each time, and the steel billet is fully compacted; after each stretching, the steel billet is heated to 1200±20℃ and kept warm for 8-10h; Step 4) The steel billet of step 3) is first upset 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 nth upsetting in step 3); Then draw it into a rectangular thick plate blank, the blank size: width is B m , thickness is T m , length is L m , where: 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 strong pressure extension in step 3); Step 5) heating the steel billet of step 4) to 1000-1100° C. and keeping the temperature for 2-3 hours, so that the steel billet has sufficient plasticity, while reducing the growth rate of grains in the steel billet and slowing down grain coarsening; Step 6) The billet is divided at the length of 0.8L2*T2 / T1 at both ends, and the billet is stretched to a step billet with a span of thickness T2, width B, and length L2 at both ends. The deformation of the span part at both ends is ≥70%, and the billet in the span part undergoes sufficient dynamic recrystallization and the grains are fully refined; the middle length is L m -1.6 The boss part of L2*T2 / T1 retains the deformation and is not forged in this step; Step 7) heating the steel billet of step 6) to 1000-1050°C and keeping the temperature for 3-4 hours. At this temperature, the steel billet has the plasticity required for the boss forming in step 8), and the grain growth rate of the steel billet is very slow, and heating will not coarsen the grains; Step 8), the boss portion of the steel billet in step 7) is stretched to a step slab with a cross-sectional size of width B, thickness T1, and length L1. During forging, the boss portion has a deformation amount of 30% to 40%, which allows sufficient dynamic recrystallization to occur and fully refine the boss grains; Step 9) heating the step slab to 1000-1100° C. and keeping the temperature for 2-3 hours. At this temperature, the steel billet has the plasticity required for bending the step slab in step 10), and the grain growth rate of the steel billet is very slow, and heating will not coarsen the grains. Step 10) Using an arc anvil, bend the side of the step slab section by section into a stainless steel arc-shaped step forging with an inner diameter of R1 and an outer diameter of R2.

2. The free forging method for large stainless steel arc-shaped step forgings according to claim 1, characterized in that: In step 1), Among them, D0 and L0 need to satisfy the following formulas respectively: D0 is 0.85~0.91[B*(L1*T1+2L2*T2)] 1 / 3 , L0 is 1.7 to 1.9 [B*(L1*T1+2L2*T2)] 1 / 3 , Among them, B is the width of the target large stainless steel arc step forging, L is the total arc length of the target large stainless steel arc step forging; L1 is the arc length of the boss part of the target large stainless steel arc step forging, L2 is the arc length of one side of the target large stainless steel arc step forging excluding the boss part, T1 is the total thickness of the target large stainless steel arc step forging, T2 is the thickness of the target large stainless steel arc step forging excluding the boss part, R1 is the inner diameter of the target large stainless steel arc step forging, and R2 is the outer diameter of the target large stainless steel arc step forging.

3. The free forging method of large stainless steel arc-shaped step forgings according to claim 1, characterized in that: In step 3), Among them, the billet after upsetting needs to satisfy the following formula: 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 , The drawn billet needs to satisfy the following formula: D n =0.996 n *D0,L n =0.996 n *L0, which can ensure that the deformation of each upsetting and each strong pressing and drawing is ≥50%, fully compacting the stainless steel billet, breaking the internal columnar crystals, and refining the grains; n refers to the nth upsetting and strong stretching performed, n = 1.5*m 0.2 [n is an integer], the value of n should be selected as the weight of the forging increases, but not exceeding 4, and m is the weight of the billet.

4. The free forging method for large-scale stainless steel arc-shaped step forgings according to claim 1, characterized in that: The arc anvil width H is controlled within the range of L / 6≤H≤L / 4, and the anvil advance amount P of each anvil during the bending process is controlled within the range of H / 2≤P≤2H / 3, ensuring that the curves of each arc segment of the forging are smoothly connected during the bending process.

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