38crmoal continuous casting billet and its forging method

Abstract

The application provides a 38CrMoAl continuous casting billet and a forging method thereof, and the steps are as follows: 1) plugging pretreatment is performed on the two end faces of the sawed continuous casting billet; 2) the continuous casting billet is heated; 3) the length of the continuous casting billet is pulled out on a ladder-shaped anvil; 4) after the billet is returned to the furnace and is kept warm, the surface is compacted by light forging with a radial forging hammer; 5) the surface is water-cooled; 6) the finished product is forged; and 7) slow cooling is performed after forging. Compared with the prior art, the application uses the continuous casting billet to produce plastic mold steel forging material, fully utilizes the advantages of the continuous casting billet, such as less oxidized inclusions, small point-like segregation of fast and uniform crystallization, high material yield and low cost, and through the continuous casting billet pretreatment, the forging type anvil length pulling and the hard shell forging process designed by the application, the continuous center defects of the continuous casting billet are effectively filled, and the high-quality plastic mold steel without flaw detection defects is produced.

Description

Technical Field

[0001] This invention belongs to the field of special steel forging production, specifically relating to a 38CrMoAl continuous casting billet and its forging method, which is a process method for producing high-quality plastic mold steel by rapid diameter combined forging of continuous casting billets. Background Technology

[0002] 38CrMoAl is a high-aluminum steel, and the Al contained in the steel is the main element for forming nitrides. After nitriding, an aluminum nitride layer is easily formed on the surface. The surface strength and hardness are improved by relying on the dispersion strengthening effect of aluminum nitride. Since the steel contains molybdenum, it suppresses high-temperature tempering brittleness and has good hardenability. It is widely used in the manufacture of plastic molds.

[0003] Currently, the widely used plastic mold steels are mainly produced by ingot forging. Because 38CrMoAl is prone to oxidation and has poor fluidity, compared to the fully protected pouring process of continuous casting, secondary oxidation of the molten steel is unavoidable during ingot casting, resulting in surface or subcutaneous inclusions, which easily lead to near-surface cracks after forging. At the same time, the uniform cooling of ingots is significantly worse than that of continuously cast billets, and the difference in crystallization conditions leads to severe point segregation in ingots, affecting the overall performance of the material.

[0004] Compared to ingots, continuously cast billets have advantages such as less internal point segregation and oxide inclusions, relatively uniform structure, high yield, and low cost. However, due to continuous defects such as central porosity and shrinkage cavities, conventional flat anvil or V-anvil drawing forging processes cannot guarantee the forging penetration of the billet core.

[0005] A patent published on December 6, 2022, with publication number CN115433797A, discloses a method for producing high-quality 38CrMoAl continuously cast round billets for mold steel. The process steps are as follows: converter smelting + LF refining + VD + continuous casting; wherein: in the converter smelting step, a high carbon extraction method is used to control the steel output C≥0.15% and P≤0.010%; and SiCaBa is used for deoxidation and alloying; in the VD step, 9.5 kg / t of aluminum ingots are added at once after slag deoxidation. This method improves Al alloying efficiency, reduces aluminum loss rate, and optimizes refining slag by combining theoretical research with industrial practice, thereby improving steel purity and optimizing the castability of continuous casting. However, it does not disclose how to solve the problem of continuity defects in the center of the continuously cast billet. Summary of the Invention

[0006] The purpose of this invention is to provide a 38CrMoAl continuous casting billet and its forging method. The method uses continuous casting billets to produce plastic mold steel forgings, making full use of the advantages of continuous casting billets, such as less oxidation inclusions during the entire casting process, rapid and uniform crystallization with small point segregation, high yield and low cost. Through the combined process of continuous casting billet pretreatment, forging anvil elongation and hard shell forging designed in this invention, the continuity defects in the center of the continuous casting billet are effectively eliminated, and high-quality plastic mold steel without flaw detection defects is produced.

[0007] The specific technical solution of this invention is as follows:

[0008] A method for forging 38CrMoAl continuously cast billets includes the following steps:

[0009] 1) Pre-treatment of sealing the two ends of the sawn continuous casting billet;

[0010] 2) Heating of continuously cast billets;

[0011] 3). Pull out the trapezoidal anvil to create the blank;

[0012] 4) After heat preservation in the furnace, lightly forge the surface with a radial forging hammer to compact it;

[0013] 5) Surface water cooling;

[0014] 6) Finished product forging;

[0015] 7) Slow cooling after forging.

[0016] In step 1), the sealing pretreatment method is specifically as follows: sawing the continuous casting billet along the axial direction, and then using 20-50# carbon steel plate for overlay welding or using TE61-20 type high temperature resistant and anti-oxidation coating for sealing treatment on both ends of the sawn continuous casting billet;

[0017] In step 2), the heating specifically involves: preheating the continuous casting billet to 600±20℃ for 1.5-2.5 hours, then raising the temperature to 800±20℃ and holding it for 1.5-2 hours, and then raising the temperature to 1200±20℃ and holding it for 5-6 hours.

[0018] Preferably, in step 2), the temperature is increased from 600±20℃ to 800±20℃ at a heating rate of 60-80℃ / h;

[0019] In step 2), the temperature is increased from 800±20℃ to 1200±20℃ at a heating rate of 80-100℃ / h;

[0020] In step 3), a trapezoidal anvil is used for drawing and blanking. A trapezoidal anvil tooling is used. During the drawing process, the width ratio of the feeding anvil is 0.54-0.8. The first pass reduction rate is 5-7%, and the intermediate heavy pass reduction rate is 15-22%.

[0021] In step 3), the initial forging temperature is ≥1020℃ and the final forging temperature is ≥800℃.

[0022] In step 4), the reheating process specifically involves reheating the billet at 1200±20℃ for 1.5-2 hours.

[0023] In step 4), the surface compaction of the radial forging light hammer is specifically: the billet after being kept warm in the furnace is subjected to two passes of light hammer radial forging: the single pass reduction rate is 3-8%, the total reduction rate is 7-12%, the step amount is 50-70mm, and the forging frequency is 485-620ms / time.

[0024] In step 5), specifically: the forging is rotated through the water spray cooling zone at a rotation angle of 10° per cycle, with each cycle lasting 260 milliseconds, and the water spray volume is 5m³ / min. 3 / minute;

[0025] In step 5), when the forging billet reaches the forging position through water spray cooling, the surface temperature is 910-970℃, forming a temperature difference of 150-210℃ with the core, creating the physical conditions for hard shell forging.

[0026] In step 6), the finished product forging specifically involves: performing two heavy hammer forgings with a total reduction rate of 35-43%; setting the single-pass reduction rate to 18-22% deformation rate; followed by pre-finishing and finishing passes with a reduction rate of 4-6% to ensure the roundness and surface quality of the forgings; the initial forging temperature is ≥900℃ and the final forging temperature is ≥820℃.

[0027] In step 7), the slow cooling after forging specifically means: after forging, the temperature is ≥700℃ when the material is placed in the pit and slow-cooled for 36-54 hours. The hardness after slow cooling is 180-210HB.

[0028] The present invention provides a forging process for 38CrMoAl continuously cast billets, which can thoroughly and effectively forge together the central continuous porosity, shrinkage cavities, and crack defects in the continuously cast billets, so that the ultrasonic testing level reaches GB / T 6402-2008 level 4 or GB / T 4162-2022 level A or above.

[0029] The design principle of this invention is as follows: 38CrMoAl has a high Al content, making it highly susceptible to oxidation. Its molten steel has poor fluidity, easily causing flow blockage during casting. After solidification, the billet is prone to subsurface defects such as subcutaneous bubbles and slag inclusions. Simultaneously, due to rapid solidification at the billet center, insufficient feeding, and agglomeration of aluminum nitride inclusions, defects such as shrinkage cavities, porosity, and cracks occur in the billet core. If these subsurface and core defects are not effectively addressed and eliminated during subsequent forging, they will affect the quality of the final product. Therefore, to effectively eliminate these adverse factors, it is necessary to prevent oxidation of core defects in the billet. While ensuring uniform and thorough firing of the billet, forging is performed to allow both the subsurface and core to receive greater pressure and equivalent strain, effectively forging away defects and obtaining a high-quality product.

[0030] In this invention, firstly, by sealing the end face of the continuously cast billet, air is prevented from entering the internal defect channel of the continuously cast billet center, effectively preventing the oxidation of internal defects of the continuously cast billet during heating, and creating favorable conditions for subsequent effective forging.

[0031] The continuously cast billet is then slowly heated in the heating furnace until the core reaches the specified temperature and is held for 5-6 hours to ensure uniform heating and good plasticity.

[0032] Further, by adopting a trapezoidal anvil tooling with a feed anvil width ratio of 0.54-0.8 and a drawing process with a reduction rate of 15-22% in the intermediate heavy pressure pass, the surface and core of the continuous casting billet can obtain greater pressure and equivalent strain. At this time, the surface defects of the continuous casting billet can be repaired, while the central defects can be improved but not completely eliminated.

[0033] The continuously cast billet is then returned to the heating furnace and held at 1200±20℃ for 1.5-2 hours to restore its plasticity.

[0034] Further, high-frequency fast-strike light hammer forging at 485-620ms / time is used to further compact the secondary surface layer of the continuous casting billet. Water spraying and rapid cooling reduce the surface temperature of the continuous casting billet to 910-970℃, creating a temperature difference with the high temperature (1060-1180℃) at the center of the continuous casting billet, thus creating the conditions for hard shell forging JTS method.

[0035] Further utilizing the JTS method principle of hard shell forging (the surface and subsurface temperatures are relatively low, and the deformation resistance is greater than that of the high-temperature central area, which is conducive to stress transmission to the center), a single-pass forging hammer with a large reduction diameter of 18-22% is used to cause severe deformation of the core with low deformation resistance, thereby compacting and welding the central defects.

[0036] In the above process, the upstream and downstream processes complement each other and are crucial for the successful welding of secondary surface and central defects such as porosity, shrinkage cavities, and cracks. End face sealing is a prerequisite for ensuring the welding of central defects. The trapezoidal anvil elongation allows both the secondary surface and center of the continuously cast billet to receive greater compressive stress and effective deformation, and welding secondary surface defects can initially improve central defects. Meanwhile, radial forging of the hard shell mainly induces severe deformation in the center, which is a key process for welding central defects and improving flaw detection quality.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] 1. It adopts continuous casting billet forging, which has the characteristics of small point segregation, less inclusions formed by secondary oxidation on the surface and sub-surface, high yield and low cost.

[0039] 2. The center of the sawn rear end face of the continuously cast billet is loose and the shrinkage cavity is exposed, which easily becomes a channel for air to enter the interior. During heating, this causes oxidation at the defect site, destroying the intergranular bonding force and thus hindering the effective forging of internal defects. Welding or high-temperature coating to seal the center defects of the continuously cast billet before furnace heating can effectively prevent oxidation of internal defects and create favorable conditions for subsequent effective forging.

[0040] 3. The present invention adopts a trapezoidal anvil design that combines the advantages of traditional drawing tooling flat anvil and V-shaped anvil: its θ-angled anvil surface ensures that the secondary surface metal on the X-axis and Z-axis cross-section of the forging billet generates large strain, while the convex anvil surface restricts the outward flow of the secondary surface metal below it, achieving the effect of increasing the deformation of the core metal of the forging billet by the flat anvil, thus taking into account the effective strain on the secondary surface and core of the billet, so that the interior of the forging billet obtains larger and more uniform compressive stress and equivalent strain, which is beneficial to expanding the welding range of internal defects of the forging billet.

[0041] 4. When using a trapezoidal anvil for drawing, with an anvil width ratio of 0.54-0.8 and a reduction rate of 15-22%, the core of the billet is subjected to a strong triaxial compressive stress state. Compared to the dual compressive and tensile stress state of the core during traditional flat anvil drawing, this method improves the forging effect of core defects and has high drawing efficiency, making it less prone to billet axis deviation. Compared to traditional V-shaped anvil drawing, the trapezoidal anvil significantly expands the range of large deformation zones within the cross-section during the feed rate, enabling the core and subsurface metal of the forging billet to simultaneously obtain larger compressive stress and equivalent strain, which helps to expand the forging range of internal defects in the forging.

[0042] 5. Radial forging of hard shells creates a temperature difference of 150-210℃ between the surface temperature and the core temperature of the billet, expanding the difficult-to-deform zone on the surface and effectively transmitting pressure to the core of the forging billet. This results in greater equivalent deformation in the core of the billet, effectively eliminating defects such as porosity, air holes, and cracks in the core of the billet.

[0043] 6. Due to the current continuous casting billet specification of Φ600mm, it is difficult to achieve flawless inspection of Φ200-380mm specifications. However, this invention can solve the problem through process design.

[0044] Compared with existing technologies, this invention uses continuously cast billets as raw materials and, through the above process combination and parameter control, can produce high-quality, low-cost plastic mold steel ∮200-380 large-size round bars. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the process of the present invention;

[0046] Figure 2 A schematic diagram of the trapezoidal anvil tool being extended;

[0047] Figure 3 The flaw detection results for Example 1 show no obvious defects.

[0048] Figure 4 The flaw detection results for Example 2 show no obvious defects.

[0049] Figure 5 The flaw detection results for Example 3 showed no obvious defects;

[0050] Figure 6 The flaw detection results are shown in Comparative Example 1;

[0051] Figure 7 The flaw detection results are shown in Comparative Example 2;

[0052] Figure 8 The flaw detection results are shown in Comparative Example 3;

[0053] Figure 9 This is the flaw detection result for Comparative Example 4. Detailed Implementation

[0054] The invention will now be described in further detail with reference to specific examples.

[0055] A method for forging 38CrMoAl continuously cast billets includes the following steps:

[0056] Step 1) Axially saw the continuous casting billet, and then use 20-50# carbon steel plate to overlay the two ends of the sawn continuous casting billet or use TE61-20 high temperature resistant and anti-oxidation coating to seal the ends.

[0057] Step 2) Heating the continuous casting billet: Preheat the continuous casting billet to 600±20℃ for 1.5-2.5 hours, then raise the temperature to 800±20℃ and hold for 1.5-2 hours, then raise the temperature to 1200±20℃ and hold for 5-6 hours; wherein, the temperature is raised from 600±20℃ to 800±20℃ at a heating rate of 60-80℃ / h, and from 800±20℃ to 1200±20℃ at a heating rate of 80-100℃ / h.

[0058] Step 3) Trapezoidal anvil drawing and blanking: The trapezoidal anvil tooling is used for fast forging drawing and blanking. During the drawing process, the feed anvil width ratio is 0.54-0.8, the first pass reduction rate is 5-7%, and the intermediate heavy pass reduction rate is 15-22%. The initial forging temperature is ≥1020℃, and the final forging temperature is ≥800℃.

[0059] Step 4) After reheating in the furnace, light hammer forging is performed to compact the surface: After step 3), the billet is reheated in the furnace at 1200±20℃ for 1.5-2 hours, and then hoisted to the radial forging plant for two passes of light hammer radial forging: the single pass reduction rate is 3-8%, the total reduction rate is 7-12%, the step amount is 50-70mm, and the forging frequency is 485-620ms / time.

[0060] Step 5) Perform water spraying to create a temperature difference between the inner and outer surfaces: Operate the forging machine jaws to rotate the forging through the water spray cooling zone in finishing dry-running mode, with a rotation angle of 10° / cycle, each cycle lasting 260 milliseconds, and a water spray volume of 5m³ / cycle. 3 / minute, when the forging billet reaches the forging position through water spray cooling, the surface temperature is 910-970℃, forming a temperature difference of 150-210℃ with the core, creating the physical conditions for hard shell forging.

[0061] Step 6) Finished product forging: Perform two heavy hammer high-pressure radial forgings with a total reduction rate of 35-43%; set the single-pass reduction rate to 18-22%, followed by pre-finishing and finishing passes with a reduction rate of 4-6% to ensure the roundness and surface quality of the forgings; the initial forging temperature is ≥900℃ and the final forging temperature is ≥820℃.

[0062] Step 7) Slow cooling after forging: After forging, place the product in the pit at ≥700℃ and slow cool for 36-54 hours. The hardness after slow cooling is 180-210HB.

[0063] The above production method can thoroughly and effectively forge and repair the central continuous porosity, shrinkage cavities, and cracks in the continuously cast billet, so that the ultrasonic testing level can reach GB / T 6402-2008 level 4 or GB / T 4162-2022 level A or above.

[0064] Example 1

[0065] A forging process for 38CrMoAl continuously cast billets is disclosed. The plastic mold steel is 38CrMoAl, with the following chemical composition: C: 0.381%, Si: 0.339%, Mn: 0.41%, Cr: 1.397%, Mo: 0.186%, Al: 0.847%, P: 0.011%, S: 0.001%, and the balance being Fe and unavoidable impurities. The product specifications are φ330mm × 8m; the billet used is a continuously cast billet with a specification of φ600mm, and the sawn length is 2700mm.

[0066] 1) The two sawn ends of the continuously cast billet are sealed by welding carbon steel plates, and the sealing area should at least cover the surface of the central defect;

[0067] 2) Heating of continuous casting billet after end face sealing: Preheat at 600℃ for 2 hours, then heat to 800℃ at a heating rate of 70℃ / h and hold for 2 hours, then heat from 800℃ to 1200℃ at a heating rate of 100℃ / h and hold for 5.5 hours.

[0068] 3) Trapezoidal anvil drawing of continuously cast billets: Trapezoidal anvil tooling is used for rapid forging and drawing of billets. During the drawing process, the feed anvil width ratio is 0.68, the first pass reduction rate is 6%, and the intermediate heavy pass reduction rate is 18%. The initial forging temperature is 1050℃, and the final forging temperature is 830℃.

[0069] 4) Forging the surface of the billet: Return the billet to the furnace and keep it at 1200℃ for 1.5 hours. Then, it is hoisted to the forging plant for two passes of light hammer forging: the single pass reduction rate is 6%, the total reduction rate is 10%, the step amount is 60mm, and the forging frequency is 520ms / time.

[0070] 5) Spraying the billet surface: Operate the forging machine jaws to rotate the forging through the water spray cooling zone in finishing dry-running mode, with a rotation angle of 10° / cycle, each cycle lasting 260 milliseconds, and a water spray volume of 5m³ / cycle. 3 / minute, when the forging billet reaches the forging position through water spray cooling, the surface temperature is 945℃, forming a temperature difference of 180℃ with the core, creating the physical conditions for hard shell forging.

[0071] 6) Finished product forging: Two heavy hammer forging processes are performed, with a total reduction rate of 40%; the deformation rate for each pass is set at 20%, followed by pre-finishing and finishing passes with a reduction rate of 5% to ensure the roundness and surface quality of the forging. Initial forging temperature: 930℃, final forging temperature: 830℃.

[0072] 7) Slow cooling: After forging, the sample is placed in the pit at 732℃ and slowly cooled for 48 hours. The hardness after slow cooling is 188HB.

[0073] The flaw detection results of the product in Example 1 are as follows: Figure 3 As shown, no obvious defects were observed.

[0074] Example 2

[0075] A forging process for 38CrMoAl continuously cast billets is disclosed. The plastic mold steel is 38CrMoAl, with the following chemical composition: C: 0.393%, Si: 0.315%, Mn: 0.414%, Cr: 1.424%, Mo: 0.185%, Al: 0.865%, P: 0.018%, S: 0.003%, and the balance being Fe and unavoidable impurities. The product specifications are φ350mm×8m; the billet used is a continuously cast billet with a specification of φ600mm, and the sawn length is 2700mm.

[0076] 1) The two sawn ends of the continuously cast billet are sealed by welding carbon steel plates, and the sealing area should at least cover the surface of the central defect;

[0077] 2) Heating of continuous casting billet after end face sealing: Preheat at 600℃ for 2 hours, then heat to 800℃ at a heating rate of 60℃ / h and hold for 2 hours, then heat from 800℃ to 1200℃ at a heating rate of 100℃ / h and hold for 5 hours.

[0078] 3) Trapezoidal anvil drawing of continuously cast billets: Trapezoidal anvil tooling is used for rapid forging and drawing of billets. During the drawing process, the feed anvil width ratio is 0.55, the first pass reduction rate is 5%, and the intermediate heavy pass reduction rate is 22%. The initial forging temperature is 1035℃, and the final forging temperature is 820℃.

[0079] 4) Forging the surface of the billet: Return the billet to the furnace and keep it at 1200℃ for 1.5 hours. Then, it is hoisted to the forging plant for two passes of light hammer forging: the single pass reduction rate is 3%, the total reduction rate is 7%, the step amount is 50mm, and the forging frequency is 485ms / time.

[0080] 5) Spraying the billet surface: Operate the forging machine jaws to rotate the forging through the water spray cooling zone in finishing dry-running mode, with a rotation angle of 10° / cycle, each cycle lasting 260 milliseconds, and a water spray volume of 5m³ / cycle. 3 / minute, when the forging billet reaches the forging position through water spray cooling, the surface temperature is 910℃, forming a temperature difference of 150℃ with the core, creating the physical conditions for hard shell forging.

[0081] 6) Finished product forging: Two heavy-hammer high-pressure radial forgings are performed, with a total reduction rate of 43%; the deformation rate for each pass is set at 22%, followed by pre-finishing and finishing passes with a reduction rate of 4% to ensure the out-of-roundness and surface quality of the forgings. Initial forging temperature: 935℃, final forging temperature: 837℃.

[0082] 7) Slow cooling: After forging, the sample is placed in the pit at 756℃ and slowly cooled for 54 hours. The hardness after slow cooling is 182HB.

[0083] The flaw detection results of the product in Example 2 are as follows: Figure 4 As shown, no obvious defects were observed.

[0084] Example 3

[0085] A forging process for 38CrMoAl continuously cast billets is disclosed. The plastic mold steel is 38CrMoAl, with the following chemical composition: C: 0.362%, Si: 0.324%, Mn: 0.409%, Cr: 1.412%, Mo: 0.181%, Al: 0.901%, P: 0.013%, S: 0.001%, and the balance being Fe and unavoidable impurities. The product specifications are φ350mm×8m; the billet used is a continuously cast billet with a specification of φ600mm, and the sawn length is 2700mm.

[0086] 1) The two sawn ends of the continuously cast billet are sealed by welding carbon steel plates, and the sealing area should at least cover the surface of the central defect;

[0087] 2) Heating of continuous casting billet after end face sealing: Preheat at 600℃ for 2 hours, then heat to 800℃ at a heating rate of 80℃ / h and hold for 2 hours, then heat from 800℃ to 1200℃ at a heating rate of 100℃ / h and hold for 6 hours.

[0088] 3) Trapezoidal anvil drawing of continuously cast billets: Trapezoidal anvil tooling is used for rapid forging and drawing of billets. During the drawing process, the feed anvil width ratio is 0.8, the first pass reduction rate is 7%, and the intermediate heavy pass reduction rate is 15%. The initial forging temperature is 1043℃, and the final forging temperature is 828℃.

[0089] 4) Forging the surface of the billet: Return the billet to the furnace and keep it at 1200℃ for 2 hours. Then, it is hoisted to the forging plant for two passes of light hammer forging: the single pass reduction rate is 8%, the total reduction rate is 12%, the step amount is 70mm, and the forging frequency is 620ms / time.

[0090] 5) Spraying the billet surface: Operate the forging machine jaws to rotate the forging through the water spray cooling zone in finishing dry-running mode, with a rotation angle of 10° / cycle, each cycle lasting 260 milliseconds, and a water spray volume of 5m³ / cycle. 3 / minute, when the forging billet reaches the forging position through water spray cooling, the surface temperature is 970℃, forming a temperature difference of 210℃ with the core, creating the physical conditions for hard shell forging.

[0091] 6) Finished product forging: Two heavy-hammer high-pressure radial forgings are performed, with a total reduction rate of 35%; the deformation rate for each pass is set at 18%, followed by pre-finishing and finishing passes with a reduction rate of 6% to ensure the out-of-roundness and surface quality of the forgings. Initial forging temperature: 925℃, final forging temperature: 852℃.

[0092] 7) Slow cooling: After forging, the sample is placed in the pit at 732℃ and slowly cooled for 36 hours. The hardness after slow cooling is 205HB.

[0093] The flaw detection results of the product in Example 3 are as follows: Figure 5 As shown, no obvious defects were observed.

[0094] Comparative Example 1

[0095] A forging process for 38CrMoAl continuously cast billets, using 38CrMoAl plastic mold steel as the material. Its chemical composition is: C: 0.379%, Si: 0.335%, Mn: 0.401%, Cr: 1.401%, Mo: 0.189%, Al: 0.835%, P: 0.012%, S: 0.001%, with the balance being Fe and unavoidable impurities. The product specifications are φ330mm × 8m; the billet used is a continuously cast billet with a specification of φ600mm, and a sawn length of 2700mm; the specific steps include:

[0096] 1) The two sawn ends of the continuously cast billet are sealed by welding carbon steel plates, and the sealing area should at least cover the surface of the central defect;

[0097] 2) Heating of continuous casting billet: Preheat at 600℃ for 2 hours, then heat to 800℃ at a heating rate of 80℃ / h and hold for 2 hours, then heat from 800℃ to 1200℃ at a heating rate of 100℃ / h and hold for 6 hours.

[0098] 3) Flat anvil drawing for long blanking: using Standard flat anvil The billet is drawn and stretched using a rapid forging process. The anvil width ratio during the drawing process is 0.8, the first pass reduction rate is 5%, and the intermediate heavy pass reduction rate is 15%. The initial forging temperature is 1040℃, and the final forging temperature is 820℃.

[0099] 4) Finished product forging: The radial forging process involves two heavy hammer forgings with a total reduction rate of 43%. The single-pass reduction rate is set at 22%, followed by pre-finishing and finishing passes with a reduction rate of 4% to ensure the roundness and surface quality of the forgings. Initial forging temperature: 954℃, final forging temperature: 860℃.

[0100] 5) Slow cooling: After forging: 773℃ into the pit, slow cooling for 48 hours, hardness after slow cooling: 197HB.

[0101] The flaw detection results of Comparative Example 1 are as follows Figure 6 As shown, although the end is sealed according to the present invention, However, using a conventional flat anvil The drawing and forging process did not involve reheating in the furnace after drawing, nor did it involve light forging with a forging hammer to compact the surface and surface. Water cooling allows for direct forging of the finished product. This results in a significant central defect, with a maximum defect equivalent of Φ6.2mm.

[0102] Comparative Example 2

[0103] A forging process for 38CrMoAl continuously cast billets, using 38CrMoAl plastic mold steel as the material. Its chemical composition is: C: 0.376%, Si: 0.357%, Mn: 0.439%, Cr: 1.408%, Mo: 0.172%, Al: 0.833%, P: 0.023%, S: 0.001%, with the balance being Fe and unavoidable impurities. The product specifications are φ330mm × 8m; the billet used is a continuously cast billet with a specification of φ600mm, and a sawn length of 2700mm; the specific steps include:

[0104] 1) No sealing pretreatment is performed on the two sawn ends of the continuously cast billet. Directly load into the furnace for heating;

[0105] 2) Heating of continuous casting billets with unsealed end faces: Preheat at 600℃ for 2 hours, then heat to 800℃ at a heating rate of 80℃ / h and hold for 2 hours, then heat from 800℃ to 1210℃ at a heating rate of 100℃ / h and hold for 6 hours.

[0106] 3) Trapezoidal anvil drawing of continuous casting billet: The trapezoidal anvil tooling used for quick forging and drawing of billet has a feed anvil width ratio of 0.75 during the drawing process, a first pass reduction rate of 6%, and an intermediate heavy pass reduction rate of 16%. The initial forging temperature is 1050℃, and the final forging temperature is 850℃.

[0107] 4) Forging the billet surface: Return the billet to the furnace and keep it at 1200℃ for 2 hours. Then, it is hoisted to the forging plant for two passes of light hammer forging: the single pass reduction rate is 5%, the total reduction rate is 9%, the step amount is 55mm, and the forging frequency is 562ms / time.

[0108] 5) Spraying the billet surface: Operate the forging machine jaws to rotate the forging through the water spray cooling zone in finishing dry-running mode, with a rotation angle of 10° / cycle, each cycle lasting 260 milliseconds, and a water spray volume of 5m³ / cycle. 3 / minute, when the forging billet reaches the forging position through water spray cooling, the surface temperature is 925℃, forming a 180℃ temperature difference with the core, creating the physical conditions for hard shell forging.

[0109] 6) Finished product forging: Two heavy-hammer high-pressure radial forgings are performed, with a total reduction rate of 40%; the single-pass reduction rate is set at 20%, followed by pre-finishing passes and finishing passes with a reduction rate of 5% to ensure the out-of-roundness and surface quality of the forgings. Initial forging temperature: 935℃, final forging temperature: 835℃.

[0110] 7) Slow cooling: After forging, the sample is placed in the pit at 768℃ and slowly cooled for 52 hours. The hardness after slow cooling is 192HB.

[0111] The flaw detection results of Comparative Example 2 are as follows Figure 7 As shown, although it is carried out according to the present invention, the long blanking is drawn with a trapezoidal anvil and the hard shell is forged by radial forging and heavy hammer forging, However, the ends of the billet were not sealed.Its central defect is obvious, with a maximum defect equivalent of Φ4.6mm.

[0112] Comparative Example 3

[0113] A forging process for 38CrMoAl continuously cast billets, using 38CrMoAl plastic mold steel as the material. Its chemical composition is: C: 0.388%, Si: 0.323%, Mn: 0.414%, Cr: 1.416%, Mo: 0.183%, Al: 0.875%, P: 0.013%, S: 0.002%, with the balance being Fe and unavoidable impurities. The product specifications are φ330mm × 8m; the billet used is a continuously cast billet with a specification of φ600mm, and a sawn length of 2700mm; the specific steps include:

[0114] 1) The two sawn ends of the continuously cast billet are sealed by welding carbon steel plates, and the sealing area should at least cover the surface of the central defect;

[0115] 2) Heating of continuous casting billet after end face sealing: Preheat at 600℃ for 2 hours, then heat to 800℃ at a heating rate of 80℃ / h and hold for 2 hours, then heat from 800℃ to 1200℃ at a heating rate of 100℃ / h and hold for 6 hours.

[0116] 3) Trapezoidal anvil drawing of continuous casting billet: The trapezoidal anvil tooling used for quick forging and drawing of billet has a feed anvil width ratio of 0.8 during the drawing process, a first pass reduction rate of 7%, and an intermediate heavy pass reduction rate of 15%. Forging temperature: 1055℃, final forging temperature: 855℃.

[0117] 4) Finished product forging: Directly perform two-pass heavy hammer forging with a total reduction rate of 40%; the single-pass reduction rate is set at 22%, followed by pre-finishing and finishing passes with a reduction rate of 4% to ensure the roundness and surface quality of the forging. Initial forging temperature: 945℃, final forging temperature: 840℃.

[0118] 5) Slow cooling: After forging: 787℃ into the pit, slow cooling for 52 hours, hardness after slow cooling: 186HB.

[0119] The flaw detection results of Comparative Example 3 are as follows Figure 8 As shown, although the end is sealed according to the present invention, a trapezoidal anvil is used for long blanking. After the billet was opened, it was not heat-preserved in the furnace, nor was the surface compacted by light hammer forging or surface water cooling performed; it was directly forged into finished product. make, Its central defect is quite obvious, with a maximum defect equivalent of Φ3.1mm.

[0120] Comparative Example 4

[0121] A forging process for 38CrMoAl continuously cast billets is disclosed. The plastic mold steel material is 38CrMoAl, with the following chemical composition: C: 0.372%, Si: 0.289%, Mn: 0.412%, Cr: 1.426%, Mo: 0.195%, Al: 0.869%, P: 0.017%, S: 0.001%, and the balance being Fe and unavoidable impurities. The product specifications are φ350mm×8m; the billet used is a continuously cast billet with a specification of φ600mm, and the sawn length is 2700mm.

[0122] 1) The two sawn ends of the continuously cast billet are sealed by welding carbon steel plates, and the sealing area should at least cover the surface of the central defect;

[0123] 2) Heating of continuous casting billet after end face sealing: Preheat at 600℃ for 2 hours, then heat to 800℃ at a heating rate of 80℃ / h and hold for 2 hours, then heat from 800℃ to 1200℃ at a heating rate of 100℃ / h and hold for 5 hours.

[0124] 3) Trapezoidal anvil drawing of continuously cast billets: A trapezoidal anvil fixture is used for rapid forging and drawing of the billet. During the drawing process, the width-to-width ratio of the feed anvil is: 0.4 The initial forging reduction rate is 5%, and the intermediate heavy forging reduction rate is 15%. The initial forging temperature is 1036℃, and the final forging temperature is 822℃.

[0125] 4) Forging the surface of the billet: Return the billet to the furnace and keep it at 1200℃ for 1.5 hours. Then, it is hoisted to the forging plant for two passes of light hammer forging: the single pass reduction rate is 5%, the total reduction rate is 10%, the step amount is 55mm, and the forging frequency is 590ms / time.

[0126] 5) Spraying the billet surface: The forging is rotated through the water spray cooling zone in finishing dry-running mode by the forging jaws of the rotary forging machine. The rotation angle is 10° / cycle, and each cycle lasts 260 milliseconds. Spray water volume at 3m 3 / minute When the forging billet reaches the forging position after being cooled by water spray, the surface temperature is... The temperature difference between 1020℃ and the heart is only 80℃. The hard shell forging effect is poor.

[0127] 6) Finished product forging: Perform fixed-pass radial forging with a fixed elongation rate, and the total reduction rate is 35%; Single pass set at 10% deformation Rate Afterwards, a pre-finishing pass with a 4% reduction rate and a finishing pass are set to ensure the out-of-roundness and surface quality of the forging. Initial forging temperature: 965℃, final forging temperature: 882℃.

[0128] 7) Slow cooling: After forging, place in the pit at 790℃ and slow cool for 36 hours. Hardness after slow cooling: 218HB.

[0129] The flaw detection results of Comparative Example 4 are as follows Figure 9As shown, although it is executed according to the complete process procedure of this invention, the trapezoidal anvil drawing and the water cooling of the sprayed billet surface are not included. The process parameters for forging finished products in radial forging cannot meet the requirements of this invention. Secondly, both surface and central defects are quite obvious. The maximum subcutaneous defect equivalent is Φ3.7mm, and the maximum central defect equivalent is Φ7.2mm.

[0130] Table 1. Flaw detection results of each embodiment and comparative example.

[0131]

[0132]

[0133] The data underlined above do not meet the requirements of this invention.

[0134] The above examples are preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above examples based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A method for forging 38CrMoAl continuously cast billets, characterized in that, The forging method for the 38CrMoAl continuous casting billet includes the following steps: 1) Pre-treatment of sealing the two ends of the sawn continuous casting billet; 2) Heating of continuously cast billets; 3). Pull out the trapezoidal anvil to create the billet; 4) After returning to the furnace for heat preservation, lightly hammer the radial forging machine to compact the surface; 5) Surface water cooling; 6) Finished product forging; 7) Slow cooling after forging; In step 3), a trapezoidal anvil is used for drawing and opening the billet. During the drawing process, the width ratio of the feeding anvil is 0.54-0.8, the first pass reduction rate is 5-7%, and the intermediate heavy-pressure pass reduction rate is 15-22%. In step 4), the reheating process specifically involves reheating the billet at 1200±20℃ for 1.5-2 hours. In step 4), the compaction of the radial forging surface by light hammer forging specifically refers to the following: after the billet is kept warm in the furnace, it is subjected to two passes of light hammer radial forging: the single pass reduction rate is 3-8%, the total reduction rate is 7-12%, the step amount is 50-70mm, and the forging frequency is 485-620ms / time.

2. The forging method for 38CrMoAl continuously cast billets according to claim 1, characterized in that, In step 2), the heating specifically involves preheating the continuously cast billet to 600±20℃ for 1.5-2.5 hours, then raising the temperature to 800±20℃ and holding it for 1.5-2 hours, and then raising the temperature to 1200±20℃ and holding it for 5-6 hours.

3. The forging method for 38CrMoAl continuously cast billets according to claim 1, characterized in that, In step 3), the initial forging temperature is ≥1020℃ and the final forging temperature is ≥800℃.

4. The forging method for 38CrMoAl continuously cast billets according to claim 1, characterized in that, In step 5), specifically: the forging is rotated through the water spray cooling zone at a rotation angle of 10° per cycle, with each cycle lasting 260 milliseconds, and the water spray volume is 5m³ / min. 3 / minute.

5. The forging method for 38CrMoAl continuously cast billets according to claim 1 or 4, characterized in that, In step 5), when the forging billet reaches the forging position through water spray cooling, the surface temperature is 910~970℃, forming a temperature difference of 150-210℃ with the core.

6. The forging method for 38CrMoAl continuously cast billets according to claim 1, characterized in that, In step 6), the finished product forging specifically involves: performing two heavy hammer high-pressure radial forgings with a total reduction rate of 35-43%; setting the single-pass reduction rate to 18-22% deformation rate, followed by pre-finishing passes and finishing passes with a reduction rate of 4-6%; the initial forging temperature is ≥900℃, and the final forging temperature is ≥820℃.

7. A 38CrMoAl continuous casting billet forged by the 38CrMoAl continuous casting billet forging method as described in any one of claims 1-6.

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