Improved precision forging hammer head and precision forging method for improving low-magnification dendritic structure of continuous casting billet

Abstract

The present application relates to a kind of precision forging hammer head and precision forging method for improving continuous casting billet low multiple dendritic structure, and the multifunctional hammer head of precision forging machine includes four hammer heads identical in structure, and appearance presents "T" shape, two sides of length direction center line are asymmetrically distributed with two faces, respectively, feeding face and reinforcing rib plate face, "T" shape shaping face is in the middle of feeding face and reinforcing rib plate face, "T" shape shaping face has angle with feeding face and reinforcing rib plate face, there are open groove respectively symmetrically distributed in the two sides of reinforcing rib plate face, the feeding face of 1# hammer head is installed with the feeding face of 3# hammer head face to face;The reinforcing rib plate face of 2# hammer head is installed with the reinforcing rib plate face of 4# hammer head face to face, when hammer head is closed, adjacent two hammer heads are mutually inlayed at open groove, only need to be forged and formed by one precision forging machine one fire time, i.e. low multiple dendritic structure defect can be greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of forging technology, specifically relating to a precision forging hammer and a precision forging method that can greatly improve the low-magnification dendritic structure of continuously cast billets by requiring only one precision forging machine for one forging operation. Background Technology

[0002] For CrNiMo alloy structural steel with a carbon content of <0.25%, the cooling process in the Φ400 continuous casting billet crystallizer is under non-equilibrium cooling conditions. After the homogeneous transformation, the composition of the newly obtained solid solution grains is non-uniform. The core that crystallizes first contains more high-melting-point component atoms, while the outer edge that crystallizes later contains more low-melting-point component atoms. Since solid solution grains usually grow in a dendritic manner, the branches contain more high-melting-point metal elements, while the inter-branchs contain more low-melting-point metal elements, resulting in non-uniform composition within the same grain and the formation of well-developed dendritic segregation. This can be improved by breaking up the dendrites during the later forging deformation. If the deformation is not reasonable, it will appear in the low-magnification microstructure after forging, affecting the quality of the forging.

[0003] In this industry, the problem of dendrite segregation is generally solved by heating the billet for high-temperature homogenization and using upsetting during forging to increase the forging ratio. However, when the length-to-diameter ratio of a Φ400 continuously cast billet is greater than 8.0, it is basically impossible to increase the forging ratio and break the columnar grains by upsetting. The solution is to use a hydraulic press to forge the billet into a flat shape and roll it into a round shape to form the finished product, or to first use a hydraulic press for high-speed forging to forge the billet into a flat shape and then transfer it to a precision forging machine to forge the finished product. This can effectively solve or improve the dendritic structure, but the forging efficiency of the hydraulic press is too slow and does not help to improve production efficiency. The combined forging of the hydraulic press and the precision forging machine requires two machines, which increases production costs. Furthermore, the effective diameter of the forging is smaller after the billet is opened, and the temperature drops quickly. During the forging process of the finished product, surface cracks are easily formed, which increases the machining allowance and the number of times the forging is reheated in the furnace, resulting in high manufacturing costs. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of low forging efficiency, the need for two forging machines, rapid cooling of finished products, and the need for increased roughing allowances and multiple forging processes in the traditional process of forging Φ400 continuously cast billets of low carbon CrNiMo steel with an aspect ratio greater than 8.0 using a hydraulic press to forge flat square billets into finished products, or first using a hydraulic press forging machine to forge flat square billets into intermediate billets, and then transferring them to a precision forging machine to forge the finished products. The invention provides a precision forging hammer and precision forging method that directly uses a precision forging machine to achieve flat square forging and forging into round billets in a single forging process, thereby improving the low dendritic structure of continuously cast billets.

[0005] The technical solution of this invention is implemented as follows:

[0006] A precision forging hammerhead for improving the low-magnification dendritic structure of continuously cast billets, by decoupling the hammerhead linkage function of the precision forging machine, realizes the separate operation function of the R group and L group of hammerheads of the precision forging machine, and then utilizes the multi-functional hammerhead of the precision forging machine to achieve the function of forging flat squares and forging round bars in the same heat treatment; characterized in that:

[0007] The multi-functional hammerhead for the precision forging machine comprises four identical hammerheads mounted on the hammerhead base plate of the precision forging machine. Compared with conventional forging hammerheads, the multi-functional hammerhead for the precision forging machine has a "T" shape in appearance, with two asymmetrically distributed surfaces on both sides of its length centerline: a feed surface and a reinforcing rib surface. The larger surface is the feed surface, and the narrower surface is the reinforcing rib surface. The "T"-shaped forming surface is located between the feed surface and the reinforcing rib surface.

[0008] The "T"-shaped shaping surface forms an angle of 8-10° with the feed surface and an angle of 10-15° with the reinforcing rib plate surface. The angle between the "T"-shaped shaping surface and the feed surface cannot be greater than the angle between the "T"-shaped shaping surface and the reinforcing rib plate surface. The "T"-shaped shaping surface is designed to have an angle with both the feed surface and the reinforcing rib plate surface. An open groove is symmetrically distributed on both sides of the reinforcing rib plate surface. The four hammers with such identical structures are assembled on the hammer base plate of the precision forging machine. After installation, when viewed from the same side, the feed surface of hammer #1 is installed face-to-face with the feed surface of hammer #3; the reinforcing rib plate surface of hammer #2 is installed face-to-face with the reinforcing rib plate surface of hammer #4. When the hammers are closed, adjacent hammers are interlocked in the open groove without interference.

[0009] A method for precision forging using a precision forging hammer head that improves the low-magnification dendritic structure of continuously cast billets, characterized in that the specific forging process is as follows:

[0010] Step 1) Billet heating stage: After preheating the Φ400 continuous casting billet at 700-800℃, rapid heating is adopted, and the holding time at 1200~1270℃ is ≥6H;

[0011] Step 2) Forging main deformation stage: The heated Φ400mm continuous casting billet is quickly transferred to the precision forging machine for forging. The A control machine clamps the billet, and the initial forging temperature is controlled at 900~1150℃.

[0012] During the first forging pass, the A and B control mechanisms rotate. The R group hammers mainly perform downward forging, while the L group hammers assist in forging. The hammer forging frequency is 60 to 90 times per minute. The forging speed is controlled at ≥7 meters per minute. The R group hammers forge from 400mm down to H=320mm, at which point a bulge appears on the side of the forging. The L group hammers only perform auxiliary forging and continue to forge down to H=400mm.

[0013] During the second forging, the A and B control mechanisms rotate, the R group hammers assist in forging, and the L group hammers perform the main deformation forging, forging from a thickness of H=400mm to H=325mm. At this time, due to plastic deformation, the R group forging exhibits lateral bulging. The R group hammers only perform auxiliary forging, forging to H=320mm. The forging frequency is 60 times / minute to 90 times / minute, and the pulling speed is controlled at ≥7 meters / minute.

[0014] During the third forging pass, the A and B control mechanisms rotate. The R group hammers are mainly forged and deformed, from a thickness of H=320mm to H=250mm. The L group hammers show lateral bulging and only perform auxiliary forging, from H=325mm to H=320mm. The forging frequency is 60 to 90 times per minute, and the pulling speed is controlled at ≥7 meters per minute. At this time, the billet is a flat steel with rounded corners of R20 to R40mm.

[0015] During the fourth forging pass, the A and B operating machines rotate 45° in the same direction, the R and L hammer heads are raised to Φ420mm, and then the rotation stops. A pulls and strikes, forging the diagonal, and R and L hammers are lowered to H=340mm. One pass is pulled and struck, and the pulling and striking speed is ≥4 meters / minute. At this time, the cross-section is a rounded flat steel with a diameter of 250mm*320mm.

[0016] During the fifth forging pass, the A and B operating machines rotate 45° in the same direction again. The L group hammer head undergoes the main deformation, forging from 320mm to H=250mm. A bulge appears on the side, and the R group hammer head undergoes the auxiliary deformation, continuing to forge to 250mm. The forging speed is ≥4m / min, and at this time the diagonal of the square steel is 353mm.

[0017] Step 3) Finishing and forming stage; A and B operating machines resume rotation function, lift the hammer Φ360mm and use a forging frequency of 180 times / minute to finish the size, and pull the hammer at a speed of 1.5~2.5 meters / minute.

[0018] The present invention has the following beneficial effects:

[0019] The main implementation of the technical solution of this invention lies in the use of a multi-functional precision forging hammer. The precision forging machine can forge flat square steel into round steel in one pass. During the precision forging process, low-frequency forging and large rotation angle are used to increase the deformation. Every two passes, flat square steel is forged alternately, with the middle beveling forged into rounded square steel, and then the rounded square steel is forged into an octagon, and finally rotated and forged into round steel. This can effectively break the branches of dispersed dendrites, greatly improve the distribution state of dendrites in low magnification structure, and achieve the purpose of refining low magnification structure.

[0020] The round steel billets with a diameter of 200mm or less forged using this invention have a uniform microstructure at low magnification and are free of dendrites. They can be forged using only one precision forging machine, which significantly improves forging efficiency and reduces industrial production costs. Attached Figure Description

[0021] Figure 1 Front view of the precision forging hammerhead described in this invention.

[0022] Figure 2 A top view of the precision forging hammerhead described in this invention.

[0023] Figure 3 Left view of the precision forging hammerhead described in this invention.

[0024] Figure 4 Assembly diagram of the R and L groups of hammer heads of the precision forging hammer head described in this invention.

[0025] Figure 5 The diagram showing the change in the cross-section of the billet during the first forging pass to the finished product, as described in this invention.

[0026] The diagram is labeled as follows: 1 is the reinforcing rib plate of the precision forging hammerhead; 2 is the "T" shaped surface of the precision forging hammerhead; 3 is the feed surface of the precision forging hammerhead; 4 is the open groove on both sides of the reinforcing rib plate of the precision forging hammerhead; 5 is the base plate bolt hole; 6 is the hoisting hole. Detailed Implementation

[0027] To achieve forging from flat square bars to round bars in a single pass on a precision forging machine, we designed a precision forging hammer (such as...). Figures 1-4 ).

[0028] like Figure 4 As shown, the precision forging hammerhead is a set of four hammerheads with identical structures, which are installed on the hammerhead base plate of the precision forging machine. After installation, when viewed from the same direction, they are named hammerhead #1, hammerhead #2, hammerhead #3, and hammerhead #4 in a clockwise direction. Hammerhead #1 and hammerhead #3 form a group, named group L; hammerhead #3 and hammerhead #4 form a group, named group R. During installation, the center lines of hammerheads in group R and group L are perpendicular to each other.

[0029] like Figure 2 As shown, the multi-functional hammerhead of the precision forging machine consists of four identical hammerheads mounted on the hammerhead base plate of the precision forging machine; the hammerheads of groups R and L have a "T" shape in appearance, and the forging and shaping surface of each hammerhead is also designed to be "T" shaped, as shown in the top view. Figure 2 As shown in the middle, it is called the "T" shaped shaping surface 2.

[0030] Combined with top view Figure 2The four hammers, which are identical in structure, have two asymmetrically distributed surfaces on both sides of their center line along their length: the feeding surface 3 and the reinforcing rib surface 1. For ease of description, the larger surface is referred to as the feeding surface 3 and the narrower surface as the reinforcing rib surface 1.

[0031] Compared with conventional forging hammers, the main feature of the multi-functional hammerhead of the precision forging machine is that its appearance is "T" shaped. Figure 2 The feed surface 3 and the reinforcing rib surface 1 are asymmetrically distributed on both sides of the center line along its length. The larger surface is the feed surface 3 and the narrower surface is the reinforcing rib surface 1. The "T" shaped shaping surface 2 is located in the middle of the feed surface 3 and the reinforcing rib surface 1, as shown by label 2 in the top view.

[0032] The "T"-shaped shaping surface 2 forms an angle of 8-10° with the feed surface 3 and an angle of 10-15° with the reinforcing rib plate surface 1. The angle between the "T"-shaped shaping surface 2 and the feed surface 3 cannot be greater than the angle between the "T"-shaped shaping surface 2 and the reinforcing rib plate surface 1. The "T"-shaped shaping surface 2 is designed with a certain angle with the feed surface 3 and the reinforcing rib plate surface 1 in order to better meet the forging requirements and avoid the mismatch between the forging deformation and elongation speed and the drawing speed, which would cause some forging fold defects on the surface of the forging.

[0033] On both sides of the reinforcing rib plate 1, there is a symmetrically distributed open groove 4. Four hammers with identical structures are assembled onto the hammer base plate of the precision forging machine. After installation, when viewed from the same side, the feed surface 3 of hammer #1 faces the feed surface 3 of hammer #3; the reinforcing rib plate 1 of hammer #2 faces the reinforcing rib plate 1 of hammer #4. When the hammers are closed, adjacent hammers interlock in the open groove 4 without interference. The R and L groups of hammers, according to the precision forging machine's split-processing function, can forge different sizes separately. The installed hammers have the function of forging flat squares and round shapes. 5 is the base plate bolt hole; 6 is the lifting hole.

[0034] Forging example: Taking a Φ400*3000 continuous casting billet of steel grade 20CrNiMo as an example, it is planned to forge a round bar with a specification of Φ200, and the low magnification structure is inspected after forging.

[0035] A precision forging hammer and method for improving the low-magnification dendritic structure of continuously cast billets are disclosed. The method involves first deactivating the linkage function of the precision forging machine hammers, enabling the separate operation of the R-group and L-group hammers. Then, utilizing the multi-functional hammers of the precision forging machine, both flat squares and round bars can be forged in the same heat treatment cycle. The specific precision forging method is as follows:

[0036] Step 1) Put the Φ400mm continuous casting billet cold ingot into the furnace, preheat it at 700~800℃ for 3 hours, rapidly heat it to 1250℃ and hold it for 6 hours. The precision forging machine is equipped with a multi-functional precision forging hammer head in advance. After the continuous casting billet is heated and held at the temperature, it is taken out of the furnace and transferred to the precision forging machine for forging.

[0037] Step 2) Quickly transfer the heated Φ400mm continuous casting billet into the precision forging machine for forging. The A control machine clamps the billet, and the initial forging temperature is controlled at 900~1150℃.

[0038] During the first forging pass, the A and B control mechanisms rotate. The R group hammers mainly perform downward forging, while the L group hammers assist in forging. The hammer forging frequency is 60 times / minute, and the pulling speed is 7.5 meters / minute. The R group hammers forge from 400mm down to H=320mm, at which point a bulge appears on the side of the forging. The L group hammers only perform auxiliary forging and continue to forge down to H=400mm.

[0039] During the second forging, the A and B control mechanisms rotate, the R group hammers assist in forging, and the L group hammers perform the main deformation forging, forging from a thickness of H=400mm to H=325mm. At this time, due to plastic deformation, the R group forging exhibits lateral bulging. The R group hammers only perform auxiliary forging, forging to H=320mm. The forging frequency remains at 60 times / minute, and the pulling speed is controlled at 7.0~7.5 meters / minute.

[0040] During the third forging pass, the A and B control mechanisms rotate. The R group hammers are mainly forged and deformed, forging from a thickness of H=320mm to H=250mm. The L group hammers show lateral bulging and only perform auxiliary forging, forging from H=325mm to H=320mm. The forging frequency is 60 times / minute, and the pulling speed is controlled at 7.0~7.5 meters / minute. At this time, the billet is a flat steel with rounded corners.

[0041] During the fourth forging pass, the A and B operating machines rotate 45° in the same direction, the R and L hammer heads are raised to Φ420mm, and then the rotation stops. A pulls and strikes, forging the diagonal, and R and L hammers are lowered to H=340mm. The pulling and striking speed is controlled at 4~6 meters / minute. One pass is completed, and at this time the cross-section is a rounded flat steel with a diameter of 250mm*320mm.

[0042] In the fifth pass, the A and B manipulators rotate 45° in the same direction again. The L group hammer head undergoes the main deformation, forging from 320mm to H=250mm. A bulge appears on the side. The R group hammer head assists in the deformation, continuing to forge to 250mm. The forging speed is controlled at 4~6 meters / minute. After one pass, the diagonal of the square steel is approximately 353mm.

[0043] Step 3) is the forming and finishing stage. The A and B operating machines resume their rotation function. The Φ360mm hammer is forged at a forging frequency of 180 times / minute to finish forging to Φ200mm. The deformation process is Φ353mm-Φ305mm-Φ235mm-Φ200mm. The forging speed is 1.5~2.5 meters / minute. The finish forging process is completed. After annealing and exiting the furnace, low magnification tests are performed on both ends of the forging, and no dendrite structure is found.

Claims

1. A precision forging hammer head for improving the low-magnification dendritic structure of continuous casting billets, by removing the precision forging machine hammer head linkage function, realizing the precision forging machine R group and L group hammer head distribution function, and then using the precision forging hammer head to realize the function of forging flat and round steel in the same fire; characterized in that: the precision forging hammer head comprises four hammer heads with the same structure, which are installed on the precision forging machine hammer head base plate; compared with the conventional forging hammer head, the precision forging hammer head presents a "T" shape in appearance, and two sides of the center line in the length direction are asymmetrically distributed with two faces, which are the feeding face (3) and the reinforcing rib plate face (1), that is, the large face is the feeding face (3), and the narrow face is the reinforcing rib plate face (1); the "T" shaped shaping face (2) is in the middle of the feeding face (3) and the reinforcing rib plate face (1); the "T" shaped shaping face (2) forms an angle of 8-10° with the feeding face (3) and an angle of 10-15° with the reinforcing rib plate face (1), wherein the angle between the "T" shaped shaping face (2) and the feeding face (3) cannot be greater than the angle between the "T" shaped shaping face (2) and the reinforcing rib plate face (1), the "T" shaped shaping face (2) is designed to have an angle with the feeding face (3) and the reinforcing rib plate face (1), and there is an open groove (4) symmetrically distributed on both sides of the reinforcing rib plate face (1); the precision forging hammer head is a pair of hammer heads, which is composed of four hammer heads with the same structure, and is assembled on the hammer head base plate of the precision forging machine; when observed from the same side after installation, they are named 1# hammer head, 2# hammer head, 3# hammer head and 4# hammer head in clockwise direction, wherein 1# hammer head and 3# hammer head form a group and are named L group, and 3# hammer head and 4# hammer head form a group and are named R group; the center lines of the R group and L group hammer heads are perpendicular to each other when installed; the feeding face (3) of 1# hammer head is installed face to face with the feeding face (3) of 3# hammer head; the reinforcing rib plate face (1) of 2# hammer head is installed face to face with the reinforcing rib plate face (1) of 4# hammer head; when the hammer heads are closed, the adjacent two hammer heads are embedded with each other at the open groove (4) without interference. The specific forging process is as follows:

2. A method of finish forging using the finish forging hammer head of claim 1 for improving the macro dendritic structure of a continuously cast bloom, characterized by: Step 1), billet heating stage: after preheating Φ400 continuous casting billets at 700-800℃, rapid heating is adopted, and the temperature is kept at 1200-1270℃ for ≥6H; Step 2), main deformation stage of forging: after heating the Φ400mm continuous casting billets, the billets are quickly transferred to the precision forging machine for forging, the A manipulator clamps the billets, and the initial forging temperature is controlled at 900-1150℃; In the first pass, the A and B manipulators rotate, the R group hammer head mainly hammers, and the L group hammer head assists in forging, the hammering frequency is 60-90 times per minute, the frequency forging is adopted, and the pulling and hitting speed is controlled at ≥7m / min, wherein the R group hammer head hammers from 400mm to H=320mm, at this time the drum belly appears on the side of the forged part, the L group hammer head only assists in forging, and still hammers to H=400mm. ​ The second pass forging, A, B two operating machine rotation function, R group hammer head auxiliary forging, L group hammer head as the main deformation forging, from the thickness H = 400 to H = 325 mm, at this time R group forging due to plastic deformation, appear lateral bulging, R group hammer head only auxiliary forging, forging to H = 320 mm, forging frequency 60 times / minute ~ 90 times / minute, the drawing speed control in ≥7 meters / minute; The third pass forging, A, B two operating machine rotation function, R group hammer head mainly forging deformation, from the thickness H = 320 mm to H = 250 mm, L group hammer head appear lateral bulging, L group hammer head only auxiliary forging, from H = 325 mm to H = 320 mm, forging frequency 60 times / minute ~ 90 times / minute, the drawing speed control in ≥7 meters / minute, at this time the blank is a flat steel with R20 ~ R40 mm fillet; The fourth pass forging, A, B operating machine to the same direction rotation 45°, R, L group hammer head to Φ420 mm, then stop rotating, A drawing, forging diagonal, R, L hammer down to H = 340 mm, a pass, drawing speed ≥4 meters / minute, at this time the section is 250 mm*320 mm fillet flat steel; The fifth pass forging, A, B operating machine to the same direction rotation 45° again, L group hammer head main deformation, from 320 mm to H = 250 mm; Side appear bulging, R group hammer head auxiliary deformation, still hammer forging to 250 mm, drawing speed ≥4 meters / minute, at this time the square steel diagonal 353 mm; Step 3), finishing forming stage; A, B operating machine restore rotation function, hammer Φ360 mm using 180 times / minute forging frequency, finish forging to finished product size, drawing speed 1.5 ~ 2.5 meters / minute.

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