CN115351071B - Rolling technology for inhibiting hot upsetting cracks of medium-small excellent steel - Google Patents
Rolling technology for inhibiting hot upsetting cracks of medium-small excellent steel Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/16—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling wire rods, bars, merchant bars, rounds wire or material of like small cross-section
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B27/00—Rolls, roll alloys or roll fabrication; Lubricating, cooling or heating rolls while in use
- B21B27/02—Shape or construction of rolls
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B27/00—Rolls, roll alloys or roll fabrication; Lubricating, cooling or heating rolls while in use
- B21B27/06—Lubricating, cooling or heating rolls
- B21B27/10—Lubricating, cooling or heating rolls externally
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B39/00—Arrangements for moving, supporting, or positioning work, or controlling its movement, combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B39/14—Guiding, positioning or aligning work
- B21B39/16—Guiding, positioning or aligning work immediately before entering or after leaving the pass
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/004—Heating the product
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D37/00—Tools as parts of machines covered by this subclass
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B27/00—Rolls, roll alloys or roll fabrication; Lubricating, cooling or heating rolls while in use
- B21B27/06—Lubricating, cooling or heating rolls
- B21B27/10—Lubricating, cooling or heating rolls externally
- B21B2027/103—Lubricating, cooling or heating rolls externally cooling externally
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Abstract
The invention discloses a rolling process for inhibiting hot upsetting cracks of medium and small bar excellent special steel, wherein the opening of a normal burner is controlled to be 50%, the opening of a local high-temperature burner is controlled to be 30%, the pressure of gas is controlled to be 8-10KPa, the pressure of air is controlled to be 4-5KPa, the temperature of a high-temperature section of a heating furnace is reduced as much as possible when a small unit optimizes the heating temperature, a 2# box-shaped hole pattern and a 3# elliptic box hole pattern with the corner R=20 mm and the hole depth=10 mm are designed, and the width of a box-shaped hole pattern locking mouth-the edge width of a rolled piece is more than or equal to 2mm and less than or equal to 5mm; the diameter D of the hole-shaped base circle of the vertical rolling round rolled piece is more than or equal to the value of the slot bottom and more than or equal to the value of the slot opening, and the principle of reforming the vertical rolling inlet guide plate is as follows: the width L is 8-10mm larger than the width L of the rolled piece, and the height 2H of the guide plate is 8-10mm larger than the height H of the rolled piece; the guide wheel hole type radian R1 is changed into a radian R which is completely matched with a rolled piece, the internal appearance structure of the guide Wei Gaban is changed from a rectangle to an ellipse, the ellipse radian R and the rolled piece arc are the same diameter R arc, and the contact part of the corner of the rolled piece and the contact part of the clamping plate form smooth and gentle transition.
Description
Technical Field
The invention relates to a rolling process for inhibiting hot upsetting cracks of medium and small excellent steel.
Background
The surface cracks of the medium and small excellent special steel are usually detected through a hot upsetting test and a metallographic test; the surface crack of the medium-small excellent special steel is a serious defect which often occurs, and often causes abnormal cracking or fracture due to stress concentration at the crack position, so that the quality of a downstream terminal product is seriously influenced; however, the thermal upsetting cracks have different morphological surfaces, so that the forming reason is complex, and the related factors are more, so that qualitative analysis and quantitative analysis are difficult to perform when the defects are researched. At present, the research on the hot upsetting defect is very few in China, and no part of research is more remarkable than the systematic research, which is a serious defect on the research on the surface quality of the excellent steel.
The eight-steel small-sized unit is transformed from the early 2000 years to develop and roll excellent round steel products of small and medium rods, mainly high-quality carbon structural steel and alloy structural steel products such as sucker rod steel, gear steel, spring round steel and the like. During the use process of downstream users, the base materials of the sucker rod steel and the gear steel round steel are firstly subjected to forging and pressing, and the spring round steel is required to be bent and deformed. If the round steel parent metal does not have qualified surface quality, quality defects such as cracking, material explosion, fracture and the like can occur in the deformation processing process, and the continuous production of users is influenced.
Because the reason for generating the hot upsetting crack defect is complex, the research and the summary of the small-sized unit are not thorough in the early stage, and a practical and effective method for judging and controlling the hot upsetting crack defect is not established. When the hot upsetting crack defect occurs in the production process, no effective solution exists, and most of the problems are solved in an attempted way by stopping the machine and replacing the groove and the guide. The primary hot upsetting performance is not good, the checking and confirmation of the rolling groove and the guide are required, the groove and the guide are replaced, and the heating furnace is heated and cooled. When the rolling is debugged, the problem that the daily operation rate is affected by the fact that the hot upsetting is not suitable for disposal for 2-4 hours is often solved, the normal plan changing time is eliminated, and the daily operation rate of the small-sized unit round steel is only about 77%.
Disclosure of Invention
The invention aims to provide a rolling process for inhibiting hot upsetting cracks of medium and small excellent steel, which designs a pass and a guide system with the specification of 12-60mm of round excellent steel, and realizes mass production and stable quality of factories through process test and optimization.
The invention adopts the technical proposal that a rolling process for inhibiting hot upsetting cracks of the medium and small excellent steel,
1) The heating process for preventing surface cracks of the high-grade steel comprises the following steps: the opening degree of a normal burner is controlled to be 50%, the partial high-temperature burner is controlled to be 30%, the gas pressure is controlled to be 8-10KPa, the air pressure is controlled to be 4-5KPa, the flame length is controlled, and hot upsetting cracks caused by overheating are controlled; heating temperature control: the temperature of a high-temperature section of a heating furnace is reduced as much as possible when the heating temperature of a small-sized unit is optimized, the temperature of the high-temperature section is generally controlled below 1150 ℃, the temperature is quickly reduced below 1100 ℃ when the temperature is kept, the interior of the furnace at 1160-1120 ℃ of the high-temperature section is controlled to be a reducing atmosphere, the heating time is 24 minutes, and the excess coefficient is controlled to be 1.02; the heating section 1170-1120 ℃ is controlled to be in a weak oxidizing atmosphere, the heating time is controlled to be 25 minutes, the excess coefficient is controlled to be 1.05, the gas heat value is used as feedforward, the air-coal ratio is set to be 2.1-2.5, the opening of an air valve and a gas valve is controlled by utilizing the valve characteristic, when the temperature is changed and approaches to the target temperature, the air-coal flow is controlled, the residual oxygen amount of flue gas is used as feedback control, the air-fuel ratio is corrected in real time, the optimal air-coal ratio is achieved, the residual oxygen amount is controlled to be 3-8%, the weak oxidizing atmosphere and the reducing atmosphere in a high-temperature area furnace are realized, and the decarburization layer is restrained, so that the defect of wrinkles and hot upsetting cracks is effectively prevented;
2) The rolling process for preventing surface cracks of the excellent steel comprises the following steps: designing a 2# box-shaped hole pattern and a 3# elliptic box-shaped hole pattern with the corners R=20mm and the hole depths=10mm, wherein the locking width of the box-shaped hole pattern is more than or equal to 2mm and less than or equal to 5mm; the diameter D of the hole-shaped base circle of the vertical rolling round rolled piece is more than or equal to the value of the slot bottom and more than or equal to the value of the slot opening, and the principle of reforming the vertical rolling inlet guide plate is as follows: the width L is 8-10mm larger than the width L of the rolled piece, and the height 2H of the guide plate is 8-10mm larger than the height H of the rolled piece.
The guide wheel hole type radian R1 is changed into a radian R which is completely matched with the rolled piece, so that the supporting contact part of the rolled piece is changed from point contact to surface contact, and the supporting effect is enhanced; the design of each pass hole type effectively eliminates hot upsetting cracks generated by overfilling and folding the hole type; optimizing and modifying each pass rolling guide wheel of the full specification, and adapting the hole type radian R of the guide wheel to the elliptical rolling piece radian R1 to solve the defect of indentation hot upsetting cracks; changing the internal appearance structure of the guide Wei Gaban from rectangular to elliptical, wherein the arc R of the elliptical and the arc R of the rolled piece are the same diameter, so that the contact part of the corner of the rolled piece and the contact part of the clamping plate form smooth and gentle transition; guide Wei Gaban: rough rolling: the size of the rolled piece is +15; and (3) middle rolling: the size of the rolled piece is +8; finish rolling: the dimension of the rolled piece is +3; the contact surfaces of the inner walls of the clamping plates are curved surfaces, the chamfer positions are designed in a smooth transition mode of an R arc, the R arc of the rolling guide wheel is consistent with the R arc of the elliptic rolled piece, and each frame of guide is designed according to the principle so as to effectively prevent the rolling piece in the middle pass from twisting and scratching, and hot upsetting cracks generated by folding caused by continuous rolling in the later pass; the roller cooling water pipe with the spray water outlet width of 115mm is arranged, so that the problem that the rolling groove is uniformly cooled to avoid local groove burning cracks is effectively solved; the rough rolling adopts a box-shaped hole and an R arc transition design at the hole type corner, so that a machining surface is formed at the casting blank corner, and the problem of hot upsetting cracks caused by subsequent pass inheritance of surface defects is solved.
The invention has the following effects:
table 1 2017-2021.11 Small and medium rod excellent special steel round steel benefit accounting table
Yield benefit promotes: the method is improved from 69.77 percent of 2017 to 91.51 percent of 2021, the yield is improved by 22.4 percent, and the economic benefit is improved by 3831 ten thousand yuan per year;
yield increasing economic benefit: the production of the round steel excellent special steel is about 3 hours before 2017 because of hot upsetting cracks, the rolling groove, guide and material adjustment days are all about 3 hours, the average station time is 60t/h according to each small specification, the daily yield is affected by 180t/d, the production of the excellent round steel is 10 months in the whole year, the production of the excellent round steel is carried out 15 days in each month, the production is increased by 27000t in the whole year, and the annual marginal benefit sum of the production is increased by 801.3 multiplied by 27000 = 2163.5 ten thousand yuan/year;
total accumulated economic benefit = 3831+2163.5 = 5995 ten thousand yuan/year.
Detailed Description
A rolling process for inhibiting hot upsetting cracks of medium and small excellent steel is implemented according to the following steps:
1. the control technology for preventing over-burning and overheat hot upsetting cracking comprises the following steps: the local overheating and overburning mainly is that the pressure control of a gas burner is unreasonable, and the flame is directly sprayed on the steel billet in an overlong way, so that the temperature of the steel billet in the area is overhigh and exceeds the overheating temperature, and the local overheating of the steel billet is generated. The opening of the front valve of the burner is adjusted, the opening of the normal burner is controlled to be 50%, the partial high-temperature burner is controlled to be 30%, the gas pressure is controlled to be 8-10KPa, the air pressure is controlled to be 4-5KPa, the flame length is controlled, and the partial overheating phenomenon is solved.
2. Control technique for preventing decarbonization from causing hot upsetting fold cracking is shown in table 2:
table 2 shows the heating temperature system of medium and small rod excellent special steel
Heating temperature control: the temperature of the high-temperature section of the heating furnace is reduced as much as possible when the heating temperature of the small-sized unit is optimized, the temperature of the high-temperature section is generally controlled below 1150 ℃, and the temperature is quickly reduced below 1100 ℃ when the temperature is kept.
Control of furnace atmosphere: the excess coefficient of the residual oxygen soaking section of the small unit is controlled to be 1.02; the heating section is controlled to be in a weak oxidizing atmosphere, and the excess coefficient is controlled to be 1.05. The heat value of the gas is used as feedforward, the air-coal ratio is set according to 2.1-2.5, the opening of the air and gas valve is controlled by utilizing the valve characteristic, and the air and gas flow is controlled when the temperature is changed and approaches to the target temperature. The residual oxygen amount of the flue gas is used as a feedback control, the air-fuel ratio is corrected in real time, the optimal air-gas ratio is achieved, and the residual oxygen amount is controlled to be 3-8%. The furnace in the high temperature area is in a weak oxidizing atmosphere and a reducing atmosphere, and the decarburization layer is reduced.
3. The control technology for preventing the casting blank corner cracks from inheriting hot upsetting cracks comprises the following steps: a 2# box type hole pattern and a 3# oval box type hole pattern with corners r=20 mm and hole depths=10 mm were designed. The advantages of using this process design are as follows: (1) the method can effectively process 'weld' on the corners of the casting blank to reduce or even eliminate the defects of the corners; (2) the problem of excessively high cold speed at the corners is fundamentally avoided, and (3) the problem that a square rolled piece is rolled for a long time by a flat roller to form a box-shaped hole and overflow from the edge of the box-shaped hole to form a wider thin ear due to abrasion is avoided.
4. The control technology for preventing hole pattern overfilling and hot upsetting cracking comprises the following steps: according to the following: the width of the hole type locking notch, the edge width of the rolled piece, is more than or equal to 2mm and less than or equal to 5mm; the diameter D of the hole-type base circle of the vertical rolling round rolled piece is more than or equal to the bottom value of the groove and more than or equal to the value of the notch; hole design principle craftsman compares the measured rolled piece size of each pass with a small basic hole pattern system, and the craftsman identifies that the basic hole pattern systems No. 2, no. 8 and No. 10 have the defect of process design (the same precision rolling pass of each specification is the same), and process optimization is performed immediately.
5. The control technology for preventing the rolled piece from pouring steel and hot upsetting cracking comprises the following steps: the guide and guard device is an essential rolled piece guide device in rolling, and is used for guiding rolled pieces to roll according to a predetermined rolling track. The unreasonable design of the guide and guard process can cause the oval rolled piece to twist and bite into the round hole, and the oval rolled piece becomes diagonal biting, commonly called as 'pouring steel'. The diagonal biting means that the relative rolling reduction deltah is increased, the expansion quantity is greatly increased according to the expansion model, the metal in the expansion direction overflows to the roll gap to form lugs, and the lugs are folded through subsequent rolling. The principle of reforming the vertical rolling inlet guide plate is as follows: the width L is 8-10mm larger than the width L of the rolled piece, and the height 2H of the guide plate is 8-10mm larger than the height H of the rolled piece. The guide wheel hole type radian R1 is changed into the radian R which is completely matched with the rolled piece, so that the supporting contact part of the rolled piece is changed from point contact to surface contact, and the supporting effect is enhanced.
6. The control technology for preventing the guide wheel from indentation and hot upsetting cracking comprises the following steps: the middle part of the rolling guide and guard guide wheel of the lower line is often rusted, and the edge part is severely worn compared with other parts. This phenomenon indicates that the guide wheel is 2-point contact rather than surface contact when supporting the rolled piece, and only the wheel edge is in contact with the rolled piece. Not only has poor supporting effect, but also is easy to cause surface indentation on a hot rolled piece, and can still form folding after continuous rolling in the subsequent pass; the process technicians optimize and modify the rolling guide wheels of all the passes of the full specification, and adapt the radian R1 of the elliptical rolled piece with the hole type radian R of the guide wheels, so that the defect of hot upsetting cracks of the indentation type is overcome.
7. The control technology for preventing the guide Wei Gaban from scratching the hot upsetting crack comprises the following steps: aiming at the scratch generated by the contact of the rolled piece and the sharp angle of the inner wall of the guide Wei Gaban, the technical staff changes the internal appearance structure of the guide Wei Gaban from a rectangle to an ellipse, and the arc R of the ellipse and the arc R of the rolled piece are the same diameter, so that the contact part of the corner of the rolled piece and the contact part of the clamping plate form smooth and gentle transition;
8. the control technology for preventing the hot upsetting cracking caused by roller marks and abnormal wear comprises the following steps: the key point of roll mark folding is the cooling of the roll surface, and a small-sized unit technician changes the form of a roll cooling water pipe from a spray head type to a double-water-pipe spray type water pipe, improves the form of the roll cooling water pipe according to 1.2 times of the width of a groove, and expands the width of the water pipe from 95.8mm to 115mm at present, thereby greatly improving the large-area cracking of the roll surface.
Claims (1)
1. A rolling process for inhibiting hot upsetting cracks of medium and small excellent steel is characterized by comprising the following steps of:
1) The heating process for preventing surface cracks of the high-grade steel comprises the following steps: the opening degree of a normal burner is controlled to be 50%, the partial high-temperature burner is controlled to be 30%, the gas pressure is controlled to be 8-10KPa, the air pressure is controlled to be 4-5KPa, the flame length is controlled, and hot upsetting cracks caused by overheating are controlled; heating temperature control: the temperature of a high-temperature section of the heating furnace is reduced as much as possible when the heating temperature of the small-sized unit is optimized, the temperature of the high-temperature section is controlled below 1150 ℃, the temperature is rapidly reduced below 1100 ℃ when the temperature is kept, the interior of the furnace at 1160-1120 ℃ of the high-temperature section is controlled to be a reducing atmosphere, the heating time is 24 minutes, and the excess coefficient is controlled to be 1.02; the heating section 1170-1120 ℃ is controlled to be in a weak oxidizing atmosphere, the heating time is controlled to be 25 minutes, the excess coefficient is controlled to be 1.05, the gas heat value is used as feedforward, the air-coal ratio is set to be 2.1-2.5, the opening of an air valve and a gas valve is controlled by utilizing the valve characteristic, when the temperature is changed and approaches to the target temperature, the air-coal flow is controlled, the residual oxygen amount of flue gas is used as feedback control, the air-fuel ratio is corrected in real time, the optimal air-coal ratio is achieved, the residual oxygen amount is controlled to be 3-8%, the weak oxidizing atmosphere and the reducing atmosphere in a high-temperature area furnace are realized, and the decarburization layer is restrained, so that the defect of wrinkles and hot upsetting cracks is effectively prevented;
2) The rolling process for preventing surface cracks of the excellent steel comprises the following steps: designing a 2# box type hole pattern and a 3# elliptic box type hole pattern with a corner hole pattern chamfer angle of 20mm and a hole depth of 10mm, wherein the locking width of the box type hole pattern is more than or equal to 2mm and less than or equal to 5mm; the diameter D of the hole-shaped base circle of the vertical rolling round rolled piece is more than or equal to the value of the slot bottom and more than or equal to the value of the slot opening, and the principle of reforming the vertical rolling inlet guide plate is as follows: the width L is 8-10mm larger than the width L of the rolled piece, and the height 2H of the guide plate is 8-10mm larger than the height H of the rolled piece; the hole type radian of the guide wheel is changed into the radian which is completely matched with the rolled piece, so that the supporting contact part of the rolled piece is changed from point contact to surface contact, and the supporting effect is enhanced; the design of each pass hole type effectively eliminates hot upsetting cracks generated by overfilling and folding the hole type; the rolling guide wheels of all the passes are optimized and modified, the hole type radian of the guide wheels is adapted to the radian of the elliptical rolling piece, and the defect of hot upsetting cracks of the indentation type is overcome; changing the internal appearance structure of the guide Wei Gaban from rectangular to elliptical, wherein the arc of the elliptical and the arc of the rolled piece are the same-diameter arc, so that the contact part of the corner of the rolled piece and the contact part of the clamping plate form smooth and gentle transition; guide Wei Gaban: rough rolling: the size of the rolled piece is +15; and (3) middle rolling: the size of the rolled piece is +8; finish rolling: the dimension of the rolled piece is +3; the contact surfaces of the inner walls of the clamping plates are curved surfaces, the chamfer positions are designed in a circular arc smooth transition mode, the circular arc of the rolling guide wheel is consistent with that of an elliptic rolled piece, and each frame of guide is designed according to the principle so as to effectively prevent the rolling piece in the middle pass from twisting and scratching, and hot upsetting cracks generated by folding caused by continuous rolling in the later pass; the roller cooling water pipe with the spray water outlet width of 115mm is arranged, so that the problem that the rolling groove is uniformly cooled to avoid local groove burning cracks is effectively solved; the rough rolling adopts a box-shaped hole and a hole-shaped corner to form a machining surface for the corner of the casting blank, so that the problem of hot upsetting cracks caused by subsequent pass inheritance of surface defects is solved.
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| JP2000017379A (en) * | 1998-06-30 | 2000-01-18 | Nippon Steel Corp | Steel sheet improved in fatigue crack propagating characteristic by crystal orientation control and its production |
| CN103882201A (en) * | 2014-03-19 | 2014-06-25 | 武汉钢铁(集团)公司 | Rolling process capable of improving hot-upsetting performance of 20 Cr steel |
| CN111347022A (en) * | 2018-12-24 | 2020-06-30 | 新疆八一钢铁股份有限公司 | Control method for improving qualified rate of 30CrMoA hot upsetting of sucker rod steel |
| CN111014316A (en) * | 2019-12-25 | 2020-04-17 | 新疆八一钢铁股份有限公司 | Phi 13 spring round steel hot upsetting crack control method |
| CN111687209B (en) * | 2020-05-13 | 2022-03-01 | 中天钢铁集团有限公司 | Rolling process of medium-carbon high-sulfur alloy steel wire rod |
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