CN108277443B

CN108277443B - Support roll of wide and thick plate mill with width of more than 4200mm and manufacturing process thereof

Info

Publication number: CN108277443B
Application number: CN201810083907.7A
Authority: CN
Inventors: 蒋新亮; 赵欣; 杨萍; 陈先毅; 李英; 赵秀清
Original assignee: Erzhong Deyang Heavy Equipment Co Ltd
Current assignee: Erzhong Deyang Heavy Equipment Co Ltd
Priority date: 2018-01-29
Filing date: 2018-01-29
Publication date: 2019-12-24
Anticipated expiration: 2038-01-29
Also published as: CN108277443A

Abstract

The invention relates to a supporting roll and a manufacturing process thereof, in particular to a wide and thick plate rolling mill supporting roll with the thickness of more than 4200mm and a manufacturing process thereof, and belongs to the technical field of forging. The supporting roller comprises the following chemical components in percentage by mass: c: 0.50 to 0.65, Si: 0.17 to 0.50, Mn: 0.80-2.0, 0.30-0.70 of Ni0.30-0.70, Cr: 1.60 to 2.5, Mo: 0.30-1.00, V: 0.10-0.35, P is less than or equal to 0.020, S is less than or equal to 0.010, Cu is less than or equal to 0.15, H is less than or equal to 1.0ppm, and the balance is iron and inevitable impurities. The novel material for the extra-large forged steel supporting roller has low carbon content, increases alloy elements of chromium, nickel and vanadium, has a microstructure of bainite and pearlite, reduces solidification segregation of large steel ingots while improving the toughness of the material, and has good comprehensive performance and long service life.

Description

Support roll of wide and thick plate mill with width of more than 4200mm and manufacturing process thereof

Technical Field

The invention relates to a supporting roll and a manufacturing process thereof, in particular to a wide and thick plate rolling mill supporting roll with the thickness of more than 4200mm and a manufacturing process thereof, and belongs to the technical field of forging.

Background

The wide and thick plates are important strategic materials and are widely used for large ships with the weight of more than 10 million tons, large-caliber oil and gas straight welded pipes, as well as the fields of weapon armors, huge bridge structural steel, offshore drilling platform structural steel, nuclear power station containment vessels, large dam gates, high-pressure boiler steel plates, steelmaking blast furnace shells, large oil and gas storage tanks, large mechanical structural steel, die steel, super high-rise buildings and the like, and particularly in the field of military shipbuilding, the large single-weight wide and thick plates are indispensable.

The supporting rollers are key stress parts and consumable spare parts on the wide and thick plate rolling mill, a pair of supporting rollers are assembled on each frame to support the working rollers, the size is large, the delivery weight reaches more than 200 tons, and the weight of the adopted steel ingot reaches more than 450 tons. The supporting roller has high performance requirement, multiple production links and great technical difficulty, is one of the integral forged steel products with the highest geometric dimension and specification grade in the heavy machinery industry at present in the world, and is shown in figure 1.

The manufacture of the oversized forged steel supporting roller product not only needs great technical equipment and production means with strong capability, but also needs materials with reasonable design, high quality and reliability. At present, the support roll of the 4200-5500 mm ultra-wide and thick plate mill in China is almost all close to the import.

At present, the production factories of the super-huge type supporting roller are few internationally, the carbon content of the traditional steel material is 0.70% -1%, the chromium content is 0.9-1.6, and the steel does not contain vanadium, and the hydrogen content in the steel is not required, so the steel has the following defects: (1) because the steel ingot used by the oversize supporting roller is 340 t-450 t, the carbon content of the material is very high, the segregation of carbon elements is quite serious along with the upsizing of the steel ingot, the carbon content can reach more than 1.5 percent in the center part of the riser head of the supporting roller, massive carbides and serious reticular carbides are formed in the material and are not easy to eliminate, so that the supporting roller is often broken in the heat treatment and use processes; (2) because the content of alloy elements in the material is low, the microstructure is pearlite, the hardness of the surface of the roller body and a working layer is low, HS 45-HS 50 has poor wear resistance, pits and early peeling are frequently generated on the roller surface, the consumption of the supporting roller is high, and the service life is short; (3) because massive carbides and serious reticular carbides are formed in the material, the toughness is poor, and fatigue cracks often occur on the surface in the using process; (4) because the strength and the hardness of the pearlite material are relatively low, tempering at a low temperature is needed to ensure the hardness during performance heat treatment, so that the residual stress of the supporting roller is increased, and the hydrogen content in steel is not required, so that white spots or fractures are generated in the supporting roller due to overlarge stress and high hydrogen content.

56-58 discloses that 70Cr3Mo and 70Cr3NiMo materials have serious steel ingot segregation, so that the toughness of the center part of the support roll is reduced and the accident resistance is reduced.

Disclosure of Invention

The first technical problem to be solved by the invention is to provide a support roll of a wide and thick plate rolling mill with the thickness of 4200mm or more, which has good obdurability and less solidification segregation.

In order to solve the technical problem, the supporting roll of the wide and thick plate mill with the diameter of more than 4200mm comprises the following chemical components in percentage by mass: c: 0.50 to 0.65, Si: 0.17 to 0.50, Mn: 0.80-2.0, 0.30-0.70 of Ni0.30-0.70, Cr: 1.60 to 2.5, Mo: 0.30-1.00, V: 0.10-0.35, P is less than or equal to 0.020, S is less than or equal to 0.010, Cu is less than or equal to 0.15, H is less than or equal to 1.0ppm, and the balance is iron and inevitable impurities.

Preferably, the supporting roller comprises the following chemical components in percentage by mass: c: 0.50 to 0.64, Si: 0.17 to 0.39, Mn: 0.81 to 2.0, 0.30 to 0.70 of Ni0, Cr: 1.60 to 2.5, Mo: 0.61-1.00, V: 0.16-0.35, P is less than or equal to 0.020, S is less than or equal to 0.010, Cu is less than or equal to 0.15, H is less than or equal to 1.0ppm, the balance is iron and inevitable impurities, and the preferable V: 0.16 to 0.29.

Furthermore, the hardness HS 53-HS 65 of the roller body of the supporting roller, the uniformity delta HS of the hardness of the roller body is less than or equal to 4HS, and the depth of a hardening layer of the roller body is more than or equal to 100 mm; the impact power Ak is not less than 39J; the hardness of the roll neck is HS 37-HS 40; the metallographic structure of the surface of the roller body is bainite, the working layer is a bainite and pearlite tempering structure, the grain size is not coarser than 5 grade, and carbides in the material are in spherical dispersion distribution.

Further, the preparation method of the supporting roller comprises the following steps:

(1) smelting and ingot casting: the molten steel is subjected to rough smelting, refining, alloying and vacuum casting to form steel ingots; wherein the chemical composition of the steel is as described above.

Further, the preparation method of the supporting roller further comprises the following steps:

(2) forging: heating the vacuum steel ingot, cutting off the harmful part at the tail of the ingot, upsetting, drawing out, cutting off the harmful part at a riser, and forging a supporting roll blank;

(3) heat treatment after forging: normalizing, spheroidizing annealing and tempering;

(4) rough machining: roughly processing and forming a forging blank;

(5) final heat treatment: the process form is quenching and tempering.

Preferably, the rough smelting of the molten steel in the step (1) adopts an electric furnace, the alloying and refining of the molten steel adopt a ladle refining furnace, and the vacuum casting adopts vacuum chamber drip degassing casting; and (3) carrying out upsetting and drawing on a press machine in the step (2).

Preferably, the hydrogen content of the steel ingot 340 t-450 t obtained by vacuum casting is less than 1 ppm.

Preferably, the step (4) further comprises performing ultrasonic flaw detection on the rough-machined forged piece, and detecting the internal quality condition of the forged piece blank.

Preferably, the quenching in the step (5) is heated to above 850 ℃, preferably to 850-1010 ℃, and the cooling mode is air blast and spray cooling.

The second technical problem to be solved by the invention is to provide a manufacturing process of a support roll of a wide and thick plate rolling mill with the thickness of more than 4200mm, which comprises the following steps:

(1) smelting and ingot casting: the molten steel is subjected to rough smelting, refining, alloying and vacuum casting to form steel ingots; wherein the chemical composition of the steel is as described above;

(4) rough machining: roughly processing and forming a forging blank;

(5) final heat treatment: the process form is quenching and tempering, the quenching is preferably heated to above 850 ℃, preferably to 850-1010 ℃, and the cooling mode is preferably blast and spray cooling.

Has the advantages that:

compared with the traditional material, the new material designed by the invention has the following advantages:

1. the microstructure of the support roller is bainite on the surface of the roller body, and the working layer is bainite plus pearlite; the toughness of the material is improved while the hardness of the material is improved; the solidification segregation of large steel ingots is reduced, massive carbides and serious reticular carbides in the material are eliminated, the carbides in the material are in spherical dispersion distribution through inspection, a material matrix is strengthened, the wear resistance is improved, heat treatment cracking and roller breakage during use are prevented, a coarse-grain mixed crystal phenomenon which often occurs in the traditional material is prevented, the toughness is further improved, the risk of fatigue peeling of the surface of a roller body is remarkably reduced, pits and cracks on the roller surface in the steel rolling process are reduced, and the service life of a supporting roller is prolonged.

2. The depth of the working layer of the supporting roller is more than 100mm, and is increased by 50mm compared with the traditional material; the hardness is HS 53-HS 56, the hardness is improved by HS 6-HS 8 compared with the traditional material, and if the tempering temperature is the same as that of the traditional material, the hardness is improved by HS15, so that pits on the surface of the roller body are greatly reduced when the roller is used, the roller has better wear resistance and fatigue resistance, and the service life is longer.

3. Due to the improvement of chemical elements, the hot cracking risk of a forging piece in the forging process is prevented, the feasibility of the process is improved, and the support roller which meets the technical requirements and has excellent use quality can be manufactured by the manufacturing process. The grain of the material is refined, and the hardenability, the mechanical property of the supporting roller and the hardness uniformity are improved. Through smelting, forging and proper heat treatment, the produced support roller can meet the following technical requirements:

(1) the hardness HS 53-HS 65 of the roller body, the uniformity delta HS of the hardness of the roller body is less than or equal to 4HS, and the depth of a hardening layer of the roller body is more than or equal to 100 mm; the impact power Ak is not less than 39J;

(2) the hardness of the roll neck is HS 37-HS 40;

(3) the metallographic structure of the surface of the roller body is bainite, the working layer is a bainite and pearlite tempering structure, the grain size is not coarser than 5 grade, and carbides in the material are in spherical dispersion distribution.

Drawings

FIG. 1 is a schematic view of an oversized support roll;

FIG. 2 is a rough drawing of the example.

1-a roll body; 2-roll neck; and 3, rolling a working layer of the roller body.

Detailed Description

A wide and thick plate rolling mill supporting roll with the thickness of more than 4200mm comprises the following chemical components in percentage by mass: c: 0.50 to 0.65, Si: 0.17 to 0.50, Mn: 0.80-2.0, 0.30-0.70 of Ni0.30-0.70, Cr: 1.60 to 2.5, Mo: 0.30-1.00, V: 0.10-0.35, P is less than or equal to 0.020, S is less than or equal to 0.010, Cu is less than or equal to 0.15, H is less than or equal to 1.0ppm, and the balance is iron and inevitable impurities.

The chemical components of the material are the key for determining the service performance of the forged steel supporting roller, and according to the use requirements and research results of the super-huge forged steel supporting roller, the selection principle of each alloy element is as follows:

(1)C

carbon is one of the main components of the roll material, and has a large influence on the hardness, wear resistance and contact fatigue performance of the roll. The hardness of the steel after quenching is mainly determined by the content of C in the steel, and the hardness value of the steel after quenching is almost in an increasing trend along with the increase of the content of C. Because the cross section diameter of the supporting roll is large, large residual stress exists after quenching, and the excessive residual stress is one of main reasons for roll peeling and roll breakage. To avoid this effect, the roll should be tempered at a higher temperature after quenching to effectively relieve residual stress. Practice shows that when the roller is tempered after quenching, the roller with high C content has higher hardness after tempering than the roller with low C content due to high quenching hardness. From this, it is known that selection of an appropriate C content for the roll material is one of measures for reducing residual stress and preventing flaking.

Back-up rolls are subjected to large cyclic contact stresses on the work surface, thereby requiring high contact fatigue strength of the roll to avoid flaking and cracking. The C content of the steel has an important influence on the contact fatigue because the magnitude of the contact fatigue strength depends greatly on the level of the plastic deformation resistance of the steel, and the plastic deformation resistance of the steel can be improved by increasing the number and dispersion of the second phase particles, and it is necessary to control the C content to an appropriate level. Generally, when the C content is more than 0.60%, excessive network carbides or coarse bulk carbides are likely to precipitate in the matrix structure, and the hardness and wear resistance are improved by increasing the number of carbides, but the plasticity and toughness are much reduced. Along with the addition of alloy elements, the ingot shape of a smelted steel ingot is increased, and C has segregation to a great extent in the process of molten steel solidification, wherein the segregation can reach 20-50 percent, so that the great segregation not only increases the hot working difficulty, but also causes the roller performance to be uneven, cracks occur on the surface of a local area, the thermal shock resistance is greatly reduced, and the anti-stripping and anti-accident capability of the supporting roller is deteriorated.

Through a large number of experiments, the C content of the oversize supporting roller material is controlled to be 0.55-0.65%, and the oversize supporting roller material is combined with other alloy elements, so that the performance of the supporting roller is effectively improved, segregation is reduced, high-temperature plasticity and strength of the material are improved, and the forging deformation sequence at high temperature is ensured.

(2)Si

Si belongs to non-carbide forming elements, can strengthen a matrix, improve the tempering stability of a structure, and simultaneously can improve deformation resistance and impact fatigue resistance, but too much Si content can aggravate the segregation of a large steel ingot, so that the forgeability of the material is poor, and the decarburization tendency is increased. When the Si content is controlled to be 0.17-0.50%, the Si interacts with other metal components of the invention, and the comprehensive performance is good.

(3)Mn

Mn belongs to an element for expanding an austenite phase, and simultaneously reduces the decomposition temperature of super-cooled austenite, so that the hardenability is improved, but excessive manganese is added to cause the carbon segregation to be intensified, and cause the core tissue of the supporting roller to separate out net-shaped or massive carbide. The Mn content of the material is not high, and the Mn content is controlled to be 1.0-2 percent to interact with other metal components of the material, so that the material has good comprehensive performance.

(4)Cr

Cr is the most main alloy element in the supporting roll steel, is a strong carbide forming element, is mainly present in M3C and M7C3 types, and is dissolved and dissolved in solid solution for most of the Cr element during quenching and heating. The Cr element remarkably increases the stability of austenite, improves the hardenability and hardenability of steel, and improves the wear resistance and fatigue resistance of steel. When the Cr content is too high, the carbide content is too much, and when the Cr content is controlled to be 1.6-2.5%, the Cr of the invention interacts with other metal components of the invention, so that the comprehensive performance is good.

(5) Mo and V

The addition of Mo can form M2C type carbide, and can raise the hardenability and tempering stability of the roller and improve the wear resistance of the material. When the content of Mo is less than 1.00 percent, the support roll is beneficial to obtaining bainite fine-grained structures on the working layer. The Mo content is too high, so that the segregation of the large steel ingot is increased, the high-temperature plasticity of the material is reduced, the heat deformation resistance is increased, and the risk of forging cracks is increased. Comprehensively considering, for the super large supporting roller, when the content of Mo is controlled to be 0.3-1.0%, the Mo interacts with other metal components of the invention, and the comprehensive performance is good.

The addition of V can form fine VC particles which can play a role in strengthening and can also refine austenite grains, but the effect is not obvious when V is more than 0.35 percent, and the brittleness risk and the crack sensitivity are increased. The material V is reasonably controlled below 0.35 percent.

Preferably, the supporting roller comprises the following chemical components in percentage by mass: c: 0.50 to 0.64, Si: 0.17 to 0.39, Mn: 0.80-2.0, Ni: 0.30-0.70, Cr: 1.60 to 2.5, Mo: 0.61-1.00, V: 0.16-0.35, P is less than or equal to 0.020, S is less than or equal to 0.010, Cu is less than or equal to 0.15, H is less than or equal to 1.0ppm, and the balance is iron and inevitable impurities.

Preferably, the preparation method of the supporting roller further comprises the following steps:

(4) rough machining: roughly processing and forming a forging blank;

(5) final heat treatment: the process form is quenching and tempering.

Preferably, the quenching in the step (5) is heated to above 850 ℃, and the cooling mode is air blast and spray cooling.

(3) hot-forming after forging;

(5) final heat treatment: the process form is quenching and tempering, the quenching is preferably heated to above 850 ℃, and the cooling mode is preferably blast air and spray cooling.

The following examples are provided to further illustrate the embodiments of the present invention and are not intended to limit the scope of the present invention.

Example 1

(1) Smelting and ingot casting: the molten steel is primarily smelted by an electric arc furnace, added into a ladle refining furnace for refining and alloying, and then trickled and degassed by a vacuum ingot casting chamber to cast 450t of large steel ingots, and the hydrogen content in the steel is reduced to below 1 ppm.

The weight percentage of the chemical components is as follows: 0.59C, 0.43 Si, 1.24 Mn, 0.34 Ni, 2.06 Cr, 0.54 Mo, 0.25V, 0.15P, 0.008S, 0.10 Cu, 0.8ppm H, and the balance iron and other unavoidable impurities.

(2) Forging: heating the steel ingot, cutting off the harmful part at the tail of the ingot, upsetting, drawing out, cutting off the harmful part at a riser, and forging a supporting roll blank;

(4) rough machining and ultrasonic flaw detection: and (3) processing the forging blank according to a rough machining drawing which is detailed in a drawing 2, and carrying out ultrasonic flaw detection to detect the internal quality of the forging blank so as to completely meet the requirements of ordering technical conditions.

(5) Final heat treatment: the process form is 'quenching and zone tempering', the steel is heated to 900 +/-20 ℃ for quenching, and the cooling mode is blast air, spray cooling and tempering. The super-large supporting roll for the five-meter wide and thick plate rolling mill shown in the figure 1 is obtained after final heat treatment, the roll body HS 53-56, the uniformity HS3 of the hardness of the roll body, the depth 105mm of a hardening layer of the roll body, Ak 39J, bainite on the surface of the roll body, a working layer, bainite and pearlite structures are adopted, carbides in the material are distributed in a spherical dispersion mode, the grain size is 5 grades, the hardness of a roll neck is HS 37-HS 40, and the using effect is good.

Example 2

(1) Smelting and ingot casting: the molten steel is primarily smelted by an electric arc furnace, added into a ladle refining furnace for refining and alloying, and then trickled and degassed by a vacuum ingot casting chamber to be cast into a 340t large-sized steel ingot, and the hydrogen content in the steel is reduced to below 1ppm, and the chemical components (mass percentage) are as follows: c is 0.62, Si is 0.38, Mn is 1.18, Ni is 0.34, Cr is 1.96, Mo is 0.49, V is 0.20, P is 0.016, S is 0.006, Cu is 0.008, H is 0.9ppm, and the balance is iron and other trace elements in the scrap.

(5) Final heat treatment: the process form is 'quenching and tempering', the temperature is heated to 900 +/-20 ℃, quenching is carried out, and the cooling mode is blast air, spray cooling and tempering. The surface hardness of the oversize supporting roll for the 4200mm wide and thick plate rolling mill obtained after final heat treatment is as follows:

the roll body HS 54-57 has the advantages that the uniformity of the hardness of the roll body HS3 is uniform, the depth of a hardening layer of the roll body is 107mm, Ak is 41J of surface bainite of the roll body, a working layer is a bainite plus pearlite structure, carbides in the material are in spherical dispersion distribution, the grain size is 6 grades, the hardness of a roll neck is HS 37-HS 40, and the use effect is good.

Claims

The wide and thick plate mill support roll with the thickness of more than 1.4200mm is characterized in that the support roll comprises the following chemical components by mass percent: c: 0.50 to 0.65, Si: 0.17 to 0.50, Mn: 0.80-2.0, 0.30-0.70 of Ni0.30-0.70, Cr: 1.60 to 1.96, Mo: 0.30-1.00, V: 0.10-0.35, P is less than or equal to 0.020, S is less than or equal to 0.010, Cu is less than or equal to 0.15, H is less than or equal to 1.0ppm, and the balance is iron and inevitable impurities;

the preparation method of the supporting roller comprises the following steps:

(1) smelting and ingot casting: the molten steel is subjected to rough smelting, refining, alloying and vacuum casting to form steel ingots;

and the steel ingot is a 340 t-450 t large steel ingot obtained by vacuum casting.
2. A support roll of a wide and thick plate mill with the width of more than 4200mm according to claim 1, wherein the chemical composition of the support roll is as follows by mass percent: c: 0.50 to 0.64, Si: 0.17 to 0.39, Mn: 0.81 to 2.0, Ni0.30 to 0.70, Cr: 1.60 to 1.96, Mo: 0.61-1.00, V: 0.16-0.35, P is less than or equal to 0.020, S is less than or equal to 0.010, Cu is less than or equal to 0.15, H is less than or equal to 1.0ppm, and the balance is iron and inevitable impurities.
3. A wide and thick plate mill backup roll of 4200mm or more according to claim 2, wherein said V: 0.16 to 0.29.
4. The backup roll of a wide and thick plate mill with the width of 4200mm or more according to claim 1 or 2, wherein the hardness of the roll body of the backup roll is HS 53-HS 65, the uniformity of the hardness of the roll body is delta HS less than or equal to 4HS, and the depth of the hardening layer of the roll body is more than or equal to 100 mm; the impact power Ak is not less than 39J; the hardness of the roll neck is HS 37-HS 40; the metallographic structure of the surface of the roller body is bainite, the working layer is a bainite and pearlite tempering structure, the grain size is not coarser than 5 grade, and carbides in the material are in spherical dispersion distribution.
5. A backup roll for a wide and thick plate mill of 4200mm or more according to claim 1, wherein said method for manufacturing the backup roll further comprises the steps of:

(2) forging: heating the vacuum steel ingot, cutting off the harmful part at the tail of the ingot, upsetting, drawing out, cutting off the harmful part at a riser, and forging a supporting roll blank;

(3) heat treatment after forging: normalizing, spheroidizing annealing and tempering;

(4) rough machining: roughly processing and forming a forging blank;

(5) final heat treatment: the process form is quenching and tempering.
6. The backup roll for wide and thick plate mill of 4200mm or more according to claim 5, wherein said rough smelting of molten steel in step (1) uses an electric furnace, said alloying and refining of molten steel uses a ladle refining furnace, and said vacuum casting uses vacuum chamber drip degassing casting; and (3) carrying out upsetting and drawing on a press machine in the step (2).
7. A wide and thick plate mill backup roll with a width of 4200mm or more according to claim 5, characterized in that the hydrogen content of the large-sized steel ingot 340t to 450t obtained by vacuum casting is 1ppm or less.
8. The wide and thick plate mill support roll of 4200mm or more according to claim 5 or 7, characterized by that, said step (4) further includes carrying on the ultrasonic flaw detection to the rough formed forging, detect the forging blank internal quality condition.
9. The backup roll of a wide and thick plate mill of 4200mm or more according to claim 5 or 7, wherein the quenching in step (5) is heated to 850 ℃ or more, and the cooling method of the quenching is blast air + spray cooling.
10. A wide and thick plate mill backup roll greater than 4200mm according to claim 9, characterized in that said quenching and heating of step (5) is to 850 ℃ -1010 ℃.
11. A process for manufacturing a backup roll of a wide and thick plate mill more than 4200mm as claimed in claim 1 or 2, wherein the process comprises: (1) smelting and ingot casting: the molten steel is subjected to rough smelting, refining, alloying and vacuum casting to form steel ingots; wherein the chemical composition of the steel is as defined in claim 1 or 2;

(2) forging: heating the vacuum steel ingot, cutting off the harmful part at the tail of the ingot, upsetting, drawing out, cutting off the harmful part at a riser, and forging a supporting roll blank;

(3) heat treatment after forging: normalizing, spheroidizing annealing and tempering;

(4) rough machining: roughly processing and forming a forging blank;

(5) final heat treatment: the process form is quenching and tempering, and the quenching is heated to above 850 ℃.
12. A process for manufacturing a back-up roll of a wide and thick plate mill of 4200mm or more according to claim 11, wherein (5) the final heat treatment: and quenching and heating to 850-1010 ℃.
13. A process for manufacturing a back-up roll of a wide and thick plate mill of 4200mm or more according to claim 11, wherein (5) the final heat treatment: the quenching cooling mode is blast air and spray cooling.