CN101722287B - Method for cooling continuous casting blanks and method for producing continuous casting billets comprising same - Google Patents

Abstract

The invention provides a method for cooling continuous casting blanks, which comprises the step of cooling casting blanks through spray cooling areas, and is characterized in that: the number of the spray cooling areas is at least three; the casting blanks continuously pass through the at least three spray cooling areas; and according to an order in which the casting blanks pass, temperature reduction values of the casting blanks in each spraying cooling area are gradually reduced. The invention also provides a method for producing continuous casting billets, which comprises the following steps: casting molten steel into the casting blanks; and then cooling the obtained casting blanks, wherein the method for the cooling in the second step is the method for cooling the continuous casting blanks provided by the invention. The continuous casting billets produced by the method for cooling the continuous casting blanks and the method for producing the continuous casting billets of the invention have no surface cracks and internal cracks and also have little centre porosity and little centre segregation.

Description

The cooling means of continuous-cast blank and comprise the production method of the continuous casting steel billet of this method

Technical field

The present invention relates to the cooling means of continuous-cast blank and comprise the production method of the continuous casting steel billet of this cooling means.

Background technology

Axletree is the vitals of rail truck traveling, and its quality state is directly connected to the bearing capacity and the transportation safety of axletree.Countries in the world railway interests all pays much attention to the production Technology of vehicle axle steel and the raising of quality in kind.Adopt die casting process to produce axle steel for a long time always; Yet; Continuous casting process has than die casting process that technological process is simple, the metal yield high; And the continuous casting steel billet of producing has remarkable advantages such as great surface quality, high homogeneity of ingredients and stability than the die casting steel billet, and therefore, it is imperative to adopt continuous casting process to produce the railway vehicle truck axle-steel.

In the continuous casting manufacturing technique of prior art, high-temperature molten steel continuously watered in the crystallizer condenses, treat that molten steel solidification becomes certain thickness strand after, this strand is pulled out from crystallizer, and through secondary cooling zone carry out evenly, slowly cooling.Usually the cooling means that adopts at secondary cooling zone has air cooling, the gentle water spray cooling of water-cooled.When adopting these three kinds of cooling means that continuous-cast blank is carried out the secondary cooling, the steel billet of production is prone to produce defectives such as face crack, underbead crack, center porosity and center segregation.

Therefore; Study and define rational axle steel continuous casting technology; Especially continuous casting secondary process for cooling; Solving the technical barrier of the defectives such as face crack, centre burst, center porosity and center segregation of axle steel continuous casting base existence, stably produce high-quality continuous casting steel billet, is the key link of the high-quality axletree of Development and Production.

Summary of the invention

The objective of the invention is defective, the method for the continuous casting steel billet secondary cooling of the continuous casting steel billet that can produce no face crack and underbead crack and slight center porosity and center segregation are only arranged is provided with face crack, underbead crack, center porosity and center segregation for the steel billet of the continuous casting steel billet secondary process for cooling production that overcomes prior art.

The invention provides a kind of cooling means of continuous-cast blank; This method comprises makes strand cool off through spraying and cooling area; It is characterized in that said spraying and cooling area is at least 3, strand is continuously through said at least 3 spraying and cooling area; And according to the sequencing that strand passes through, the temperature reduction value of strand in each spraying and cooling area reduces gradually.

The present invention also provides a kind of production method of continuous casting steel billet, and this method comprises molten steel is cast as strand, then the gained strand is cooled off, and it is characterized in that the method for said cooling is the cooling means of continuous-cast blank provided by the invention.

Owing to adopted the secondary cooling method of continuous casting steel billet provided by the invention, thereby the continuous casting steel billet of producing does not have face crack and underbead crack, and center porosity≤1.0 grade, center segregation≤0.5 grade.

The specific embodiment

The invention provides a kind of cooling means of continuous-cast blank; This method comprises makes strand cool off through spraying and cooling area; It is characterized in that said spraying and cooling area is at least 3, strand is continuously through said at least 3 spraying and cooling area; And according to the sequencing that strand passes through, the temperature reduction value of strand in each spraying and cooling area reduces gradually.

In the cooling means of continuous-cast blank provided by the invention, reduce successively and can realize the object of the invention as long as satisfy the temperature reduction value of strand in each spraying and cooling area.Under the preferable case, according to the sequencing that strand passes through, the ratio of the temperature reduction value of strand in adjacent two spraying and cooling area is 1:0.1-0.9, and the temperature that the while strand reduces in first cooling zone is 50-250 ℃.Meet this optimum condition, thereby the strand of producing not only defectives such as face crack and underbead crack can be overcome fully, but also center porosity and center segregation can be obviously reduced.Further under the preferable case, the ratio of the temperature reduction value of strand in adjacent two spraying and cooling area is 1:0.4-0.6, and the temperature that strand reduces in first cooling zone is 100-200 ℃.And in the cooling procedure of same continuous casting process, the ratio of the temperature reduction value of strand in each adjacent cooling zone can be for identical or different.

Said in the present invention spraying and cooling area is at least 3, though the effect of the more coolings of the number of cooling zone is good more, yet; Temperature reduction value in each adjacent cooling zone of strand satisfies under the situation of above condition; When the number of cooling zone surpassed 8, the cooling effect of strand did not have significantly and improves, therefore; The number of spraying and cooling area is preferably 3-8, most preferably is 5.

In cooling means provided by the invention; Specifically be that the strand of pulling out after the crystallization from crystallizer is carried out the secondary cooling; In order to guarantee to have certain intensity through the base shell of preliminary cooled strand; Thereby the pulling force when making this strand can bear through spraying and cooling area, so the temperature of strand is preferably 950-1250 ℃.Among the present invention, said spraying and cooling area can be through realizing the cooling to strand to said strand spray cooling agent, and the cooling agent that in spraying and cooling area, sprays can be the cooling agent of various routines; Be preferably water in the present invention, and in order to save the energy, the water under the common environment for use temperature; Said environment temperature is often referred to 5-40 ℃ temperature range; Also promptly, among the present invention, said cooling agent is preferably 5-40 ℃ water.

In cooling means provided by the invention, unqualified for the temperature reduction value Different control method that makes strand in adjacent two cooling zones, preferably control in the present invention through intensity of cooling.According to the sequencing that strand passes through, the intensity of cooling of adjacent two cooling zones reduces gradually, and " intensity of cooling " is meant the amount that refers to spray in the unit interval cooling agent of the strand on the unit length in this article.

In said spraying and cooling area is 3-8 particularly under 5 the situation, and strand through said at least 3 spraying and cooling area, is accordinged to the sequencing that strand passes through with identical speed, and the intensity of cooling of each spraying and cooling area is respectively:

$q_1=\frac{S}{450\×360}(320.96V_c^2-113.62V_c+138.51)\±7.09$

$q_2=\frac{S}{450\×360}(56.81V_c^2+10.94V_c-19.77)\±1.28$

$q_3=\frac{S}{450\×360}(46.30V_c^2+3.08V_c+14.31)\±1.14$

$q_4=\frac{S}{450\×360}(26.14V_c^2-2.50V_c+8.82)\±0.56$

$q_5=\frac{S}{450\×360}(21.49V_c^2-2.37V_c+7.32)\±0.45$

Wherein, S and V _cRepresent a numerical value separately, it is the cross-sectional area of the strand of unit that the size of S equals with the square millimeter, V _cSize equal with rice/minute be unit, the speed of strand through said at least 3 spraying and cooling area, q ₁, q ₂, q ₃, q ₄And q ₅Respectively the strand of representation unit length is in the intensity of cooling of first to the 5th spraying and cooling area, and unit be kilogram/(meter minute).

When said spraying and cooling area was 3 or 4, according to the sequencing that strand passes through, the intensity of cooling of each spraying and cooling area was respectively to go forward 3 or preceding 4.When said spraying and cooling area was 6-8, the sequencing according to strand passes through guaranteed that the intensity of cooling of the first five spraying and cooling area is respectively above q ₁, q ₂, q ₃, q ₄And q ₅And the intensity of cooling of the 5th later spraying and cooling area reduces successively and gets final product.

In said spraying and cooling area is 3-8 particularly under 5 the situation, and according to the sequencing that strand passes through, the spray rate of the cooling agent of each said spraying and cooling area is respectively:

$W_1=\frac{S}{450\×360}(80.88V_c^2-28.63V_c+34.19)\±1.78$

$W_2=\frac{S}{450\×360}(110.66V_c^2+21.32V_c+38.51)\±2.22$

$W_3=\frac{S}{450\×360}(94.21V_c^2-6.26V_c+29.12)\±1.91$

$W_4=\frac{S}{450\×360}(132.26V_c^2-12.66V_c+44.64)\±1.50$

$W_5=\frac{S}{450\×360}(49.42V_c^2-5.46V_c+16.85)\±1.03$

Wherein, S and V _cRepresent a numerical value separately, it is the cross-sectional area of the strand of unit that the size of S equals with the square millimeter, V _cSize equal with rice/minute be the speed of the strand of unit W at least through said 3 spraying and cooling area ₁, W ₂, W ₃, W ₄And W ₅The spray rate of representing the cooling agent of first to the 5th spraying and cooling area respectively, unit are kg/min.

When said spraying and cooling area was 3 or 4, according to the sequencing that strand passes through, the spray rate of the cooling agent of each spraying and cooling area was respectively to go forward 3 or preceding 4.When said spraying and cooling area was 6-8, according to the sequencing that strand passes through, the spray rate of the cooling agent of the first five spraying and cooling area was respectively above W ₁, W ₂, W ₃, W ₄And W ₅And the spray rate of the cooling agent of the 5th later spraying and cooling area reduces successively and gets final product.

As long as said five spraying and cooling area satisfy the relation that strand intensity of cooling and base shell on the above-mentioned unit length passes through the speed of spraying and cooling area respectively; The present invention does not limit for the spray mode of each cooling zone especially; Under the preferable case; First spraying and cooling area along the cast direction adopts the water spray cooling, and all the other four spraying and cooling area adopt the cooling of aerosol spray.Because first spraying and cooling area adopts water spray to force cooling, can increase intensity of cooling, guarantee that the thin solidified shell of crystallizer outlet obtains high-intensity cooling; Prevent casting billet surface backheat from the crystallizer outlet; Help preventing the casting billet surface or the subcrack that cause because of thermal stress, simultaneously, through improving intensity of cooling; Can increase thickness of solidified slab shell in secondary rapidly, help preventing approaching the bleed-out accident that bulge seriously causes because of crystallizer outlet base shell; And it is thicker at spraying and cooling area base shell subsequently; Adopt the cooling of aerosol spray; Can obviously reduce intensity of cooling and improve cooling uniformity, thereby can effectively reduce the internal-external temperature difference and the consequent thermal stress of solidified shell, reduce the danger that continuous casting billet produces underbead crack.For energy savings, the present invention adopts the water and the aerosol of normal temperature, and the temperature of preferred water and aerosol is 5-40 ℃ usually.Said aerosol can obtain after using atomizer with the aqueous water atomizing, and said atomizer can be to well known to a person skilled in the art various atomizers, and the diameter of atomizing back water droplet is 20-200 μ m, is preferably 50-100 μ m.

Under the situation of the speed that the intensity of cooling of each cooling zone and spray cool off more than satisfying; The specific water is the 0.3-0.7 kg/kg in whole cooling procedure; In order to obtain the littler and flawless continuous casting steel billet of center segregation and center porosity, the specific water is preferably the 0.447-0.538 kg/kg.Wherein, the specific water is meant every kilogram of Total Water that strand is used of cooling in the cooling zone.

As above-mentioned, in the cooling means of the present invention, the speed of strand through each spraying and cooling area is not limited especially; Yet; Consider the intensity of the base shell of strand, the speed of said strand through each spraying and cooling area be preferably 0.1-1 rice/minute, further be preferably 0.3-0.8 rice/minute.

Method provided by the invention is applicable to the cooling of various strands and the continuous casting production of various steel billets.In cooling means provided by the invention; Size for the continuous casting steel billet of producing does not limit especially; Can be for well known to a person skilled in the art the steel billet of various sizes model; Particularly more remarkable greater than steel billet each item performance boost of 200 millimeters * 200 millimeters for cross dimensions, because cross dimensions is big more, require high more for the cooling procedure in the continuous casting process.

The present invention also provides a kind of production method of continuous casting steel billet, and this method comprises molten steel is cast as strand, then the gained strand is cooled off, and wherein, the method for said cooling is the cooling means of continuous-cast blank provided by the invention.

In the production method of continuous casting steel billet provided by the invention; Do not limit the method that molten steel is cast as strand is special; Can be to well known to a person skilled in the art various casting methods, for example, generally comprise and molten steel is injected crystallizer carry out crystallization; The raw material that perhaps will form strand (or steel billet) carries out melting, then the liquid after the melting is injected crystallizer and carries out crystallization.The concrete operations of said melting and crystallization have been conventionally known to one of skill in the art.

Following examples will further specify the cooling means of continuous casting steel billet provided by the invention and the production method of continuous casting steel billet.In following each embodiment and Comparative Examples, used strand is through molten steel being injected crystallizer continuously, carrying out crystallization and obtain.The size of strand is confirmed according to the cross sectional dimensions of crystallizer.

Embodiment 1

Present embodiment is used to explain the cooling means of continuous casting steel billet provided by the invention and the production method of continuous casting steel.

With cross sectional dimensions be 450 millimeters * 360 millimeters, surface temperature is that 950 ℃ strand carries out the secondary cooling through five spraying and cooling area successively with 0.3 meter/minute speed; When passing through first spraying and cooling area, adopts on the base shell water spray cooling; Thereby the temperature that strand is reduced in first spraying and cooling area is 100 ℃; When passing through all the other four spraying and cooling area, adopts on the base shell cooling of aerosol spray; Water and the temperature of aerosol of spray are 15 ℃, and according to the sequencing of strand through spraying and cooling area, and the ratio of temperature reduction value all is controlled to be 1:0.4 during through each adjacent spraying and cooling area with strand.According to the sequencing of strand through spraying and cooling area; The water yield of five spraying and cooling area is respectively 33.60 kg/min, 54.87 kg/min, 35.72 kg/min, 52.75 kg/min and 19.66 kg/min; In five spraying and cooling area on the unit length intensity of cooling of strand be respectively 133.31 kilograms/(minute rice), 28.16 kilograms/(minute rice), 19.40 kilograms/(minute rice), 10.42 kilograms/(minute rice) and 8.54 kilograms/(minute rice), thereby obtain LZ50 axletree continuous casting steel billet sample A1.

Embodiment 2

Present embodiment is used to explain the cooling means of continuous casting steel billet provided by the invention and the production method of continuous casting steel.

With cross sectional dimensions be 380 millimeters * 280 millimeters, surface temperature is that 1250 ℃ strand carries out the secondary cooling through five spraying and cooling area successively with 0.8 meter/minute speed; When passing through first spraying and cooling area, adopts on the base shell water spray cooling; Thereby the temperature that strand is reduced in first spraying and cooling area is 200 ℃; When passing through all the other four spraying and cooling area, adopts on the base shell cooling of aerosol spray; Water and the temperature of aerosol of spray are 35 ℃, and according to the sequencing of strand through spraying and cooling area, and the ratio of temperature reduction value all is controlled to be 1:0.6 during through each adjacent cooling zone with strand.According to the sequencing of strand through spraying and cooling area; The water yield of five spraying and cooling area is respectively 42.09 kg/min, 83.42 kg/min, 55.71 kg/min, 78.65 kg/min and 29.11 kg/min; In five spraying and cooling area on the unit length intensity of cooling of strand be respectively 167.00 kilograms/(minute rice), 42.82 kilograms/(minute rice), 30.63 kilograms/(minute rice), 15.54 kilograms/(minute rice) and 12.66 kilograms/(minute rice), thereby obtain JZ35 axletree continuous casting steel billet sample A2.

Embodiment 3

Present embodiment is used to explain the cooling means of continuous casting steel billet provided by the invention and the production method of continuous casting steel.

With cross sectional dimensions be 450 millimeters * 360 millimeters, surface temperature is that 1100 ℃ strand carries out the secondary cooling through five spraying and cooling area successively with 0.5 meter/minute speed; Wherein, When passing through first spraying and cooling area, adopts on the base shell water spray cooling; Thereby the temperature that strand is reduced in first spraying and cooling area is 150 ℃, adopts the cooling of aerosol spray when the base shell passes through all the other four spraying and cooling area, and the water of spray and the temperature of aerosol are 25 ℃; And according to the sequencing of strand through spraying and cooling area, the ratio of temperature reduction value all is controlled to be 1:0.5 during through each adjacent cooling zone with strand.According to the sequencing of strand through spraying and cooling area; The water yield of five spraying and cooling area is respectively 40.82 kg/min, 76.84 kg/min, 49.54 kg/min, 71.38 kg/min and 26.48 kg/min; In five spraying and cooling area on the unit length direction intensity of cooling of strand be respectively 161.94 kilograms/(minute rice), 39.44 kilograms/(minute rice), 27.43 kilograms/(minute rice), 14.11 kilograms/(minute rice) and 11.51 kilograms/(minute rice), thereby obtain JZ35 axletree continuous casting steel billet sample A3.

Embodiment 4

Present embodiment is used to explain the cooling means of continuous casting steel billet provided by the invention and the production method of continuous casting steel.

Method according to embodiment 3 obtains JZ35 axletree continuous casting steel billet sample A4, and different is that the temperature that strand is reduced in first cooling zone is controlled to be 300 ℃, and will in each adjacent cooling zone, the ratio of the temperature reduction value of strand all be controlled to be 1:0.08.

Embodiment 5

Present embodiment is used to explain the cooling means of continuous casting steel billet provided by the invention and the production method of continuous casting steel.

Method according to embodiment 3 obtains JZ35 axletree continuous casting steel billet sample A5, and different is that the temperature that strand is reduced in first cooling zone is controlled to be 45 ℃, and will in each adjacent cooling zone, the ratio of the temperature reduction value of strand all be controlled to be 1:0.95.

Embodiment 6

Present embodiment is used to explain the cooling means of continuous casting steel billet provided by the invention and the production method of continuous casting steel.

Method according to embodiment 3 obtains JZ35 axletree continuous casting steel billet sample A6, and different is that five spraying and cooling area all adopt the water spray cooling.

Embodiment 7

Present embodiment is used to explain the cooling means of continuous casting steel billet provided by the invention and the production method of continuous casting steel.

Method according to embodiment 3 obtains JZ35 axletree continuous casting steel billet sample A7, and different is that spraying and cooling area is 3, and first adopts the water spray cooling, the cooling of all the other two employing aerosols.

Comparative Examples 1

Method according to embodiment 3 obtains JZ35 axletree continuous casting steel billet reference sample D1, and different is, the intensity of cooling of strand in five spraying and cooling area be 161.94 kilograms/(minute rice).

The continuous casting steel billet performance test

Whether visual observations continuous casting steel billet sample A1-A7 and D1 exist face crack, and its underbead crack, center porosity and center segregation defective are detected and grade according to YB/T153-1999, and its result is shown in Table 1.

Table 1

	A1	A2	A3	A4	A5	A6	A7	D1
									Face crack	Do not have	Do not have	Do not have	Do not have	Do not have	Do not have	Do not have	Have
Underbead crack	0	0	0	0	0	0	0	1.5
									Center porosity	0.5	0.5	0.5	1.0	1.0	1.0	1.0	2.0
Center segregation	0.5	0.5	0.5	0.5	0.5	0.5	0.5	1.5

Can find out that from table 1 continuous casting steel billet that adopts the cooling means of continuous casting steel billet provided by the invention to produce does not have face crack and underbead crack, and center porosity and center segregation are very little, have obviously promoted each item performance of continuous casting steel billet.

Claims (8)

1. the cooling means of a continuous-cast blank; This method comprises makes strand cool off through spraying and cooling area; It is characterized in that said spraying and cooling area is at least 3, strand is continuously through said at least 3 spraying and cooling area; And according to the sequencing that strand passes through, the temperature reduction value of strand in each spraying and cooling area reduces gradually; Said spraying and cooling area is through realizing the cooling to strand to said strand spray cooling agent, and before first spraying and cooling area, the temperature of said strand is 950-1250 ℃; Said cooling agent is 5-40 ℃ a water; Strand through said at least 3 spraying and cooling area, is accordinged to the sequencing that strand passes through, the intensity of cooling of each said spraying and cooling area with identical speed; Be the amount that sprays the cooling agent of the strand on the unit length in the unit interval, be respectively:

$q_1=\frac{S}{450\×360}({320.96V}_c^2-{113.62V}_c+138.51)\±7.09$

$q_2=\frac{S}{450\×360}({56.81V}_c^2+10{.94V}_c+19.77)\±1.28$

$q_3=\frac{S}{450\×360}({46.30V}_c^2+{3.08V}_c+14.31)\±1.14$

$q_4=\frac{S}{450\×360}({26.14V}_c^2-{2.50V}_c+8.82)\±0.56$

$q_5=\frac{S}{450\×360}({21.49V}_c^2-{2.37V}_c+7.32)\±0.45$

Wherein, S and V _cRepresent a numerical value separately, it is the cross-sectional area of the strand of unit that the size of S equals with the square millimeter, V _cSize equal with rice/minute be the speed of the strand of unit q at least through said 3 spraying and cooling area ₁, q ₂, q ₃, q ₄And q ₅Respectively the strand of representation unit length is in the intensity of cooling of first to the 5th spraying and cooling area, and unit be kilogram/(meter minute).

2. method according to claim 1, wherein, according to the sequencing that strand passes through, the ratio of the temperature reduction value of strand in adjacent two spraying and cooling area is 1: 0.1-0.9, the temperature that strand reduces in first cooling zone is 50-250 ℃.

3. method according to claim 2, wherein, according to the sequencing that strand passes through, the ratio of the temperature reduction value of strand in adjacent two spraying and cooling area is 1: 0.4-0.6, the temperature that strand reduces in first cooling zone is 100-200 ℃.

4. method according to claim 1, wherein, according to the sequencing that strand passes through, the spray rate of the cooling agent of each said spraying and cooling area is respectively:

$W_1=\frac{S}{450\×360}({80.88V}_c^2-{28.63V}_c+34.91)\±1.78$

$W_2=\frac{S}{450\×360}({110.66V}_c^2+{21.32V}_c+38.51)\±2.22$

$W_3=\frac{S}{450\×360}({94.21V}_c^2-{6.26V}_c+29.12)\±1.91$

$W_4=\frac{S}{450\×360}({132.26V}_c^2-{12.66V}_c+44.64)\±1.50$

$W_5=\frac{S}{450\×360}({49.42V}_c^2-{5.46V}_c+16.85)\±1.03$

Wherein, S and V _cRepresent a numerical value separately, it is the cross-sectional area of the strand of unit that the size of S equals with the square millimeter, V _cSize equal with rice/minute be unit, the speed of strand through said at least 3 spraying and cooling area, W ₁, W ₂, W ₃, W ₄And W ₅The spray rate of representing the cooling agent of first to the 5th spraying and cooling area respectively, unit are kg/min.

5. method according to claim 1, wherein, the speed of said strand through each spraying and cooling area be 0.1-1 rice/minute.

6. method according to claim 5, wherein, the speed of said strand through each spraying and cooling area be 0.3-0.8 rice/minute.

7. method according to claim 5, wherein, the type of cooling of first spraying and cooling area that said strand passes through is the cooling of flow spray, the type of cooling of all the other spraying and cooling area is the cooling of aerosol spray.

8. the production method of a continuous casting steel billet, this method comprise molten steel are cast as strand, then the gained strand are cooled off, and it is characterized in that the method for said cooling is the cooling means of any described continuous-cast blank among the claim 1-7.