CN102847732B - Hot rolling spray cooling method for large cylinder - Google Patents

Abstract

The invention relates to a hot rolling spray cooling method for a large cylinder, which is characterized in that an upper spray device and a lower spray device are manufactured; after a large cylinder is rolled, the cylinder is clamped by an upper roller and a lower roller, so that the cylinder is rotated by the driving of frictional force; additionally, the lower spray device extends into the cylinder, and the upper spray device is arranged outside the cylinder; the length of cooling water pipes on the upper spray device and the lower spray device is regulated, so that a connecting line of all of the cooling water pipes on each spray device near the wall end of the cylinder forms a semicircle shape which is concentric with the cylinder; and additionally, the quantity ratio of the cooling water pipes on an upper spray collecting plate and a lower spray collecting plate of the upper spray device and the lower spray device and the flow ratio of cooling water are regulated, so as to cool the inner and outer surfaces of the large cylinder at the same cooling speed after rolling. The hot rolling spray cooling method has the advantages that the problem of uneven cooling of the traditional cylinder heat treatment is solved, the cooling efficiency is increased, the coefficient of heat transfer of the surface of the cylinder is increased on the initial stage of cooling, and the surface quality of the cylinder is greatly increased.

Description

A kind of large-scale shell ring hot rolling spraying cooling method

Technical field

The invention belongs to cooling technology field, relate to and be a kind ofly rolled into the spraying cooling method after shape for large-scale shell ring.

Background technology

Large-scale shell ring continuous rolling, as a kind of emerging technique, has the advantages such as precision is high, allowance is few, stock utilization is high, interiors of products quality is good.The choosing and the control of process for cooling of the type of cooling after hot rolling is the critical process step ensureing large-scale shell ring product serviceability.Adopt traditional Technology for Heating Processing, when quench cooled is carried out to shell ring, because shell ring size is large, shell ring different parts axially can not cool simultaneously, cooling has the regular hour poor, easily cause temperature distributing disproportionation even, thus produce larger residual stress, cause shell ring axially and in radial direction to have larger distortion; Because shell ring is from great, easily produces moderate finite deformation diametrically when quenching and become elliptical shape, reducing the dimensional accuracy of shell ring, adverse influence is produced to shell ring performance.Time again because of quench cooled, shell ring surface easily produces steam blanket, affects the heat transfer of shell ring.In addition, prior heat treatment process cost is high, is difficult to realize mass production, can not meet the wilderness demand of domestic market to nuclear power, hydrogenation and coal liquefaction shell ring.In order to improve the efficiency of large-scale shell ring roller repairing, reducing the cost of roller repairing, improving the mechanical property of shell ring, be necessary that research adopts new process for cooling to replace traditional Technology for Heating Processing.

Spraying cooling is a kind of effective heat-transferring method, has high cooling capacity, is water pressurization to be broken shape or vaporific to become to be similar to slope, forms drop bundle and impacts cooled object.Existing spraying cooling method adopts synchronous spray cooling device to cool, and after cooling, shell ring surfaces externally and internally temperature difference is comparatively large, and inhomogeneous cooling is even.

Summary of the invention

The object of this invention is to provide a kind of large-scale shell ring hot rolling spraying cooling method that can solve the even problem of inhomogeneous cooling that traditional shell ring heat treatment occurs.

Technical scheme of the present invention is as follows:

Make a upper spray equipment and one lower spray equipment that the cooling water pipe on lower water spray collection plate is formed by lower water spray collection plate and vertical distribution that the cooling water pipe on upper water spray collection plate is formed by upper water spray collection plate and vertical distribution, after large-scale shell ring rolling terminates, on, bottom roll is with less drafts clamping shell ring, shell ring is rotated under the drive of frictional force, same spray equipment at present extend into shell ring inside, upper spray equipment is outside relative with lower spray equipment at shell ring, in adjustment, on lower spray equipment, cooling water pipe length makes the line of the nearly shell ring wall end of all cooling water pipes on each spray equipment form the semicircle shape concentric with shell ring, simultaneously in adjustment, lower spray equipment upper, the number ratio of cooling water pipe and the flow-rate ratio of cooling water on lower water spray collection plate, realize in large-scale shell ring, the rear same cooling rate of rolling of outer surface cools.

In method of the present invention, how accurately the upper and lower water spray of setup algorithm collects the flow-rate ratio of plate cooling water, is ensure that the inside and outside surface film thermal conductance of shell ring is identical or close, realizes the key that the inside and outside surface of shell ring cools with cooling rate.

From the analysis of spraying cooling mechanism, the shock zone area immediately below the impact velocity of current and nozzle determines the size of convection transfer rate.If the angle that spray cooling device covers is θ, shell ring wall thickness is B, and equivalent redius is R, and outer surface cooling arc length is L ₁, inner surface is L ₂, the quantity of surfaces externally and internally cooling water pipe is respectively n ₂, n ₁, see accompanying drawing 4

If spraying cooling water pipe is round nozzle, its heat flow density has following form

${\mathrm{hf}}_{\mathrm{lm}}=C{v}_l^{0.5}{d}_c^{1.608}{\mathrm{\ΔT}}_{\mathrm{sat}}^{0.14}---\left(1\right)$

C in formula---coefficient, by the degree of supercooling Δ T of liquid _subdetermine, Δ T _sub=T _sat-T _c, T _satfor the saturation temperature point of cooling fluid, T _cfor coolant temperature, K

ν _l---cooling fluid column impact speed, m/s

D _c---liquid-column impingement diameter, mm

Δ T _sat---Δ T _sat=T _s-T _sat, T _sfor surface of steel plate temperature, K

Hf _lm1, hf _lm2---heat flow density, W/m ²

Make hf _lm1=hf _lm2, then have

$C{v}_{l1}^{0.5}{d}_c^{1.608}{\mathrm{\ΔT}}_{\mathrm{sat}}^{0.14}=C{v}_{l2}^{0.5}{d_{c2}}^{1.608}{\mathrm{\ΔT}}_{\mathrm{sat}}^{0.14}---\left(2\right)$

V in formula _l1, v _l2---upper and lower nozzle water flow arrives speed during upper surface of steel plate, m/s

D _c1, d _c2---diameter during current arrival steel plate upper and lower surface, mm

Can obtain

$\frac{v_{l1}}{v_{l2}}=\frac{d_{c2}^{3.216}}{d_{c1}^{3.216}}---\left(3\right)$

And $d_{c1}=\frac{L_1}{n_1},d_{c2}=\frac{L_2}{n_2},L_1=\mathrm{\θ}(R-\frac{B}{2}),L_2=\mathrm{\θ}(R+\frac{B}{2})$

Again according to the continuity equation of fluid, during current arrival steel plate upper and lower surface, diameter becomes

$d_{c1}=d_1\sqrt{v_1/v_{l1}},d_{c2}=d_2\sqrt{v_2/v_{l2}}---\left(4\right)$

Order $\frac{d_{c2}^{3.216}}{d_{c1}^{3.216}}=k$

Then have

$\frac{v_{l1}}{v_{l2}}=k={\left[\frac{(R+\frac{B}{2})n_1}{(R-\frac{B}{2})n_2}\right]}^{3.216}---\left(5\right)$

Speed during upper and lower nozzle water flow arrival upper surface of steel plate is respectively

$v_{l1}=\sqrt{v_1^2+2g{H}_1}---\left(6\right)$

$v_{l2}=\sqrt{v_2^2+2g{H}_2}---\left(7\right)$

By formula (6), formula (7) is brought formula (5) into and is obtained

$\frac{\sqrt{v_1^2+2g{H}_1}}{\sqrt{v_2^2-2g{H}_2}}=k---\left(8\right)$

H in formula ₁, H ₂---the distance of upper and lower cooling water pipe nozzle distance surface of steel plate, mm

V ₁, v ₂---the water velocity of upper and lower cooling water pipe jet expansion, is respectively

$v_1=\frac{4q}{\mathrm{\π}{d}_1^2}---\left(9\right)$

$v_2=\frac{4R_{1}q}{\mathrm{\π}{d}_2^2}---\left(10\right)$

Q in formula---upper water spray collection plate cooling water pipe nozzle flow

R ₁---upper and lower water spray collection plate cooling water pipe nozzle flow ratio

D ₁, d ₂---upper and lower water spray collection plate cooling water pipe nozzle diameter, mm

Simultaneous formula (5), formula (8), formula (9) and formula (10) can solve flow-rate ratio R ₁with cooling water pipe number ratio n ₁/ n ₂between relation and R ₁value.

Its pass is $\frac{\sqrt{{\left(\frac{4q}{\mathrm{\π}{d}_1^2}\right)}^2+2g{H}_1}}{\sqrt{{\left(\frac{4q{R}_1}{\mathrm{\π}{d}_2^2}\right)}^2-2g{H}_2}}={\left[\frac{(R+\frac{B}{2})n_1}{(R-\frac{B}{2})n_2}\right]}^{3.216}---\left(11\right)$

Known by foregoing, the number ratio of jet density and cooling water pipe can be adjusted to realize the identical or close of the inside and outside surperficial convection transfer rate of shell ring.

Method of the present invention, by regulating the quantity of the cooling water pipe of upper and lower water spray collection plate, changes cooled region area;

Method of the present invention, by regulating the length of the cooling water pipe of upper and lower water spray collection plate, changes the length of cooling arc;

Method of the present invention, by regulating quantity and the length of the cooling water pipe of upper and lower water spray collection plate, accurately calculates the inside and outside surperficial convection transfer rate of shell ring, realizes the roller repairing of different size shell ring.

The feature of large-scale shell ring hot rolling spraying cooling method of the present invention is: 1, shell ring limit rotation limit cooling, has corrected the ovality because residual stress causes, ensure that the dimensional accuracy of shell ring; 2, regulate the water yield on the inside and outside surface of shell ring, make the inside and outside surperficial cooling rate of shell ring identical, avoid the appearance of surface warp, ensure that the surface quality of shell ring; 3, there is the speed of cooling and the advantage such as uniformity is high, production efficiency is high, integrated cost is low compared with original shell ring Technology for Heating Processing; 4, compared with existing spraying cooling method, the method highly versatile, can realize the roller repairing of the shell ring of different size; Upper and lower water spray collection plate cooling water inflow can be realized by the number ratio changing cooling water pipe, and the water yield is more simple than regulation and control.

Beneficial effect of the present invention:

The present invention preferably resolves the even difficult problem of large-scale shell ring inhomogeneous cooling, the injection shell ring surface that cooling water is substantially vertical, increases and amasss with shell ring direct contact surface, be easy to the steam blanket breaking through shell ring surface, thus eliminate the impact that steam blanket conducts heat on shell ring.After adopting this method, not only can realize the oxide skin of surfaces externally and internally with cooling rate cooling, effective removing shell ring surface, improve cooling effectiveness, and increase the coefficient of heat transfer on shell ring surface in the cooling starting stage, can the surface quality of raising shell ring by a relatively large margin.

Accompanying drawing explanation

Fig. 1 is spraying cooling schematic diagram after the medium-and-large-sized shell ring hot rolling of method of the present invention;

Fig. 2 is upper spray equipment schematic diagram in method of the present invention;

Fig. 3 is lower spray equipment schematic diagram in method of the present invention;

Fig. 4 is the relation in method of the present invention between each variable of spray equipment;

Fig. 5 is that the water yield of upper water spray collection plate cooling water pipe in method of the present invention compares changing trend diagram;

Fig. 6 is that in method of the present invention, the water yield compares the graph of a relation with the number ratio of cooling water pipe.

Detailed description of the invention

Embodiment

Method 1: by the spraying cooling method adopting the present invention to propose, rear spraying cooling is rolled to large-scale shell ring and simulates.The uniformity of shell ring surfaces externally and internally Temperature Distribution after analysis employing the method.

The specification of the shell ring adopted: external diameter: d ₁=5830mm, internal diameter: d ₂=4796mm, width: 2680mm; The rotating speed of top and bottom rolls is 0.3rad/s.The base attribute of material: yield limit: 58MPa; Elastic modelling quantity: 90000MPa; Poisson's ratio: 0.3; Its surplus such as density, specific heat is the function of temperature.Be 0.1rad/s by calculating known shell ring rotating speed, setting its initial temperature is 900 DEG C.The height of adjustment cooling water pipe makes the circular arc of its end and shell ring concentric and at a distance of 50mm, meanwhile, the angle in spraying cooling arc and the shell ring center of circle is 60 degree, and its schematic diagram is as Fig. 1.

Upper and lower water spray collection plate cooling water pipe diameter is identical, gets water spray and integrates the jet density of plate cooling water as 160m ³/ h, calculating known water yield ratio through this method is 1.8, thus calculates jet density that lower water spray integrates plate cooling water as 288m ³/ h.According to the relation between the number ratio of cooling water pipe and flow-rate ratio, the number ratio of known upper and lower water spray collection plate cooling water pipe is 0.55.

Get arbitrarily 2 points on shell ring surfaces externally and internally, be designated as A point, B point, variation tendency is as shown in table 1 in time to analyze its temperature

Table 1 shell ring surfaces externally and internally node temperature variation tendency in time

Time/s	The number of turns/q	Outer surface/DEG C	Inner surface/DEG C	The temperature difference/DEG C
					62.8	1	145.723	141.118	4.605
314	5	127.162	124.037	3.125
					628	10	105.285	102.962	2.323
942	15	91.249	88.955	2.294
					1257.6	20	83.556	81.619	1.937
1570	25	72.934	70.851	2.083
					1884	30	69.604	66.902	2.702

As can be known from the above table, adopt spraying cooling mode of the present invention, the inside and outside surface temperature of shell ring is more or less the same, and becomes stepped slow decline, and maximum temperature difference is 4.605 DEG C, and cooling evenly.

Method 2: adopt traditional quenching technical cooling, in like manner get A point and B point on the inside and outside surface of shell ring, situation of change is as shown in table 2 in time to record its temperature

Table 2 shell ring surfaces externally and internally node temperature variation tendency in time

Time/s	The number of turns/q	Outer surface/DEG C	Inner surface/DEG C	The temperature difference/DEG C
					62.8	1	195.72	142.11	53.61
314	5	187.16	165.03	22.13
					628	10	155.28	133.96	21.32
942	15	120.24	100.95	19.29

1257.6	20	109.55	95.61	13.94
					1570	25	89.93	81.85	8.08
1884	30	74.60	63.90	11.7

Adopt quenching technical as can be known from the above table, when cooling initial, shell ring cooling slowly, and the effect due to steam blanket makes surface temperature change between 62.8-314s little, and has the trend of temperature recovery when 628s.Extend in time, steam blanket breaks gradually and the violent agitation heat exchange of water makes shell ring surface temperature sharply decline.Maximum temperature difference is 53.61 DEG C, and inhomogeneous cooling is even.

Method 3: adopt existing synchronous spray cooling device cooling, in like manner get A point and B point on the inside and outside surface of shell ring, situation of change is as shown in table 3 in time to record its temperature

Surfaces externally and internally node temperature variation tendency in time after the quenching of table 3 shell ring

Time/s	The number of turns/q	Outer surface/DEG C	Inner surface/DEG C	The temperature difference/DEG C
					62.8	1	204.02	190.28	13.74
314	5	173.26	158.74	14.52
					628	10	198.30	170.29	28.01
942	15	124.92	115.49	9.43
					1257.6	20	109.65	100.39	9.26
1570	25	88.29	73.72	14.57
					1884	30	71.38	59.17	12.21

As can be known from the above table, adopt existing synchronous spray cooling device cooling, shell ring inside and outside surface temperature difference is comparatively large, and maximum temperature difference is 28.01 DEG C.

Method 1, method 2 and method 3 is carried out contrast can find out, the spraying cooling method that the present invention proposes effectively can carry out Homogeneous cooling to shell ring, and the cycle that is simple to operate, that greatly reduce shell ring production.

Claims (2)

1. one kind large-scale shell ring hot rolling spraying cooling method, it is characterized in that: make a upper spray equipment and one lower spray equipment that the cooling water pipe on lower water spray collection plate is formed by lower water spray collection plate and vertical distribution that the cooling water pipe on upper water spray collection plate is formed by upper water spray collection plate and vertical distribution, after large-scale shell ring rolling terminates, on, bottom roll is with less drafts clamping shell ring, shell ring is rotated under the drive of frictional force, same spray equipment at present extend into shell ring inside, upper spray equipment is outside relative with lower spray equipment at shell ring, in adjustment, on lower spray equipment, cooling water pipe length makes the line of the nearly shell ring wall end of all cooling water pipes on each spray equipment form the semicircle shape concentric with shell ring, simultaneously in adjustment, lower spray equipment upper, the number ratio of cooling water pipe and the flow-rate ratio of cooling water on lower water spray collection plate, realize in large-scale shell ring, the rear same cooling rate of rolling of outer surface cools, described shell ring rolling terminates rear cooling water inflow and compares R ₁with cooling water pipe number ratio n ₁/ n ₂between pass be:

in formula: q is upper water spray collection plate cooling water pipe nozzle flow; R ₁it is upper and lower water spray collection plate cooling water pipe nozzle flow ratio; d ₁, d ₂upper and lower water spray collection plate cooling water pipe nozzle diameter respectively; H ₁, H ₂the distance of upper and lower cooling water pipe nozzle distance surface of steel plate respectively; n ₁, n ₂the quantity of outer surface and inner surface cooling water pipe respectively; B is shell ring wall thickness; R is shell ring equivalent redius;

By regulating the quantity of the cooling water pipe of upper and lower water spray collection plate, change cooled region area; By regulating the length of the cooling water pipe of upper and lower water spray collection plate, change the length of cooling arc.

2. large-scale shell ring hot rolling spraying cooling method according to claim 1, it is characterized in that: by regulating quantity and the length of the cooling water pipe of upper and lower water spray collection plate, the inside and outside surperficial convection transfer rate of accurate calculating shell ring, realizes the roller repairing of different size shell ring.