A kind of discharging type screw steel finished product rolling mill pass and screw steel production method

Abstract

The application discloses a kind of discharging type screw steel finished product rolling mill pass and screw steel production method, the base circle size of the discharging type screw steel finished product rolling mill pass is less than the minimum value of national standard of corresponding specification screw steel inner diameter, and the roll gap size of the discharging type screw steel finished product rolling mill pass is greater than the national standard reference roll gap of corresponding specification;A kind of discharging type screw steel finished product rolling mill pass and screw steel production method of the application, the screw steel produced meets relevant standards, and has higher negative tolerance level.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of threaded steel production, in particular to a discharging type threaded steel finished product rolling mill pass and a threaded steel production method. BACKGROUND

[0002] At present, the selling mode of threaded steel in the market is mainly based on the theoretical weight, so the method of negative tolerance rolling is adopted in the threaded steel production process to obtain maximum profit (negative tolerance=(actual weight-theoretical weight) / theoretical weight), but the negative tolerance threshold of the product of the domestic large steel plant is far higher than the national standard due to the process limitation, and the enterprise loss effect is obvious due to the recent sharp decline in steel price, so it is particularly important to reduce the cost by increasing the negative tolerance level at this time.

[0003] The traditional rolling is to gradually collect the material of the finished product frame K1 to make the negative tolerance increased, and the defect is that the inner diameter is reduced under the premise of ensuring the base circle, which has little effect on the negative tolerance, and the maximum threshold of the negative tolerance is reached when the inner diameter is ensured within the national standard range, which is still far from the national standard requirement of the negative tolerance. SUMMARY

[0004] The present application aims to overcome the above-mentioned deficiencies, and provides a discharging type threaded steel finished product rolling mill pass and a threaded steel production method, which can produce threaded steel meeting the relevant standards and having a high negative tolerance level.

[0005] The discharging type threaded steel finished product rolling mill pass provided by the present application has a base circle size smaller than the national standard minimum value of the inner diameter of the threaded steel of the corresponding specification, and a roll gap size greater than the national standard reference roll gap of the corresponding specification.

[0006] Further, the base circle size φ 放 is smaller than the national standard minimum value of the inner diameter of the threaded steel of the corresponding specification, and the roll gap size h 国min is greater than the national standard reference roll gap of the corresponding specification. 实 标 wherein φ 国min is the national standard minimum value of the inner diameter of the threaded steel of the corresponding specification, h 实 is the actual roll gap, and h 标 is the national standard reference roll gap of the corresponding specification.

[0007] Further, the actual roll gap h 实 is K*h 标 , wherein K is a set parameter.

[0008] Further, 1

[0009] Further, the base circle size φ 放 and the actual roll gap h 实 satisfy S 放 = S​收 S / (1+a), wherein, S 放 S / (1+a), wherein, S 收 S / (1+a), wherein, S

[0010] According to another aspect of the present application, there is also provided a method for producing threaded steel, comprising the following steps: a rolling piece enters a finishing rolling II unit, and passes through N finishing rolling mills in sequence in the finishing rolling unit before reaching a finished rolling mill, and the pass of the finished rolling mill is the above-mentioned pass of the finished rolling mill for the rolling piece.

[0011] Further, the method further comprises the following steps: after the rolling piece is rolled through the finishing rolling II unit, the rolling piece is cooled through a water cooling device, and the water pressure of the water cooling device is controlled to rapidly cool the temperature of the rolling piece to 880-920 DEG C.

[0012] Further, the method further comprises the following steps: the rolling mill before the finished rolling mill is regarded as a to-be-adjusted mill stand, and the rolling reduction of the rolling mill of the to-be-adjusted mill stand is adjusted according to the rolling pressure of the finished rolling mill.

[0013] Further, the method for adjusting the rolling reduction of the rolling mill of the to-be-adjusted mill stand is as follows: each time the rolling piece passes through the finishing rolling II unit, the roll gap of the rolling mill of the to-be-adjusted mill stand is reduced by M, until the rolling pressure of the finished rolling mill is within a predetermined range.

[0014] Further, M is 0.05 mm.

[0015] The present application has the following beneficial effects: the pass of the finished rolling mill for the rolling piece according to the present application can greatly improve the negative tolerance level of the threaded steel by reducing the base circle and then increasing the inner diameter in the form of material discharge (i.e. in the form of increasing the roll gap), and the effect is much better than other methods, the operation is simple, the effect is obvious, and the production product can meet the relevant standards, and the economic benefits of the factory are effectively improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a production equipment layout diagram of a method for producing threaded steel according to an embodiment of the present application;

[0017] Figure 2 is a process flow diagram of a method for producing threaded steel according to an embodiment of the present application;

[0018] Figure 3 is a schematic diagram of the pass of the finished rolling mill for the φ12 threaded steel according to an embodiment of the present application;

[0019] Figure 4is a schematic diagram of a φ12 screw steel corresponding to a finished rolling mill pass of the present application in the prior art.

[0020] Fig. 1 is a rough rolling mill group, 2 is a medium rolling mill group, 3 is a finishing rolling I group, 4 is a finishing rolling II group, 5 is a flying shear, 6 is a cooling bed, 7 is a pre-water cooling device, 8 is a water cooling device. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0022] The finished rolling mill pass of the discharge type screw steel in the embodiment is smaller than the national standard minimum value of the inner diameter of the corresponding specification screw steel, and the roll gap size of the finished rolling mill pass of the discharge type screw steel is greater than the national standard reference roll gap of the corresponding specification.

[0023] Specifically, the base circle size φ 放 and the actual roll gap h 实 satisfy the following conditions:

[0024] (1) φ 放 = φ 国min -h 实 +h 标 ;

[0025] (2) h 实 = K * h 标 , 1 < K ≤ 1.5;

[0026] (3) S 放 = S 收 / (1+a), and 0 < a ≤ δ;

[0027] S 放 = π*(φ 放 / 2) 2 +(φ 放 / 2)*(h 实 -h 标 );

[0028] S 收 = π*(φ 收 / 2) 2 -(φ 收 / 2)*(h 标 -h 收实 ).

[0029] Wherein, φ 国minh is the minimum value of the inner diameter of the corresponding standard screw steel according to the national standard, h 实 h is the actual roll gap, h 标 h is the reference roll gap of the corresponding standard screw steel according to the national standard, K is a set parameter, a is a set difference value, and 0 < a ≤ δ, δ is the difference between the maximum value of the negative tolerance of the screw steel produced by the existing finished product pass and the negative tolerance of the corresponding standard screw steel according to the national standard, φ 收 h is the inner diameter of the screw steel of the finished product stand pass in the prior art, h 收实 h is the actual roll gap of the finished product stand pass in the prior art.

[0030] Figure 1 is a production equipment layout of a screw steel production method in an embodiment of the present application; Figure 2 is a process flow diagram of a screw steel production method in an embodiment of the present application.

[0031] As shown in Figure 1 and Figure 2 , the screw steel production method of the present embodiment comprises the following steps:

[0032] After the billet is heated to the required roughing temperature (950-1100°C) in the heating furnace, it is sent out of the furnace by the furnace discharge roller way, and after descaling by the high-pressure water descaling device in front of the roughing mill group 1, it is sent into rolling by the furnace discharge roller way. When the rolling line fails and the billet has been discharged or the discharged billet is unqualified hot billet, the discharged billet can be removed from the rolling line by the post-furnace scrap removal device. When a fault occurs during the production process of the rear process, the pre-roughing pinch shear cuts the billet that has not entered the roughing mill group 1, and the billet is offline.

[0033] The rolling line is equipped with a roughing mill group of 17 stands, a medium rolling mill group of 24 stands, a finishing rolling I group of 36 stands (of which No. 15 stand is a double station), a finishing rolling II group of 43 stands (of which No. 20 stand is a double station), a total of 20 stands. A pre-water cooling device 7 is provided after the medium rolling mill group 2 and after the finishing rolling I group 3 for controlling the temperature of the rolled piece entering the finishing rolling mill group. The rolled piece is rolled through the roughing, medium rolling, finishing rolling I group 3, and finishing rolling II group 4 in sequence to form a straight bar of Φ12mm-Φ40mm. According to different rolling specifications, the rolling pass and the number of stands used are also different. The maximum rolling speed of the finished product is guaranteed to be 18.0m / s.

[0034] After the billet is rolled for 7 passes in the rough rolling mill set 1, the rolled piece is cut by the 1# flying shear 5, and then enters the intermediate rolling mill set 2 for rolling for 4 passes. After pre-water cooling, the rolled piece is cut by the 2# flying shear 5, and then enters the finishing rolling I set 3 for rolling for 0-6 passes. After pre-water cooling, the rolled piece is cut by the 3# flying shear 5, and then enters the finishing rolling II set 4 for rolling for 2-3 passes to form the final required finished product section size. When a fault occurs downstream of the rolling line, the 1#, 2# and 3# flying shears 5 are automatically started to continuously cut the rolled piece for fragmentation to prevent the accident from further expanding. To meet different production requirements for cutting, the 15# and 20# are provided with horizontal / vertical double-position rolling mills to realize full-line non-twist rolling and improve the product surface quality. The 3# flying shear 5 has the function of cutting the head and tail of the single-line and two-cut rolled pieces.

[0035] The pass of the finished product rack in the finishing rolling II set 4 is the above-mentioned discharging type screw rod finished product rolling mill pass. In addition, because the finished product rack pass is a discharging pass, compared with the traditional receiving pass, the rolling pressure is increased, so the rolling mill before the finished product rolling mill is regarded as a to-be-adjusted rack, and the rolling pressure of the to-be-adjusted rack is adjusted according to the rolling pressure of the finished product rolling mill. The specific adjustment method is: each time the rolled piece passes through the finishing rolling II set, the roll gap of the rolling mill of the to-be-adjusted rack is reduced by M, until the rolling pressure of the finished product rolling mill is within the predetermined range. Wherein, M is 0.05mm.

[0036] The bar immediately out of the finishing rolling II set 4 enters the water cooling device 8 to quickly cool the rolled piece to the vicinity of the phase transition region (880-920℃) to control the growth of austenite grains and ferrite grains, and finally obtain higher tensile strength and improve the organizational performance of the reinforcing bar. The use of the discharging type pass will increase the compression ratio and thus increase the pressure of the finished product rack under the premise of keeping the front rack and process unchanged, so the cooling water pressure of the rolling mill and the water tank needs to be increased to compensate for the increased temperature. According to the requirements of different steel grades and specifications of the product, the use number of the water cooling device and the water quantity are set to achieve the required rolled piece temperature. When producing new national standard materials, it is necessary to ensure that the surface does not enter the martensite and bainite transformation region, the base circle does not appear tempered martensite and closed-loop structure different from the base body, and the core surface hardness difference is ≯40HV, which meets the requirements of the new national standard for hot-rolled reinforcing bars.

[0037] The water-cooled rolled piece is sent to the double-length flying shear 5, and is cut into double-length pieces with length suitable for the cooling bed 6 by the double-length flying shear 5. The segmented rolled piece is conveyed by the input roller way, is braked by the friction brake plate, and is sent to the step rack type cooling bed 6. The rolled piece is sampled, is aligned, and is cooled on the cooling bed 6. The sampling data is sent to the rolling mill for the operator to adjust the rolling mill parameters. The aligned roller way aligns one end of the rolled piece towards the output direction of the cooling bed 6. The rolled piece is formed into a row of steel groups in a certain interval and quantity by the chain type conveying machine, and is sent to the output roller way of the cooling bed 6 in a row by the steel conveying trolley device. The output roller way of the cooling bed 6 conveys the steel unloaded from the cooling bed 6 to the cutting shear to be cut into a fixed length.

[0038] The fixed-length material is conveyed away by the cutting roller way, is aligned, is counted, and is separated on the steel conveying rack after alignment. Two steel conveying racks are arranged, and each of the first and second steel conveying racks is provided with a set of automatic counting and separating device and a set of automatic baling machine, weighing device and unloading rack corresponding to the subsequent process. After counting, alignment, baling and weighing, the fixed-length material is printed with a label. A re-counting counter and a label printing robot are arranged beside all the finished product collecting racks. After the label is welded, the finished product is conveyed to the 5-meter platform by the descending mechanism, is conveyed to the finished product warehouse unloading rack by the roller way, and can be conveyed to the warehouse for storage by the electromagnetic lifting.

[0039] Embodiment

[0040] Figure 3 is a schematic diagram of the φ12 deformed steel bar corresponding to the blanking type deformed steel bar finished rolling mill pass in the embodiment of the present application; Figure 4 is a schematic diagram of the φ12 deformed steel bar corresponding to the finished rolling mill pass in the prior art.

[0041] The blanking type deformed steel bar finished rolling mill pass in the embodiment is used for producing φ12 deformed steel bars. The upper limit of the negative tolerance of the φ12 deformed steel bar is -6%, and the inner diameter required by the national standard is 11.5±0.4. The reference roller gap h of the national standard is 1.5 mm. 标

[0042] As shown in Figure 4 , the minimum value of the inner diameter of the conventional blanking type pass is 11.2 mm, and 0.1 mm is given for blanking. Under normal circumstances, the actual roller gap is 1.4 mm, and the inner diameter just meets the national standard. At this time, the measured negative tolerance level is only -4.2%.

[0043] And using the blanking type pass as shown in Figure 3 , the inner diameter of the base circle breaks the conventional less than the national standard requirement. By making the roller gap larger to about 2.2, the inner diameter has met the national standard, and the negative tolerance level of the produced deformed steel bar reaches -5.4%, which is much higher than that of the conventional blanking type.

[0044] ​To sum up, the specific application examples of the present application do not constitute a limitation on the scope of protection of the present application, and equivalent replacement technical solutions fall within the scope of protection of the present application.

Claims

1. A pass for a bar-in-coil mill, characterized in that, The base circle size of the roughing type screw steel finished rolling mill pass is less than the minimum value of the inner diameter of the screw steel of the corresponding specification according to the national standard, and the roll gap size of the roughing type screw steel finished rolling mill pass is greater than the reference roll gap of the corresponding specification according to the national standard. The base circle size φ 放 = φ 国min -h 实 +h 标 , wherein the φ 国min is the national standard minimum value of the inner diameter of the screw thread steel of the corresponding specification, the h 实 is the actual roll gap, and the h 标 is the national standard reference roll gap of the corresponding specification. Wherein, the actual roll gap h 实 = K * h 标 , wherein, the K is a set parameter; 1 < K ≤ 1.5; the base circle size φ 放 , and the actual roll gap h 实 value meet S 放 = S 收 / (1 + a), wherein, the S 放 is the inner circle cross-sectional area of the billet type threaded steel finished product rolling mill pass, the S 收 is the inner circle cross-sectional area of the existing finished product pass of the corresponding specification, the a is a set difference value, and 0 < a ≤ δ, the δ is the difference value of the maximum value of the negative tolerance of the threaded steel produced by the existing finished product pass of the corresponding specification and the national standard negative tolerance of the corresponding specification.

2. A method of producing threaded steel, characterized by, The method comprises the following steps: The rolled piece enters the finishing rolling II unit, and passes through N finishing rolling mills in sequence in the finishing rolling unit and then reaches the finished rolling mill, and the pass of the finished rolling mill is the roughing type screw steel finished rolling mill pass in claim 1.

3. A method of producing threaded steel according to claim 2, characterized in that, The method further comprises the following steps: after the rolled piece is rolled by the finishing rolling II unit, the rolled piece passes through a water cooling device, the water pressure of the water cooling device is controlled, and the temperature of the rolled piece is rapidly cooled to 880-920 DEG C.

4. The method of producing threaded steel according to claim 2, characterized in that, The method further comprises the following steps: therefore, the rolling mill before the finished rolling mill is regarded as a to-be-adjusted mill stand, and the reduction amount of the rolling mill of the to-be-adjusted mill stand is adjusted according to the rolling pressure of the finished rolling mill.

5. The method of producing threaded steel according to claim 4, characterized in that, The method for adjusting the reduction amount of the rolling mill of the to-be-adjusted mill stand is: each time the rolled piece passes through the finishing rolling II unit, the roll gap of the rolling mill of the to-be-adjusted mill stand is reduced by M, until the rolling pressure of the finished rolling mill is within a predetermined range.

6. A method of producing threaded steel according to claim 5, characterized in that, The M is 0.05 mm.

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