A method for controlled rolling and controlled cooling of HRB400E steel grade matched with a wire rod Morgan mill and a Daniele reducing mill

Abstract

The application discloses a kind of wire Morgan rolling mill supporting Danelli reducing sizing machine HRB400E steel kind control rolling and cooling method, comprising:1), heating furnace heating section temperature range 1120-1180 ℃, soaking section temperature range 1140-1160 ℃, in furnace time 80-90 minutes;2), opening rolling temperature is controlled according to 980±30 ℃;3), finishing rolling entrance temperature is controlled according to 860-900 ℃;4), reducing sizing machine entrance temperature is controlled according to 800-840 ℃;5), spitting silk temperature is controlled according to 900-920 ℃, and a group of water tank cooling is opened before pre-water cooling section finishing rolling, and four groups of water tank cooling are opened after water cooling section finishing rolling;Finishing rolling unit cooling water pressure is controlled between 4.5~4.8kPa;6, fan is all off.The purpose of the application is to realize the low temperature high speed temperature control rolling of wire, and finally obtain high quality, good stability hot rolled deformed bar, and meanwhile, the alloy cost of deformed bar is better reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of rolling process, in particular to a kind of Morgan wire rod mill matched with Danieletto reducing sizing mill HRB400E steel grade controlled rolling and controlled cooling method. BACKGROUND

[0002] At present, the HRB400E steel bar produced by Baotou Steel is the mainstream of building steel bar, and the production mode of HRB400E steel bar has been single for a long time, the alloy cost is high, which does not meet the concept of sustainable development, and the cost of each production link is high.

[0003] The 1# line of Baotou Steel Long Material Plant is a high-speed wire rod production plant, and the main rolling mill equipment is the Morgan fifth-generation rolling mill introduced from Morgan, which includes pre-finishing mill, finishing mill, pinch roll and wire laying machine, etc. The 1# line of Baotou Steel Long Material Plant is matched with Danieletto reducing sizing mill set after finishing mill in 2020, but there is a problem of controlled cooling connection between Morgan fifth-generation rolling mill and Danieletto reducing sizing mill. It is necessary to study the coordinated control of the two kinds of rolling mills to ensure that the rolling line can realize low-temperature high-speed controlled rolling of wire rod after adopting Danieletto reducing sizing mill set, and can produce low-alloy component deformed steel bar to achieve the purpose of reducing alloy cost. In order to obtain HRB400E hot rolled deformed steel bar with high quality and good stability, a simple and easy-to-operate micro-alloyed HRB400E steel bar controlled rolling and controlled cooling production process with stable product performance needs to be designed to obtain products with strong competitiveness in specifications, yield, quality and performance. SUMMARY

[0004] The purpose of the present application is to provide a kind of Morgan wire rod mill matched with Danieletto reducing sizing mill HRB400E steel grade controlled rolling and controlled cooling method, to realize low-temperature high-speed controlled rolling of wire rod, and finally obtain hot rolled deformed steel bar with high quality and good stability, and better reduce the alloy cost of deformed steel bar.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0006] The present application provides a kind of Morgan wire rod mill matched with Danieletto reducing sizing mill HRB400E steel grade controlled rolling and controlled cooling method, which comprises:

[0007] 1), the temperature range of heating furnace heating section is 1120-1180℃, the temperature range of soaking section is 1140-1160℃, and the furnace time is 80-90 minutes;

[0008] 2), the opening rolling temperature is controlled at 980±30℃;

[0009] 3), the finishing mill inlet temperature is controlled at 860-900℃;

[0010] 4), the reducing sizing mill inlet temperature is controlled at 800-840℃;

[0011] 5), the wire drawing temperature is controlled at 900-920 DEG C, a group of water tank cooling is opened before the finishing rolling, four groups of water tank cooling are opened after the finishing rolling, and the wire drawing temperature is adjusted; the cooling water pressure of the finishing rolling mill is controlled between 4.5-4.8 kPa;

[0012] 6, the fan is fully closed, the large difference between the cooling speeds of the lap joint points and the non-lap joint points is avoided, and the performance fluctuation of the disc screw is caused; the speed setting of the Stelmor line roller is shown in the following table:

[0013]

[0014] The mass percentage chemical composition of the disc screw is: C 0.22-0.25%, Si 0.50-0.60%, Mn 1.30-1.40%, P≤0.045, S≤0.045, the rest is Fe and inevitable impurities.

[0015] Further, the disc screw performance is well controlled, the tensile strength difference between the same circles is 19 MPa, the yield strength difference between the same circles is 16 MPa, and the elongation and the maximum force total elongation difference is 4.5%.

[0016] Further, the disc screw grain size is 11-12 levels.

[0017] Compared with the prior art, the beneficial technical effects of the present application are:

[0018] By designing the HRB400E steel bar control rolling and control cooling production process matched with the Morgan wire rod mill and the Danielevibration reducing machine, low-temperature high-speed temperature control rolling of the wire rod can be realized. Thus, the hot rolled screw steel with higher quality and good stability is obtained. Meanwhile, the alloy cost of the screw steel is better reduced. For domestic enterprises using the Morgan fifth generation high-speed wire rod mill matched with the Danielevibration reducing machine, we think that the present application has practical popularization value. The benefit is shown as follows: according to the production of 60,000 tons of hot rolled screw steel products per year, the alloy reduction benefit of 46 yuan per ton of steel product is calculated, 256,000 yuan can be created, 150 tons of broken products are reduced due to the stable process per year, the difference between the finished product and the scrap steel is about 2000 yuan per ton, 30,000 yuan of benefit can be created due to the reduction of broken products caused by the stable process per year, and the direct economic benefit is about 286 (million yuan) per year. BRIEF DESCRIPTION OF DRAWINGS

[0019] The present application will be further described below in combination with the description of the drawings.

[0020] Figure 1 The metallographic structures under different rolling temperatures are compared, wherein a is the grain size after process adjustment (11-12 levels), and b is the grain size before process adjustment (10-11 levels). DETAILED DESCRIPTION

[0021] A wire rod Morgan rolling mill is matched with a DanieI reducing sizing mill, and a HRB400E steel grade controlled rolling and controlled cooling method, comprising:

[0022] A 150mmx150mmx12000mm continuous casting billet is used as raw material, and a Φ8-16mm disc screw is rolled. The chemical composition of the continuous casting billet before and after the process adjustment is shown in Table 1.

[0023] Table 1 HRB400E chemical composition before and after process adjustment

[0024]

[0025]

[0026] The HRB400E steel bar rolling process flow is as follows:

[0027] Continuous casting billet acceptance and feeding→steel billet heating→high-pressure water descaling→rough rolling mill rolling→intermediate rolling mill rolling→pre-precision rolling mill rolling→precision rolling mill rolling→reducing sizing mill rolling→controlled water cooling→diameter gauge→wire feeder→stelmor roller cooling→coiling→trimming and surface quality inspection→packing→weighing→labeling→warehousing.

[0028] The HRB400E steel grade controlled rolling and controlled cooling method of the wire rod Morgan rolling mill matched with the DanieI reducing sizing mill is as follows:

[0029] 1. The heating furnace heating section temperature range is 1120-1180℃, the soaking section temperature range is 1140-1160℃, and the furnace time is 86 minutes. The purpose is to eliminate the as-cast organization segregation, dissolve the carbide and homogenize the austenite, while avoiding high heating temperature and long heating time, which leads to coarse austenite grains.

[0030] 2. The opening rolling temperature is controlled at 980±30℃; the purpose is to make the austenite grains not too coarse, to lay a good foundation for grain size control in subsequent rolling, and to improve the product performance.

[0031] 3. The precision rolling inlet temperature is controlled at 860-900℃; the diffusion speed of carbon in austenite is reduced under low temperature rolling, the carbon precipitation amount in austenite is reduced, fine pearlite interlamellar spacing and fine ferrite structure can be obtained, and the strength and toughness of the product are significantly improved.

[0032] 4. The reducing sizing mill inlet temperature is controlled at 800-840℃; rolling in the two-phase zone can cause dynamic recrystallization of ferrite, carbon is washed out in the form of fine carbide due to the enrichment of carbon in the austenite in the two-phase zone, and fine ferrite and pearlite mixture is obtained, thereby improving the strength and toughness of the deformed steel bar.

[0033] 5. The wire drawing temperature is controlled at 900-920℃, a group of water boxes is opened for pre-water cooling section before finish rolling, four groups of water boxes are opened for water cooling section after finish rolling, which can be adjusted according to the wire drawing temperature. The cooling water pressure of the finish rolling mill train is controlled between 4.5-4.8kPa;

[0034] 6. The fan is fully closed to avoid the large difference between the cooling speeds of the lap joint and the non-lap joint, thereby causing the performance fluctuation of the disc screw same circle, and finally obtaining stable mechanical properties. The Stelmor line roller speed setting is shown in the following table:

[0035] Table 2 Low-cost HRB400E roller speed

[0036]

[0037] Under the condition of adopting Morgan rolling mill matched with Daniele reducing mill train, the mechanical properties completely meet the requirements of GB / T1499.2-2018 national standard by using the newly given process parameters, and the target of reducing alloy components by controlling temperature rolling is achieved.

[0038] Table 2 Mechanical properties of low-cost HRB400E steel bar

[0039] No. Tensile strength / MPa Tensile strength / MPa No. Tensile strength / MPa Tensile strength / MPa 1 460 678 13 483 693 2 467 701 14 457 673 3 452 668 15 461 705 4 477 697 16 489 719 5 481 705 17 449 670 6 454 666 18 488 717 7 458 690 19 469 698 8 481 711 20 429 676 9 475 677 21 435 687 10 457 714 22 469 716 11 475 700 23 441 670 12 460 673 24 465 700 Max 480.84 714.00 Max 489.07 718.75 Min 451.89 665.90 Min 428.65 669.50 Mean 466.24 689.96 Mean 461.27 693.61

[0040] The same circle of the test disc screw is taken for inspection, and the performance is shown in Table 3. It is found that the same circle performance of the low-cost steel bar by low-temperature rolling is well controlled, the tensile strength same circle difference is 19MPa, the yield strength same circle difference is 16MPa, and the elongation and maximum force total elongation difference is 4.5%.

[0041] Table 3 Same circle performance comparison

[0042] No. Tensile strength / MPa Tensile strength / MPa Elongation / % Total elongation / % 1 665 470 29.0 15.0 2 646 465 24.5 12.0 3 652 464 25.5 11.0 4 665 455 29.0 14.5 5 655 460 26.0 11.0 6 650 454 27.0 12.5 7 660 463 29.0 15.5 Difference 19 16 4.5 4.5

[0043] The disc screw is taken for inspection of microstructure, and the disc screw cross-section radius 1 / 4 is taken at the same time, and the comparison method is used for rating, as shown in Table 4. Figure 1 It is found that the low-temperature rolling realizes the refinement of the grain size, and the low-temperature rolling can refine the grain size to 11-12 grade.

[0044] The above-described embodiments are only used to describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements of the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A controlled rolling and controlled cooling method for HRB400E steel coiled rebar produced using a Morgan wire rod mill paired with a Danieli reducing and sizing mill, characterized in that... include: 1) The heating section of the furnace has a temperature range of 1120-1180℃, the soaking section has a temperature range of 1140-1160℃, and the furnace time is 80-90 minutes; 2) The initial rolling temperature should be controlled at 980±30℃; 3) The inlet temperature of the finishing mill should be controlled at 860-900℃; 4) The inlet temperature of the reducing and sizing mill should be controlled at 800-840℃; 5) The wire drawing temperature is controlled at 900-920℃. One set of water tanks is used for cooling in the pre-cooling section before finishing milling, and four sets of water tanks are used for cooling in the water cooling section after finishing milling. Adjustments are made according to the wire drawing temperature. The cooling water pressure of the finishing mill is controlled between 4.5 and 4.8 kPa. 6) Turn off all fans to avoid fluctuations in the performance of the coiled screw due to significant differences in cooling rates between the overlapping and non-overlapping points; the speed settings for the Steyrmo line roller conveyor are shown in the table below: The chemical composition of the spiral conch by mass percentage is as follows: C 0.22-0.25%, Si 0.50-0.60%, Mn 1.30-1.40%, P≤0.045%, S≤0.045%, with the remainder being Fe and unavoidable impurities.

2. The controlled rolling and controlled cooling method for HRB400E steel coiled wire rod using a Morgan wire rod mill paired with a Danieli reducing and sizing mill, as described in claim 1, is characterized in that... The performance of the coiled rebar is well controlled, with a tensile strength difference of 19 MPa, a yield strength difference of 16 MPa, an elongation difference of 4.5%, and a maximum force total elongation difference of 4.5%.

3. The controlled rolling and controlled cooling method for HRB400E steel coiled wire rod using a Morgan wire rod mill paired with a Danieli reducing and sizing mill, as described in claim 1, is characterized in that... The grain size of the spiral is 11-12.

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