CN106825473B

CN106825473B - Method for improving surface quality of high-strength weather-resistant H-shaped steel

Info

Publication number: CN106825473B
Application number: CN201611231803.3A
Authority: CN
Inventors: 孟保仓; 张怀军; 刘岩军; 陈建新; 张达先
Original assignee: Baotou Iron and Steel Group Co Ltd
Current assignee: Baotou Iron and Steel Group Co Ltd
Priority date: 2016-12-28
Filing date: 2016-12-28
Publication date: 2020-01-31
Anticipated expiration: 2036-12-28
Also published as: CN106825473A

Abstract

The invention discloses methods for improving the surface quality of high-strength weather-resistant H-shaped steel, which are characterized in that in the continuous casting process of a beam blank, the straightening temperature of the casting blank is 830-900 ℃, a crack sensitive area is avoided, the casting machine pulling speed is controlled for 0.90-1.10 min, the specific water amount of secondary cooling is 0.7-0.8L/kg, the water amount of a crystallizer is 4100L/min, the water inlet temperature of the crystallizer is 25-30 ℃, the arc centering of the crystallizer is less than or equal to 100 mu m, the superheat degree of tundish molten steel is 20-25 ℃, low alkalinity and high viscosity are adopted for protective slag, double water ports are adopted for full-protection casting, the water port immersion depth is 70-80mm, the joint of a long water port and a large ladle is sealed by argon, and after continuous casting is finished, the casting blank is subjected to slow cooling for more than or equal to 24 hours.

Description

Method for improving surface quality of high-strength weather-resistant H-shaped steel

Technical Field

The invention relates to metallurgy continuous casting technologies, in particular to methods for improving the surface quality of high-strength weather-resistant H-shaped steel.

Background

Compared with Q235B or Q345B ordinary carbon steel, the high-strength weather-resistant H-shaped steel has excellent performances such as high strength, atmospheric corrosion resistance and welding, is widely applied to the fields of ocean platforms, power transmission towers or railway bridges, quantitative alloy elements (Cu, P, Cr, Ni and the like) are added during smelting of the ordinary steel, the corrosion resistance is 2-8 times that of the ordinary carbon steel, along with the high-rise and large-span of buildings, the demand of the high-strength weather-resistant H-shaped steel is increased, the quality requirement on the steel is increased, the later maintenance cost of the high-strength weather-resistant H-shaped steel is low, the environmental pollution is small, the economic benefit of the whole life cycle of the building is good, the special-shaped section of the weather-resistant H-shaped steel is complex, the specific surface area is large, the cooling is uneven, the strain force is large, and the crack is easily generated inside a web plate.

Disclosure of Invention

The invention aims to provide methods for improving the surface quality of high-strength weather-resistant H-shaped steel, which are used for solving the surface quality problem of weather-resistant H-shaped steel special-shaped continuous casting billets and can obtain the special-shaped continuous casting billets with qualified quality.

The technical scheme is as follows:

method for improving surface quality of high-strength weather-proof H-shaped steel, during continuous casting of shaped blank, the straightening temperature of the casting blank is 830-900 deg.C, the crack sensitive area is avoided, the casting machine pulling speed is controlled at 0.90-1.10 m/min, the specific water amount of secondary cooling is 0.7-0.8L/kg, the crystallizer water inlet temperature is 25-30 deg.C, the crystallizer arc centering is less than or equal to 100 μm, the molten steel superheat degree of tundish is 20-25 deg.C, the protective slag is low-alkalinity and high-viscosity, the casting is fully protected by double water ports, the water port immersion depth is 70-80mm, the connection part of the long water port and the ladle is sealed by argon, and after the continuous casting, the casting blank is stacked and slowly cooled for more than or equal to 24 hours.

, adjusting the water quantity of the crystallizer to 4100L/min, adjusting the height of the water blower and the blank surface to 8mm, and additionally adding sets of compressed air pipelines at the tail end of the sector 2 section for auxiliary purging.

, inspecting the surface quality of the weather-proof H-shaped steel special-shaped continuous casting billet on a cooling bed, simultaneously performing hot acid low-power inspection on the internal quality and tracking and inspecting the quality of subsequent rolled steel and hot-processed steel.

, continuously casting to obtain the beam blank with the cross-section size of 730mm × 370mm × 90 mm.

Compared with the prior art, the invention has the technical effects that:

the invention overcomes the defects of the prior art, and is used for solving the surface quality problem of the weather-resistant H-shaped steel special-shaped continuous casting billet so as to obtain the special-shaped continuous casting billet with qualified quality. The weathering steel contains alloy components such as Cu, Cr and the like, has strong crack sensitivity, and has the advantages of complex section size of the continuous casting of the special-shaped blank, uneven cooling, large stress, easy occurrence of quality defects such as longitudinal crack of a web plate and the like in the continuous casting production, and the problem of improving the quality defects of the large-section special-shaped continuous casting blank by utilizing a high-pulling-speed weak cooling process, thereby achieving the purpose of improving the rolling quality and performance of the weathering steel. With the deep development and application of the technology, the benefit is more and more remarkable in the aspect of controlling the high-strength and weather-resistant steel quality.

The sectional dimension of the special-shaped blank is 730mm multiplied by 370mm multiplied by 90mm, which is different from the sectional dimension of the special-shaped blank casting machine for producing weather-resistant H-shaped steel by various steel enterprises at home and abroad at present.

By applying the high-pulling-speed weak cooling technology to the continuous casting of the section of the high-strength weathering steel beam blank, the quality defect problems of longitudinal cracking and the like of the weathering steel web plate can be reduced, and the expected economic benefit is more than 300 ten thousand yuan per year.

Detailed Description

The technical solution of the present invention will be described in detail with reference to exemplary embodiments. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art.

The process flow of the beam blank continuous casting comprises the following steps: molten iron KR method desulfurization → 90t top-bottom combined blown converter → 100tLF refining furnace → ladle turret → tundish → crystallizer → second cooling zone of sector segment → straightening machine → flame cutting → output roller table → step cooling bed → casting blank steel feeding heating furnace → rolling mill → straightening → cooling.

The invention adopts a high-drawing-speed weak cooling process, reasonably matches the drawing speed, the superheat degree, the crystallizer water quantity and the water inlet temperature, secondary cooling, the crystallizer arc alignment precision, the optimization of a water blower and the like according to the molten steel component characteristics of the weathering steel, solves the surface quality problem of the deformed blank in the continuous casting process of producing the weathering H-shaped steel deformed blank and obtains the weathering H-shaped steel deformed continuous casting blank with qualified quality by reasonably utilizing the technical measures of protective slag and the like.

A method for improving the surface quality of high-strength weather-resistant H-shaped steel is characterized in that in the continuous casting process of a beam blank, the straightening temperature of the casting blank is 830-900 ℃, and a crack sensitive area is avoided; controlling the casting speed of the casting machine to be 0.90-1.10 m/min, wherein the specific water amount of secondary cooling is 0.7-0.8L/kg; the water quantity of the crystallizer is 4100L/min, the water inlet temperature of the crystallizer is 25-30 ℃, the arc centering of the crystallizer is less than or equal to 100 mu m, the superheat degree of the molten steel of the tundish is 20-25 ℃, and the covering slag adopts low alkalinity and high viscosity; and (3) adopting double-water-port full-protection pouring, wherein the immersion depth of a water port is 70-80mm, the joint of a long water port and a ladle is sealed by adopting argon, and after the continuous pouring is finished, stacking and slow cooling are carried out on the casting blank for more than or equal to 24 hours.

The height between the water blower and the blank surface is adjusted to be 8mm, sets of compressed air pipelines are additionally arranged at the tail end of the sector 2 section for auxiliary blowing, and the beam blank with the section size of 730mm multiplied by 370mm multiplied by 90mm is produced by continuous casting.

The surface quality of the weather-resistant H-shaped steel special-shaped continuous casting billet is inspected on a cooling bed, and meanwhile, the internal quality is subjected to hot acid low-power inspection and the quality of subsequent rolled steel and hot-processed steel is tracked and inspected.

No obvious quality defects on the surface and the inside of the casting blank are found in the inspection process, the casting blank has good quality, and indexes such as casting blank center porosity, shrinkage cavity and segregation meet the requirements, the chemical components of various steel grades are shown in the table 1, and the invention is further illustrated in the step by combining the table 2 and the table 3 with the embodiment.

TABLE 1 chemical composition of each example (mass%/%)

Examples of the invention	C	Si	Mn	P	S	V	Cr	Ni	Cu
										Example 1	0.09	0.49	0.45	0.082	0.004	0.47	0.48	0.28	0.25
Example 2	0.08	0.47	0.44	0.086	0.003	0.50	0.44	0.24	0.23
										Example 3	0.07	0.46	0.42	0.085	0.005	0.48	0.46	0.25	0.22
Example 4	0.09	0.48	0.43	0.084	0.006	0.45	0.43	0.22	0.26

TABLE 2 continuous casting Process parameters for each example

TABLE 3 straightening temperature for each surface of the cast slab in each example

Examples of the invention	Flange top/. degree C	Flange R Angle/. degree C	Web median/. degree.C
				Example 1	840	900	860
Example 2	830	870	853
				Example 3	842	880	846
Example 4	850	876	850

After the pouring is finished, the surface quality of the special-shaped continuous casting billet is checked on a cooling bed, meanwhile, the internal quality is subjected to hot acid low-power inspection, the quality of subsequent rolled steel and hot-processed steel is tracked and checked, no obvious quality defects of the surface and the internal quality of the casting billet are found in the checking process, and the good quality of the casting billet meets the requirements. The results of the surface quality test of the cast slab are shown in table 4.

TABLE 4 quality of casting blank surface for each example

Examples of the invention	Web crack rate/%
		Example 1	1.0
Example 2	0.6
		Example 3	0.5
Example 4	0.8

As can be seen from Table 4, each example has good surface quality, the crack rate of the web is controlled below 1.0/% and the requirement of the casting blank quality is met.

As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.

Claims

The method for improving the surface quality of high-strength weather-resistant H-shaped steel is characterized in that in the continuous casting process of a special-shaped blank, the straightening temperature of the casting blank is 830 ℃ and 900 ℃ to avoid a crack sensitive area, the casting machine pulling speed is controlled to be 0.90-1.10 m/min, the specific water amount of secondary cooling is 0.7-0.8L/kg, the special-shaped blank with the section size of 730mm multiplied by 370mm multiplied by 90mm is produced by continuous casting, the water inlet temperature of a crystallizer is 25-30 ℃, the arc centering of the crystallizer is less than or equal to 100 mu m, the water amount of the crystallizer is 4100L/min, the height of a water blower and the blank surface is adjusted to be 8mm, sets of compressed air pipelines are additionally arranged at the tail end of a sector 2 section for auxiliary blowing, the superheat degree of molten steel of a tundish is 20-25 ℃, low-alkalinity and high viscosity of protective slag are adopted, double-water ports full-protection pouring is adopted, the water gap immersion depth is 70-80mm, the connection position of a long water nozzle and a large ladle is sealed by adopting argon, after continuous cooling, slow stacking is carried out for more than or longer than 24 hours, the H-shaped steel surface quality inspection, the hot rolled steel blank quality inspection and the subsequent hot.