CN104328356A - Manufacturing method of thin-specification high-strength-structure steel plate with steckel mill - Google Patents

Abstract

The invention discloses a manufacturing method of thin-specification high-strength-structure steel plates with a steckel mill. The steel plate includes following chemical components, by weight, 0.02-0.10% of carbon, 0.20-0.50% of silicon, 1.10-1.60% of manganese, not more than 0.010% of phosphorus, not more than 0.0050% of sulfur, 0.10-0.60% of nickel, not more than 0.50% of copper, not more than 0.50% of molybdenum, not more than 0.60% of chromium, not more than 0.060% of niobium, not more than 0.040% of vanadium, not more than 0.035% of titanium, not more than 0.0020% of boron, 0.020-0.050% of aluminum and the balance of ferrum and unavoidable impurities. The steel plate is manufactured through smelting and refining, a reasonable controlled rolling and controlled cooling technology and a reasonable thermal-treatment technology. The steel plate is excellent in performances, is 630-780MPa in tensile strength, is 500-600MPa in yield strength, is not less than 18% in ductility, is not more than 0.85 in yield strength ratio, is not less than 100J in low-temperature toughness at -40 DEG C, is excellent in strength-toughness matching and low in yield strength ratio, is excellent in anti-shock performance, is stable in manufacturing technology and is strong in operability of the manufacturing technology.

Description

The manufacture method of Thin Specs high strength structure steel plate produced by a kind of Steckel mill

Technical field

The present invention relates to a kind of manufacture method of high performance structures steel, the manufacture method of Thin Specs high strength structure steel plate produced by a kind of Steckel mill specifically.

Background technology

In recent years, domestic and international low-alloy high-strength steel have employed low-carbon microalloyed, high-purity homogenizing and grain refinement technology production in a large number on metallurgical technology.Along with the continuous refinement of crystal grain, while the intensity of steel and toughness are improved, also improve the yield tensile ratio of steel.The yield tensile ratio of general high intensity fine grain steel more than 0.85, even more than 0.90.For common engineering structure, the restriction to yield tensile ratio of relevant technological standard, design specifications and technical qualification is wider.But for energy dissipation project organization and Plastic Design structure, along with the yield strength of steel brings up to more than 420MPa, consider from safety perspective, design department carries out considered critical to the requirement of yield tensile ratio never to be had loosening.

Concerning iron and steel technical study and iron and steel enterprise, for meeting this kind of important feature design of (surpassing) Highrise buildings and using steel user demand, in the urgent need to research and development novel high-performance structural steel, make it have the various features such as high strength (more than 500MPa), low yield strength ratio (yield tensile ratio≤0.85), excellent low-temperature flexibility, good welding property and weather resistance.

China railways bridge construction is to future developments such as high speed, heavy duty, large span, full weldering nodes.Current domestic use Bridge Steel yield strength scope is generally 345 ~ 420MPa.For adapting to the requirement of bridge technology progress, integrating the high performance structures steel of the multinomial performances such as high strength, high tenacity, low yield strength ratio, is a collection of yet to be built greatly across the preferred material of heavy haul railway bridge key member.

For meeting large-scale steel structure bridge, (surpassing) Highrise buildings to the demand of high performance structures steel, Kind of Steels Used in Engineering Structures plate is towards high strength, high tenacity, the contour performance future development of low yield strength ratio.

Summary of the invention

The object of this invention is to provide the manufacture method that Thin Specs high strength structure steel plate produced by a kind of Steckel mill, the method, by reasonable component design, cooling controlling and rolling controlling process and rational thermal treatment process, obtains the low yield strength ratio high strength structure steel plate of excellent performance.

The object of the invention is to be achieved through the following technical solutions:

The manufacture method of Thin Specs high strength structure steel plate produced by a kind of Steckel mill, it is characterized in that: in the method, the chemical composition of steel plate is by weight percentage, C:0.02 ~ 0.10%, Si:0.20 ~ 0.50%, Mn:1.10 ~ 1.60%, P :≤0.010%, S :≤0.0050%, Ni:0.10 ~ 0.60%, Cu :≤0.50%, Mo :≤0.50%, Cr :≤0.60%, Nb :≤0.060%, V :≤0.040%, Ti :≤0.035%, B :≤0.0020%, Alt :≤0.050%, all the other are Fe and inevitable impurity; Impurity element in chemical composition controls: O≤0.0010%, N≤0.0080%, H≤0.0003%; Comprise following operation:

Smelt continuous casting process: desulfurizing iron pre-treatment, converter smelting, LF refining, RH vacuum-treat, continuous casting; After desulfurizing iron process, sulphur content controls at [S]≤0.002%, converter strictly controls [P] content, and LF adopts white slag operation desulfating and deoxidation, and RH vacuumizes process and strictly controls gas content; Continuous casting controls tundish temperature liquidus line+5 ~ 35 DEG C;

Curling furnaceman's skill: curling furnace temperature controls at 750 ~ 950 DEG C;

Rolling technology: adopt Controlled Rolling And Controlled Cooling, continuous blank heating temperature is 1160 DEG C ~ 1250 DEG C, steel plate thickness≤30mm when curling stove is rolled, steel billet temperature >=900 DEG C when entering curling stove rolling first, finishing temperature is 780 ~ 950 DEG C, and throwing steel speed is 0.5 ~ 3.0m/s;

Cooling control technology: roll rear controlled cooling model, controlling cold rear red temperature is 450 ~ 650 DEG C, air cooling subsequently.

This manufacture method also comprises following heat treatment step:

Steel plate is heated between 450 ~ 600 DEG C, carries out tempering heat treatment, and tempering time controls at (1.0 ~ 3.0) min/mm × thickness of slab+10min.

Chemical composition is one of key factor affecting continuously cast bloom internal soundness and plate property, and the present invention obtains excellent over-all properties to make described steel, and limit the chemical composition of described steel, reason is:

C: carbon is the one of the chief elements affecting high-strength steel mechanical property, improved the intensity of steel by gap solid solution, during too high levels, toughness and weldability will be deteriorated, and carbon content control of the present invention is 0.02 ~ 0.10%.

Si: silicon is the deoxidant element that steel-making is necessary, has certain solution strengthening effect; Silicone content is too high, is unfavorable for plate surface quality and low-temperature flexibility, and silicone content of the present invention controls 0.20 ~ 0.50%.

Mn: manganese has thinning microstructure, improves the effect of intensity and low-temperature flexibility, and with low cost.When Fe content is too high, easily cause continuously cast bloom macrosegregation.Fe content of the present invention controls 1.10 ~ 1.60%.

Ni: nickel can improve the intensity of steel, toughness and corrosion resistance nature, suppresses carbon precipitation from austenite, reduces grain boundary carbide and separates out tendency, significantly reduces intergranular carbide quantity.But along with nickel content increases, production cost can significantly increase, and nickel content of the present invention controls 0.10 ~ 0.60%.

Cu: copper can suppress polygonal ferrite and pearlitic formation, promotes cryo tissue bainite or martensitic transformation.Copper too high levels affects the toughness of steel, and causes temper brittleness, and in the present invention, copper content control is ≤0.50%.

Mo: the cost of alloy of molybdenum is high, can increase cost during a large amount of interpolation, and reduce toughness and weldability.Molybdenum content of the present invention controls≤0.50%.

Cr: chromium makes steel have good hardening capacity, and chromium is stronger carbide forming element, also keeps steel to have higher toughness after tempering while can improving the intensity of steel, and precipitation and the segregation of carbide can be suppressed in drawing process; Chromium can improve the atmospheric corrosion resistance of steel in addition, but higher chromium content can cause temper brittleness, grain growth, and unfavorable to welding property, should control≤0.60%.

Nb: trace niobium has pinning effect to austenite grain boundary, suppresses the recrystallize of deformed austeaite, and forms precipitate when cooling or tempering, improves intensity and toughness.When niobium addition level is greater than 0.060%, toughness reduces, and causes continuously cast bloom surface crack to produce, and also has deterioration effect in addition to welding property.Content of niobium of the present invention controls≤0.060%.

Ti: titanium can fix the GN 2 in steel, forms titanium nitride, stops the grain growth in heating, rolling, welding process, improve the toughness of mother metal and welded heat affecting zone.Titanium Composition Control of the present invention is ≤0.035%.

Al: aluminium is a kind of important deoxidant element, adds the aluminium of trace, effectively can reduce the inclusion content in steel in molten steel, and crystal grain thinning.But too much aluminium, can promote that continuously cast bloom produces surface crack and reduces slab quality, Holo-Al content should control≤0.050%.

In steel, impurity element is as S, P etc., and described in meeting grievous injury, the low-temperature flexibility of steel and the nearly weld metal zone of welding, increases continuous casting slab segregation degree.Sulphur, phosphorus content should control below S≤0.0050% and P≤0.010%.Other inevitable impurity element, is controlled as: O≤0.0015%, N≤0.0040%, H≤0.00010%.

The present invention is designed by reasonable component, converter smelting, LF and RH refining, optimizes cooling controlling and rolling controlling process production and obtains Thin Specs (thickness is less than or equal to 12mm) high strength structure steel plate.Plate property of the present invention is good, and tensile strength is 630 ~ 780MPa, and yield strength is 500 ~ 600MPa, and unit elongation is >=18%, yield tensile ratio≤0.85 ,-40 DEG C of low-temperature flexibility >=100J, has good obdurability coupling and low yield tensile ratio, stable processing technique.

The invention has the beneficial effects as follows:

1, the present invention adopts converter smelting, continuous casting to produce high strength structure engineering steel plate, adapts to numerous domestic and international steel enterprise and produces.The present invention adopts TMCP or TMCP+T explained hereafter height structural steel, and with short production cycle, rhythm is fast, reduces production cost, improves production efficiency.

2, the present invention is designed by reasonable component, adopts low-carbon (LC), low-phosphorous sulphur smelting technology, coordinates, effectively enhance the toughness and tenacity of low alloy steel with other trace alloying elements.Adopt Controlled Rolling And Controlled Cooling, and rational tempering heat treatment, ensure that steel plate Microstructure and properties is even, obtain low yield strength ratio high-performance engineering structural steel.

Accompanying drawing explanation

Fig. 1 is 12mm thick high strength structure steel plate tissue topography figure in embodiment 3.

Embodiment

A manufacture method for Thin Specs high strength structure steel plate produced by Steckel mill, adopts low-carbon (LC), low-phosphorous sulphur smelting technology, coordinates, effectively enhance the toughness and tenacity of low alloy steel with other trace alloying elements.Adopt Controlled Rolling And Controlled Cooling and rational tempering heat treatment, ensure that steel plate Microstructure and properties is even, obtain the high-strength Kind of Steels Used in Engineering Structures of low yield strength ratio.Main operational path is: desulfurizing iron pre-treatment → converter smelting → LF refining → RH refining → continuous casting → strand inspection, judgement → strand examination → heating steel billet → de-scaling → rolling → cooling → flaw detection → tempering → cutting, sampling → spray printing mark → warehouse-in.

The main chemical compositions (wt.%) of table 1 embodiment of the present invention

Adopt Controlled Rolling And Controlled Cooling, continuous blank heating temperature is 1160 DEG C ~ 1250 DEG C, steel plate rolling thickness≤30mm when curling stove is rolled, steel billet temperature >=900 DEG C when entering curling stove rolling first, finishing temperature is 780 ~ 950 DEG C, and throwing steel speed is 0.5 ~ 3.0m/s.Roll rear controlled cooling model, controlling cold rear red temperature is 450 ~ 650 DEG C, air cooling subsequently.

Table 2 rolling process for cooling parameter list

Embodiment	Thickness mm	Enter curling furnace temperature DEG C first	Finishing temperature DEG C	Red temperature DEG C	Throw steel speed m/s
						Embodiment 1	8	1007	862	641	1.2
Embodiment 2	10	1014	849	638	1.2
						Embodiment 3	12	1016	845	629	1.1

Steel plate carries out tempering heat treatment, and tempering temperature is 450 ~ 600 DEG C, and tempering time controls within (1.0 ~ 3.0) min/mm × thickness of slab+10min.Thermal treatment concrete technology parameter is as shown in table 3.

Table 3 heat treatment process parameter table

Embodiment steel plate is organized as a small amount of F of GB+, organizes based on granular bainite+ferrite after tempering heat treatment.Fig. 1 is that in embodiment 3, Thin Specs high strength structure steel plate metallographic structure photo produced by the thick Steckel mill of 12mm, and visible steel plate fine microstructures is even, and organizational composition is a small amount of F of GB+.

As shown in table 4 according to steel plate stretching performance of the present invention, low-temperature flexibility is as shown in table 5.The plate property result of the embodiment of the present invention is good, tensile strength is 630 ~ 780MPa, yield strength is 500 ~ 600MPa, unit elongation is >=18%, yield tensile ratio≤0.85 ,-40 DEG C of low temperature impact of collision >=100J, there is good obdurability coupling and low yield strength ratio, anti-seismic performance is excellent, and stable processing technique is workable.

Table 4 embodiment of the present invention steel plate stretching performance

Embodiment	Thickness/mm	Yield strength MPa	Tensile strength MPa	Unit elongation %	Yield tensile ratio
						Embodiment 1	8	533	654	20	0.815
Embodiment 2	10	541	649	21	0.834
						Embodiment 3	12	530	642	21	0.826

Table 5 embodiment of the present invention steel plate low-temperature flexibility

Claims (2)

1. the manufacture method of a Steckel mill production Thin Specs high strength structure steel plate, it is characterized in that: in the method, the chemical composition of steel plate is by weight percentage, C:0.02 ~ 0.10%, Si:0.20 ~ 0.50%, Mn:1.10 ~ 1.60%, P :≤0.010%, S :≤0.0050%, Ni:0.10 ~ 0.60%, Cu :≤0.50%, Mo :≤0.50%, Cr :≤0.60%, Nb :≤0.060%, V :≤0.040%, Ti :≤0.035%, B :≤0.0020%, Alt :≤0.050%, all the other are Fe and inevitable impurity; Impurity element in chemical composition controls: O≤0.0010%, N≤0.0080%, H≤0.0003%; Comprise following operation:

Smelt continuous casting process: desulfurizing iron pre-treatment, converter smelting, LF refining, RH vacuum-treat, continuous casting; After desulfurizing iron process, sulphur content controls at [S]≤0.002%, converter strictly controls [P] content, and LF adopts white slag operation desulfating and deoxidation, and RH vacuumizes process and strictly controls gas content; Continuous casting controls tundish temperature liquidus line+5 ~ 35 DEG C;

Curling furnaceman's skill: curling furnace temperature controls at 750 ~ 950 DEG C;

Rolling technology: adopt Controlled Rolling And Controlled Cooling, continuous blank heating temperature is 1160 DEG C ~ 1250 DEG C, steel plate thickness≤30mm when curling stove is rolled, steel billet temperature >=900 DEG C when entering curling stove rolling first, finishing temperature is 780 ~ 950 DEG C, and throwing steel speed is 0.5 ~ 3.0m/s;

Cooling control technology: roll rear controlled cooling model, controlling cold rear red temperature is 450 ~ 650 DEG C, air cooling subsequently.

2. the manufacture method of Thin Specs high strength structure steel plate produced by Steckel mill according to claim 1, it is characterized in that: this manufacture method can comprise following heat treatment step:

Steel plate is heated between 450 ~ 600 DEG C, carries out tempering heat treatment, and tempering time controls at (1.0 ~ 3.0) min/mm × thickness of slab+10min.