CN102051525A - Method for producing steel plate used for Q420qE bridge at low cost - Google Patents

Abstract

The invention relates to a method for producing a steel plate used for a Q420qE bridge at cost, which belongs to the technical field of structural steel for bridges. The steel plate comprises the following components by weight percent: 0.14% to 0.17% of C, 0.20% to 0.50% of Si, 1.40% to 1.60% of Mn, 0.035% to 0.05% of Nb, 0.005% to 0.02% of Ti, smaller than or equal to 0.005% of S, smaller than or equal to 0.02% of P, 0.020% to 0.06% of Als and the balance of Fe and unavoidable impurities. The technological process for producing the steel plate is as follows: blast furnace hot metal, pre-desulfurization of hot metal, smelting by a converter, LF and RH refining, continuous casting of sheet billets, heating of plate blanks, rolling by a 4300 mill, ACC quick cooling, cooling in pile, flaw detection, sampling and inspecting of finished products, warehousing and delivery. The method has the advantages that the production cost is reduced and each property meets the requirements of national standards.

Description

A kind of low-cost Q420qE bridge production method of steel plate

Technical field

The invention belongs to the structural steel for bridge technical field, particularly a kind of low-cost Q420qE bridge adopts TMCP explained hereafter other bridge steel of the thick Q420qE level of 10-40mm cheaply with the production method of steel plate.

Background technology

Basic traffic facilities fast developments such as current China Express Railway, traffic over strait, the steel structure bridge span increases, load increases, the user has all had bigger variation to steel structure bridge with requirements such as the kind of steel plate, quality, services: propose steel plate and will have higher strength and toughness, good fracture and aging performance also will have welding property, fatigue property and resistance to atmospheric corrosion etc. preferably.Bridge also progressively is upgraded to 420MPa and above rank by the low-alloy bridge plate of 345 ~ 370MPa gradually with the yield strength of steel, has high-strong toughness, easily welding and the high-performance Bridge Steel of atmospheric corrosion resistance also begin to use.

Be subjected to national economy to stimulate pulling, more than 50 bridge of the whole nation newly-built large bridge of plan in 2010, annual plate of moderate thickness demand is estimated to reach about 3,000,000 tons, and the service bridge beam slab is estimated more than 1,000,000 tons.Though mainly use Q345qC/D/E, Q370qC/D/E series, high-end Q420q begins short run to be adopted.Price competition is more and more fierce, must control production cost on the basis of stabilized product quality, brings into play the tooling device ability as much as possible, the high-quality economical Bridge Steel of developing low-cost.

Along with China's microalloying and controlled rolling and controlled cooling broad application, the production of Bridges in Our Country steel is developed rapidly.But when other steel grade of production higher intensity level Q420q, need to add microalloy elements such as Nb, V, Ti usually in steel at present, and other improves along with the steel strength level, the consumption of ton steel interalloy element also increases thereupon.For reducing the alloy content in traditional Nb-V-Ti combined microalloying Q420q steel, utilize refined crystalline strengthening and precipitation strength mechanism, produce and do not add microalloy element V, the Q420qE steel plate of low Nb, Ti content, by adopting rational cooling controlling and rolling controlling process, make steel plate obtain good metallographic structure and mechanical property, thereby reduce production costs.

Summary of the invention

The object of the present invention is to provide the production method of a kind of low-cost Q420qE bridge with steel plate, mainly is based on continuously cast bloom, handles by rational controlled rolling and technology for controlled cooling, produces the following Q420qE steel plate of 10-40mm.Reduced production cost, every performance satisfies the GB requirement simultaneously.

10-40mm Q420qE steel plate composition by weight percentage is designed to:

C:0.14～0.17%, Si:0.20～0.50%, Mn:1.40～1.60%, Nb:0.035～0.05%, Ti:0.005～0.02%, S :≤0.005%, P≤0.02%, Als:0.020～0.06%, surplus is Fe and unavoidable impurities.

The technical process of producing is: blast-melted → molten iron pre-desulfurization → converter smelting → LF+RH refining → sheet billet continuous casting → strand cleaning → slab heats → 4300 mill millings → ACC and cools off fast → and cooling in heap → flaw detection → finished product sampling, check → warehouse-in, shipping; The following technical parameter of control in rolling technology:

(1) presses above chemical composition design and technical process smelting 220,250,320mm heavy slab, the bar plate heating stove of packing into after clear inspection heats, Heating temperature is 1150～1210 ℃, heat-up time 230-430min, come out of the stove after high-pressure water descaling (high pressure water pressure is 19MPa) enters mill milling then.

(2) finished product thickness 10mm～19mm steel plate roughing start rolling temperature is controlled at 1000～1150 ℃, treats that temperature thickness is 2 times of Finished Steel plate thickness; The finish rolling start rolling temperature is controlled at 910～930 ℃, and finish to gauge surface of steel plate temperature is controlled at 790～830 ℃.

Finished product thickness 20mm～40mm steel plate roughing start rolling temperature is controlled at 1000～1150 ℃, treats that temperature thickness is 2 times of Finished Steel plate thickness; The finish rolling start rolling temperature is controlled at 900～920 ℃, and finish to gauge surface of steel plate temperature is controlled at 790～830 ℃.

(3) steel plate adopts the laminar flow cooling.Finished product thickness 10mm～19mm steel plate begins to cool down temperature 800-820 ℃, sets 570～590 ℃ of final cooling temperatures, sets 15～18 ℃/s of cooling rate; Finished product thickness 20mm～40mm steel plate begins to cool down temperature 800-820 ℃, sets 550～570 ℃ of final cooling temperatures, sets 16～19 ℃/s of cooling rate.

(4) finished product thickness is greater than 30mm steel plate cooling back stacking slow cooling, cooling in heap time 〉=24 hour.

The Q420qE bridge steel that the present invention produces only adds micro-Nb, Ti alloy, improves performance by strong water-cooled, reduces production costs; Can produce thickness is 10～40mm; Adopt with continuously cast bloom, TMCP explained hereafter, over-all properties satisfies GB GB/T714-2008 requirement, and stable performance: yield strength 430-480MPa, tensile strength 545-594MPa, elongation after fracture 20.5-30%,-40 ℃ of summers are more vertical on average more than 170J than impact absorbing energy, and cold-bending property is good.

Embodiment

According to the chemical ingredients scope that the invention provides scheme, according to above-mentioned technical process, in converter, smelt 220mm * 1800 * L, 250mm * 2000 * L, 250mm * 2400 * L continuously cast bloom, difference rolling 16mm, 24mm, 28mm, 32mm, 36mm, 40mm steel plate on wide and heavy plate mill, its chemical ingredients sees Table 1, rolling and water-cooling process parameter sees Table 2 and table 3, and the performance situation sees Table 4.

The chemical ingredients of table 1 steel plate (weight, %)

The heating of table 2 steel plate, water-cooling process parameter

Specification/mm	?	Tapping temperature ℃	Heat-up time min	Final cooling temperature ℃	Water-cooled speed ℃/s
						16?	Average	1202?	324?	584?	16.6?
?	Fluctuation range	1159-1233?	233-401?	472-630?	15.8-17.7?
						24?	Average	1206?	415?	489?	17.4?
?	Fluctuation range	1191-1215?	323-431?	411-588?	16.2-18.78?
						28?	Average	1191?	391?	565?	17.9?
?	Fluctuation range	1174-1208?	286-437?	545-575?	16.2-18.6?
						32?	Average	1200?	396?	548?	17.15?
?	Fluctuation range	1197-1203?	381-411?	535-561?	16.5-18.79?
						36?	Average	1205?	395?	596?	17?

?	Fluctuation range	1189-1214?	350-428?	522-632?	16.6-18.1?
						40?	Average	1204?	421?	591?	17.5?
?	Fluctuation range	1198-1211?	346-435?	524-624?	16.2-18.1?

The rolling technological parameter of table 3 trial-production steel plate

The mechanical property of table 4 trial-production steel plate

Claims (2)

1. the production method of a low-cost Q420qE bridge usefulness steel plate is characterized in that,

10-40mm Q420qE steel plate composition by weight percentage is designed to: C:0.14～0.17%, Si:0.20～0.50%, Mn:1.40～1.60%, Nb:0.035～0.05%, Ti:0.005～0.02%, S :≤0.005%, P≤0.02%, Als:0.020～0.06%, surplus are Fe and unavoidable impurities;

The technical process of producing is: blast-melted → molten iron pre-desulfurization → converter smelting → LF+RH refining → sheet billet continuous casting → strand cleaning → slab heats → 4300 mill millings → ACC and cools off fast → and cooling in heap → flaw detection → finished product sampling, check → warehouse-in, shipping; The following technical parameter of control in rolling technology:

(1) presses above chemical composition design and technical process smelting 220,250,320mm heavy slab, the bar plate heating stove heating of after clear inspection, packing into, Heating temperature is 1150～1210 ℃, heat-up time 230-430min, come out of the stove after high-pressure water descaling enters mill milling then;

(2) finished product thickness 10mm～19mm steel plate roughing start rolling temperature is controlled at 1000～1150 ℃, treats that temperature thickness is 2 times of Finished Steel plate thickness; The finish rolling start rolling temperature is controlled at 910～930 ℃, and finish to gauge surface of steel plate temperature is controlled at 790～830 ℃;

Finished product thickness 20mm～40mm steel plate roughing start rolling temperature is controlled at 1000～1150 ℃, treats that temperature thickness is 2 times of Finished Steel plate thickness; The finish rolling start rolling temperature is controlled at 900～920 ℃, and finish to gauge surface of steel plate temperature is controlled at 790～830 ℃;

(3) steel plate adopts the laminar flow cooling: finished product thickness 10mm～19mm steel plate begins to cool down temperature 800-820 ℃, sets 570～590 ℃ of final cooling temperatures, sets 15～18 ℃/s of cooling rate; Finished product thickness 20mm～40mm steel plate begins to cool down temperature 800-820 ℃, sets 550～570 ℃ of final cooling temperatures, sets 16～19 ℃/s of cooling rate;

(4) finished product thickness is greater than 30mm steel plate cooling back stacking slow cooling, cooling in heap time 〉=24 hour.

2. method according to claim 1 is characterized in that, the high pressure water pressure of high-pressure water descaling is 19MPa.