CN102851604A

CN102851604A - Production method of high-strength steel plate with yield strength of 690MPa

Info

Publication number: CN102851604A
Application number: CN2012103659007A
Authority: CN
Inventors: 杨雄; 路璐; 高志国; 刘莉; 王海明; 张辉; 康利明
Original assignee: Baotou Iron and Steel Group Co Ltd
Current assignee: Baotou Iron and Steel Group Co Ltd; Inner Mongolia Baotou Steel Union Co Ltd
Priority date: 2012-09-22
Filing date: 2012-09-22
Publication date: 2013-01-02

Abstract

The invention provides a production method of a high-strength steel plate with yield strength of 690MPa. The steel plate consists of the following chemical components in percentage by weight: 0.04-0.09 percent of C, 0.25-0.50 percent of Si, 1.4-1.7 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.010 percent of S, less than or equal to 0.45 percent of Cr, less than or equal to 0.20 percent of Mo, 0.04-0.05 percent of Nb, 0.05-0.07 percent of V, 0.005-0.020 percent of Ti, 0.0005-0.0025 percent of B and the balance of Fe and inevitable impurities. A low-carbon micro-alloying design is adopted, and an integrated tissue consisting of annealed martensite and annealed bainite is obtained through online quenching (DQ) and tempering processes (T) after rolling, so that good matching among strength, plasticity and toughness is realized, the production cost is reduced simultaneously, and the production efficiency is increased.

Description

A kind of production method of yield strength 690MPa grade high-strength steel plate

Technical field

The invention belongs to the Hi-Stren steel field, particularly a kind of production method of high tensile steel plate of 690MPa level.

Background technology

It is generally acknowledged that yield strength is called high tensile steel plate greater than the steel plate of 345MPa.Along with engineering machinery, coal mine machinery to future developments such as equipment maximization, lightweight, heavy lifts, the high tensile steel plate consumption presents ever-increasing trend, intensity rank improves also very fast, traditional engineering machinery mainly improves intensity take solution strengthening, precipitation strength as leading with high tensile steel plate, wherein carbon and alloying element content are higher, mostly adopt the off-line modifier treatment, increased the production cost of steel enterprise.At present, a lot of Heavy Plate Rolling Lines have all been equipped ultrafast cooling system (Ultra-Fast Cooling system), such as Baosteel, Anshan iron and steel plant, Shoudu Iron and Steel Co, Laigang etc., can realize press quenching (the Direction Quench of steel plate, be called for short DQ), a new generation's controlled rolling and controlled cooling technology is widely used in steel production, realize the strengthening mechanisms such as phase transformation strengthening, refined crystalline strengthening and subgrain reinforcement by appropriate design alloying element content and controlled rolling and controlled cooling parameter, obtain the matched well of steel strength, plasticity, toughness and weldability.

Summary of the invention

The production method that the purpose of this invention is to provide a kind of high-strength high-toughness steel plate of yield strength 690MPa level.Outstanding advantage of the present invention is that slab adopts press quenching (DQ)+tempering (T) explained hereafter to go out the high-strength high-toughness steel plate of yield strength 690MPa level after controlled rolling, not only reduced production cost, has also improved production efficiency.

Technical scheme of the present invention:

The chemical ingredients of a kind of yield strength 690MPa grade high-strength of the present invention steel plate is by weight percentage

C:0.04～0.09%, Si:0.25～0.50%, Mn:1.4～1.7%, P :≤0.020%, S :≤0.010%, Cr≤0.45%, Mo≤0.20%, Nb:0.04～0.05%, V:0.05～0.07%, Ti:0.005～0.020%, B:0.0005～0.0025%, surplus are Fe and inevitable impurity.

Preparation method, main technologic parameters and the principle analysis of a kind of yield strength 690MPa grade high-strength steel plate of the present invention are as follows

1, heating and rolling:

1180～1220 ℃ of Heating temperatures, soaking time are 120～180min.Adopt the two-stage control rolling technology, namely the austenite recrystallization district is rolling rolling with austenite non-recrystallization district.When rolling in the austenite recrystallization district, start rolling temperature is 1130～1180 ℃, and the 1st～2 reduction in pass should be greater than 10%, and next has at least 1～2 percentage pass reduction to be controlled at 20～40%, in order to abundant refinement original austenite grains; When rolling in austenite non-recrystallization district, 900～950 ℃ of start rolling temperatures, the accumulation draft is greater than 60%, and finishing temperature is 810～840 ℃.

2, cooling

After controlled rolling finished, steel plate entered accelerated cooling device, and the speed of cooling above by 25 ℃/s is cooled to below 300 ℃, realizes online direct quenching.

3, tempering heat treatment

Determine that according to experimental result the optimum tempering temperature of steel plate is 500～600 ℃, soaking time is 20min+t * 2.5min/mm, and wherein t is steel plate thickness, and unit is nn.

Beneficial effect of the present invention is:

1, by low-carbon microalloyed design, reduce the noble element content such as Mo and Ni, reduced cost of alloy; Abandon traditional off-line hardening and tempering process and transferred to adopt press quenching+tempering process, reduced process cost, improved production efficiency.

2, by rational chemical composition design, and take above-mentioned technique can obtain more than a kind of yield strength 690MPa, more than the tensile strength 770MPa, unit elongation is more than 14%, and the steel plate with favorable low-temperature impact toughness and welding property.

Description of drawings

Fig. 1 is the metallographic structure figure of the embodiment of the invention 1 steel plate.

Embodiment

Below for a more detailed description to the present invention with embodiment.These embodiment only are the descriptions to best mode for carrying out the invention, scope of the present invention are not had any restriction.

Embodiment 1

Press the chemical ingredients shown in the table 1 and smelt, and be cast into steel ingot, with Heating Steel Ingots to 1220 ℃, be incubated 150 minutes, it is rolling to carry out the fs at experimental mill, and namely the austenite recrystallization district is rolling, and start rolling temperature is 1170 ℃, the 1st～2 reduction in pass should be greater than 10%, next has at least 1～2 percentage pass reduction to be controlled at 20～40%, when rolled piece thickness is 60mm, treats that at roller-way temperature is to 900 ℃, it is rolling to carry out subsequently subordinate phase, and namely austenite non-recrystallization district is rolling.The rolling purpose in austenite non-recrystallization district is in order to guarantee that it has enough deflections in the non-recrystallization district, more highdensity dislocation accumulative total is arranged, for ferrite transformation provides more favourable forming core condition in the austenite of distortion.Larger distortion also is conducive to the separating out of carboritride of Nb, because the effect that deformation inductdion is separated out, larger pass deformation rate will be conducive to the formation of precipitate and make its more tiny and disperse, simultaneously, tiny and precipitate and pinning effect thereof disperse provide highdensity forming core place and stop it to grow up and alligatoring for ferrite, and this strength and toughness for steel all plays favourable effect.Finishing temperature is controlled at the low-temperature zone in non-recrystallization district, and this humidity province is near transformation temperature Ar simultaneously ₃

Finishing temperature is 840 ℃, and finished steel plate thickness is 20mm.After the rolling end, steel plate enters and accelerates cooling (ACC) device, is cooled to 270 ℃, cold bed cooling after the water outlet with the speed of 25 ℃/s.Afterwards steel plate is carried out tempering heat treatment, 500 ℃ of tempering temperatures, soaking time are 20min+t * 2.5min/mm, and wherein t is steel plate thickness, and unit is mm.

Because steel plate has accumulated the very high dislocation of density and high strain energy in the operation of rolling, highdensity dislocation will with precipitate Nb (CN) particle interaction of Nb, finish to air cooling (relaxation) process of accelerating cooling rolling, this interaction impels at the inner in a large number tiny Polygons dislocation cell structures that form of austenite crystal, the Nb atom is separating out on the dislocation cell wall in the segregation on the dislocation wall and a large amount of fine Nb (CN), stablized this Polygons cell structure with certain misorientation.Simultaneously, the moderate finite deformation of a passage has the effect of inducing ferrite transformation, under this inducing action, and Ar ₃Point increases, so-called " strain-induced transformation " phenomenon namely appears, at the larger deflection in non-recrystallization humidity province, the intragranular nucleation that will be conducive to acicular ferrite, can make simultaneously martensite island on the bainite matrix more even dispersion that distributes, finally obtain the integrated tissue of lath-shaped bainite and martensite.

Embodiment 2

Embodiment is with embodiment 1, and wherein Heating temperature is 1200 ℃, is incubated 150 minutes, fs, rolling start rolling temperature was 1160 ℃, and rolled piece thickness is 54mm, and the rolling start rolling temperature of subordinate phase is 910 ℃, finishing temperature is 830 ℃, and finished steel plate thickness is 18mm; The steel plate speed of cooling is 25 ℃/s, and final cooling temperature is 280 ℃.Afterwards steel plate is carried out tempering heat treatment, 550 ℃ of tempering temperatures, soaking time are 20min+t * 2.5min/mm, and wherein t is steel plate thickness, and unit is mm.

Embodiment 3

Embodiment is with embodiment 1, and wherein Heating temperature is 1200 ℃, is incubated 150 minutes; Fs, rolling start rolling temperature was 1150 ℃, and rolled piece thickness is 48mm; The rolling start rolling temperature of subordinate phase is 910 ℃, and finishing temperature is 840 ℃, and finished steel plate thickness is 16mm; The steel plate speed of cooling is 27 ℃/s, and final cooling temperature is 300 ℃.Afterwards steel plate is carried out tempering heat treatment, 600 ℃ of tempering temperatures, soaking time are 20min+t * 2.5min/mm, and wherein t is steel plate thickness, and unit is mm.

The chemical ingredients of table 1 embodiment of the invention 1～3 (wt%)

Embodiment	C	Si	Mn	P	S	Cr	Mo	B	Nb	V	Ti
												1	0.078	0.25	1.70	0.007	0.007	0.38	0.12	0.0024	0.040	006	0.014
2	0.090	0.48	1.57	0.006	0.002	0.40	0.15	0.0008	0.049	0.05	0.012
												3	0.065	0.29	1.37	0.008	0.003	0.34	0.14	0.0020	0.050	0.07	0.013

Steel plate to the embodiment of the invention 1～3 carries out mechanical properties test, and assay sees Table 2.

The mechanical property of the steel plate of table 2 embodiment of the invention 1～3

Claims

1. the production method of a yield strength 690MPa grade high-strength steel plate, it is characterized in that, the chemical ingredients of described steel plate is C:0.04～0.09%, Si:0.25～0.50%, Mn:1.4～1.7%, P by weight percentage :≤0.020%, S :≤0.010%, Cr≤0.45%, Mo≤0.20%, Nb:0.04～0.05%, V:0.05～0.07%, Ti:0.005～0.020%, B:0.0005～0.0025%, surplus are Fe and inevitable impurity.

2. the production method of a yield strength 690MPa high tensile steel plate as claimed in claim 1 is characterized in that:

Smelt according to chemical ingredients claimed in claim 1, and be cast into steel ingot, the method that steel ingot is manufactured described steel plate is as follows:

1), heating and rolling:

(a), in heat-processed, Heating temperature is 1180～1220 ℃, soaking time is 120～180min;

(b), rolling: as rollingly to be divided into the fs and subordinate phase is rolling:

Fs is rolling in the austenite recrystallization district, and in the operation of rolling, start rolling temperature is 1130～1180 ℃, and the 1st～2 reduction in pass should be greater than 10%, and all the other have at least 1～2 percentage pass reduction to be controlled at 20～40%;

Subordinate phase is rolling in austenite non-recrystallization district, 900～950 ℃ of start rolling temperatures, and in the operation of rolling, the accumulation draft is greater than 60%, and finishing temperature is 810～840 ℃;

2), cooling:

In process of cooling, steel plate enters accelerated cooling device, is cooled to below 300 ℃ with the speed of 20～25 ℃/s, realizes press quenching, air cooling after the water outlet;

3), tempering heat treatment

The steel plate tempering temperature is controlled at 500～600 ℃, and soaking time is 20min+t * 2.5min/mm, and wherein t is steel plate thickness, and unit is mm.