CN103361573A

CN103361573A - 420MPa grade vanadium-containing nitrogen steel and production method thereof

Info

Publication number: CN103361573A
Application number: CN201210092226XA
Authority: CN
Inventors: ***; 赵坦; 李广龙; 原思宇; 高冰; 郭晓波; 王军生; 钟莉莉; 李宏杰
Original assignee: Angang Steel Co Ltd
Current assignee: Angang Steel Co Ltd
Priority date: 2012-03-30
Filing date: 2012-03-30
Publication date: 2013-10-23

Abstract

The invention discloses 420MPa grade vanadium-containing nitrogen steel and a production method thereof. The 420MPa grade vanadium-containing nitrogen steel comprises the following components in percentage by weight: 0.04-0.07% of C, 0.30-0.50% of Si, 1.50-1.70% of Mn, 0.30-0.50% of Cu, 0.10-0.30% of Ni, 0.20-0.40% of Cr, 0.04-0.06% of V, 0.012-0.014% of N, 0.02-0.04% of Al and the balance of Fe and inevitable impurities. The production method comprises the following steps of: beginning to blow nitrogen into a vacuum melting furnace after the end of refining, and controlling the pressure of the nitrogen at 550-560Pa; controlling the heating temperature at 1050-1100 DEG C before rolling, performing heat preservation for 100-110min, controlling the initial rolling temperature of a slab at 1000-1050 DEG C, and repeatedly rolling to the target thickness; and controlling the initial cooling temperature at 700-800 DEG C, controlling the cooling speed at 10-20 DEG C/s, and controlling the self-tempering temperature at 450-550 DEG C.

Description

A kind of 420MPa level aluminiferous nitrogen steel and production method thereof

Technical field

The invention belongs to metal structure steel technical field, specially refer to a kind of 420MPa level aluminiferous nitrogen steel and production method thereof.

Background technology

Along with society and expanding economy, more and more higher in use load-carrying of steel, antidetonation, anti-corrosion etc. performance requriements, thereby, require steel excellent intensity and toughness, good weldability, low yield tensile ratio not only will be arranged guaranteeing break resistance under the large load, and good atmospheric corrosion resistance will be arranged to improve work-ing life and the security of member.

The publication number CN101760704A of Ma'anshan Iron and Steel Co., Ltd's application, " a kind of aluminiferous nitrogen is economical high-strength and high-weather-resistance hot rolled H-shaped with steel and rolling method thereof " patent, obtained high strength, high tenacity and the high-weatherability that the method is produced hot rolled H-shaped, but its carbon containing is up to 0.12%, will reduce the welding use properties of material.

" middle silicon-vanadium-nitrogen microalloyed medium carbon steel " patent of Ma'anshan Iron and Steel Co., Ltd's application, its number of patent application is: 200510039213.6, the steel product cost that utilizes this patent to produce is lower, but the higher C:0.37 of its carbon content～0.44%, must cause its welding property lower, and lack necessary alloying element, so that the weather resistance of steel is relatively poor, the use range of steel is narrower.

" a kind of manufacture method of 460 MPa grade yield strength low-alloy high-tensile structural steel sheet material " patent of Northeastern University's application, its number of patent application is: 03134046.6, the 460MPa level structure steel plate that utilizes this technology to produce, be added with Nb:0.01～0.02%, increase steel-making cost, also may have the casting blank cleavage phenomenon to occur; C:0.13～0.20% must reduce toughness and the impact property of steel; 1200～1250 ℃ of Heating temperatures, the energy amount of disappearing consumption is larger; Finishing temperature is lower, and is higher to the Capability Requirement of milling train between 780～820 ℃, affects rhythm of production and production efficiency.

" having the high-yield strength non-quenched and tempered steel plate " Chinese patent of Amada Co., Ltd.'s Kobe Steel, Ltd application, its number of patent application is: 200610092574.1, utilize the steel plate that bridge structure is used that can be used as of this technology production, its yield strength can reach about 450～500MPa, but because it contains higher Nb, Ti, Ni element, weight percent is respectively 0.06,0.03,0.8, not only increase ton steel cost, return continuous casting production and bring very large technical difficulty, be unfavorable for the production of large industrialization continuous casting, and superfluous Ti can cause the reduction of impelling strength;

By above contrast patent as can be known, there is following deficiency in structural steel at present: 1, carbon content is higher, reduces toughness and the welding property of steel; 2, contain higher Ni, Nb, Ti alloying element, production cost is higher; 3, low-temperature impact toughness is lower, so that the safety in utilization of steel plate cold district reduces.

Summary of the invention

In order to overcome the shortcoming of above-mentioned prior art, the purpose of this invention is to provide that a kind of composition is reasonable, technique is simple, low cost, high-corrosion resistance, lower welding preheating requirement and the Structural Steel Plate of high-yield strength, its yield strength has reached 420MPa, do not contain Nb element, less Ni element, and have good impact property.

The present invention is with lower C content, cancellation Nb, interpolation V, N element are essential characteristic, in the present invention, the content of its chemical composition (Wt%): C0.04%～0.07%, Si0.30%～0.50%, Mn1.50%～1.70%, Cu0.30%～0.50%, Ni0.10%～0.30%, Cr0.20%～0.40%, V0.04%～0.06%, N0.012%～0.014%, Al0.02%～0.04%, all the other are Fe and inevitable impurity.

So the present invention selects above alloying element kind and content thereof to be: C: carbon affects very large on intensity, toughness, welding property.Carbon too low strength does not reach target call, and carbon is higher than 0.11%, makes extension, toughness drop.The present invention determines optimal content 0.04～0.07%;

Si: silicon is the bioelement of deoxidation in steel making.The effect that also has certain solution strengthening.In order to obtain the degree of cleaning of sufficient deoxidation effect and raising steel, the content range of silicon of the present invention is 0.30～0.50%;

Mn: manganese is the principal element that improves intensity and toughness, and cost is very cheap, is main adding elements of the present invention, and content is limited to 1.50～1.70%;

Al: aluminium is deoxidant element, can be used as the AlN forming element, and crystal grain thinning effectively is for the scope that reaches good deoxidation effect Al content of the present invention is Al0.02～0.04%;

Cu: copper not only on welded heat affecting zone hardening and not impact of toughness, can make again the intensity of mother metal improve, and low-temperature flexibility is improved greatly, can also improve especially the corrosion resistance nature of American Standard Bridge Steel.But the copper too high levels easily cracks or makes surface quality to worsen when heating or hot rolling, must add an amount of Cu to stop the generation of crackle, and in the present invention, the content of Cu is controlled at 0.30～0.45%;

Ni: nickel is on welded heat affecting zone hardening and not impact of toughness, the intensity of mother metal is improved, and low-temperature flexibility is improved greatly, but its expensive price can cause the cost of steel to improve significantly, and the purpose of adding nickel element mainly is the tendency that stops the high steel billet of copper content to crack when heating or hot rolling, therefore among the present invention, the content of Ni is controlled at 0.10～0.30%;

Cr can enlarge ferrite area, improves quench hardening, corrosion proof advantage, therefore added Cr among the present invention, its content is 0.20～0.40%;

V and C, N have extremely strong avidity, form stable V (C, N) compound, improve the hardness of steel.The compound of disperse can crystal grain thinning, improves the Coarsening Temperature of crystal grain; With the displacement solute atoms when existing, V atomic ratio iron atom size is large in steel for V, and easily segregation on dislocation line produces strong effect of dragging to climb of dislocation, Recrystallization nucleation is suppressed, thereby recrystallize is had strong interception; V can form phase in the middle of the gaps such as VC or VN in steel, in recrystallization process, because of VC, VN is to anchoring of dislocation and to effects such as the migration of subgrain boundary stop, thereby greatly increased the time of recrystallize, when being higher than critical temperature, V element shows as the solute drag mechanism to the effect of recrystallize, and when being lower than critical temperature, then show as and separate out pinning mechanism, the characteristics of V in steel improve austenitic recrystallization temperature exactly, thereby reach the purpose of refine austenite crystal grain, V (C, N) promote the ferritic formation of intracrystalline separating out of HAZ, make ferrite and pearlite be evenly distributed on intracrystalline and crystal boundary, thereby improve the toughness of heat affected zone, be conducive to the raising of welding property, content of vanadium is 0.04～0.06% among the present invention;

Nitrogen forms special nitride as easy as rolling off a log the combination with V, Al of interstitial atom, adds N in the V steel, can improve the Precipitation Temperature of carbonitride in austenite of V, and N content is 0.012～0.014% among the present invention;

Impurity element P≤0.020% in the steel, S≤0.005% is to reduce the deleterious effect of impurity element.

The used production technique of production yield strength 420MPa aluminiferous nitrogen steel of the present invention comprises smelting, controlled rolling and control cooling.Its feature is as follows: in the smelting process, refining begins to be blown into nitrogen in vacuum melting furnace after finishing, and the pressure-controlling of nitrogen is at 550-560Pa; Heating and temperature control before rolling 1050～1100 ℃ to guarantee tiny austenite crystal, be incubated 100～110 minutes, play the effect of rolling rear crystal grain thinning when making the austenite homogenizing.The slab start rolling temperature is controlled between 1000～1050 ℃, arrives target thickness through repeat-rolling; Open cold temperature between 700～800 ℃, speed of cooling is between 10～20 ℃/s, and red temperature obtains bainite structure at last between 450～550 ℃.

Bridge steel plate by such scheme production has following beneficial effect: 1, the yield strength fluctuation range is 420～515MPa, and the TMCP hot-rolled state can be delivered goods; 2 ,-20 ℃ impact is greater than 150J, corrosion resistance index I 〉=6.0, and the steel use range is wide; 3, add lower-cost V, N element in the chemical composition.

Description of drawings

Fig. 1 is the Typical Bainite organization chart of the embodiment of the invention 4.

Embodiment

Following examples only are some optimum embodiments of the present invention, aforementioned invention scope and technique means are not had any restriction.

The present invention takes the 200Kg vacuum induction furnace to smelt, refining begins to be blown into nitrogen in vacuum melting furnace after finishing, the pressure-controlling of nitrogen is at 558Pa, smelt the steel ingot that is cast into 65Kg after finishing, be rolled at the 500mm Experimental Rolling Mill for Plate, the heating and temperature control before rolling is at 1080 ℃, to guarantee tiny austenite crystal, be incubated 110 minutes, then coming out of the stove is rolled.

Chemical composition of the present invention and production technique: its steel ingot is smelted into composition as shown in table 1, rolling technological parameter such as table 2, and object performance will reach result as shown in table 3.

Each embodiment smelting component of table 1, Wt%

Each embodiment processing parameter of table 2

Numbering	Thickness mm	Heating temperature ℃	Start rolling temperature ℃	Open cold temperature ℃	Red temperature ℃
						1#	20	1080	1050	752	490
2#	20	1080	1050	740	470
						3#	20	1080	1050	742	460
4#	15	1080	1035	732	525
						5#	15	1080	1040	730	530

Each embodiment object performance of table 3

Claims

1. a 420MPa level aluminiferous nitrogen steel and production method thereof, the content that it is characterized in that its chemical composition is C0.04～0.07, Si0.30～0.50, Mn1.50～1.70, Cu0.30～0.50, Ni0.10～0.30, Cr0.20～0.40, V0.04～0.06, N0.012～0.014, Al0.02～0.04 by weight percentage, and all the other are Fe and inevitable impurity.

2. the production method of a 420MPa level aluminiferous nitrogen steel according to claim 1, comprise smelting, controlled rolling and control cooling, it is characterized in that in the described smelting process, refining begins to be blown into nitrogen in vacuum melting furnace after finishing, and the pressure-controlling of nitrogen is at 550-560Pa; Heating and temperature control before rolling is incubated 100～110 minutes at 1050～1100 ℃; The slab start rolling temperature is controlled between 1000～1050 ℃, arrives target thickness through repeat-rolling; Open cold temperature between 700～800 ℃, speed of cooling is between 10～20 ℃/s, and red temperature is between 450～550 ℃.