CN104073721B - Angle steel and production method for steel tower that a kind of ductile-brittle transition temperature is low - Google Patents

Abstract

The steel tower angle steel that ductile-brittle transition temperature is low, its component and wt% are: C:0.10～0.15%, Si:0.5～0.8%, Mn:1.3～1.6%, P≤0.015%, S≤0.015%, Ti:0.01～0.03%, V:0.03～0.06%, N≤0.005%, Nb:0.025～0.05%, Ca:0.001～0.007%, B:0.001～0.002%, lanthanide series: 0.001～0.005%, Als:0.015～0.035%; Production stage: conventional smelting and strand; Strand nature stacking is cooled to room temperature; Strand is heated; Roughing; Finish rolling; Natural air cooling is stand-by to room temperature. Angle steel ductile-brittle transition temperature of the present invention is low, transition temperature, below-50 DEG C, meets the use in any region of China completely, and mechanical property meets the requirement of GB Q420, excellent surface quality, in the situation that can produce in enormous quantities without transformation in existing weaponry and equipment.

Description

Angle steel and production method for steel tower that a kind of ductile-brittle transition temperature is low

Technical field

The present invention relates to a kind of high strength steel tower angle steel and production method thereof, specifically belong to a kind of ductile-brittle transition temperature lowAngle steel its production method for steel tower.

Background technology

Electric power pylon is mainly used in electric power pylon construction with high-strength angle steel. Conventionally by timber structure, reinforced concrete structureOr the rod shaped structure of steel pole structure is called bar, the pyramidal structure of steel is called tower. Transmission tower is the built on stilts power line conductive of supportingLine and ground wire, and make between them and and the earth between distance under various possible atmospheric environments, meet electric insulationThe rod of safety and power frequency electromagnetic field restriction and the structures of turriform. Along with lead high pressure, UHV transmission line and heavy in sectionThe construction of line transmission line of electricity, electric power pylon, to large load, large member future development, makes before the application of the high-strength angle steel matchingScape is very wide. Adopt high-strength angle steel can reduce member section, reduce steel using amount, save engineering cost, can also reduce structureDeadweight, can reduce tower weight 4%～6% for tangent tower, and angle tower can reduce tower weight 4%～7%, and overall tower weight can reduce approximately 5%.This is significant to transmission line construction.

Along with economic great development, trans-regional power transmission becomes a kind of trend. It is huge that this just exists variations in temperature, just as meState, south is very large with the high Mountain area in the north and plateau extreme temperature in winter difference, and even can in the high Mountain area in the north and plateauLower than-40 DEG C, this is to transmission of electricity steel tower, and the resistance to low temperature of angle steel used is a huge test. If steel tower is used angleSteel Yin Wendu is low and cause that brittle failure will have a strong impact on people's life and industrial production. Therefore, develop a kind of low-temperature impact-resistantHigh-strength corner iron there is important economic and social benefit

Chinese Patent Application No. is the patent documentation of CN200910073969.0, discloses a kind of high-strength Q 420 C level steel towerAngle steel, its chemical composition proportioning is: C0.10～0.16%, Mn1.15～1.45%, Si0.30～0.50%, S, P≤0.025%, V0.070～0.100%, Ti0.004～0.010%, surplus Fe, Ceq≤0.42%. The document exists notFoot is only to have proposed the impact flexibility requirement of 0 DEG C, and toughness is lower, illustrates that its ductile-brittle transition temperature is very high ,-10 DEG C of left and right,The severe cold area that can not meet under lower temperature is used.

Chinese Patent Application No. is the patent documentation of CN201310441360.0, discloses a kind of electric power pylon with low temperature resistantImpact angle steel, the percentage by weight of described angle steel chemical composition is: C:0.05～0.15%, and Mn:1.20～1.60%, Si:0.01～0.05％，V：0.02～0.10％，Ni：0.02～0.06％，Ca：0.001～0.005％，Cr：0.01～0.20%, Cu:0.10～0.25%, P:0.01～0.03%, Mo:0.20～0.35%, S:0.005～0.02%, all the other areFe. Its ductile-brittle transition temperature is lower than-50 DEG C, but its yield strength is low, can not meet the use of high-level large specification power transmission tower.

Chinese Patent Application No. is the patent documentation of CN201210135125.6, discloses a kind of anti-severe cold high-strength hot-rolledAngle steel, its component and weight percent content: C:0.06%～0.20%, Si:0.20%～0.50%, Mn:1.10%～1.50%, P≤ 0.015%, S≤0.010%, V:0.030%～0.070%, Nb:0.015%～0.050%, Ni:0.10%～0.60%, and meetCEV=C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15≤0.40%; Its yield strength is greater than 550MPa, tensile strength >=680MPa, elongation after fracture >=24%, ballistic work >=55J at-40 DEG C. Its ballistic work all exceedes 55J in the time of-40 DEG C, but tough crisp turningTemperature is-42 DEG C, and ductile-brittle transition temperature temperature surplus is too little, can not use in extreme condition.

Summary of the invention

The present invention is directed to the deficiency that above-mentioned prior art exists, provide a kind of and ensureing that its mechanical property meets GB Q420The prerequisite of requirement under, low angle steel and the production method for steel tower of ductile-brittle transition temperature of ductile-brittle transition temperature <-50 DEG C.

Realize the measure of above-mentioned purpose:

The steel tower angle steel that ductile-brittle transition temperature is low, its component and weight percent content are: C:0.10～0.15%、Si：0.5～0.8%、Mn：1.3～1.6%、P≦0.015%、S≦0.015%、Ti：0.01～0.03%、V：0.03～0.06%, N≤0.005%, Nb:0.025～0.05%, Ca:0.001～0.007%, B:0.001～0.002%, lanthanide series:0.001～0.005%, Als:0.015～0.035%, all the other are Fe and inevitable impurity element.

Produce the method for the angle steel that a kind of ductile-brittle transition temperature is low, its step:

1) conventional smelting and strand, controls tapping temperature at 1670～1700 DEG C, and middle Baogang coolant-temperature gage is controlled at steel grade liquidAbove 20～30 DEG C of phase temperature line, Casting speed is not higher than 1.8m/min;

2) strand is carried out to nature stacking and be cooled to room temperature;

3), to strand heating, control soaking zone temperature is: 1033～1133 DEG C, the heat time is at 103 ~ 123min;

4) carry out roughing, and control its start rolling temperature and exist: 983～1083 DEG C;

5) carry out finish rolling, control its finishing temperature 788 ~ 858 DEG C of scopes;

6) natural air cooling is stand-by to room temperature.

The effect of each element and master operation in the present invention

C: be to expand and stable austenite element, improve the most effective element of steel strength, also can improve the height of heat resisting steelTemperature intensity, but when its content is lower than 0.10% time, thus can cause that mechanical property is not enough and increase alloy addition level has increased lifeProduce cost, when its content is high by 0.15%, can produce plasticity and toughness and decline, especially impact flexibility obviously declines, and improves that it is tough crispTransition temperature, therefore, C of the present invention is chosen in 0.10 ~ 0.15%.

Si: be a kind of displacement intensified element of cheapness, can significantly improve the intensity of steel, yield strength, but Si can be tightHeavily damage the low-temperature flexibility of steel, improve ductile-brittle transition temperature, thus should not be too high, select the scope of Si 0.5～0.8%.

Mn: be mainly the intensity that solid solution improves material in ferrite, it is again good deoxidier and desulfurizing agent, containsThe fragility causing because of sulphur can be eliminated or weaken to a certain amount of manganese, thereby improve the processing characteristics of steel, but meeting when manganese too high levelsMake the tendency of grain coarsening, continuous casting and cooling control after rolling did not easily produce white point at that time, thus select the scope of Mn 1.3～1.6%。

P, S: as harmful element, its content is more low better. S too high levels, can form a large amount of MnS and be mingled with, and reduces steelThe mechanical performance of material, therefore content is more low better, so select scope ≤0.025% of S; P, easily at cyrystal boundary segregation, increases steelFragility, low temperature impact properties is declined to a great extent, therefore content is more low better, so select scope ≤0.025% of P.

B: add the boron of minute quantity can significantly affect the performance of material in steel, it suppresses P, S segregation and ruptures along brilliant, carriesHigh impact property, improves form and the distribution of field trash, and boron dissolves in solid solution crystal lattice is distorted, the boron on crystal boundaryCan stop again field trash further to be grown up, make field trash become tiny, rounding, is uniformly distributed in crystal boundary, has strengthened crystal boundary, makes materialThe toughness of material improves. In the time that the content of boron is greater than 0.003%, it no longer increases with the increase of content the effect of steel, increases on the contraryAdded cost, the content of boron is controlled at 0.001～0.002% scope.

Ti: be a kind of strong carbide and nitride forming element, easily form the tiny particle such as TiC and TiN, TiCHighly stable with TiN, effectively pinning crystal boundary, crystal grain thinning, and there is the stable effect of the tissue of heating again. On a small quantityTi just can make the intensity of steel and low-temperature flexibility improve, and in the time of the too high levels of Ti, forms thick carbonitride, on the contraryImpact property to steel is bad, improves ductile-brittle transition temperature, therefore the scope of Ti is 0.01～0.03%

Nb: be strong carbide section bar element, Austenite Grain Growth can suppress hot rolling time, thinning microstructure, raising steelComprehensive mechanical property, but Nb too high levels easily makes precipitated phase thick and weaken precipitating reinforcing effect, and can significantly increase cost.Range of choice Nb is 0.025～0.05%.

V: be micro alloyed steel the most frequently used be also one of the most effective intensified element. The effect of vanadium is by forming VN, V(CN) affect tissue and the performance of steel, it is mainly Precipitation in the ferrite of austenite grain boundary, refinement ferrite crystalline substanceGrain, thereby intensity and the low-temperature flexibility of raising material. V is lower than 0.03% time, and precipitating reinforcing effect can not meet mechanical property to be wantedAsk, V is higher than 0.05% time, and precipitation strength makes intensity too high and cause toughness variation.

Al: be to determine nitrogen agent as the deoxidation in when steel-making, the N in Al and steel forms tiny indissoluble AlN particle, plays and prevents workWith, and then refinement ferrite crystal grain, Al content is too low, and refining effect is not obvious, and Al too high levels has reduced flowing of molten steelProperty, form a large amount of Al₂O₃Understand at nozzle clogging, thereby block the mouth of a river, so select the scope of Al 0.015～0.035%.

Ca: can cleaning molten steel, improve the degree of purity of steel, make the MnS nodularization of steel, the potential of performance material, its content mistakeGao Shi, easily forms thick non-metallic inclusion, so range of choice is 0.001～0.007%.

Lanthanide series: in this application, purify crystal boundary and rotten field trash by it, by improving the intensity of crystal boundary, reduceThe possibility that crackle is expanded by the perforation of defect, thus while making material withstand shocks load, can absorb more Crack ExtensionEnergy, and then make the application ductile-brittle transition temperature reduce. But its content, as higher than 0.005%, will weaken crystal boundary, shapeBecome crisp hard phosphide, iron-rare earth intermetallic compound etc., thereby worsen the impact property of material, and to reducing ductile-brittle transitonTemperature is unfavorable. So be chosen in 0.001～0.005% scope.

Why adopt start rolling temperature to exist: 1000～1100 DEG C, finish rolling finishing temperature is the scope of 820～880 DEG C,Object is that finishing temperature more approaches phase transition temperature, and the original austenite grains of steel billet is less, makes to roll accordingly by rolling deformationThe austenite crystal that system ends is also less, thereby makes crystal grain obtain refinement, and combination property improves, be also conducive to simultaneously vanadium,The precipitate of niobium is separated out more tiny and disperse.

Compared with prior art, its angle steel ductile-brittle transition temperature is low in the present invention, and transition temperature is below-50 DEG C, completely fullFoot is in the use in any region of China, and mechanical property meets the requirement of GB Q420, and excellent surface quality, in existing weaponry and equipmentIn situation without transformation, can produce in enormous quantities.

Brief description of the drawings

Accompanying drawing is impact fracture shape appearance figure of the present invention;

Impact microfracture surface of the present invention such as is all at the axle dimple shape on whole section, and large and dark dimple distributes more equalEven and quantity is also more, also have little dimple in large dimple the inside, demonstrate steel and there is higher toughness.

Detailed description of the invention

Below the present invention is described in detail:

Table 1 is the value list of various embodiments of the present invention and comparative example;

Table 2 is the main technologic parameters list of various embodiments of the present invention and comparative example;

Table 3 is various embodiments of the present invention and the list of comparative example Performance Detection situation.

Various embodiments of the present invention are produced according to following steps:

1) conventional smelting and strand, controls tapping temperature at 1670～1700 DEG C, and middle Baogang coolant-temperature gage is controlled at steel grade liquidAbove 20～30 DEG C of phase temperature line, Casting speed is not higher than 1.8m/min;

2) strand is carried out to nature stacking and be cooled to room temperature;

3), to strand heating, control soaking zone temperature is: 1033～1133 DEG C, the heat time is at 103 ~ 123min;

4) carry out roughing, and control its start rolling temperature and exist: 983～1083 DEG C;

5) carry out finish rolling, control its finishing temperature 788 ~ 858 DEG C of scopes;

6) natural air cooling is stand-by to room temperature.

It should be noted that the application forbids to water to surface after strand carries out nature stacking cooling stage and finish rolling.

The thickness specification that below test is produced is at 16 ~ 35mm.

The chemical composition list (wt%) of table 1 embodiment of the present invention and comparative example

The main technologic parameters list of table 2 various embodiments of the present invention and comparative example

Note: the reference liquidus temperature of steel grade of the present invention is 1505 DEG C

The mechanical property contrast list of table 3 various embodiments of the present invention and comparative example

As can be seen from Table 3, at normal temperatures, mechanical property of the present invention can be suitable with the rigidity of producing at present, but tough crispTransition temperature is lower, below-50 DEG C, illustrates that the low-temperature flexibility of steel of the present invention will greatly good and common contrast angle steel, completeOne-tenth can meet at China's any one location builds the requirement that electric power pylon uses in the winter time.

Above-described embodiment only exemplifies for the best, and is not the restriction to embodiments of the present invention.

Claims (2)

1. the high strength steel tower angle steel that ductile-brittle transition temperature is low, its chemical composition is by weight: C:0.13～0.15%、Si：0.61～0.8%、Mn：1.3～1.6%、P≦0.015%、S≦0.015%、Ti：0.01～0.03%、V：0.03～0.06%, N≤0.005%, Nb:0.025～0.05%, Ca:0.001～0.007%, B:0.001～0.002%, lanthanide series:0.001～0.005%, Als:0.015～0.035%, all the other are Fe and inevitable impurity element.

2. the method for angle steel for the high strength steel tower that a kind of ductile-brittle transition temperature described in production claim 1 is low, its step:

1) conventional smelting and strand, controls tapping temperature at 1670～1700 DEG C, and middle Baogang coolant-temperature gage is controlled at steel grade liquid phase temperatureAbove 20～30 DEG C of degree line, Casting speed is not higher than 1.8m/min;

2) strand is carried out to nature stacking and be cooled to room temperature;

3), to strand heating, control soaking zone temperature and be: 1033～1050 DEG C or 1100 ~ 1133 DEG C, the heat time 103 ~123min；

4) carry out roughing, and control its start rolling temperature and exist: 983～1083 DEG C;

5) carry out finish rolling, control its finishing temperature 788 ~ 858 DEG C of scopes;

6) natural air cooling is stand-by to room temperature.