CN102367545A - A572Gr50 boron-added-steel steel plate and production method thereof - Google Patents

Abstract

The invention discloses an A572Gr50 boron-added-steel steel plate, which comprises the following chemical ingredients in percentage by mass (unit: weight percent): 0.12 to 0.19 of C, 0.20 to 0.40 of Si, 1.15 to 1.45 of Mn, at most 0.020 of P, at most 0.007 of S, at most 0.10 of micro alloy elements (V+Ti), at most 0.050 of Als, at most 0.0018 of B and the balance of Fe and residue elements. The carbon equivalent [Ceq=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15] is lower than or equal to 0.44. A series of production methods of converter smelting, LF refining, heating, rolling, cold control and slow cooling are adopted, in addition, chemical ingredient design of polyelement composite micro alloy elements is reasonably adopted, the LF process is used for ensuring the cleanness of the steel quality, the goal that the grade sum of each kind of impurities does not exceed 3.0 is reached, the steel grain size reaches 9.0 to 10.0 grade through the rolling controlling and cold controlling, Ti is added to be combined with N in the steel, the effective boron content in the steel is improved, and the generation of cracks of the steel plate caused by boron addition is avoided. Through the effective implementation of the measures, the A572Gr50 boron-added-steel steel plate with the performance assurance and fault detection assurance is successfully produced.

Description

A kind of A572Gr50 adds boron steel steel plate and working method thereof

Technical field

The invention belongs to the steel plate production technical field, be specifically related to a kind of A572Gr50 and add boron steel steel plate and working method thereof.

Background technology

Along with China's steel industry develop rapidly; The enterprise of domestic export steel plate increases gradually, and the market competition of outlet steel plate is growing more intense, and early stage is because the yield of boron is unstable; And low-alloy adds boron steel and is prone to cause crystal grain thick; Make the performance inconsistency lattice of steel plate, the A572Gr50 outlet steel plate qualification rate of production is lower, and the outlet steel plate adopts the mode of mopping to handle more; Add boron and produce the A572Gr50 steel plate, always stably manufactured on a large scale because of reasons such as its production difficulty are big, the tooling requirement is special.

Summary of the invention

To the problems referred to above, the present invention provides the A572Gr50 of a kind of guaranteed cost, guarantor's flaw detection to add boron steel steel plate and working method thereof.

A kind of A572Gr50 adds the boron steel steel plate; Comprise following chemical components in mass percent (unit; Wt%): C:0.12～0.19, Si:0.20～0.40, Mn:1.15～1.45, P :≤0.020, S :≤0.007, micro alloying element (V+Ti)≤0. 10, Als :≤0.050; B :≤0.0018, other is Fe and relict element.

The carbon equivalent of said chemical ingredients≤0.44.

The function analysis of above-mentioned chemical element is following:

C: be most basic strengthening element in the steel, improve intensity, but the welding property that C influence steel with influence toughness, take all factors into consideration, what the content of carbon was controlled as far as possible hangs down.

Si: be the solution strengthening element, favourable to the intensity that improves steel plate.

Mn: be the solution strengthening element, all favourable to intensity and the toughness that improves steel plate.

P: unfavorable to welding, and have certain cold shortness, and in this steel grade, belong to harmful element, that should control is low as far as possible.

S: be prone to form the MnS type impurity, have certain red brittleness, in this steel grade, belong to harmful element, that should control is low as far as possible.

V, Ti: in steel, can combine, form fine carbide or carbonitride, can play crystal grain thinning and dispersion-strengthened action, thereby reach the net effect of the obdurability of effective raising steel, and have nitrogen fixation, improve effective boron ratio with C, N.

Al: can play the crystal grain thinning strengthening effect;

B: the hardening capacity that improves steel plate.

For achieving the above object, A572Gr50 adds the working method that the boron steel steel plate takes and comprises the steps:

Converter smelting: tapping carbon>=0.07%, tapping P≤0.015%, S≤0.012%, point blows number of times and must not avoid slag under the tapping process greater than 2 times;

LF refining: guarantee that the white slag hold-time is controlled at more than the 15min;

Heating: the holding temperature of dead soaking pit is controlled at 1200 ℃～1300 ℃;

Rolling: adopt two stage rolling, 1050 ℃～1150 ℃ of stage start rolling temperatures, two-stage start rolling temperature are at 820-900 ℃, and reduction in pass is 15-20mm, finishing temperature 800-880 ℃;

Control cold: return red temperature 600-680 ℃;

Slow cooling: go into burial pit temperature >=300 ℃; Cooling in heap time >=20 hour.

Because the present invention is through converter smelting, LF refining, heating, rolling, cold, a series of working methods of slow cooling of control; And through reasonably taking the chemical composition design of polynary composite micro-alloyed element, LF technology guarantees the cleanliness factor of steel, reaches each type impurity rank summation and is no more than 3.0; Make the grain fineness number of steel reach 9.0～10.0 grades through controlled rolling and controlled cooling; Add that N combines in Ti and the steel, effective boron content in the raising steel avoids the adding of boron to cause the crackle generation of steel plate; Through the above-mentioned effective enforcement that waits measure, the A572Gr50 that successfully produced guaranteed cost, protects flaw detection adds the boron steel steel plate.Hot metal pretreatment to whole thermal treatment whole process, has been worked out strict process point control standard, and strict the execution, the quality in kind of product has reached the A572Gr50 requirement.Its ys is controlled at 365～445 MPa, and tensile strength is controlled at 485～545 MPa, and yield tensile ratio all≤0.80; Elongation is controlled at 22%-27%;-20 ℃ of V-type ballistic works are controlled at 112～197J; Performance index have satisfied the requirement of A572Gr50 steel plate fully, and steel plate is examined the crackle rate outward below 0.29%.

Description of drawings

Below in conjunction with accompanying drawing, the present invention is done further elaboration.

Fig. 1 is the metallographic structure figure (100X) of TMCP of the present invention after rolling.

Embodiment

Guaranteed cost of the present invention, the A572Gr50 that protects flaw detection add the boron steel steel plate and comprise following chemical components in mass percent (unit; Wt%): C:0.12～0.19, Si:0.20～0.40, Mn:1.15～1.45, P :≤0.020, S :≤0.007, micro alloying element (V+Ti)≤0. 10, Als :≤0.050; B :≤0.0018, other is Fe and relict element.

Carbon equivalent [Ceq=C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15] :≤0.44.

The working method that the present invention takes comprises: converter smelting, LF refining, heating, rolling, cold, the slow cooling of control, and in said converter smelting, tapping carbon>=0.07%; Tapping P≤0.015%; S≤0.012%, point blows number of times and must not avoid slag under the tapping process greater than 2 times; In said LF refining: take the big quantity of slag to carry out slag making, guarantee that the white slag hold-time is controlled at more than the 15min; Pine in said adding: the holding temperature of dead soaking pit is controlled at 1200 ℃～1300 ℃; Said rolling in: adopt two stage rolling, 1050 ℃～1150 ℃ of stage start rolling temperatures adopt high temperature low speed to depress rolling greatly; The two-stage start rolling temperature is at 820-900 ℃; Two-stage takes to depress for a short time rolling, and reduction in pass is 15-20mm, finishing temperature 800-880 ℃; In said control is cold: return red temperature 600-680 ℃; In said slow cooling: go into burial pit temperature>=300 ℃; Cooling in heap time>=20 hour.

Embodiment 1

Through converter smelting, LF refining, heating, rolling, cold, the slow cooling of control, the A572Gr50 that acquisition is described in table 1 below chemical ingredients adds boron steel steel plate Finished Steel, and wherein said A572Gr50 adds boron steel steel plate mechanical mechanics property to be seen like following table 3.

The chemical ingredients of table 1 embodiment 1 steel

Embodiment 2

Through converter smelting, LF refining, heating, rolling, cold, the slow cooling of control, the A572Gr50 that acquisition is described in table 2 below chemical ingredients adds boron steel steel plate Finished Steel, and wherein said A572Gr50 adds boron steel steel plate mechanical mechanics property to be seen like following table 3.

The chemical ingredients of table 2 embodiment 2 steel

The steel-making composition: the chemical composition design of steel plate of the present invention adopts low-carbon-equivalent, and Mn-Nb-V-Ti is ferritic+perlitic steel, and the strengthening mechanism of application is build up, refined crystalline strengthening, precipitation strength and solution strengthening.Main and other element formation carbide of C plays build up and precipitation strength effect, improves armor plate strength; Mn mainly plays solution strengthening and reduces transformation temperature, works to improve armor plate strength; Rolling through the two-stage, the C of V, Nization thing are separated out, and improve armor plate strength.For guaranteeing flaw detection, take the Clean Steel smelting technology simultaneously, the steel grade of keeping under strict control [P], [S], [N], [H], [O] five big harmful constituent contents.

Converter smelting: control tapping carbon>=0.07%, tapping P≤0.015%, S≤0.012% by Clean Steel smelting technology standard; Point blows number of times and must not avoid slag under the tapping process greater than 2 times.

The LF refining: take the big quantity of slag to carry out slag making, really how the white slag hold-time is controlled at more than the 15min, stops the rare phenomenon of slag; Carry out the Argon operation in strict accordance with the Argon standard, forbid blowing cruelly.

Heating: adopt the two-stage heating, heating zone temperature＜1000 ℃, two heating zone temperature are controlled at 1220～1280 ℃, and the soaking zone temperature is controlled at 1200～1260 ℃.

Rolling: adopt two stage rolling, 1050 ℃～1150 ℃ of stage start rolling temperatures, the rolling requirement of " high temperature, low speed, depress greatly " is adhered in strictness, for guaranteeing the distortion infiltration, working roll rolling line speed is by≤1.5m/s control; Cool steel thickness is 100-180mm, and the two-stage start rolling temperature is at 820～880 ℃, and the two-stage takes to depress for a short time rolling, and reduction in pass is 15-25mm, finishing temperature 780-860 ℃.

Control cold: rolling back gets into a little less than twice of the ACC cold, reduces the surface and the inner temperature difference as far as possible, guarantees to return red temperature at 600-680 ℃, is sent to powerful straightener after the cooling and carries out hot straightening.

Slow cooling: carry out slow cooling after steel plate rolls off the production line, go into burial pit temperature >=400 ℃, cooling in heap time >=20 hour.

Main and other element formation carbide of Chemical Composition: C plays build up and precipitation strength effect, improves armor plate strength; Mn mainly plays solution strengthening and reduces transformation temperature, works to improve armor plate strength; Rolling through the two-stage, the C of V, Nization thing are separated out, and improve armor plate strength, and B improves hardening capacity; P, S content are controlled in the lower scope, and in a word, whole Composition Control is more stable, satisfy the composition design requirements of A572Gr50 steel plate for tall building.

Surface quality requires to carry out by standard is strict.

Flaw detection is carried out three grades of non-destructive testing standards of JB/T2970-2004 and is carried out.

Composition and mechanical mechanics property are pressed ASTM A572M-01 and are carried out, and specifically see table 3.

Table 3 A572Gr50 adds boron steel steel plate mechanical mechanics property

This is produced the thick A572Gr50 of 37-92mm altogether as a trial and adds 217 batches of boron steels, and wherein: ys is controlled at 365-445MPa, and tensile strength is controlled at 485-545MPa, and yield tensile ratio all≤0.80; Elongation is controlled at 22%-27%;-20 ℃ of V-type ballistic works are controlled at 112-197J; Performance index have satisfied the A572Gr50 development requires fully.

Outer inspection and flaw detection: the steel plate of being developed is examined outward, and the percentage of A-class goods 99.2% only accounts for 0.29% because of crackle causes outer inspection not conform to, and detects a flaw by JB/T 2970-2004, and closing three grades of rates is 99.41%, has reached desired result.

Metallographic examination is seen like following table 4

Table 4 metallographic structure

Associative list 4 and Fig. 1 analysis, the steel plate after rolling is organized as ferritic and perlite, and grain fineness number reaches the 9.0-10.0 level.

Claims (3)

1. an A572Gr50 adds the boron steel steel plate; It is characterized in that: comprise following chemical components in mass percent (unit; Wt%): C:0.12～0.19, Si:0.20～0.40, Mn:1.15～1.45, P :≤0.020, S :≤0.007, micro alloying element (V+Ti)≤0. 10, Als :≤0.050; B :≤0.0018, other is Fe and relict element.

2. a kind of A572Gr50 as claimed in claim 1 adds the boron steel steel plate, it is characterized in that: the carbon equivalent of said chemical ingredients≤0.44.

3. a kind of A572Gr50 as claimed in claim 1 adds the boron steel steel plate, it is characterized in that: comprise following production stage:

Converter smelting: tapping carbon>=0.07%, tapping P≤0.015%, S≤0.012%, point blows number of times and must not avoid slag under the tapping process greater than 2 times;

LF refining: guarantee that the white slag hold-time is controlled at more than the 15min;

Heating: the holding temperature of dead soaking pit is controlled at 1200 ℃～1300 ℃;

Rolling: adopt two stage rolling, 1050 ℃～1150 ℃ of stage start rolling temperatures, two-stage start rolling temperature are at 820-900 ℃, and reduction in pass is 15-20mm, finishing temperature 800-880 ℃;

Control cold: return red temperature 600-680 ℃;

Slow cooling: go into burial pit temperature >=300 ℃; Cooling in heap time >=20 hour.

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