CN102766820B

CN102766820B - Hot rolled strip steel with yield strength higher than 600MPa for mine rescue capsule and preparation method of hot rolled strip steel

Info

Publication number: CN102766820B
Application number: CN2012102470905A
Authority: CN
Inventors: 李长生; 马彪; 李涛
Original assignee: Northeastern University China
Current assignee: Northeastern University China
Priority date: 2012-07-17
Filing date: 2012-07-17
Publication date: 2013-11-20
Anticipated expiration: 2032-07-17
Also published as: CN102766820A

Abstract

A hot rolled strip steel with yield strength higher than 600MPa for a mine rescue capsule and a preparation method of the hot rolled strip steel belongs to the technical field of metallurgy materials. The hot rolled strip steel comprises, by weight percent, 0.04-0.08% of C, 0.1-0.3% of Si, 1.5-1.7% of Mn, 0.01-0.05% of Al, 0.4-0.5% of Mo, 0.4-0.6% of Cr, 0.04-0.06% of Nb, 0.02-0.05% of Ti, 0.2-0.35 of Cu, not more than 0.01% of P, not more than 0.01% of S, and the balance Fe. A metallographic structure of the hot rolled strip steel is granular bainite with the yield strength no less than 600MPa, tensile strength no less than 800MPa, and elongation percentage after fracture no less than 18% at room temperature. The yield strength is no less than 450MPa, tensile strength is no less than 650MPa, and elongation percentage after fracture is no less than 19% at a high temperature of 500 DEG C. Impact energy at 20 DEG C is larger than 47J. Cold bending property is qualified. Atmospheric corrosion resistance index I under industrial environments is no less than 4.5. Sensitivity coefficient Pcm of welding cold crack is not more than 0.26%. The preparation method includes: smelting molten steel according to the preset components, casting ingots, heating, rough rolling, finish rolling to obtain the strip steel with thickness of 4-14mm, and fast cooling to obtain the finished hot rolled strip steel. The hot rolled strip steel has fine room-temperature and high-temperature mechanical performance and fine erosion resistance.

Description

A kind of yield strength higher than the escape capsule of mine of 600MPa with hot rolled strip and preparation method

Technical field

The invention belongs to the metallurgical material technical field, particularly a kind of yield strength higher than the escape capsule of mine of 600MPa with hot rolled strip and preparation method.

Background technology

Escape capsule of mine is a kind of modernization safety control equipment of urgent danger prevention while protecting down-hole miner to meet with an accidet, and the mine industry is increasing for the market requirement of life-saving capsule in recent years, and the development prospect of escape capsule of mine equipment manufacture is wide.

At present, body ferrous materials used in escape capsule of mine cabin is mainly carbon structural steel and the low-alloy high-strength steels such as 45 steel, Q235, Q345 and Q460, and the yield strength of these materials is 200 ~ 500MPa, and the indexs such as toughness and bending meet the demands substantially.But due to the industrial environment complexity of down-hole, the high temperature gas flow, methane and the H that for example produce during gas explosion ₂The corrosive gasess such as S, the hot strength of existing escape capsule body material and the service requirements that corrosion resistance nature is difficult to meet life-saving capsule.

For this reason, a kind of yield strength of exploitation becomes pendulum extremely urgent task in face of scientific and technical personnel higher than the special-purpose hot rolled strip of the good escape capsule of mine of the over-all properties such as shock-resistant, high temperature resistant, corrosion-resistant of 600MPa.

Summary of the invention

For the technical problem of existing escape capsule of mine with the steel existence, the invention provides a kind of yield strength higher than the escape capsule of mine of 600MPa with hot rolled strip and preparation method, purpose is to meet the service requirements of escape capsule of mine with steel by suitable alloying element design and preparation method.

Yield strength of the present invention is C higher than the escape capsule of mine of 600MPa with the hot rolled strip chemical composition by weight percentage: 0.04 ~ 0.08 %, Si: 0.1 ~ 0.3 %, Mn:1.5 ~ 1.7 %, Al: 0.01 ~ 0.05 %, Mo:0.4 ~ 0.5 %, Cr: 0.4 ~ 0.6 %, Nb:0.04 ~ 0.06 %, Ti: 0.02 ~ 0.05 %, Cu:0.2 ~ 0.35 %, P≤0.01 %, S≤0.01 %, surplus is Fe.

Its metallographic structure is granular bainite, room temperature yield strength>=600 MPa, tensile strength>=800 MPa, elongation after fracture>=18 %, 500 ℃ of drawing by high temperature yield strength>=450MPa, tensile strength>=650 MPa, elongation after fracture>=19 %, 20 ℃ of ballistic work>47 J(impact specimens are of a size of 55 mm * 10 mm * 5 mm), cold-bending property is qualified, atmospheric corrosion resistance sex index I under industrial environment>=4.5, welding cold cracking sensitivity coefficient P _Cm≤ 0.26 %.

Yield strength of the present invention is carried out with the preparation method of hot rolled strip according to the following steps higher than the escape capsule of mine of 600MPa:

(1) by the chemical composition of setting: weight percent C: 0.04 ~ 0.08 %, Si: 0.1 ~ 0.3 %, Mn:1.5 ~ 1.7 %, Al: 0.01 ~ 0.05 %, Mo:0.4 ~ 0.5 %, Cr: 0.4 ~ 0.6 %, Nb:0.04 ~ 0.06 %, Ti: 0.02 ~ 0.05 %, Cu:0.2 ~ 0.35 %, P≤0.01 %, S≤0.01 %, surplus is the Fe smelting molten steel and casts strand, and slab thickness is 150 ~ 250 mm;

(2) strand is heated to 1200 ~ 1250 ℃, insulation 1 h, roughing 3 ~ 5 passages, the roughing start rolling temperature is 1120 ~ 1170 ℃, and finishing temperature is 980 ~ 1070 ℃, and obtaining thickness is the intermediate blank of 30 ~ 50 mm;

(3) intermediate blank is carried out to finish rolling 5 ~ 7 passages, the finish rolling start rolling temperature is 950 ~ 1030 ℃, and finishing temperature is 780 ~ 860 ℃, and the finish rolling draught per pass is controlled at 15 ~ 40 %, and obtaining thickness is the band steel of 4 ~ 14 mm;

(4) the band steel after finish rolling is cooled to 450 ~ 700 ℃ with the speed of 10 ~ 40 ℃/s, batches and obtains the thick hot rolled strip product of 4 ~ 14 mm.

What time following the design of interalloy element of the present invention considered:

C is one of the most effective solution strengthening element in steel, but along with the increase of C content can reduce its formability and weldability, and low C content is conducive to guarantee that steel have good moulding and toughness, therefore, the content of C is controlled in low scope;

Mn is common reductor and sweetening agent, can solution strengthening and phase transformation strengthening effect, reduce

Figure 2012102470905100002DEST_PATH_IMAGE002

Transformation temperature, be conducive to refinement ferrite crystal grain in course of hot rolling, and the Mn element can also improve the impelling strength of steel simultaneously, reduces ductile-brittle transition temperature.But the too high levels of Mn easily forms segregation line, causes the microstructure and hardness of steel inhomogeneous, and reduces the spot welding ability, so the content of Mn is controlled at 1.6 % left and right;

Si is reductor commonly used in steel, and solid solution, in ferrite, can effectively improve ferritic intensity, but ferritic ductility is had to disadvantageous effect, but the too high levels of Si is harmful to the plate surface quality, reduces the plasticity and toughness of material.Therefore, the content of Si is controlled at 0.2 % left and right;

Al is that the nitrogen agent is determined in deoxidation commonly used in steel, belongs to ferrite former, can form the AlN of small and dispersed as the forming core particle, crystal grain thinning, but the too high levels of Al easily forms alumina inclusion, diminishes plasticity and toughness and welding property, therefore, the content of Al is controlled at 0.03 % left and right;

Mo can significantly increase the hardening capacity of material, in high-strength steel, add Mo, strongly hinder separating out and growing up of proeutectoid ferrite, the C curve of perlite and bainite transformation is obviously separated, make under identical cooling conditions more easily to occur bainite transformation, to obtain good performance, therefore, the content of Mo is controlled at 0.45 % left and right;

Cr can improve the hardening capacity of steel, can improve erosion resistance and anti-hydrogen induced cracking ability simultaneously, and can improve the abrasion resistance properties of steel.The Cr element can also reduce the velocity of diffusion of C simultaneously, suppresses ferrite and pearlite and changes, and bainite transformation is moved to cold zone, reduces the Bainite Phases of Some height, and therefore, the content of Cr is controlled at 0.5 % left and right;

Nb is best element in controlled rolling, can effectively postpone austenite recrystallization, improves austenite recrystallization temperature, thereby stops Austenite Grain Growth, crystal grain thinning.By the adjustment of rolling and process for cooling parameter, the Nb that can make part solid solution state with the form Precipitation of carbonitride, plays the effect of precipitation strength to ferrite in ferrite.Especially in the situation that Mo exists, Nb separates out small and dispersed more, and the precipitation strength effect is also more obvious.The interaction of trace Nb and the elements such as Cu, B, reduce transformation temperature greatly, and bainitic transformation can be changed at lower temperature, after phase transformation, obtains tiny lath of bainite, and therefore, the content of Nb is controlled at 0.05 % left and right;

Ti adds trace Ti in Hi-Stren steel, can improve the intensity of steel, improve cold forming capability and the welding property of steel, mainly utilize Ti and C, the good affinity of N, the TiN that forms, thus in heating of plate blank and the operation of rolling, pass through to suppress the austenite crystal that AUSTENITE GRAIN COARSENING obtains refinement, in addition, the TiN particle can suppress the grain coarsening of welded heat affecting zone, thereby improves the low-temperature flexibility of welded heat affecting zone.TiC can separate out in lower temperature, thereby produces the precipitation strength effect, but excessive Ti can damage the toughness of steel, and therefore, the content of Ti is controlled at 0.035 % left and right;

Cu can effectively improve the atmospheric corrosion resistance of steel, from but requisite interpolation element weathering steel.Secondly, Cu can form tiny ε-Cu at 400 ~ 650 ℃ and separate out, and with the form of precipitation strength, effectively improves intensity, Cu can also improve welding property and the processability of steel, but excessive Cu can increase the hot cracking tendency of steel, and therefore, the content of Cu is controlled at 0.28 % left and right;

S and P S element are the major impurity elements that causes steel hot-short, and easily produce segregation and cause banded structure, and sulfide inclusion diminishes the plasticity and toughness of material, and the P element causes the cold short of steel, namely reduces the low-temperature flexibility of material, and easily produce segregation.Therefore, the content of S and P should be respectively less than 0.01 %;

Adopt the foundation of controlled rolling and Controlled cooling process: by the austenite recrystallization controlled rolling of high-temperature zone, abundant refine austenite crystal grain; The finish rolling finishing temperature is controlled at 780 ~ 860 ℃, makes in the operation of rolling to produce larger accumulation strain; By rolling rear cooling and proper temperature fast, batch, obtain granular bainite microstructure.

Many particulate state islands that are comprised of residual austenite or martensite are distributing in granular bainite microstructure, matrix is played to the effect that second-phase is strengthened, improve work hardening capacity, reduce yield tensile ratio, make material carry the high-intensity while, have good moulding and toughness.Hot rolled strip metallographic structure of the present invention is granular bainite, room temperature yield strength>=600 MPa, tensile strength>=800 MPa, elongation after fracture>=18 %, 500 ℃ of drawing by high temperature yield strength>=450MPa, tensile strength>=650 MPa, elongation after fracture>=19 %, 20 ℃ of ballistic work>47 J(impact specimens are of a size of 55 mm * 10 mm * 5 mm), cold-bending property is qualified, atmospheric corrosion resistance sex index I under industrial environment>=4.5, welding cold cracking sensitivity coefficient P _Cm≤ 0.26 %.With existing general carbon steel, compare, more met the industrial application demand of escape capsule of mine with hot rolled strip.

The accompanying drawing explanation

Fig. 1 is the metallographic structure figure of the hot rolled strip of the embodiment of the present invention 1;

Fig. 2 is the metallographic structure figure of the hot rolled strip of the embodiment of the present invention 2;

Fig. 3 is the metallographic structure figure of the hot rolled strip of the embodiment of the present invention 3.

Embodiment

It is Leica DMIRM type opticmicroscope that the metallographic structure of the hot rolled strip of the embodiment of the present invention is observed to what adopt;

Room temperature tensile, 500 ℃ of drawing by high temperature, 180 ° of pliability tests (D=3a) are all to carry out on CMT5105-SANS microcomputer controlled electronic universal testing machine;

Wherein the room temperature tensile sample is made square-section standard tensile sample by GB/T228-2002,500 ℃ of drawing by high temperature samples are made square-section standard tensile sample by GB/T4338-1995,20 ℃ of impact test equipments are Instron 9250HV drop hammer impact testing machine, and impact specimen is of a size of 55 mm * 10 mm * 5 mm.

Embodiment 1

(1) by the chemical composition of setting: weight percent C:0.05 %, Si: 0.2 %, Mn:1.5 %, Al: 0.01%, Mo:0.4 %, Cr:0.5 %, Nb: 0.04 %, Ti: 0.05 %, Cu: 0.2 %, P≤0.01 %, S≤0.01 %, surplus is Fe, smelting molten steel cast the strand of 180 mm * 1300 mm * 10020 mm in 200 tons of converters;

(2) strand is heated to 1200 ℃, insulation 1 h, rolling roughing 3 passages on 2050 mm hot continuous mills, the roughing start rolling temperature is 1120 ℃, and finishing temperature is 980 ℃, and obtaining thickness is the intermediate blank of 30mm;

(3) intermediate blank is carried out to finish rolling 6 passages, the finish rolling start rolling temperature is 950 ℃, and finishing temperature is 780 ℃, and the finish rolling draught per pass is controlled at 15 ~ 40 %, and obtaining thickness is the band steel of 4 mm, between finishing stand, adopts water-cooled;

(4) the band steel after finish rolling is cooled to 450 ℃ with the speed of 40 ℃/s, batches, and the hot rolled strip product thickness that finally obtains is 4 mm.

Its metallographic structure as shown in Figure 1, is all granular bainite microstructure, and lath of bainite interface and original austenite crystal prevention become unintelligible, the island small and dispersed that distributes on ferrite matrix.

The mechanical property detected result is: yield strength 616 MPa, tensile strength 812 MPa, elongation after fracture 18.7 %; 500 ℃ of drawing by high temperature yield strength 461 MPa, tensile strength 667 MPa, elongation after fracture 20.2 %; 20 ℃ of ballistic work 52 J(impact specimens are of a size of 55 mm * 10 mm * 5 mm), the clod wash test passes; Atmospheric corrosion resistance sex index I=4.9 under industrial environment, welding cold cracking sensitivity coefficient P _Cm=0.19 %.

Embodiment 2

(1) by the chemical composition of setting: weight percent C: 0.06 %, Si:0.3 %, Mn:1.6 %, Al:0.04 %, Mo: 0.45 %, Cr: 0.6 %, Nb: 0.05 %, Ti:0.02 %, Cu: 0.25 %, P≤0.01 %, S≤0.01 %, surplus is Fe, smelting molten steel cast the strand of 200 mm * 1300 mm * 10020 mm in 200 tons of converters;

(2) strand is heated to 1230 ℃, insulation 1 h, rolling roughing 4 passages on 2050 mm hot continuous mills, the roughing start rolling temperature is 1150 ℃, and finishing temperature is 1020 ℃, and obtaining thickness is the intermediate blank of 41 mm;

(3) intermediate blank is carried out to finish rolling 7 passages, the finish rolling start rolling temperature is 1000 ℃, and finishing temperature is 820 ℃, and the finish rolling draught per pass is controlled at 15 ~ 40 %, and obtaining thickness is the band steel of 8 mm, between finishing stand, adopts water-cooled;

(4) the band steel after finish rolling is cooled to 610 ℃ with the speed of 28 ℃/s, batches, and the hot rolled strip product thickness that finally obtains is 8 mm.

Its metallographic structure as shown in Figure 2, is all granular bainite microstructure, and lath of bainite interface and original austenite crystal prevention become unintelligible, the island small and dispersed that distributes on ferrite matrix.

The mechanical property detected result is: yield strength 612 MPa, tensile strength 809 MPa, elongation after fracture 18.9 %; 500 ℃ of drawing by high temperature yield strength 459 MPa, tensile strength 661 MPa, elongation after fracture 19.8 %; 20 ℃ of ballistic work 51 J(impact specimens are of a size of 55 mm * 10 mm * 5 mm), the clod wash test passes; Atmospheric corrosion resistance sex index I=5.7 under industrial environment, welding cold cracking sensitivity coefficient P _Cm=0.22 %.

Embodiment 3

(1) by the chemical composition of setting: weight percent C: 0.08 %, Si:0.1 %, Mn:1.7 %, Al:0.05 %, Mo: 0.5 %, Cr:0.4 %, Nb:0.06 %, Ti: 0.04 %, Cu: 0.35 %, P≤0.01 %, S≤0.01 %, surplus is Fe, smelting molten steel cast the strand of 250 mm * 1300 mm * 10020 mm in 200 tons of converters;

(2) strand is heated to 1250 ℃, insulation 1 h, rolling roughing 5 passages on 2050 mm hot continuous mills, the roughing start rolling temperature is 1170 ℃, and finishing temperature is 1070 ℃, and obtaining thickness is the intermediate blank of 50 mm;

(3) intermediate blank is carried out to finish rolling 5 passages, the finish rolling start rolling temperature is 1030 ℃, and finishing temperature is 860 ℃, and the finish rolling draught per pass is controlled at 15 ~ 40 %, and obtaining thickness is the band steel of 14 mm, between finishing stand, adopts water-cooled;

(4) the band steel after finish rolling is cooled to 700 ℃ with the speed of 10 ℃/s, batches, and the hot rolled strip product thickness that finally obtains is 14 mm.

Its metallographic structure as shown in Figure 3, is mainly granular bainite microstructure, is mingled with a small amount of quasi-polygonal ferrite, and lath of bainite interface and original austenite crystal prevention become unintelligible, the island small and dispersed that distributes on ferrite matrix, but very uneven.

The hot rolled strip product thickness that finally obtains is 14 mm, and the mechanical property detected result is: yield strength 607 MPa, tensile strength 807 MPa, elongation after fracture 19.5 %; 500 ℃ of drawing by high temperature yield strength 457 MPa, tensile strength 658 MPa, elongation after fracture 19.6 %; 20 ℃ of ballistic work 49 J(impact specimens are of a size of 55 mm * 10 mm * 5 mm), the clod wash test passes; Atmospheric corrosion resistance sex index I=5.7 under industrial environment, welding cold cracking sensitivity coefficient P _Cm=0.24 %.

Claims

1. a yield strength, higher than the escape capsule of mine hot rolled strip of 600MPa, is characterized in that its chemical composition is C:0.04～0.08%, Si:0.1～0.3% by weight percentage, Mn:1.5～1.7%, Al:0.01～0.05%, Mo:0.4～0.5%, Cr:0.4～0.6%, Nb:0.04～0.06%, Ti:0.02～0.05%, Cu:0.2～0.35%, P≤0.01%, S≤0.01%, surplus are Fe; Its metallographic structure is granular bainite, in granular bainite microstructure, be distributed with the particulate state island that is formed by residual austenite or martensite, room temperature yield strength>=600MPa, tensile strength>=800MPa, elongation after fracture>=18%, 500 ℃ of drawing by high temperature yield strength>=450MPa, tensile strength>=650MPa, elongation after fracture>=19%, 20 ℃ ballistic work>47J, atmospheric corrosion resistance sex index I under industrial environment>=4.5, welding cold cracking sensitivity coefficient P _Cm≤ 0.26%.

2. a kind of yield strength according to claim 1 is used the preparation method of hot rolled strip higher than the escape capsule of mine of 600MPa, it is characterized in that carrying out according to following steps:

(1) by the chemical composition of setting: weight percent C:0.04～0.08%, Si:0.1～0.3%, Mn:1.5～1.7%, Al:0.01～0.05%, Mo:0.4～0.5%, Cr:0.4～0.6%, Nb:0.04～0.06%, Ti:0.02～0.05%, Cu:0.2～0.35%, P≤0.01%, S≤0.01%, surplus is the Fe smelting molten steel and casts strand, and slab thickness is 150～250mm;

(2) strand is heated to 1200～1250 ℃, insulation 1h, roughing 3～5 passages, the roughing start rolling temperature is 1120～1170 ℃, and finishing temperature is 980～1070 ℃, and obtaining thickness is the intermediate blank of 30～50mm;

(3) intermediate blank is carried out to finish rolling 5～7 passages, the finish rolling start rolling temperature is 950～1030 ℃, and finishing temperature is 780～860 ℃, and the finish rolling draught per pass is controlled at 15～40%, and obtaining thickness is the band steel of 4～14mm;

(4) the band steel after finish rolling is cooled to 450～700 ℃ with the speed of 10～40 ℃/s, batches and obtains the thick hot rolled strip product of 4～14mm.