CN103866185A - Preparation method for manufacturing low-cost ultrafine grain transformation-induced plastic steel seamless tube online - Google Patents
Preparation method for manufacturing low-cost ultrafine grain transformation-induced plastic steel seamless tube online Download PDFInfo
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- CN103866185A CN103866185A CN201410096226.6A CN201410096226A CN103866185A CN 103866185 A CN103866185 A CN 103866185A CN 201410096226 A CN201410096226 A CN 201410096226A CN 103866185 A CN103866185 A CN 103866185A
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Abstract
The invention relates to a preparation method for manufacturing a low-cost ultrafine grain transformation-induced plastic steel seamless tube online. The method comprises the following steps: forging, turning, heating, perforating and coldly drawing a cast ingot to obtain a seamless cold-drawn steel tube; then carrying out circulating heating and quenching treatment for over three times by adopting a medium-frequency heating induction coil; finally, air cooling, water cooling or naturally cooling to room temperature, so as to obtain the low-cost ultrafine grain transformation-induced plastic steel seamless tube. Chemical components of common low-carbon steel are utilized, so that the cost is relatively low, the tensile strength is greater than or equal to 900 MPa, the yield ratio is smaller than or equal to 0.64, the ductility is greater than or equal to 24.0%, the work hardening index is greater than or equal to 0.23, the anisotropic index is greater than or equal to 1.01, the average grain size of a microscopic structure is smaller than or equal to 3mum, and the volume fraction of the retained austenite is 11.5-19.5%.
Description
Technical field
The invention belongs to the preparation field of steel pipe, be specifically related to a kind of preparation method of online manufacture low cost superfine crystal particle transformation induced plasticity steel seamless tube.
Background technology
In recent years, development and the daily life of the problem such as climate change, energy shortage on modern industry producing day by day serious impact.Energy-saving and emission-reduction, low-carbon environment-friendly have been countries nowadays industrial development institute problem demanding prompt solutions.Be the mainstay industry that pulls the national economic development as the mark of modern industry and the automotive industry of symbol, also be high flow rate, maximum discharge, cause the key industry of environmental pollution, its a series of environment negative impacts that produce have formed the matter of utmost importance that automotive industry Faced In Sustainable Development will solve.
In order to meet the demand of environment protection; under the prerequisite that guarantees vehicle performance, realize lightweight; become the target of each Automobile Enterprises research and development product innovation, except adopting more high-intensity material, another effective way is exactly by replacing the method for solid parts to realize with hollow component.Along with the maturation of tubing inner high voltage production technology, the industrial production of high strength hollow unit has become possibility, need to have high-intensity hollow element as prerequisite and realize this scheme.Wherein phase change induction plasticity steel not only has high intensity, but also has high elongation after fracture, and its contradiction of succeeding in developing as solving intensity and plasticity provides direction, therefore becomes a large focus of automotive sheet in recent years.
At present, the thermal treatment type of heating of steel pipe is still take gas heating and resistive heating as main, majority is steel pipe integral to be put into process furnace heat, the steel pipe length processed is like this subject to the restriction of heating furnace body size, can not produce the steel pipe that large specification and length are larger, thereby limit the product specification of steel pipe; In addition, adopt this device to heat up in heat-processed slower, the zone of oxidation of steel tube surface is serious, and working efficiency is not high yet; Moreover the carrying roller road in body of heater cannot guarantee the uniform rotation of steel pipe in process furnace, it heats uneven, can cause the bending of steel pipe.
CN1267736 discloses a kind of grain ultrafining method of structural alloy steel, it is characterized in that the method adopts the technical process of circulation rapid thermal process to be: normalizing-quenching-austenitizing (A fast
c3above)-rapid quenching (Ms is following)-austenitizing (A fast
c3above)-rapid quenching (Ms is following)-... (circulation several times), concrete steps are as follows: first, in middle thermohaline liquid furnace, part is heated to A
c3+ (50～80 ℃), are incubated air cooling after 10～60 minutes, so that then microstructure homogenization, is heated to A by part in middle thermohaline liquid furnace
c3+ (30～50 ℃) so that the alloy elements such as Cr, Mo, Nb, Ti fully dissolve, soaking time is unanimously as the criterion with part section internal and external temperature, be generally 10～30 minutes, when taking out after part soaking, the oil that is placed in the following temperature of the Ms oil of quenching, so that part obtains full martensitic stucture, rapid thermal process as follows circulates after the oil of quenching: part is placed in to A
c3in the salt bath furnace of+(30～50 ℃), be incubated after 1～2 minute, take out the part oil of quenching rapidly, oil temperature, lower than Ms, is quenched 0.5～1 minute time of oil; Rapidly part is placed in to A again
c3in the salt bath furnace of+(30～50 ℃), insulation, the oil of quenching, repeat aforesaid operations 3～4 times.Although the method successfully realizes the grain ultrafining of structural alloy steel, has the following disadvantages: the material of the precious alloy such as Cr, the Mo element that (1) is only applicable to C >=0.35% and contains high level; (2) impact that does not have further detailed analysis grain ultrafining to produce mechanical property; (3) manufacturing process head, technological process more complicated, technique controlling difficulty is larger.
Summary of the invention
The problems that exist for current steel tube fabrication technique, the invention provides a kind of online low cost superfine crystal particle transformation induced plasticity steel seamless tube and preparation method thereof of manufacturing, object is to adopt intermediate-frequency induction heating technique, utilizes the chemical composition of ordinary low-carbon steel to produce the low cost superfine crystal particle transformation induced plasticity steel seamless tube with favorable comprehensive mechanical property.
A kind of online low cost superfine crystal particle transformation induced plasticity steel seamless tube of manufacturing, chemical constitution is C:0.10%～0.25% by mass percentage, Si:1.0%～1.8%, Mn:1.0%～1.9%, Nb<0.10%, Ti<0.08%, P≤0.006%, S≤0.007%, surplus is the impurity producing under Fe and smelting condition.Tensile strength >=the 900MPa of low cost superfine crystal particle transformation induced plasticity steel seamless tube, yield tensile ratio≤0.64, unit elongation >=24.0%, work hardening exponent >=0.23, anisotropic index >=1.01; The average grain size of microstructure all≤3 μ m, wherein residual austenite volume fraction is in 11.5～19.5% scopes.
Preferably, the tensile strength 900～1100MPa of low cost superfine crystal particle transformation induced plasticity steel seamless tube, yield tensile ratio 0.58～0.64, unit elongation 24.0～30%, work hardening exponent 0.23～0.35, anisotropic index 1.01～1.40; The average grain size of microstructure all≤3 μ m, wherein residual austenite volume fraction is in 11.5～19.5% scopes.
Preferred, the tensile strength 900～1000MPa of low cost superfine crystal particle transformation induced plasticity steel seamless tube, yield tensile ratio 0.58～0.64, unit elongation 24.0～30%, work hardening exponent 0.23～0.29, anisotropic index 1.11～1.35; The average grain size of microstructure all≤3 μ m, wherein residual austenite volume fraction is in 11.5～19.5% scopes.
Preferably, the yield strength 516～641MPa of low cost superfine crystal particle transformation induced plasticity steel seamless tube, tensile strength 905～1018MPa, yield tensile ratio 0.56～0.64, unit elongation 24.0～32.5%, work hardening exponent >=0.23, anisotropic index 1.1～1.5; The average grain size of microstructure all≤3 μ m, wherein residual austenite volume fraction is in 11.5～19.5% scopes.
Preferably, the strength and ductility product of low cost superfine crystal particle transformation induced plasticity steel seamless tube is 22729～30220MPa.%.
Realizing technical scheme of the present invention carries out according to following steps:
Smelt-forge rod-turning-heating-perforation-cold-drawn-intermediate-frequency induction heating-finished product
A preparation method for online manufacture low cost superfine crystal particle transformation induced plasticity steel seamless tube, is characterized in that comprising the following steps:
(1) the steel starting material after smelting are forged into bar, bar removes outside surface fold through turning and defect forms pipe, by heating of pipe blank to 1100～1250 ℃ and be incubated 2 hours laggard eleven punch 11s, then be cooled to room temperature, cooled pipe is carried out to 3～7 passage cold-drawns, obtain seamless cold drawing steel tube;
(2) adopt heating in medium frequency ruhmkorff coil to carry out circulating-heating+quench treatment>=3 times seamless cold drawing steel tube, wherein heating rate>=300 ℃/s, annealing temperature (A
c3-40 ℃)～(A
c3+ 10 ℃), annealing time 5～15s;
(3) the seamless cold drawing steel tube after annealing is cooled to 380～430 ℃ of Bainite Regions, isothermal processes 20～100s with the speed of >=50 ℃/s;
(4) isothermal steel pipe after treatment carried out air cooling, water-cooled or naturally cools to room temperature, obtaining superfine crystal particle transformation induced plasticity steel seamless tube.
Preferably, the seamless cold drawing steel tube that step 1) obtains meets size: wall thickness≤20mm, external diameter≤1000mm.
A
c3for ferrite in thermal treatment heat-processed changes austenitic temperature completely into.
The selected raw-material chemical constitution of steel of the present invention is C:0.10%～0.25% by mass percentage, Si:1.0%～1.8%, Mn:1.0%～1.9%, Nb<0.10%, Ti<0.08%, P≤0.006%, S≤0.007%, surplus is the impurity producing under Fe and smelting condition.
Compared with prior art, feature of the present invention and beneficial effect are:
1. target of the present invention is to utilize the chemical constitution study of existing ordinary low-carbon steel to develop the superfine crystal particle transformation induced plasticity steel seamless tube with favorable comprehensive mechanical property, and in industrial production, cost is lower.In addition by adjusting heat treatment process parameter, can control the each phase ratio in the microtexture of transformation induced plasticity steel seamless tube, and then obtain the transformation induced plasticity steel seamless tube of different mechanical properties, be applicable to the production of the transformation induced plasticity steel seamless tube of different chemical composition, different size, technique is relatively stable, cost is relatively low, reaches the effect of energy-conserving and environment-protective.
2. technical scheme of the present invention is to utilize heating in medium frequency ruhmkorff coil, is that ferrite+pearlitic seamless cold drawing steel tube carries out circulating-heating+quench treatment >=3 times by initial structure, thus effectively refinement grain-size, also increased grain boundary area.Because crystal boundary can be limited in certain scope viscous deformation, make distortion evenly, hinder again crack propagation simultaneously, thereby improve the strong plasticity of steel pipe, this has brought into play the potentiality of material greatly.And to meet the specification under the prerequisite of criterion, rationally controlled circulation number of times, so also can show the good prospect of energy efficient aspect.
3. technical scheme of the present invention is in the time carrying out circulating-heating+quench treatment, wherein heating rate >=300 ℃/s, super rapid heating makes the recrystallize in thermal treatment heat-processed start temperature rising, recrystallization temperature range extension, and final recrystallization crystal particle dimension reduces.The control that reduces to be subject to nucleation rate and the rate of growing up of recrystallization crystal particle dimension, when super rapid heating, do not have time enough to reply at the forming core initial stage, thereby before recrystallize, reply the deformation energy storage that consumes when lower with respect to heating rate seldom, recrystallization temperature is postponed to relatively high temperature simultaneously, and this is also that annealing temperature parameter is formulated as (A
c3-40 ℃)～(A
c3+ 10 ℃), want high cause with respect to conventional phase change induction plasticity steel annealing temperature.When super rapid heating because will require the forming core amount that reaches considerable within the limited time, so increased nucleation rate under higher recrystallization temperature, result makes grain-size more tiny, and crystal grain thinning is the only intensity that can improve, increase again the effective measure of its plastic property, thereby intensity and the plasticity of finished product phase change induction plasticity steel steel pipe synchronously increase simultaneously.In addition, super rapid heating makes to remain with a large amount of high density dislocations (as shown in Figure 6) in the final matrix of organizing, because matrix has important contribution to yield strength, thereby the yield strength higher (>=515MPa) of the transformation induced plasticity steel seamless tube for preparing of technical scheme of the present invention.
4. in the microstructure of the transformation induced plasticity steel seamless tube that technical scheme of the present invention prepares, distributing 11.5%～19.5% residual austenite of disperse, its form is not only confined to lumphy structure, and between bainite ferrite lath, can observe a large amount of sheet residual austenites, see Figure 4 and 5.Due in the process of bainitic transformation, the bainite of both sides is arranged carbon simultaneously in residual austenite, make this sheet residual austenite receive more carbon of discharging from bainite, thereby stability is higher, also larger to the contribution of phase change induction plasticity effect.And because bainite around produces hydrostatic pressure, can make martensitic transformation occur in very large range of strain, thereby make it have excellent strong plasticity coupling.
5. superfine crystal particle transformation induced plasticity steel seamless tube product of the present invention has excellent strong plasticity coupling, more than reaching 22729MPa%, in drawing process, there is not yield-point or yield point elongation, there is high work hardening exponent (n >=0.23) and anisotropic index (r >=1.01), and≤0.64 low yield strength ratio, its forming property is good, can be used as the starting material of clod wash steel tubing in different shapes; Meet the double requirements of internal high pressure forming to tubing intensity and plasticity simultaneously, thereby also can be applied to the large and complex-shaped thin-walled internal high pressure forming pipe fitting of the deflections such as automobile buffer beam.
Frequency Induction Heating quality product after treatment is good, control accuracy is high, facility investment is little, production cost is low, labor condition is good, energy-conserving and environment-protective, maintenance of the equipment are simple, is a technology being worthy to be popularized.
Accompanying drawing explanation
Fig. 1 is embodiment of the present invention intermediate-frequency induction heating process schematic representation;
Fig. 2 is the metallographic structure of the superfine crystal particle transformation induced plasticity steel seamless tube prepared of embodiment of the present invention technique 2-VI under LEICA DMIRM multifunctional optical microscope;
Fig. 3 is the metallographic structure of the superfine crystal particle transformation induced plasticity steel seamless tube prepared of embodiment of the present invention technique 2-VI under Quanta600 scanning electron microscope;
Fig. 4 is the sheet residual austenite pattern that superfine crystal particle transformation induced plasticity steel seamless tube prepared by embodiment of the present invention technique 2-VI is observed under transmission electron microscope.
Wherein (a): the light field pattern of sheet residual austenite, (b): the details in a play not acted out on stage, but told through dialogues pattern of sheet residual austenite, (c): the diffraction pattern that (a), circle identifies.
Fig. 5 is the she blocky type retained austenite pattern that the superfine crystal particle transformation induced plasticity steel seamless tube prepared in embodiment of the present invention technique 2-VI is observed under transmission electron microscope;
Wherein (a): the light field pattern of she blocky type retained austenite, (b): the details in a play not acted out on stage, but told through dialogues pattern of she blocky type retained austenite, (c): the diffraction pattern that (a), circle identifies.
Fig. 6 is the high density dislocation existing in the matrix observed under transmission electron microscope of the superfine crystal particle transformation induced plasticity steel seamless tube prepared in embodiment of the present invention technique 2-VI;
Fig. 7 is the stress strain curve figure of the superfine crystal particle transformation induced plasticity steel seamless tube prepared of embodiment of the present invention technique 5-II, 5-III, 5-IV and 5-VI.
Embodiment
In the embodiment of the present invention, the selected raw-material chemical constitution of steel is C:0.10%～0.25% by mass percentage, Si:1.0%～1.8%, Mn:1.0%～1.9%, Nb<0.10%, Ti<0.08%, P≤0.006%, S≤0.007%, surplus is the impurity producing under Fe and smelting condition.
In the embodiment of the present invention, the ingot casting after smelting is forged into bar, bar removes outside surface fold through turning and defect forms pipe, by heating of pipe blank to 1100～1250 ℃ and be incubated 2 hours laggard eleven punch 11s, then be cooled to room temperature, cooled pipe is carried out to 3～7 passage cold-drawns, be met the seamless cold drawing steel tube of size wall thickness≤20mm, external diameter≤1000mm.
In the embodiment of the present invention, adopt heating in medium frequency ruhmkorff coil to carry out circulating-heating+quench treatment>=3 times seamless cold drawing steel tube, wherein heating rate>=300 ℃/s, annealing temperature (A
c3-40 ℃)～(A
c3+ 10 ℃), annealing time 5～15s.
In the embodiment of the present invention, the seamless cold drawing steel tube after annealing is cooled to 380～430 ℃ of Bainite Regions with the speed of >=50 ℃/s, air cooling, water-cooled or naturally cool to room temperature after isothermal processes 20～100s, obtain superfine crystal particle transformation induced plasticity steel seamless tube.
Middle part line from the transformation induced plasticity steel seamless tube for preparing in the invention process example cuts out metallographic specimen, after Yan Mo ﹑ polishing, adopt 4% nitric acid alcohol to corrode, its microstructure is observed under LEICADMIRM multifunctional optical microscope and Quanta600 scanning electron microscope.Utilize the paralympic and Dislocation Morphology of H-800 type transmission electron microscope observing.
Transmission and X-ray diffraction analysis are carried out in tube wall sampling along the transformation induced plasticity steel seamless tube preparing in the invention process example, observe respectively residual austenite pattern and volume fraction.When X-ray diffractometer is measured the residual austenite relative quantity of sample, measure (220)
γ(200)
αthe diffracted intensity at peak, adopts formula V
γ=1.4I/
γ(I
α+ 1.4I
γ) try to achieve the relative quantity of residual austenite; Ferrite grain size is got 5 organization charts and is carried out analytical calculation, then averages, and grain-size adopts secant method to measure.
In the invention process example, make tension specimen from the transformation induced plasticity steel seamless tube sampling preparing by standard, effectively gauge length is 50 × 15mm, carries out Mechanics Performance Testing, draw speed 5mm/min on SANA universal testing machine.
Below the specific embodiment of the present invention is described in further detail, but embodiments of the present invention are not limited to this.
The selected steel chemical constitution of the present embodiment is C:0.101% by mass percentage, Si:1.80%, and Mn:1.09%, P:0.002%, S:0.005%, surplus is Fe.Record its A by thermal expansion curve
c1and A
c3be respectively 721 and 849 ℃.Described A
c1for ferrite in annealing heating process starts temperature to austenitic transformation, A
c3for ferrite in annealing heating process is to austenitic transformation end temp.Because the composition difference of steel is (as the variation) ﹑ changes in process parameters (as heating rate) of Tan Han Liang ﹑ silicone content etc., A
c1﹑ A
c3capital changes thereupon.Steel of the present invention records its A by thermal expansion curve
c1and A
c3.
Ingot casting after smelting is forged into bar, bar removes outside surface fold through turning and defect forms pipe, by heating of pipe blank to 1100 ℃ and be incubated 2 hours laggard eleven punch 11s, then be cooled to room temperature, cooled pipe is carried out to 5 passage cold-drawns, obtain the seamless cold drawing steel tube of wall thickness 1.2mm, external diameter 41mm.
Adopt heating in medium frequency ruhmkorff coil to carry out circulating-heating+quench treatment 4 times seamless cold drawing steel tube, concrete parameter and annealing is in table 1, wherein approximately 300 ℃/s of heating rate, annealing temperature (A
c3-39 ℃)～(A
c3+ 1 ℃), annealing time 5～15s.Seamless cold drawing steel tube after annealing is cooled to 380～430 ℃ of Bainite Regions with the speed of >=50 ℃/s, after isothermal processes 30～90s, air cooling is to room temperature, obtain superfine crystal particle transformation induced plasticity steel seamless tube, under the processing condition of formulating at the present embodiment, average grain size all≤3 μ m, in microstructure, residual austenite volume fraction is in 13.9～19.5% scopes.
The parameter and annealing of table 1 embodiment 1 and mechanical property
Wherein: n is work hardening exponent, and this index is defined by true stress strain stress relation, refer to the power exponent n in true stress S mono-true strain ε relational expression when metal sheet profiled, relational expression is as follows:
S=K ε
n, in formula, K is specific strength.
R is anisotropic index, is calculated by following formula according to volume invariance principle before and after viscous deformation:
R=ln (b/b
0)/ln (b
0/ Lb), in formula, L is that sample is formulated the gauge length after strain, b is that sample is formulated the width after strain, b
0for sample original width.
The superfine crystal particle transformation induced plasticity steel seamless tube preparing is carried out to Mechanics Performance Testing on tensile testing machine, and test result is in table 1.Under the processing condition of formulating at the present embodiment, its tensile strength >=905MPa, yield tensile ratio≤0.60, unit elongation >=27.6%, strength and ductility product >=25834MPa.%.High unit elongation, work hardening exponent (n >=0.25) and anisotropic index (r >=1.24), prove that superfine crystal particle transformation induced plasticity steel seamless tube of the present invention has good forming property under room temperature state, be suitable for the tubing processing of complicated shape.
Embodiment 2
The selected steel chemical constitution of the present embodiment is C:0.16% by mass percentage, Si:1.35%, and Mn:1.51%, P:0.005%, S:0.007%, surplus is Fe.Record its A by thermal expansion curve
c1and A
c3be respectively 735 and 870 ℃.
Ingot casting after smelting is forged into bar, bar removes outside surface fold through turning and defect forms pipe, by heating of pipe blank to 1100 ℃ and be incubated 2 hours laggard eleven punch 11s, then be cooled to room temperature, cooled pipe is carried out to 4 passage cold-drawns, obtain the seamless cold drawing steel tube of wall thickness 2.1mm, external diameter 53mm.
Adopt heating in medium frequency ruhmkorff coil to carry out circulating-heating+quench treatment 4 times seamless cold drawing steel tube, concrete parameter and annealing is in table 2, wherein approximately 400 ℃/s of heating rate, annealing temperature (A
c3-40 ℃)～(A
c3+ 10 ℃), annealing time 5～15s.Seamless cold drawing steel tube after annealing is cooled to 380～426 ℃ of Bainite Regions with the speed of >=50 ℃/s, after isothermal processes 30～90s, air cooling is to room temperature, obtain superfine crystal particle transformation induced plasticity steel seamless tube, under the processing condition of formulating at the present embodiment, average grain size all≤2.5 μ m, in microstructure, residual austenite volume fraction is in 11.6～15.7% scopes.
The parameter and annealing of table 2 embodiment 2 and mechanical property
Take technique 2-VI as example, the microstructure of low cost superfine crystal particle transformation induced plasticity steel seamless tube is described.The microstructure of superfine crystal particle transformation induced plasticity steel seamless tube prepared by embodiment 2-VI technique and scanning tissue are respectively as shown in Figures 2 and 3.As seen from the figure, tissue is made up of the residual austenite (shown in Fig. 3 arrow) of ferrite, bainite and 15.7%, average grain size is (2.0 ± 0.5) μ m, can infer, the phase change induction plasticity steel weldless steel tube that obtains matrix after colddrawing seamless pipe is carried out to Frequency Induction Heating processing after austenitizing+quench treatment continuously for several times and be ultrafine-grained (UFG) microstructure is feasible.
In tissue, the form of residual austenite is not only confined to lumphy structure, and between bainite ferrite lath, can observe a large amount of sheet residual austenites, sees Figure 4 and 5.Due in the process of bainitic transformation, the bainite of both sides is arranged carbon simultaneously in residual austenite, make this sheet residual austenite receive more carbon of discharging from bainite, thereby stability is higher, also larger to the contribution of phase change induction plasticity effect.And because bainite around produces hydrostatic pressure, can make martensitic transformation occur in very large range of strain, unit elongation reaches 25.7%.Under transmission electron microscope, observe except residual austenite is present in ferrite, high density dislocation is distributed in matrix, as shown in Figure 6, and because matrix has important contribution to yield strength, thereby the yield strength of continuous annealing steel is higher, reaches 571MPa.
The superfine crystal particle transformation induced plasticity steel seamless tube preparing is carried out to Mechanics Performance Testing on tensile testing machine, and test result is in table 2.Under the processing condition of formulating at the present embodiment, its tensile strength >=920MPa, yield tensile ratio≤0.63, unit elongation >=24.5%, work hardening exponent (n) >=0.23, anisotropic index (r) >=1.07, strength and ductility product >=22729MPa.%.
The selected steel chemical constitution of the present embodiment is C:0.184% by mass percentage, Si:1.00%, and Mn:1.87%, P:0.006%, S:0.003%, surplus is Fe.Record its A by thermal expansion curve
c1and A
c3be respectively 730 and 850 ℃.
Ingot casting after smelting is forged into bar, bar removes outside surface fold through turning and defect forms pipe, by heating of pipe blank to 1200 ℃ and be incubated 2 hours laggard eleven punch 11s, then be cooled to room temperature, cooled pipe is carried out to 4 passage cold-drawns, obtain the seamless cold drawing steel tube of wall thickness 1.20mm, external diameter 43mm.
Adopt heating in medium frequency ruhmkorff coil to carry out circulating-heating+quench treatment 4 times seamless cold drawing steel tube, concrete parameter and annealing is in table 3, wherein approximately 300 ℃/s of heating rate, annealing temperature (A
c3-40 ℃)～(A
c3+ 10 ℃), annealing time 5～10s.Seamless cold drawing steel tube after annealing is cooled to 385～430 ℃ of Bainite Regions with the speed of >=50 ℃/s, after isothermal processes 20～100s, air cooling is to room temperature, obtain superfine crystal particle transformation induced plasticity steel seamless tube, under the processing condition of formulating at the present embodiment, average grain size all≤3 μ m, in microstructure, residual austenite volume fraction is in 12.9～16.1% scopes.
The superfine crystal particle transformation induced plasticity steel seamless tube preparing is carried out to Mechanics Performance Testing on tensile testing machine, and test result is in table 3.Under the processing condition of formulating at the present embodiment, its tensile strength >=942MPa, yield tensile ratio≤0.64, unit elongation >=24.5%, work hardening exponent (n) >=0.23, anisotropic index (r) >=1.01, strength and ductility product >=23618MPa.%.
The parameter and annealing of table 3 embodiment 3 and mechanical property
Embodiment 4
The selected steel chemical constitution of the present embodiment is C:0.20% by mass percentage, Si:1.23%, and Mn:1.32%, Nb:0.0298%, Ti:0.031%, P:0.001%, S:0.004%, surplus is Fe.Record its A by thermal expansion curve
c1and A
c3be respectively 755 and 880 ℃.
Ingot casting after smelting is forged into bar, bar removes outside surface fold through turning and defect forms pipe, by heating of pipe blank to 1250 ℃ and be incubated 2 hours laggard eleven punch 11s, then be cooled to room temperature, cooled pipe is carried out to 7 passage cold-drawns, obtain the seamless cold drawing steel tube of wall thickness 0.8mm, external diameter 100mm.
Adopt heating in medium frequency ruhmkorff coil to carry out circulating-heating+quench treatment 4 times seamless cold drawing steel tube, concrete parameter and annealing is in table 4, wherein approximately 400 ℃/s of heating rate, annealing temperature (A
c3-40 ℃)～(A
c3+ 10 ℃), annealing time 5～15s.Seamless cold drawing steel tube after annealing is cooled to 380～430 ℃ of Bainite Regions with the speed of >=50 ℃/s, after isothermal processes 30～90s, air cooling is to room temperature, obtain superfine crystal particle transformation induced plasticity steel seamless tube, under the processing condition of formulating at the present embodiment, average grain size all≤2.5 μ m, in microstructure, residual austenite volume fraction is in 14.9～17.2% scopes.
The superfine crystal particle transformation induced plasticity steel seamless tube preparing is carried out to Mechanics Performance Testing on tensile testing machine, and test result is in table 4.Under the processing condition of formulating at the present embodiment, its tensile strength >=954MPa, yield tensile ratio≤0.63, unit elongation >=24.0%, work hardening exponent (n) >=0.23, anisotropic index (r) >=1.10, strength and ductility product >=23352MPa.%.
The parameter and annealing of table 4 embodiment 4 and mechanical property
The selected steel chemical constitution of the present embodiment is C:0.22% by mass percentage, Si:1.52%, and Mn:1.63%, Nb:0.099%, Ti:0.071%, P:0.004%, S:0.003%, surplus is Fe.Record its A by thermal expansion curve
c1and A
c3be respectively 723 and 876 ℃.
Ingot casting after smelting is forged into bar, bar removes outside surface fold through turning and defect forms pipe, by heating of pipe blank to 1250 ℃ and be incubated 2 hours laggard eleven punch 11s, then be cooled to room temperature, cooled pipe is carried out to 7 passage cold-drawns, obtain the seamless cold drawing steel tube of wall thickness 0.8mm, external diameter 100mm.
Adopt heating in medium frequency ruhmkorff coil to carry out circulating-heating+quench treatment 4 times seamless cold drawing steel tube, concrete parameter and annealing is in table 5, wherein approximately 300 ℃/s of heating rate, annealing temperature (A
c3-36 ℃)～(A
c3+ 4 ℃), annealing time 5～15s.Seamless cold drawing steel tube after annealing is cooled to 385～430 ℃ of Bainite Regions with the speed of >=50 ℃/s, after isothermal processes 30～100s, air cooling is to room temperature, obtain superfine crystal particle transformation induced plasticity steel seamless tube, under the processing condition of formulating at the present embodiment, average grain size all≤3 μ m, in microstructure, residual austenite volume fraction is in 16.6～19.0% scopes, in table 5.
The superfine crystal particle transformation induced plasticity steel seamless tube preparing is carried out to Mechanics Performance Testing on tensile testing machine, technique 5-II, 5-III, 5-IV and the stress strain curve of 5-VI in the time of room temperature are as shown in Figure 7, stress strain curve is all continuous yield situation, does not occur yield point elongation or upper and lower yield-point.Under the processing condition of formulating at the present embodiment, its tensile strength >=960MPa, yield tensile ratio≤0.63, unit elongation >=26.1%, work hardening exponent (n) >=0.23, anisotropic index (r) >=1.02, strength and ductility product >=25632MPa.%.
The parameter and annealing of table 5 embodiment 5 and mechanical property
The selected steel chemical constitution of the present embodiment is C:0.25% by mass percentage, Si:1.02%, and Mn:1.90%, P:0.005%, S:0.003%, surplus is Fe.Record its A by thermal expansion curve
c1and A
c3be respectively 726 and 845 ℃.
Ingot casting after smelting is forged into bar, bar removes outside surface fold through turning and defect forms pipe, by heating of pipe blank to 1100 ℃ and be incubated 2 hours laggard eleven punch 11s, then be cooled to room temperature, cooled pipe is carried out to 4 passage cold-drawns, obtain the seamless cold drawing steel tube of wall thickness 5.0mm, external diameter 1000mm.
Adopt heating in medium frequency ruhmkorff coil to carry out circulating-heating+quench treatment 7 times, wherein approximately 300 ℃/s of heating rate, annealing temperature (A seamless cold drawing steel tube
c3-35 ℃)～(A
c3+ 5 ℃), annealing time 5～15s.Seamless cold drawing steel tube after annealing is cooled to 380～430 ℃ of Bainite Regions with the speed of >=50 ℃/s, and after isothermal processes 30～100s, air cooling, to room temperature, obtains superfine crystal particle transformation induced plasticity steel seamless tube of the present invention.
Embodiment 7
The selected steel chemical composition of the present embodiment is with embodiment 5.
Ingot casting after smelting is forged into bar, bar removes outside surface fold through turning and defect forms pipe, by heating of pipe blank to 1250 ℃ and be incubated 2 hours laggard eleven punch 11s, then be cooled to room temperature, cooled pipe is carried out to 3 passage cold-drawns, obtain the seamless cold drawing steel tube of wall thickness 20mm, external diameter 33mm.
Adopt heating in medium frequency ruhmkorff coil to carry out circulating-heating+quench treatment 7 times, wherein approximately 400 ℃/s of heating rate, annealing temperature (A seamless cold drawing steel tube
c3-36 ℃)～(A
c3+ 4 ℃), annealing time 5～15s.Seamless cold drawing steel tube after annealing is cooled to 380～430 ℃ of Bainite Regions with the speed of >=50 ℃/s, and after isothermal processes 30～100s, air cooling, to room temperature, obtains superfine crystal particle transformation induced plasticity steel seamless tube of the present invention.
Claims (8)
1. a low cost superfine crystal particle transformation induced plasticity steel seamless tube, it is characterized in that, chemical constitution is C:0.10%～0.25% by mass percentage, Si:1.0%～1.8%, Mn:1.0%～1.9%, Nb<0.10%, Ti<0.08%, P≤0.006%, S≤0.007%, surplus is the impurity producing under Fe and smelting condition.Tensile strength >=the 900MPa of low cost superfine crystal particle transformation induced plasticity steel seamless tube, yield tensile ratio≤0.64, unit elongation >=24.0%, work hardening exponent >=0.23, anisotropic index >=1.01; The average grain size of microstructure all≤3 μ m, wherein residual austenite volume fraction is in 11.5～19.5% scopes.
2. low cost superfine crystal particle transformation induced plasticity steel seamless tube as claimed in claim 1, it is characterized in that, tensile strength 900～the 1100MPa of low cost superfine crystal particle transformation induced plasticity steel seamless tube, yield tensile ratio 0.58～0.64, unit elongation 24.0～30%, work hardening exponent 0.23～0.35, anisotropic index 1.01～1.40; The average grain size of microstructure all≤3 μ m, wherein residual austenite volume fraction is in 11.5～19.5% scopes.
3. low cost superfine crystal particle transformation induced plasticity steel seamless tube as claimed in claim 1 or 2, it is characterized in that, tensile strength 900～the 1000MPa of low cost superfine crystal particle transformation induced plasticity steel seamless tube, yield tensile ratio 0.58～0.64, unit elongation 24.0～30%, work hardening exponent 0.23～0.29, anisotropic index 1.11～1.35; The average grain size of microstructure all≤3 μ m, wherein residual austenite volume fraction is in 11.5～19.5% scopes.
4. low cost superfine crystal particle transformation induced plasticity steel seamless tube as claimed in claim 1 or 2, it is characterized in that, yield strength 516～the 641MPa of low cost superfine crystal particle transformation induced plasticity steel seamless tube, tensile strength 905～1018MPa, yield tensile ratio 0.56～0.64, unit elongation 24.0～32.5%, work hardening exponent >=0.23, anisotropic index 1.1～1.5; The average grain size of microstructure all≤3 μ m, wherein residual austenite volume fraction is in 11.5～19.5% scopes.
5. the low cost superfine crystal particle transformation induced plasticity steel seamless tube as described in claim 1～4 any one, is characterized in that, the strength and ductility product of low cost superfine crystal particle transformation induced plasticity steel seamless tube is 22729～30220MPa.%.
6. a preparation method for the low cost superfine crystal particle transformation induced plasticity steel seamless tube as described in claim 1～5 any one, is characterized in that comprising the following steps:
(1) the steel starting material after smelting are forged into bar, bar removes outside surface fold through turning and defect forms pipe, by heating of pipe blank to 1100～1250 ℃ and be incubated 2 hours laggard eleven punch 11s, then be cooled to room temperature, cooled pipe is carried out to 3～7 passage cold-drawns, obtain seamless cold drawing steel tube;
(2) adopt heating in medium frequency ruhmkorff coil to carry out circulating-heating+quench treatment>=3 times seamless cold drawing steel tube, wherein heating rate>=300 ℃/s, annealing temperature (A
c3-40 ℃)～(A
c3+ 10 ℃), annealing time 5～15s;
(3) the seamless cold drawing steel tube after annealing is cooled to 380～430 ℃ of Bainite Regions, isothermal processes 20～100s with the speed of >=50 ℃/s;
(4) isothermal steel pipe after treatment carried out air cooling, water-cooled or naturally cools to room temperature, obtaining superfine crystal particle transformation induced plasticity steel seamless tube.
7. the preparation method of low cost superfine crystal particle transformation induced plasticity steel seamless tube as claimed in claim 6, is characterized in that, the seamless cold drawing steel tube that step 1) obtains meets size: wall thickness≤20mm, external diameter≤1000mm.
8. the preparation method of the low cost superfine crystal particle transformation induced plasticity steel seamless tube as described in claim 6 or 7, it is characterized in that, the raw-material chemical constitution of the selected steel of stating is C:0.10%～0.25% by mass percentage, Si:1.0%～1.8%, Mn:1.0%～1.9%, Nb<0.10%, Ti<0.08%, P≤0.006%, S≤0.007%, surplus is the impurity producing under Fe and smelting condition.
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| CN108179256A (en) * | 2018-02-06 | 2018-06-19 | 东北大学 | A kind of heat treatment method for improving Cold-Rolled TRIP Steel strength and ductility product |
| CN109182923A (en) * | 2018-11-14 | 2019-01-11 | 东北大学 | A kind of low-carbon microalloyed high strength and ductility cold rolling TRIP980 Heat-Treatment of Steel method |
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