CN101838776A - High-strength and low-temperature tough steel - Google Patents
High-strength and low-temperature tough steel Download PDFInfo
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Abstract
The invention relates to steel, in particular to high-strength and low-temperature tough steel. The tough steel is characterized by comprising the following chemical components in percentage by weight: 0.26-0.35 percent of C, 0.1-0.4. percent of Si, 0.20-1.55 percent of Mn, not more than 0.030 percent of P, not more than 0.010 percent of S, 0.10-0.30 percent of Mo, two or more of not more than 0.25 percent of Cr, not more than 0.20 percent of Ni, not more than 0.20 percent of Cu, not more than 0.20 percent of V and not more than 0.05 percent of Ti, and the balance of Fe. The invention has the advantages of pure steel quality, stable texture, high strength, stability, favorable low-temperature toughness at 40 DEG C below zero, simple process, lower cost and benefit to popularization and application. The steel is the most suitable to be used for engineering machineries and railway accessories used under low temperature conditions in alpine regions, such as joint bars for railway steel rail and the like.
Description
Technical field: the present invention relates to steel, be specially a kind of high-strength and low-temperature tough steel.
Background technology: strict in technical feature about the important accessory rail joint clamping plate of railway at present, the domestic beginning after 1993 carried out the iron mark that the Ministry of Railways formulates: TB/T 2345-1993, TB/T2342.1～4-1993, employing B7 and YW52 steel are done.
Its chemical ingredients is (%):
B7 steel: C 0.50-0.62, Mn 0.50-0.80, Si 0.15-0.35, P≤0.045, S≤0.050.
Mechanical property after this steel thermal treatment is: tensile strength 〉=785MPa, yield strength 〉=520MPa, elongation 〉=9%, relative reduction in area 〉=20%, Brinell hardness HB 227～388,30 ° at clod wash angle are intact.
And U.S. side requires the mechanical property of technical acceptance under the railway casting rail joint clamping plate steel low temperature as follows:
Domesticly prove in secular application in practice that B7 and YW52 steel are only applicable to normal temperature and use to-20 ℃ situation.Because China is vast in territory, regional difference variation is bigger, and B7 and YW52 steel easily produce fracture under cold condition, so fracture accident often takes place on trunk railway, has influenced the normal operation of traffic.At present, because the continuous speed-raising of railway, to the demands for higher performance of rail joint clamping plate, the important accessory steel for railway rail joint bar of B7 and the production of YW52 steel no longer is applicable to the requirement of growing high-speed railway operation.
Before the present invention proposed, the similar technical products that relates to medium carbon low alloy steel manufacturing field was less, all proposes at special applied environment basically, and its advantage and drawback are different.Through inquiry Chinese utility model patent is arranged, Granted publication CN2516577Y " XY30 rail joint bar ", wherein the content of molybdenum is higher, scope is 0.25-0.35%, but also must contain elements such as vanadium, aluminium, niobium, rare earth, the low temperature impact test temperature is-50 ℃, and this patent weak point is that the production cost of steel is very high.And the invention steel that relates to low-carbon low-alloy steel manufacturing field is more, as Chinese patent publication number CN101235466A " a kind of high ductility negative 110 degree low-temperature steel and manufacture method thereof ", patent publication No. CN101381841A " a kind of high-intensity high-tenacity-50 ℃ low-temperature steel and manufacture method thereof " etc., though all obtained excellent low-temperature flexibility, intensity index is all lower.
Summary of the invention: the rolling technology excellent property of steel of the present invention, suitable start rolling temperature by the control steel, processing parameters such as controlled rolling accumulative total draft, every time draft of last three roads, finishing temperature, quenching temperature, cool time, tempering holding temperature, tempering insulation time, the target of the obdurability combination of the high-strength and low-temperature tough steel of realization steel.The present invention has that steel is pure, tissue is stable, intensity is high, the advantage of stable and good-40 ℃ of low-temperature flexibilities, and technology is simple, cost is lower, be beneficial to and apply.Steel of the present invention is suitable as under the extremely frigid zones cold condition engineering machinery, the railway casting steel that uses, as railway track with joint bar etc.The object of the present invention is achieved like this: chemical ingredients is by weight percentage: C 0.26-0.35, Si 0.12-0.40, Mn 1.20-1.55, P≤0.030, S≤0.010, Mo 0.10-0.30, contain in Cr≤0.25, Ni≤0.20, Cu≤0.20, V≤0.20, Ti≤0.05 two or more in addition, surplus is Fe.Chemical ingredients is by weight percentage: C 0.26, Si 0.22, Mn 1.53, P0.028, S0.010, Mo 0.11, and Cr0.24, Ni0.03, Cu0.03, V0.08, Ti0.01, surplus is Fe.C 0.30, Si 0.24, Mn 1.34, P0.014, S 0.009, Mo 0.12, Cr0.20, Ni0.01, Cu0.05, V0.07, Ti0.02, surplus is Fe.C 0.34, Si 0.33, Mn 1.43, P0.017, S0.008, Mo 0.14, Cr0.22, Ni0.02, Cu0.03, V0.09, Ti0.02, surplus is Fe.C 0.30, Si 0.31, Mn 1.43, P0.012, S0.010, Mo 0.18, Cr0.19, Ni0.02, Cu0.03, V0.09, Ti0.01, surplus is Fe.C0.27, Si 0.28, Mn 1.39, P0.010, S0.009, Mo 0.11, Cr0.23, Ni0.01, Cu0.05, V0.07, Ti0.02, surplus is Fe.C 0.32, Si 0.32, Mn 1.43, P0.024, S0.007, Mo 0.15, Cr0.20, Ni0.03, Cu0.03, V0.10, Ti0.02, surplus is Fe.Advantage of the present invention is: the present invention has that steel is pure, tissue is stable, intensity is high, the advantage of stable and good-40 ℃ of low-temperature flexibilities, and technology is simple, cost is lower, be beneficial to and apply.Steel of the present invention is suitable as under the extremely frigid zones cold condition engineering machinery, the railway casting steel that uses most, as railway track with joint bar etc.
Description of drawings: Fig. 1 is a fish tail slab tempered sorbite tissue of the present invention; Fig. 2 is fish tail slab of the present invention testing laboratory sample impact property measurement result, ballistic work (under 40 ℃).
Embodiment:
Example 1
1, a kind of chemical ingredients %:C 0.26 of steel grade, Si 0.22, Mn 1.53, P 0.028, S 0.010, Mo 0.11, Cr 0.24, Ni 0.03, Cu 0.03, V≤0.08, Ti≤0.01, surplus is Fe.
2, manufacture method: adopt the ultra high power direct current electric arc furnace to convert and join 60% molten iron, refining of LF ladle argon-blown and line feeding are handled, and carry out continuous casting according to Clean Steel technology.
3, rolling technology: the start rolling temperature 1100-1130 of steel ℃, control accumulative total draft 〉=55%, every time draft of last three roads 〉=8%, 900 ℃ of finishing temperatures.
4, heat treating regime: adopt the modifier treatment mode.
Thermal treatment heating:, come out of the stove then 940 ℃ of insulations 45 minutes.
Quench: go into water temp at 920 ± 10 ℃, water temperature is controlled at 60 ℃ ± 10 ℃, 62 seconds cool times.
Tempering: be warming up to 610 ± 10 ℃, began to calculate soaking time 50 minutes.
5, Performance Detection: fatigue strength: 5373000 times.
Example 2
1, a kind of chemical ingredients %:C 0.30 of steel grade, Si 0.24, Mn 1.34, P 0.014, S 0.009, Mo 0.12, Cr 0.20, Ni 0.01, Cu 0.05, V≤0.07, Ti≤0.02, surplus is Fe.
2, manufacture method: adopt the ultra high power direct current electric arc furnace to convert and join 62% molten iron, refining of LF ladle argon-blown and line feeding are handled, and carry out continuous casting according to Clean Steel technology.
3, rolling technology: the start rolling temperature 1095-1120 of steel ℃, control accumulative total draft 〉=55%, every time draft of last three roads 〉=8%, 850 ℃ of finishing temperatures.
4, heat treating regime: adopt the modifier treatment mode.
Thermal treatment heating:, come out of the stove then 900 ℃ of insulations 40 minutes.
Quench: go into water temp at 880 ± 10 ℃, water temperature is controlled at 40 ℃ ± 10 ℃, 62 seconds cool times.
Tempering: be warming up to 550 ± 10 ℃, began to calculate soaking time 50 minutes.
5, Performance Detection: fatigue strength: 8974000 times.
Example 3
1, a kind of chemical ingredients %:C 0.34 of steel grade, Si 0.33, Mn 1.43, P 0.017, S 0.008, Mo 0.14, Cr 0.22, Ni 0.02, Cu 0.03, V≤0.09, Ti≤0.02, surplus is Fe.
2, manufacture method: adopt the ultra high power direct current electric arc furnace to convert and join 55% molten iron, refining of LF ladle argon-blown and line feeding are handled, and carry out continuous casting according to Clean Steel technology.
3, rolling technology: the start rolling temperature 1095-1120 of steel ℃, control accumulative total draft 〉=55%, every time draft of last three roads 〉=8%, 820 ℃ of finishing temperatures.
4, heat treating regime: adopt the modifier treatment mode.
Thermal treatment heating:, come out of the stove then 900 ℃ of insulations 40 minutes.
Quench: go into water temp at 880 ± 10 ℃, water temperature is controlled at 40 ℃ ± 10 ℃, 62 seconds cool times.
Tempering: be warming up to 580 ± 10 ℃, began to calculate soaking time 50 minutes.
5, Performance Detection: fatigue strength: 6748000 times.
Example 4
1, a kind of chemical ingredients %:C 0.30 of steel grade, Si 0.31, Mn 1.43, P 0.012, S 0.010, Mo 0.18, Cr 0.19, Ni 0.02, Cu 0.03, V≤0.09, Ti≤0.01, surplus is Fe.
2, manufacture method: adopt the ultra high power direct current electric arc furnace to convert and join 58% molten iron, refining of LF ladle argon-blown and line feeding are handled, and carry out continuous casting according to Clean Steel technology.
3, rolling technology: the start rolling temperature 1150-1200 of steel ℃, control accumulative total draft 〉=55%, every time draft of last three roads 〉=8%, 840 ℃ of finishing temperatures.
4, heat treating regime: adopt the modifier treatment mode.
Thermal treatment heating:, come out of the stove then 900 ℃ of insulations 40 minutes.
Quench: go into water temp at 880 ± 10 ℃, water temperature is controlled at 40 ℃ ± 10 ℃, 62 seconds cool times.
Tempering: be warming up to 610 ± 10 ℃, began to calculate soaking time 50 minutes.
5, Performance Detection: fatigue strength: 10052700 times.
Example 5
1, a kind of chemical ingredients %:C 0.27 of steel grade, Si 0.28, Mn 1.39, P 0.010, S 0.009, Mo 0.11, Cr 0.23, Ni 0.01, Cu 0.05, V≤0.07, Ti≤0.02, surplus is Fe.
2, manufacture method: adopt the ultra high power direct current electric arc furnace to convert and join 65% molten iron, refining of LF ladle argon-blown and line feeding are handled, and carry out continuous casting according to Clean Steel technology.
3, rolling technology: the start rolling temperature 1150-1200 of steel ℃, control accumulative total draft 〉=55%, every time draft of last three roads 〉=8%, 880 ℃ of finishing temperatures.
4, heat treating regime: adopt the modifier treatment mode.
Thermal treatment heating:, come out of the stove then 920 ℃ of insulations 40 minutes.
Quench: go into water temp at 900 ± 10 ℃, water temperature is controlled at 30 ℃ ± 10 ℃, 55 seconds cool times.
Tempering: be warming up to 600 ± 10 ℃, began to calculate soaking time 60 minutes.
5, Performance Detection: fatigue strength: 10894100 times.
Example 6
1, a kind of chemical ingredients %:C 0.32 of steel grade, Si 0.32, Mn 1.43, P 0.024, S 0.007, Mo 0.15, Cr 0.20, Ni 0.03, Cu 0.03, V≤0.10, Ti≤0.02, surplus is Fe.
2, manufacture method: adopt the ultra high power direct current electric arc furnace to convert and join 50% molten iron, refining of LF ladle argon-blown and line feeding are handled, and carry out continuous casting according to Clean Steel technology.
3, rolling technology: the start rolling temperature 1120-1160 of steel ℃, control accumulative total draft 〉=55%, every time draft of last three roads 〉=8%, 840 ℃ of finishing temperatures.
4, heat treating regime: adopt the modifier treatment mode.
Thermal treatment heating:, come out of the stove then 920 ℃ of insulations 40 minutes.
Quench: go into water temp at 890 ± 10 ℃, water temperature is controlled at 30 ℃ ± 10 ℃, 60 seconds cool times.
Tempering: be warming up to 610 ± 10 ℃, began to calculate soaking time 50 minutes.
5, Performance Detection: fatigue strength: 11660000 times.
One, prior art
1, the basic problem of B7 steel
According to TB/T 2345-1993 " 43-75kg/m rail with joint bar supply technical requirements ", to chemical ingredients, the mechanical property requirements of B7 steel defined see Table 1 with table 2.
Table 1 B7 steel main chemical compositions
The main mechanical property of table 2 B7 steel
Annotate: data are the test parameter under the normal temperature condition in the table.
This standard allows the B7 steel behind heating quenching (allowing with high-temperature water or fluid), can adopt self waste heat tempering mode to handle and obtain the finished product, fundamental relation according to Metal Material ﹠ Heat Treatment, adopt and quench and the integrated operation of tempering, the difficult accurately quenching and tempering quality of control material, and might draw following problem:
(1) whether high temperature or low temperature brittleness refined zone have been avoided in strictness to workpiece auto-tempering temperature, if uncertain factor is arranged, high fragility tissue can occur.
(2) when quenching and tempering are carried out continuously, to control the isothermal transformation temperature and time of Austria's body is difficult, the misfeasance meeting causes the generation of other phase transformation.(the austenite time temperature transformation curve is referring to the relevant speciality data)
A. pearlitic structure may appear
B. the plate martensite tissue may appear
C. bainite structure may appear
(3) organize the probability problem about plate martensite occurring
It is generally acknowledged that during low levels, the back of quenching is resulting to be the lath martensite tissue in the carbon content in the steel is in; During high-content, the back of quenching is resulting to be needle-like and sheet mixed type martensitic stucture in the carbon content in the steel is in; When carbon content during near high carbon steel (being C 〉=0.6%), the resulting plate martensite tissue that mostly is.
The martensitic essential characteristic of sheet (or needle-like) is crisp rigid tissue and instability, and by the B7 summer that steel is done has been confirmed than sample v-notch shock test, what wherein the tough break area only accounted for total area of fracture has 2%.After equally above-mentioned quenching sample being carried out spending temper in 1 hour 480, resultant is sorbite+ferrite, has reduced the fatigue strength of material.
Above verification experimental verification following some conclusion:
A. the splice bar that adopts the B7 steel to make at present, the feature of the material that under normal temperature environment, enbrittled;
B. infer according to impact fracture character, the fragility of B7 steel than the alternating temperature degree be not less than+30 ℃;
C. when employing self temperature tempering, its organizational form is a plate martensite;
D. when forcing tempering, resultant is Suo Huati+ferrite, the thick fatigue property that reduces material of its metallographic structure.
Therefore, the splice bar of employing B7 steel grade manufacturing is difficult to satisfy the actual service requirements of circuit under the microthermal climate condition, brings very big hidden danger especially for the transportation safety of speed-raising, heavy-haul line.
Table 3 B7 steel matter impact property assay
Summer is than sample v-notch
| Sample number into spectrum | Test temperature ℃ | Sample cross is amassed cm 2 | Impact skill | Impelling strength ak (J/cm 2) | Tough break area % | Remarks |
| ??B7-1 | ??30 | ??0.8 | ??12.8 | ??15.2 | ??2％ | Three sample mean values |
| ??B7-2 | ??20 | ??0.8 | ??11.2 | ??13 | ??0％ | Three sample mean values |
| ??B7-3 | ??10 | ??0.8 | ??10 | ??11.8 | ??0％ | Three sample mean values |
Two, the main principle of design of low-temperature high-strength steel (to call steel of the present invention in the following text)
1,, determines the comprehensive mechanical performance requirement of steel of the present invention according to the actual working conditions of cold district.
2, the comprehensive mechanical performance requirement of steel according to the present invention, chemistry (alloy) the composition proportion element of steel is optimized in research.
3, according to mechanical property and chemical ingredients, Heat Treatment Of Steel process program of the present invention is optimized in research.
4, according to service requirements, material composition and thermal treatment process are determined the finished product metallographic structure.
5, in design steel chemical composition of the present invention and thermal treatment process, take all factors into consideration the machine condition of factory and the cold and hot technology feelings energy of material.
6, the salient features problem that exists at the B7 steel answers emphasis to solve when design steel of the present invention.
7, the rail that adopts steel of the present invention to produce should have good cost performance with joint bar (to call splice bar in the following text) product.
Three, fish tail slab comprehensive mechanical performance design requirements
1, emphasis solves five big performance issues of B7 steel.
(1) solves the high problem of brittle transition temperature
By the problem that the performance test of B7 steel and actual use are occurred, the subject matter of having verified splice bar generation fracture is that the brittle transition temperature of material is too high, when design steel low-temperature performance of the present invention, should be suitable for the service requirements of northern China and America cold district environment, so its brittle transition temperature should not be higher than-40 ℃.
(2) determine the metallographic structure problem of the finished product
Does the metallographic through determining the finished product produce and is organized as: be shown in tempering rope body (permission a little ferrite) Figure of description: fish tail slab tempered sorbite tissue for obtaining good, the stable comprehensive mechanical performance of the finished product?
3) solve the thick problem of metallographic structure
For obtaining the good low temperature mechanical property of fish tail slab of the present invention, must take the measure of thinning microstructure, grain fineness number is controlled at more than 8 grades.
4) fish tail slab of the present invention is increased the low temperature impact properties index request
For guaranteeing that material is at low temperature environment and be under the working condition of shock load, has good toughness characteristics, to prolong the work-ing life of material, impact (〉=27.12J) the quantification requirement of tough break area (FA 〉=45%) performance index when therefore in steel inspection specification of the present invention, increasing low temperature-40 ℃.
5) should increase the fatigue strength index request to fish tail slab of the present invention
The fatigue characteristic index of material can reflect certain material antifatigue destructive characteristic under given conditions indirectly.Therefore, when design steel of the present invention, in the time of should stipulating symmetric curvature load 482MPa (load alternative frequency 1000HZ), its cyclic loading is answered 〉=1,000 ten thousand times requirement (the B7 steel is about 240,000 times, is shown in Table 4)
Table 4 B7 and fish tail slab symmetric curvature stress fatigue test-results of the present invention
| Test piece number (Test pc No.) | Cycle (inferior) |
| ??1 | ??240000 |
| ??2 | ??10052700 |
| ??3 | ??27823000 |
| ??4 | ??11660000 |
2, tentatively determine fish tail slab comprehensive mechanical performance of the present invention requirement
According to the comprehensive mechanical performance contrast test result that B7 steel and fish tail slab of the present invention are carried out, and consider and tentatively steel comprehensive mechanical performance of the present invention is proposed following requirement by splice bar actual condition on the line, be shown in Table 5
The requirement of table 5 fish tail slab of the present invention comprehensive mechanical performance
Table 6 splice bar steel drift of the present invention hits performance requriements
Summer is than sample v-notch
| The trade mark | Test temperature ℃ | Sample cross is amassed cm 2 | Ballistic work J | Remarks |
| ??DY30 | ??-40 | ??0.8 | ??≥27.12 | ? |
A column data can reflect clearly that steel of the present invention has very big difference than B7 steel aspect the comprehensive mechanical performance from table 1 to table 6:
A. improving 67% aspect the material unit elongation
B. improving 125% aspect the material relative reduction in area
C. improved 575% aspect material at low temperature (40 ℃) impact toughness value (annotate: because of the B7 steel in the impact value below-40 ℃ less than 4J, therefore stopped this test)
D. improving greatly aspect material anti-fatigue performance and the tough break.
E. good bending property, 180 ° of bendings are intact.
This shows that fish tail slab of the present invention is the analogous of B7 steel institute aspect comprehensive mechanical performance.
Four, splice bar tempering of the present invention is learned the composition design
1, with manganese is matrix
The fundamental property of fish tail slab of the present invention is that the characteristic by manganese realizes.Why select the matrix composition of manganese, mainly considered following related factors as steel of the present invention:
1) manganese and iron form sosoloid, can improve steel grade ferrite and austenitic intensity and hardness;
2) manganese owing to reduce critical transition temperature, surpasses the effect to refine pearlite in steel, the also super indirectly effect to raising perlitic steel intensity;
3) manganese has enlarged the r phase region in the carbon iron balance phasor, makes the ability of steel formation and stable austenite tissue be only second to nickel;
4) manganese has tangible effect to the hardening capacity that increases steel;
5) manganese has tangible effect to reducing brittle transition temperature.
When the consumption of design manganese, the Intensity Design index of considering fish tail slab of the present invention is near the high strength scope, therefore the average of manganese content brought up to 1.4%, content range is set in ± 0.1% scope in, this content of verification experimental verification is more suitable.
2, strict control silicone content
Universal law according to the metallic substance characteristic thinks that silicon has the effect that improves the material fragility transition temperature, and silicon has the temper brittleness of aggravation manganese to be inclined to simultaneously, and makes material grains thick, reduces the fatigue lifetime of material, therefore should the strict consumption of controlling silicon.
In addition, the characteristics that silicon has thermal conduction to lag behind, when thermal treatment along with the increase of silicone content, can produce bigger internal stress at material internal, when this internal stress reached certain limit, crystal boundary can be sent out the image of breaking, and in the industry this phenomenon was referred to as " fine grain-boundary crack ".Above-mentioned phenomenon is at continuously cast bloom, section rolling, even all can take place in the product hot procedure, finally causes the unsettled feature of fatigue strength of product.For example: the spring that adopts the 60Si2CrA steel to produce, when envrionment temperature and hot processing temperature differ greatly, tend to occur the problems referred to above, can make spring be difficult to sad three static pressure in the time of seriously and rupture.
Therefore, silicone content is controlled in 0.25% ± 0.10% scope, more suitable through this content of verification experimental verification.
3, reduce carbon content and strengthen low-temperature performance
Carbon content plays an important role to the brittle transition temperature that reduces metallic substance.Generally recognize change, steel is along with the increase of carbon content, the also corresponding raising of its intensity and hardness, but plasticity and impact value descend thereupon; The brittle transition temperature of steel raises to some extent with the increase of carbon content, and scope is expansion to some extent also.Generally near room temperature, its scope is also narrower in the brittle transition temperature of the carbon steel about 0.2% for carbon content.
When designing the carbon content of fish tail slab of the present invention, when taking into full account reduction material fragility transition temperature, also will take into account the variable range of the strength of materials, its purpose makes steel of the present invention have certain extendability in practical application from now on.
Under normal conditions, when high manganese is low when closing carbon in prosperous≤0.25%, its hardening capacity obviously descends, and especially the long-pending bigger product of pair cross-section as not increasing the element of hardening capacity, is difficult to obtain martensitic stucture; When carbon content 〉=0.4%, though increased low-alloyed hardening capacity of high manganese and intensity, the probability that needle-like and plate martensite occur increases thereupon, and the fragility of material changes and also can increase simultaneously.According to the performance requriements of present existing medium carbon steel testing data and splice bar, the average of carbon content determines that 0.30% its variation range is advisable ± 0.03%.
4, take aggregate measures to reduce brittle transition temperature
By reducing carbon content, improve manganese content, thinning microstructure is avoided aggregate measures such as temper brittleness, reduces the brittle transition temperature of steel of the present invention, improves the comprehensive mechanical performance purpose to reach, be this project development worker and in an important thinking.
Controlling cost and guarantee that product has under the condition of high-strong toughness in strictness, reduce the brittle transition temperature of material significantly, is a comparatively complicated complex optimum process, at present as yet targetedly stronger alloying data and data can use for reference.Therefore, when research reduces the low-alloyed brittle transition temperature scheme of high manganese, take multiple mode to carry out complex optimum, only relied on the cold property of individual element to be difficult to satisfy performance requriements., just,, remain further to be studied to the development of steel of the present invention in view of at present as for more definite effect by the main conclusions that actual tests drew according to the universal law of Metal Material ﹠ Heat Treatment.
5, reduce the temper brittleness of manganese
Manganese is a kind of important component in the low alloying material, when strengthening consumption, the hardening capacity that reduces material fragility transition temperature, strongthener is not only arranged, the effect that improves intensity simultaneously in addition.
Manganese also can bring crystal grain thick and increase the tendency of temper brittleness to low alloy material.For avoiding the temper brittleness problem of high mangaenese steel, mainly solve by two kinds of methods.When at first formulating tempering process, under the prerequisite that guarantees material property, must avoid high temperature and low temperature brittleness refined zone.According to the regularity of distribution in Heat Treatment Of Steel temper brittleness district, quench into the steel of martensitic stucture, in 250 ℃ to 350 ℃ scopes all temper brittleness will take place, this Low-Temperature Temper Brittleness is irreversible; Temper brittleness is meant that temper brittleness will appear in steel when steel carries out tempering in 450 ℃ to 550 ℃ scopes.Its two, molybdenum element has the effect of resisting high mangaenese steel temper brittleness, has added micro-molybdenum element when design steel of the present invention, to reach the temper brittleness purpose that reduces manganese element once more.In addition, consider that molybdenum element has occupied a big chunk of raw materials cost, but it is absolutely necessary again as the element that improves hardening capacity, and the chromium element is to be used for modified element and identical with molybdenum to the contribution of carbon content equally, so can reduce raw materials cost by the mode of " with chromium for molybdenum ".Since the hardening capacity that chromium brings steel than molybdenum a little less than, hardening capacity has substantial connection again with the speed of cooling of thermal treatment process simultaneously, so answer the linkage heat treatment process condition progressively to carry out on chromium and molybdenum composition adjustment optimization problem.
6, thinning microstructure improves over-all properties
In the process of the test of fish tail slab of the present invention,,, have a strong impact on the fatigue property of material because metallographic structure is thick although taked to force the measure of the brittle transition temperature that reduces material.
Vanadium improves the grain coarsening temperature to the tissue and the crystal grain of refinement steel, can realize improving the intensity and the flexible purpose of steel.Trace amount of titanium can crystal grain thinning in addition, improves the low-temperature flexibility and the intensity of steel, and 0.005% is lower limit during interpolation, crosses and forms carbide at most, reduce low-temperature flexibility, so the upper limit is preferably 0.03%.
7, to the control principle of remaining composition
In fish tail slab of the present invention, except that main proportioning alloying element, also there are some relict elements, and the performance of steel of the present invention is produced certain influence.
(1) reply phosphorus, the strict control of element sulphur
Sulphur form with sulfide inclusion in steel exists, and the ductility of steel and toughness are reduced, and especially impact value and the impelling strength influence to material is very big.Add man-hour rolling in addition, sulfide inclusion also prolongs with the steel bearing of trend, therefore makes steel produce directivity in various degree, has reduced the use properties of steel, should be controlled in 0.010% sulphur content, purpose is exactly for indexs such as further raising low-temperature impact works.
Phosphorus can improve the brittle transition temperature of steel, is prone to cold short characteristic under low temperature environment, can be verified by shock test.Therefore, the content to phosphorus also should be strict controlled in 0.030%.
(2) content of nickel, copper is controlled
Under normal conditions, remove relatively difficulty of the nickel remain in the steel, copper fully, also there is no need.Have nickel (≤0.10%), the copper (≤0.20%) of trace in the steel, one side can increase the extension property of material, improves the ability of material atmospheric corrosion resistance on the other hand.
Five, finish testing laboratory and industrialization smelting, rolling test
1, testing laboratory's checking conclusion
According to the theoretical composition proportion scheme of fish tail slab of the present invention, carried out the smelting proof test of testing laboratory.
According to stretching, hardness, metallographic, the impact specimen that set lab scenario is made, shown in its mechanicl test result one table 7, the table 8.
Table 7 fish tail slab of the present invention testing laboratory sample mechanicalness measurement result
From the steel measuring mechanical property of the present invention interpretation of result that testing laboratory draws, every index all reaches design requirements.
2, industrialization smelting, rolling test
The industrialization smelting test work of fish tail slab of the present invention is finished by western steel Acheng Iron And Steel Co., Ltd of group (hereinafter to be referred as my company).
On September 6th, 2009, I use 65 tons of ultra high power direct current electric arc furnaces by company's steelworks, and the basis of having carried out fish tail slab of the present invention smelts continuous casting ejection after 70 tons of ladle refining furnace refinings again.Only carry out 4 stove industrialization smelting tests, 192.88 tons of actual ejection.The metallurgical quality index is shown in Table 9.
Table 9 splice bar steel continuous casting billet of the present invention macrostructure detected result
(1) splice bar section rolling test
My the Φ 650mm of Steel Mill of company blooming mill is used in the rolling splice bar section bar test of splice bar steel continuous casting billet of the present invention, and Φ 550mm finishing mill is rolled test, deformation ratio 〉=6.9.
The main technique flow process is heated to the beginning with the 160*160 square billet and rolls temperature---type is rolled in moulding------face size speed inspection------aligning---section bar quality inspection---warehouse-in that cuts off cooling that detects finishing temperature.
(2) commerical test conclusion
The section bar blank that provides according to my company's steelworks, the testing data that heat treatment process specification obtained according to my Steel Mill of company splice bar workshop, see Table 10, shown in the table 11, so far, by the steel of the present invention of industrialization test manufacture, its main chemical compositions, mechanical performance index have all reached design requirements.
Table 10 fish tail slab of the present invention industrialization sample mechanical property measurement result
Table 11 fish tail slab of the present invention industrialization sample impact property measurement result
Six, splice bar Heat Treatment Of Steel of the present invention
In view of splice bar Heat Treatment Of Steel process of the present invention relates to the core technology of enterprise, at this consistence of heat treated principle of design and actual verification conclusion only is described, do not narrate concrete parameter matters, please be understood.
1, heat treated intended purposes
Steel of the present invention is heat-treated main purpose is, is the comprehensive mechanical performance requirement of realization expection defined, and obtains the sorbite tissue of even refinement.
2, the fundamental principle of quench treatment
Fish tail slab of the present invention becomes branch to form by multiple microalloy, how accurately to grasp austenite heat-up rate and the soaking time that reaches even refinement, is a key link in the quenching technology.The test authentication, rate of heating is big more, and hysteresis phenomenon is more remarkable, and austenite transformation temperature is also higher, and also faster from perlite to austenitic transformation, the temperature of the dissolving of remaining carbide and austenite homogenization of composition is improve thereupon also.It is relevant to it may be noted that how many heat-up rate, soaking time and heating installation, materials place, and is the important factor that directly influences quenching metallographic structure quality.Therefore, enterprise should be according to composite factors such as equipment of itself situation, production breath-group, the four seasons temperature difference, by obtaining accurately suitable processing parameter after the repetition test to instruct heat treatment operation.
(1) strict control autstenitic grain size
About the control to splice bar crystalline grain of steel degree of the present invention is a comparatively complicated problems, because to relate to factor more, except that the factor that the front has been mentioned, also relevant with the super beginning grain fineness number of the inherent grain size of steel, steel.Therefore, for different-alloy proportioning and the resultant material of smelting process, the difference of its grain fineness number control is also bigger.Enterprise has only by a large amount of actual tests, just can obtain guaranteeing the careful uniform processing parameter of grain fineness number.
(2) quench treatment
The quenching technology basis of fish tail slab of the present invention is to reach under the condition of even refine austenite in strictness, is that medium carries out quench treatment with water.In quenching process, there are three critical process conditional decisions the quality of quenching quality.The first, should accurately grasp the heat-up time that reaches even refine austenite tissue; The second, determine to be suitable for steel austenite speed of cooling of the present invention; The 3rd, must accurate optimal temperature and the time of grasping the austenite isothermal transformation.Therefore, different enterprise should test processing parameter and determines according to the working condition of self.
A isothermal transformation condition
Obtain the lath martensite quenching structure, need accurately to grasp the temperature and time of austenite isothermal transformation, because fish tail slab of the present invention is to be made of multiple microalloy, its isothermal transformation condition also is by determining after the repetition test, therefore only accurately grasping above-mentioned technological process and parameter, just can obtain the ideal quenching structure.
B prevents other phase transformations to take place
In the austenite isothermal transformation, improper as heat treatment process parameter, perlite or bainitic transformation situation can appear.Therefore, enterprise's reply quench media temperature and the parameter control of the workpiece residence time should be accurate.
The constant temperature of c quenchant is handled
Whether stable the constant temperature problem of quenchant be thermal treatment quality key link, for guaranteeing that water temperature is controlled in the scope of process stipulation, my company has increased the water temperature automatic control system to quenching bath, when water temperature during near the higher limit of process stipulation, auto temperature controlled system starts heat exchanger immediately and carries out radiating treatment, when water temperature reached the technology average, heat exchanger cut out automatically.
In addition, quantity and position that automatic temperature-controlled transmitter is provided with, and the direction of the position of heat exchanger water side and convection circulation and scope should be reasonable in design, otherwise also can influence heat treated actual effect to a certain extent.
(3) temper
When formulating the tempering process scheme of steel of the present invention, emphasis has been considered following problem:
High temperature and low temperature brittleness refined zone are avoided in a strictness, prevent the fragility tissue;
B accurately formulates tempering temperature and soaking time according to conditions such as tempering equipment, workpiece shove charge quantity and placement locations, to guarantee the stability of product tempering quality.
The tempered structure check
To the tempered structure check of fish tail slab of the present invention, be last procedure that guarantees the product inner quality, by the tissue detection to industrialization test manufacture tempering heat treatment exemplar, its result meets design requirement fully.
Seven, fish tail slab production technique of the present invention and inspection after construction conclusion
1, the fish tail slab technological process of production of the present invention
Section bar list multiple length blanking---heating---hot straightening---punching---dimensional inspection---quench treatment---cooling---quenching structure sampling observation---electric furnace tempering---tempered structure sampling observation---straightening processing---visual appearance and physical dimension check---packing warehouse-in.
2, the inspection after construction conclusion of fish tail slab of the present invention (seeing the analysis report of U.S. feeler mechanism).
Eight, the technological comprehensive evaluation of steel of the present invention
About evaluation, mainly from three aspect analyses to the processing performance of steel of the present invention: the second, from smelting process the complexity aspect of chemical Composition Control is estimated; The second, estimate from material rolling quality control complexity aspect; The 3rd, estimate from material hot treatment quality control complexity aspect.
1, to the Composition Control evaluation
My company's steelworks tooling level is better, the ultra high power direct current electric arc furnace is joined external refining, Composition Control is more accurate, under the large-scale industrialization working condition, all each chemical element in the steel of the present invention can be controlled in the chemical ingredients accuracy rating of its design, through steel actual industrial smelting process of the present invention is analyzed, the qualified degree of primary smelting composition is 100%.
2, to the rolling technology evaluation
Generally speaking, the evaluation of the rolling complexity of material is depended primarily on the content of carbon and silicon in the chemical ingredients, and for the high silicon materials of high-carbon, drag is very big in roll forming, punching and aligning process, not only be difficult to moulding, and be prone to quality problems such as rolling crack.And base steel of the present invention originally belongs to the low carbon low silicon material, and its rolling technology should be good.
3, to the thermal treatment control evaluation
Mainly be reflected in control heating about evaluation and make austenite reach even refinement splice bar steel heat treatment process of the present invention, and to two aspects of control of austenite isothermal transformation.If under the prerequisite that processing parameter is determined, heat treated quality is to rely on automatic equipment to guarantee fully, and therefore the control evaluation to thermal treatment quality also is conspicuous.
Nine, the cost situation of fish tail slab of the present invention
The prime cost of fish tail slab of the present invention is made of two portions.The first, the basic cost of fish tail slab of the present invention; The second, the tooling cost of splice bar.In order to simplify calculating, be radix with B7 steel splice bar cost, adjust out the cost of steel splice bar of the present invention.
1, splice bar steel billet cost of the present invention
At present, the blank price of B7 steel is 3500 yuan/ton, and steel of the present invention has increased 0.12%Mo than B7 steel, 0.10%V, and 0.20%Cr and 0.75%Mn, therefore the material cost of steel of the present invention per ton exceeds about about 1000 yuan than B7.
2, in view of fish tail slab of the present invention and B7 steel splice bar in the key distinction that exists aspect the thermal treatment process be: workpiece waste heat temper is adopted in the B7 steel splice bar back of quenching, and steel splice bar of the present invention must carry out the electric furnace temper, therefore the electric furnace tempering cost that increases by 300 yuan in addition per ton.
3, fish tail slab price of the present invention
Fish tail slab price of the present invention is about 7000 yuan/ton at present, because the production technique of splice bar steel plate of the present invention realizes the characteristics of working continuously substantially, adopted hot charging and hot rolling of continuous casting slab, reduced the departmental cost of rolling link, add the increase of its material cost and electric furnace tempering cost, therefore steel splice bar finished product price of the present invention per ton exceeds about 2800 yuan than B7 steel splice bar.
Ten, about to fish tail slab Technological Economy of the present invention evaluation
Domestic metallic substance performance data and relevant information according to having grasped at present have high strength, the high tenacity of steel of the present invention simultaneously under low temperature-40 ℃ environment, and the metallic substance of high fatigue property still finds no the pass report.
At present, the overall development trend of external steel grade develops towards middle low-carbon (LC), micro-alloyed high strength flexible direction.Succeeding in developing of steel of the present invention and low temperature splice bar product, not only the transportation safety problem for the speed-raising of present China, heavy-haul line has solved the matter of great urgency, also provides a kind of characteristic good, broad-spectrum cryogenic material for the development of high-speed railway from now on.Therefore, the Technological Economy sexual clorminance of steel of the present invention is mainly reflected in the following aspects:
The excellent material characteristic.Fish tail slab of the present invention has one high two low characteristics, that is: Gao Meng, low-carbon (LC), low alloying, so the intensity variable range of this steel grade is very big, has the outstanding characteristics of toughness simultaneously again; Because low-carbon (LC), low-alloyed optimization function make and organize more even refinement, have increased substantially the anti-fatigue performance of material; Fish tail slab of the present invention possesses the characteristics of middle low-carbon high-manganese, and material has good hardening capacity, and the back of quenching is resulting to be ideal lath martensite tissue; Because the even refinement of tissue and lower carbon content greatly reduce the brittle transition temperature of steel of the present invention, thereby embody fabulous low-temperature performance.Therefore, this steel grade has possessed the multiple advantage of middle carbon and low-alloy simultaneously, thereby has enlarged the material scope of application.
Good operational characteristic.Because carbon hanged down silicon materials during fish tail slab of the present invention belonged to, possessed the basis of good process.By rolling, the section bar of continuously cast bloom of the present invention is hotly dashed, technological test such as finished product cold cut, characteristics such as the rolling drag that shows this steel grade is little, formed precision is high, lumber recovery is high, surface quality is good satisfy the manufacturability requirement of existing product fully.
Good fatigue resistance.According to national ferrous materials test center to fish tail slab of the present invention and B7 steel, make the tired simultaneous test of symmetrical stress in bending and show: be 41.8 times of B7 steel the fatigue lifetime of fish tail slab of the present invention at least.
Good cost performance.To the scientific evaluation method of novel material, should go the analysis-by-synthesis evaluation from cost performance and two aspects of overall economic benefit of material.Though steel splice bar finished product price of the present invention per ton has only improved about 66% than B7, aspect work-ing life, the former is more than 40 times of the latter, so the good cost performance of steel splice bar of the present invention, is that B7 steel splice bar is incomparable.
Huge economic benefit.The B7 steel splice bar that China is used for newly built railway construction and existing line maintenance every year is about ton (wherein keep in repair consumption and account for more than 60% of total amount) surplus in the of 30,000, annual expensive nearly 1.26 hundred million yuans.
From the work-ing life of fish tail slab of the present invention and B7 steel splice bar, and the overall economic efficiency aspect compares nearly 20,000 tons of the maintain and replace amount of annual B7 steel splice bar, expensive nearly 0.84 hundred million yuan every year.
According to the multiple line coefficient calculations of 90,000 kilometers of system-wides (50 meters) long welded rail track and 0.45, the B7 steel splice bar of the online use of system-wide is about 18.656 ten thousand tons, and the maintenance turnover rate that draws thus at the annual B7 steel of system-wide splice bar is 10.72%.
According to splice bar steel plate of the present invention is that the work-ing life relation of 20 times of B7 steel splice bars is calculated, and deducts the rise in price factor of splice bar steel plate of the present invention (per ton) 66% simultaneously, and annual system-wide can reduce about 7,200 ten thousand yuan of servicing materials and labour costs.
When splice bar steel plate of the present invention come into operation continuously reach 10 years after (between) to 20 years, according to the prediction of the fatigue test conclusion of this steel grade, 0 situation of paying will appear in system-wide splice bar maintenance cost in 10 years of future.Can be system-wide in the meantime and save the maintenance cost of at least 10 hundreds of millions of Chinese people's coin.
Utilization is in the time of nearly 20 years continuously when splice bar steel plate of the present invention, and the maintain and replace rate of the annual splice bar of system-wide is less than 0.6%.Therefore, system-wide can reduce to average annual about 7,000,000 yuan by present average annual 0.84 hundred million yuan to the splice bar maintenance cost in the future, and the maintenance cost fall of splice bar reaches more than 91% when the time comes.
The guarantee of transporting safely.After the splice bar steel plate input utilization of the present invention,, the more important thing is and guaranteed safety of railway transportation and unimpeded not only for the railway system has saved a huge sum of money.
Excellent property is of many uses.In view of the intensity index variable range of fish tail slab of the present invention big
800Mpa to 1200Mpa has excellent in toughness and high fatigue property simultaneously, therefore can be widely used in the manufacturing of products such as construction steel structure, railway (highway) bridge, splice bar and middle high strength bolt, nut.
11, conclusion and suggestion
A new material technology achievement of fish tail slab system of the present invention acquisition after testing laboratory, the strict checking of industrialization, every actual performance of this steel grade has surmounted the standard-required of TB/T2345-1993 to a great extent, and above-mentioned standard has been carried out necessary improving and replenishing.Determining of the every design objective of this achievement is primarily aimed at the actual needs of present railway speed increase, heavy-haul line, and thoroughly solves the performance issue that B7 steel splice bar is occurred in practice.The technical advance of steel of the present invention, the reliability of quality are confirmed by a large amount of scientific experimentations, meet the actual service requirements of railway speed increase, heavy-haul line fully.
Claims (7)
1. high-strength and low-temperature tough steel, it is characterized in that: chemical ingredients is by weight percentage: C0.26-0.35, Si 0.12-0.40, Mn 1.20-1.55, P≤0.030, S≤0.010, Mo 0.10-0.30, contain in Cr≤0.25, Ni≤0.20, Cu≤0.20, V≤0.20, Ti≤0.05 two or more in addition, surplus is Fe.
2. a kind of high-strength and low-temperature tough steel according to claim 1, it is characterized in that: chemical ingredients is by weight percentage: C 0.26, Si 0.22, Mn 1.53, P 0.028, S 0.010, Mo 0.11, Cr 0.24, Ni 0.03, Cu 0.03, V 0.08, Ti 0.01, surplus is Fe.
3. a kind of high-strength and low-temperature tough steel according to claim 1 is characterized in that: C 0.34, Si 0.33, Mn 1.43, P 0.017, S 0.008, Mo 0.14, and Cr 0.22, Ni 0.02, Cu 0.03, V 0.09, Ti 0.02, surplus is Fe.
4. a kind of high-strength and low-temperature tough steel according to claim 1 is characterized in that: C 0.30, Si 0.31, Mn 1.43, P 0.012, S 0.010, Mo 0.18, and Cr 0.19, Ni 0.02, Cu 0.03, V 0.09, Ti 0.01, surplus is Fe.
5. a kind of high-strength and low-temperature tough steel according to claim 1 is characterized in that: C 0.27, Si 0.28, Mn 1.39, P 0.010, S 0.009, Mo 0.11, and Cr 0.23, Ni 0.01, Cu 0.05, V 0.07, Ti 0.02, surplus is Fe.
6. a kind of high-strength and low-temperature tough steel according to claim 1 is characterized in that: C 0.32, Si 0.32, Mn 1.43, P 0.024, S 0.007, Mo 0.15, and Cr 0.20, Ni 0.03, Cu 0.03, V 0.10, Ti 0.02, surplus is Fe.
7. a kind of high-strength and low-temperature tough steel according to claim 1, it is characterized in that: adopt the ultra high power direct current electric arc furnace to convert and join 60% molten iron, refining of LF ladle argon-blown and line feeding are handled, carry out continuous casting according to Clean Steel technology, the start rolling temperature 1100-1200 of steel ℃, control accumulative total draft 〉=55%, every time draft of last three roads 〉=8%, finishing temperature 820-900 ℃, adopt the modifier treatment mode, thermal treatment heating: 900-940 ℃ of insulation 45 minutes, come out of the stove then, go into water temp at 880-920 ℃, water temperature is controlled at 20-60 ℃, cool time 55-62 second is warming up to 550-610 ℃, begins to calculate soaking time: 35-55 minute+thickness of slab * 1 minute/mm.
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| CN102808132A (en) * | 2011-06-01 | 2012-12-05 | 中国北车集团大同电力机车有限责任公司 | Traction seat casting and processing technology |
| CN105441788A (en) * | 2015-12-18 | 2016-03-30 | 马鞍山钢铁股份有限公司 | Vanadium-containing 12.9-grade steel for fastener applied to rail transit mobile equipment and thermal treatment process of vanadium-containing 12.9-grade steel |
| CN107746921A (en) * | 2017-12-06 | 2018-03-02 | 徐工集团工程机械有限公司 | A kind of medium carbon alloy steel and preparation method thereof |
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| CN1920080A (en) * | 2005-08-26 | 2007-02-28 | 首钢总公司 | High-toughness low-alloy constructional steel and producing method thereof |
| CN101629476A (en) * | 2009-08-05 | 2010-01-20 | 天津钢管集团股份有限公司 | High strength and high toughness petroleum casing pipe capable of bearing low temperature within -40 to -80 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102808132A (en) * | 2011-06-01 | 2012-12-05 | 中国北车集团大同电力机车有限责任公司 | Traction seat casting and processing technology |
| CN102808132B (en) * | 2011-06-01 | 2014-03-12 | 中国北车集团大同电力机车有限责任公司 | Traction seat casting and processing technology |
| CN105441788A (en) * | 2015-12-18 | 2016-03-30 | 马鞍山钢铁股份有限公司 | Vanadium-containing 12.9-grade steel for fastener applied to rail transit mobile equipment and thermal treatment process of vanadium-containing 12.9-grade steel |
| CN107746921A (en) * | 2017-12-06 | 2018-03-02 | 徐工集团工程机械有限公司 | A kind of medium carbon alloy steel and preparation method thereof |
| CN108251606A (en) * | 2018-02-02 | 2018-07-06 | 湖北谷城县东华机械股份有限公司 | A kind of ZG585-725H steel-castings and its preparation process |
| CN109014052A (en) * | 2018-09-26 | 2018-12-18 | 天长市兴宇铸造有限公司 | The casting method of traction electric machine driving end end cap on a kind of underground engines |
| CN109266975A (en) * | 2018-10-25 | 2019-01-25 | 青岛天赢智能工业股份有限公司 | A kind of high intensity high/low-temperature impact tough alloy and its preparation and heat treatment process |
| CN109266975B (en) * | 2018-10-25 | 2021-08-31 | 青岛天赢智能工业股份有限公司 | High-strength high-low-temperature impact toughness alloy and preparation and heat treatment process thereof |
| CN114427064A (en) * | 2021-11-30 | 2022-05-03 | 安阳钢铁股份有限公司 | Production method of high-strength high-low-temperature-toughness railway steel rail joint clamping plate |
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