CN109295392A - A kind of production method of great surface quality super-high strength steel - Google Patents

Abstract

The invention discloses a kind of production method of great surface quality super-high strength steel, the production process route of steel is molten iron pretreatment → converter smelting → LF external refining → VD vacuum processing → continuous casting → heating → rolling → aligning → quenching → tempering → finishing → service check → flaw detection；The chemical composition percentage composition of steel is C=0.15 ~ 0.20, Si≤0.10, Mn=1.0~1.50, P≤0.012, S≤0.003, Nb=0.010 ~ 0.030%, V=0.015 ~ 0.040, Ti=0.010 ~ 0.025, Als=0.020~0.045, Cr=0.15~0.25, Mo=0.50~0.80, Ni=0.15 ~ 0.25, B=0.0008 ~ 0.0025, CEV≤0.60, surplus are Fe and other microelements.Thickness specification 6-25mm, the steel plate of width 1500-3800mm are produced, performance indicator meets Q1100E requirement in GBT28909-2012, and surface quality is good, point caused by non-oxidation iron sheet is pressed into and pit defect.

Description

A kind of production method of great surface quality super-high strength steel

Technical field

The invention belongs to steelmaking technical field, in particular to a kind of production method of great surface quality super-high strength steel.

Background technique

As engineering machinery develops towards enlarged lightweight, steel plate use intensity rank is continuously improved, to steel plate Quality requirement is also higher and higher, including mechanical performance index and inside and outside quality etc..Since engineering machinery Service Environment is severe, greatly Multi-pass crosses japanning and carrys out antirust corrosion protection, needs to carry out smearing putty and polishing, complex procedures long flow path to workpiece before japanning.It is more and more Enterprise in order to improve the production efficiency, reduce labor intensity of workers and reduce production cost, reduction smear the intermediate processs such as putty, it is right The surface quality of steel plate proposes the strict demand of almost zero-fault, and iron scale is pressed into caused point and pit problem and becomes The key points and difficulties problem of major iron and steel enterprise's product surface quality.

Chinese patent CN 106702270 discloses a kind of " think gauge great surface quality hot rolling opening plate and its manufacturer Method ", the thickness specification 14-25mm of invention production, the hot rolling opening plate of 210~400MPa of intensity rank, start rolling temperature 950~ 1080 DEG C, 800~980 DEG C of final rolling temperature, 500~680 DEG C of coiling temperature, ultrafast cold section of intensity of cooling is 50~80 DEG C/s, preceding Section section cooling intensity is 10~30 DEG C/s, and it is low to be related to steel strength rank, cooling with big cooling rate after rolling, and may result in material There is the problem of bending precision or cracking in processing use in material.Chinese patent CN 102764760 discloses a kind of " high surface The manufacturing method of quality hot rolled steel plate ", by blank reconditioning, knobble, rolls rear air-cooled and transport at dephosphorization process optimization Protection, production yield strength are 345MPa level low alloy steel, and it is low to be related to steel strength rank, and reconditioning blank, process are needed before rolling It is more, it is at high cost, it is not suitable with allegro mass production.

Summary of the invention

This patent is intended to provide a kind of production method of great surface quality super-high strength steel, produced steel plate thickness specification 6- 25mm, strength grade are 1100MPa grades of yield strength or more, pass through reasonable chemical component, rolling mill practice and heat treatment process Design, prevents scale on surface indentation, and plate surface quality is good.

Technical solution of the present invention:

A kind of production method of great surface quality super-high strength steel, the production process route of steel be molten iron pretreatment → converter smelting → LF external refining → VD vacuum processing → continuous casting → heating → rolling → aligning → quenching → tempering → finishing → service check → Flaw detection.The chemical composition percentage composition of steel be C=0.15 ~ 0.20, Si≤0.10, Mn=1.0~1.50, P≤0.012, S≤ 0.003, Nb=0.010 ~ 0.030%, V=0.015 ~ 0.040, Ti=0.010 ~ 0.025, Als=0.020~0.045, Cr=0.15 ~0.25, Mo=0.50~0.80, Ni=0.15 ~ 0.25, B=0.0008 ~ 0.0025, CEV≤0.60, surplus are Fe and other micro- Secondary element.Critical process step includes:

(1) rolling mill practice: 1180-1230 DEG C of heating of plate blank tapping temperature, soaking time 20-30min；The pressure of three passage of roughing Rate >=15%, workpiece thickness are not less than 3 times of target rolling thicknesses, and finish rolling start rolling temperature is not higher than 860 DEG C, finishing temperature 760- 800℃；The type of cooling is water cooling, opens 720-760 DEG C of cold temperature, 450-500 DEG C of red temperature；

(2) hardening and tempering process: 890-930 DEG C of hardening heat, heating time is plate thickness mm × 3min/mm, nitrogen protection in furnace；It returns 250-450 DEG C of fiery temperature, tempering time are plate thickness mm × 6min/mm, are air-cooled to room temperature after tempering.

The final steel plate for obtaining tissue based on tempered martensite, yield strength are greater than 1100MPa, tensile strength 1200 ~ 1500MPa, elongation percentage are greater than 11%, and longitudinally, laterally Charpy-V impact power (- 40 DEG C) reaches 30J or more, plate surface quality Well, point caused by non-oxidation iron sheet is pressed into and pit defect.

Inventive principle:

Design of Chemical Composition: phosphorus content increases in steel, and yield point and tensile strength increase, but plasticity and impact reduce, and work as carbon When content is high, the welding performance of steel degenerates, it is contemplated that the weldability of super-high strength steel, phosphorus content are no more than 0.20；Carbon content is low, shadow Ring the harden ability and strength character of steel.In order to obtain yield strength 1100MPa or more, tensile strength reaches 1200MPa, controls C The content of element is 0.15 ~ 0.20.Mn is weak carbide formation element, and suitable Mn is added in steel can be improved the intensity, hard of steel The concentration product of degree and harden ability, but Mn too high levels in steel, segregation zones manganese and sulphur is high, and the cross that can deteriorate steel is precipitated in manganese sulfide To and thickness directional properties；To avoid harm brought by high manganese, it is 1.0~1.50 that the present invention, which designs Mn content,.Si element energy The elastic limit of steel, yield point and tensile strength are significantly improved, but the O in Si and steel reacts SiO generated₂It is formed with FeO FeO/Fe₂SiO₄Eutectoid product or 2FeSiO₂, FeO is pinned at the surface layer of iron matrix by this product, during de-scaling very Difficulty is completely removed.To meet requirement of the steel performance index to harden ability, addition Cr, Mo, Ni member usually improves harden ability.Ni It when content is high, is enriched in iron scale, the rich Ni metal twine of formation links up iron scale and matrix, coexists with Cr So that adhesion layer thickness increases, de-scaling is more difficult.In heating process, the S in Ni and furnace gas, which reacts, generates low melting point NiS, destroys the protective film generated under cryogenic conditions, oxidation aggravation, and iron scale thickness increases.In order to reduce Cr, Ni to oxidation The adverse effect of iron sheet control, design improve harden ability element based on Mo, are aided with a small amount of Cr and Ni.Nb element can be improved Non-recrystallization temperature realizes the Unhydrated cement rolling in higher temperature, and two stage rolling temperature of the present invention is lower, is added few Measure Nb.

Rolling mill practice: blank heating temperature is low, and alloying component cannot be dissolved completely, heating of plate blank is impermeable and Temperature Distribution not , unevenness is deformed when rolling easily causes rolling difficult；Heating temperature is excessively high, and slab is easy overheat even burning, and iron oxide Skin is easy fusing and is attached on steel slab surface, is difficult to remove.Heating rate is fast, and heating time is short, and FeO content is high in iron scale, It combines closely with matrix, de-scaling is difficult；Heating time is long, and iron oxide skin thickness increases, and also results in iron scale difficulty and goes Except the problem of.The finish rolling stage uses zerolling, avoids iron scale indentation caused by rolling in high temperature section, but needs to consider The load and material of zerolling milling train lead to the problem of mixed crystal, and rolling temperature cannot be too low.Not pre-straightening after rolling passes through ACC is cooled to 450-500 DEG C, avoids FeO eutectoid reaction temperature, is transformed into Fe3O4 quantity when reducing FeO cooling, avoids steel plate Fe3O4 is pressed into form pit defect when aligning.

Heat treatment process: for Fe at 570 DEG C or less, main group of iron scale becomes Fe₃O₄And Fe₂O₃, form one layer of oxygen Compound protective film has good inoxidizability, and at high temperature, oxide group becomes FeO, Fe₃O₄And Fe₂O₃, anti-oxidant impatient It falls sharply low.Heat treatment process formulates the demand for also needing to take into account requirement and the destressing of steel grade performance, keeps material stress small, is distributed Uniformly.

The present invention has the utility model has the advantages that the present invention is obtained by reasonable chemical component, rolling mill practice and Design of Heat Treatment Process It is thick to obtain 6 ~ 25mm, 1500 ~ 3800mm wide ultrahigh-strength steel plates, performance indicator is met the requirements of the standard, and plate surface quality is good, nothing Point and pit defect.(1) it is designed in ingredient design using low-carbon-equivalent, harden ability is improved by Mo, B, reduces and promotes oxidation Iron sheet generates or improves the addition of Si, Cr, Ni element of iron scale stickiness.(2) rolling uses zerolling, and reduction rolled Iron scale indentation may in journey.(3) reasonable cooling velocity and final cooling temperature, reduce iron scale thickness, avoid rectifying after rolling Fe3O4 is pressed into form pit defect when straight.(4) scale-free heating is quenched, surface of steel plate steel bonding is prevented；After lonneal, steel plate Surface forms oxide film, improves the inoxidizability of material.

Specific embodiment

The contents of the present invention are further illustrated below with reference to embodiment.

The production of one: 8mmQ1100E great surface quality ultra-high strength steel plate of embodiment

The composition content mass percent of steel are as follows: C=0.17, Si=0.05, Mn=1.25, P=0.011, S=0.0021, Nb= 0.015, V=0.020%, Ti=0.018, Als=0.030, Cr=0.16, Mo=0.57, Ni=0.18, B=0.0016, CEV=0.54, Surplus is Fe and other microelements.Critical process step includes:

(1) rolling mill practice: after the heated stove heating of slab, tapping temperature be 1190 DEG C, soaking time 29 minutes, 7 passage of roughing Workpiece thickness is 55mm afterwards, and wherein roughing mill rolls last three percentage pass reduction 15% or more, and 850 DEG C of open rollings of finish rolling are whole Rolling temperature is 763-786 DEG C, is rolled into the steel plate with a thickness of 11mm, opens 730-758 DEG C of cold temperature, and cooling rate be averaged 18 DEG C/S, end 455-485 DEG C of cold temperature.

(2) hardening and tempering process: quenching temperature is 915 DEG C, cool time 24min, and tempering temperature is 350 DEG C, tempering Time is 48min, and steel plate is air-cooled to room temperature after tempering.

After conditioned processing the yield strength of steel plate be 1255MPa, tensile strength 1375MPa, elongation percentage 15%, -40 DEG C 1/2 size v-notch Charpy impact work value 73J, 81J, 75J, obdurability matching is good, and plate surface quality is good, non-oxidation The defects of point caused by iron sheet is pressed into and pit.

The production of two: 11mmQ1100E great surface quality ultra-high strength steel plate of embodiment

The composition content mass percent of steel are as follows: C=0.16, Si=0.07, Mn=1.24, P=0.010, S=0.0018, Nb= 0.016, V=0.019%, Ti=0.017, Als=0.031, Cr=0.18, Mo=0.61, Ni=0.20, B=0.0018, CEV=0.54, Surplus is Fe and other microelements.Critical process step and parameter:

(1) rolling mill practice: after the heated stove heating of slab, tapping temperature be 1205 DEG C, soaking time 26 minutes, 7 passage of roughing Workpiece thickness is 60mm afterwards, and wherein roughing mill rolls last three percentage pass reduction 15% or more, and 853 DEG C of open rollings of finish rolling are whole Rolling temperature is 765-790 DEG C, is rolled into the steel plate with a thickness of 15mm, opens 726-755 DEG C of cold temperature, and cooling rate be averaged 18 DEG C/S, end 460-491 DEG C of cold temperature.

(2) hardening and tempering process: the steel plate after aligning three times carries out modifier treatment, and quenching temperature is 920 DEG C, quenching Time is 33min, and tempering temperature is 350 DEG C, and tempering time 66min, steel plate is air-cooled to room temperature after tempering.

After conditioned processing the yield strength of steel plate be 1213MPa, tensile strength 1357MPa, elongation percentage 15.5%, -40 DEG C 3/4 size v-notch Charpy impact work value 81J, 65J, 72J, obdurability matching is good, and plate surface quality is good, anaerobic The defects of changing point caused by iron sheet is pressed into and pit.

Claims (1)

1. a kind of production method of great surface quality super-high strength steel, process route is outside molten iron pretreatment → converter smelting → LF furnace Refining → VD vacuum processing → continuous casting → heating → rolling → aligning → quenching → tempering → finishing → service check → flaw detection, Be characterized in that: the chemical composition percentage composition of steel be C=0.15 ~ 0.20, Si≤0.10, Mn=1.0~1.50, P≤0.012, S≤ 0.003, Nb=0.010 ~ 0.030%, V=0.015 ~ 0.040, Ti=0.010 ~ 0.025, Als=0.020~0.045, Cr=0.15 ~0.25, Mo=0.50~0.80, Ni=0.15 ~ 0.25, B=0.0008 ~ 0.0025, CEV≤0.60, surplus are Fe and other micro- Secondary element；Critical process step includes:

(1) rolling mill practice: 1180-1230 DEG C of heating of plate blank tapping temperature, soaking time 20-30min；The pressure of three passage of roughing Rate >=15%, workpiece thickness are not less than 3 times of target rolling thicknesses, and finish rolling start rolling temperature is not higher than 860 DEG C, finishing temperature 760- 800℃；The type of cooling is water cooling, opens 720-760 DEG C of cold temperature, 450-500 DEG C of red temperature；

(2) hardening and tempering process: 890-930 DEG C of hardening heat, heating time is plate thickness mm × 3min/mm, nitrogen protection in furnace；It returns 250-450 DEG C of fiery temperature, tempering time are plate thickness mm × 6min/mm, are air-cooled to room temperature after tempering.