CN105543678A - Steel wire rod for high-strength boron-contained and annealing-free fastening piece and preparation method thereof - Google Patents

Abstract

The invention discloses a steel wire rod for a high-strength boron-contained and annealing-free fastening piece and a preparation method thereof. The steel wire rod for the high-strength boron-contained and annealing-free fastening piece comprises the following chemical components in percentage by weight: 0.20-0.24 wt% of C, Si not more than 0.04 wt%, 0.50-0.70 wt% of Mn, 0.25-0.35 wt% of Cr, 0.035-0.055 wt% of Ti, 0.035-0.055 wt% of Als, 0.0045-0.0060 wt% of B, S not more than 0.004 wt%, P not more than 0.012 wt%, O not more than 0.0015 wt%, H not more than 0.00015 wt%, and the balance of Fe and inevitable impurities. The preparation method comprises the steps of molten iron pretreatment desulfurization, molten steel smelting, deoxidation alloying, molten steel LF furnace refining, molten steel VD furnace vacuum refining, molten steel pouring, steel blank heating and controlled rolling and controlled cooling. The steel wire rod for high-strength boron-contained and annealing-free fastening piece is high in cleanness, few in inclusions, excellent in hardenability, proper in strength and hardness and excellent in ductility and toughness and cold heading and upsetting deformation capacity, can directly form a 10.9-grade high-level standard part through cold heading without needing spheroidizing annealing, reduces the processing procedures and the steel consumption, and reduces the production cost.

Description

High intensity non-annealed steel for fastener wire rod of a kind of boracic and preparation method thereof

Technical field

The invention belongs to field of material technology, be specifically related to high intensity non-annealed steel for fastener wire rod of a kind of boracic and preparation method thereof.

Background technology

Steel for fastener is the steel for standard part adopting cold-heading extruding shaping technique production interchangeability higher.Steel for fastener utilizes plastic forming of metals shaping at normal temperatures, material inside organization is tight, the mechanical property of product is good, work material loses less, productivity effect is high, energy expenditure is low, product size precision is high, surface smoothness good, is widely used in the production of all kinds of fastening pieces such as the bolt of cold upset forming, nut, screw, rivet and bearing pin and spare and accessory parts.

In recent years, along with the product restructuring of Investment in fastener industry, fastening piece is from low strength to high intensity non-annealed development, and from high energy consumption to resource-conserving, development becomes inexorable trend.Boracic 10B21 cold heading steel has good plasticity and cold heading performance, wire rod original hardness is low, can shorten or exempt from carbide annealing process, cold heading cracking rate is low, there is the advantages such as intensity is high, hardening capacity is good after Tempering and Quenching, become the major demands product that each steel for fastener enterprise manufactures high-intensity fasteners.Current domestic boracic 10B21 the cold heading steel is basically by converter+LF stove refining+continuous casting+high speed wire rolling explained hereafter, in steel, gas content and inclusion are relatively high, oxygen level >25ppm, hydrogen richness >2ppm, non-metallic inclusion is mostly 0.5-1.0 level, in addition, the microstructure proportioning of steel does not reach optimization, cause the plasticity and toughness of steel lower, it is cold-formed and deformability is limited, wire rod 1/4 cold upsetting qualification rate is low, constrains the application of this product at 10.9 grades of high-level standardized component.

The patent of current domestic existing high-intensity fasteners steel and paper studies report, but the plasticity and toughness of steel and relative reduction in area lower, product is mostly only for the production of 8.8 grade high-strength bolts.As the patent " the high-intensity fasteners steel of a kind of titaniferous and boron hot rolling soft and production method thereof " of Iron And Steel Co., Ltd of Shanxi Xintai City application, the chemical composition of steel is: C0.19-0.38wt%, Si≤0.30wt%, Mn0.50-1.48wt%, P≤0.025wt%, S≤0.015wt%, Ti≤0.050wt%, B≤0.0045wt%, adopt the explained hereafter such as converter smelting, the refining of LF stove, continuous casting, high speed wire rolling, wire rod hardness 80-90HRB, relative reduction in area only 48%, microstructure has a small amount of bainite, and product is for the manufacture of 8.8 grades of fastening pieces, the patent " the cold pier steel of high-intensity fasteners Micro Alloying two-phase and manufacture method thereof " of Baoshan Iron & Steel Co., Ltd's application, the chemical composition of steel is: C0.06-0.15wt%, Si0.60-0.90wt%, Mn1.40-2.00wt%, P≤0.025wt%, S≤0.025wt%, Al≤0.040wt%, converter (or electric furnace) is adopted to smelt, the refining of LF stove, continuous casting (or die casting), the explained hereafter such as high speed wire rolling, wire rod metallographic structure is 15 ~ 30% martensites (or containing a small amount of bainite)+70 ~ 85% ferritic structure, mechanical property Rm >=550MPa, elongation A16-23%, relative reduction in area Z27-66%, product is for the production of 8.8 grade high-strength fasteners, the patent " a kind of high-strength corrosion-resisting steel for fastener " of Jiangsu Shagang Group Huaigang Tegang Co., Ltd's application, the chemical composition of steel is: C0.14-0.17wt%, Si0.17-0.24wt%, Mn0.50-0.70wt%, Cr0.85-0.95wt%, P≤0.020wt%, S≤0.020wt%, adopt converter smelting, the refining of LF stove, continuous casting, high speed wire rolling explained hereafter, the tensile strength Rm490-520MPa of steel, unit elongation 30%, the husky steel in Jiangsu is sweet hopes the paper " exploitation of boron-containing cold heading steel 10B21 gren rod " that the people such as benefit deliver, the chemical composition of steel is: C0.18-0.23wt%, Si≤0.10wt%, Mn0.60-0.90wt%, P≤0.035wt%, S≤0.030wt%, B0.0010-0.0030wt%, Al0.020-0.035wt%, electrosmelting, the refining of LF stove, continuous casting, high line cooling controlling and rolling controlling process is adopted to produce, wire rod tensile strength Rm505-550MPa, elongation A25-30%, relative reduction in area Z64-70%, product is for the production of 8.8 grade high-strength fasteners.Plasticity and toughness and the machining deformation ability of existing boracic high-intensity fasteners steel can't be met the need of market, and therefore, develop a kind of product that can solve the problem and are very important.

Summary of the invention

The first object of the present invention is to provide a kind of boracic high intensity non-annealed steel for fastener wire rod; Second object is to provide the preparation method of the described high intensity non-annealed steel for fastener wire rod of boracic.

The first object of the present invention realizes like this, the high intensity non-annealed steel for fastener wire rod of described boracic has the chemical composition of following weight percents: C0.20 ~ 0.24wt%, Si≤0.04wt%, Mn0.50 ~ 0.70wt%, Cr0.25 ~ 0.35wt%, Ti0.035 ~ 0.055wt%, Als0.035 ~ 0.055wt%, B0.0045 ~ 0.0060wt%, S≤0.004wt%, P≤0.012wt%, O≤0.0015wt%, H≤0.00015wt%, and all the other are Fe and inevitable impurity.

The second object of the present invention is achieved in that and comprises the following steps:

A, molten iron pretreatment desulfurizing: by chemical composition C4.5 ~ 5.0wt%, Si0.30 ~ 0.50wt%, Mn0.25 ~ 0.50wt%, P0.090 ~ 0.110wt%, S≤0.020wt%, all the other the blast-melted KR of being transported to method molten iron preprocessing units for Fe and inevitable impurity carry out desulfurization process, it is 2200 ~ 2400mm that stirring-head depth of penetration controls, by 15.0 ~ 17.0kg/t _steelamount, add conventional CaO matter sweetening agent and carry out desulfurization process, churning time control be 8 minutes; Carry out after stirring terminates taking off rear slag operation, to ensure in ladle molten iron face exposed>=4/5, scratch clean desulfurization slag; After pre-treatment, hot metal composition control is: C4.5 ~ 4.8wt%, Si0.30 ~ 0.50wt%, Mn0.25 ~ 0.50wt%, P0.090 ~ 0.110wt%, S≤0.004wt%, and all the other are Fe and inevitable impurity;

B, smelting molten steel: by chemical composition C4.5-4.8wt%, Si0.30-0.50wt%, Mn0.25-0.50wt%, P0.090-0.110wt%, S≤0.004wt%, all the other are the dark desulphurised hot metal of step A pre-treatment of Fe and inevitable impurity, chemical composition C0.16-0.25wt%, Si0.12-0.25wt%, Mn0.45-0.70wt%, P0.015-0.030wt%, S0.018-0.035wt%, all the other are high-quality steel scrap and the chemical composition C3.2-3.4wt% of Fe and inevitable impurity, Si0.30-0.50wt%, Mn0.30-0.50wt%, P0.070-0.090wt%, S0.020-0.035wt%, all the other low phosphorus and sulphur pig irons for Fe and inevitable impurity add in LD converter, carry out conventional top bottom blowing, respectively by 40.0 ~ 45.0kg/t _steel, 18.0 ~ 22.0kg/t _steel, 3.0 ~ 5.0kg/t _steeladd-on, add lime, light dolomite, the slag making of magnesite ball, control endpoint carbon content>=0.08wt%, tapping temperature≤1640 DEG C, tapping forward direction ladle bottom adds quickened lime and carries out wash heat, and lime adding amount is 2.5kg/t _steel, adopt omnidistance bottom argon blowing technology during tapping, it is 20 ~ 35NL/min that argon flow amount controls,

C, deoxidation alloying: step B is smelted complete molten steel tapping, when the molten steel amount in ladle is greater than 1/4, by following deoxidation alloying order: ferro-aluminum → high carbon ferro-chrome → high carbon ferromanganese, adds following material: successively by 2.2 ~ 3.0kg/t in ladle _steelamount, add the ferro-aluminum of following masses ratio: Al70.5wt%, all the other are Fe and inevitable impurity; By 4.1 ~ 5.8kg/t _steelamount, add the high carbon ferro-chrome of following masses ratio: Cr56.7wt%, C7.2wt%, all the other are Fe and inevitable impurity; By 5.4 ~ 8.1kg/t _steelamount, add the high carbon ferromanganese of following masses ratio: Mn75.6wt%, C6.7wt%, all the other are Fe and inevitable impurity; Above-mentioned alloy is added when ladle molten steel amount reaches 4/5; After tapping, molten steel is hung and delivers to LF stove refining procedure;

D, the refining of molten steel LF stove: complete molten steel of step C being tapped winches to LF stove refining station and connects argon gas band, the little argon amount Argon of unlatching argon gas employing 20 ~ 30NL/min 2 minutes, then lower electrode adopts gear 7 ~ 9 grades to change slag; Be energized after 3 minutes, lift electrode and observe stove internalization slag situation, thermometric, sampling afterwards; If slag condition is rarer, add lime 4.0 ~ 6.0kg/t _steel, then add calcium carbide 0.5kg/t _steelresidue adjustment, controlling basicity of slag is 5.5 ~ 7.0; According to steel sample analysis result, add alloy, aluminum shot adjustment molten steel component, control molten steel oxygen activity≤5ppm; Suitably strengthening argon flow amount is afterwards 40 ~ 50NL/min, by 1.9 ~ 2.9kg/t _steelamount, add the ferrotianium of following masses ratio: Ti33.5wt%, all the other are Fe and inevitable impurity, soft blow argon 3 minutes; Afterwards by 0.3 ~ 0.4kg/t _steelamount, add the ferro-boron of following masses ratio: B21.5wt%, all the other are Fe and inevitable impurity, soft blow argon 2 minutes; Carry out wire feeding process after afterwards liquid steel temperature being heated to 1665 ~ 1675 DEG C, feeding has the aluminium calcium line of following masses ratio: Ca57.2wt%, Al36.5wt%, all the other are Fe and inevitable impurity, and wire-feeding velocity is 2.5m/s, and line feeding amount is 150m; Line feeding terminates to adopt flow to be that the little argon gas amount of 20 ~ 30NL/min carries out soft blow argon to molten steel, and the soft blow time is 2 minutes, adds conventional large bag molten steel covering agent afterwards, and add-on controls, for 1.0kg/t steel, then molten steel to be winched to VD stove vacuum refinement station;

E, the vacuum refinement of molten steel VD stove: after D step molten steel is winched to VD vacuum refining furnace, connect Argon pipe, and the little argon amount Argon of unlatching argon gas employing 20 ~ 30NL/min 2 minutes, determines oxygen to molten steel afterwards and determine hydrogen, thermometric sampling simultaneously; After sampling, vacuum container cover car is opened to working position, close vacuum container cover, vacuumize, when vacuum is evacuated to 60Pa, starts to carry out guarantor's Fruit storage, carry out BOTTOM ARGON BLOWING process simultaneously, it is 40 ~ 60NL/min that argon flow amount controls, 15 minutes liquid steel degassing treatment times under vacuum tightness 60Pa condition; Close vacuum main valve after Fruit storage, promote cover, to liquid steel sampling with determine oxygen and determine hydrogen; Carry out the process of little argon gas amount soft blow argon to molten steel afterwards, argon flow amount is 20 ~ 30NL/min, and soft argon blowing time is 2 minutes; After molten steel soft blow argon terminates, add conventional large bag molten steel covering agent, add-on controls as 1.0kg/t _steel, then molten steel is winched to casting station;

F, molten steel casting: be 1525 ~ 1535 DEG C at tundish temperature, pulling rate is 2.1 ~ 2.3m/min, two cold specific waters are 1.1 ~ 1.3L/kg, M-EMS Current intensity is 300A, running frequency is under the condition of 2.5HZ, adopts R9m straight arc continuous straightening 5 machine 5 to flow the steel billet that the molten steel whole process protection continuous casting of step B is become section 150mm × 150mm by small billet casting machine;

G, heating steel billet: it is in the process furnace of 1080 ~ 1120 DEG C that F step steel billet is sent into soaking zone furnace temperature, heat 50 ~ 70 minutes, steel billet tapping temperature is 940 ~ 980 DEG C, squama is gone out by high pressure water, push to 5 base positions before inlet of rolling mill and treat that warm area carries out the naturally cooling of 3 ~ 5 minutes, finally enter mill milling with the start rolling temperature of 900 ~ 920 DEG C;

H, controlled rolling and controlled cooling: be rolled by the high-speed rod-rolling mill that 28 frames sent into by the steel billet of G step are under the rolling condition of 0.15 ~ 0.25m/s in speed, roughing 6 passages, be under the rolling condition of 10.0 ~ 15.0m/s afterwards in speed, in roll 12 passages, before carrying out finish rolling afterwards, pre-water-cooled control is cold, is 120 ~ 150m at cooling water inflow ³cold 2 ~ 3 seconds are controlled under/h, be 840 ~ 860 DEG C at final rolling temperature afterwards, speed is under the rolling condition of 20 ~ 65m/s, finish rolling 5 ~ 10 passages, be 820 ~ 835 DEG C in temperature afterwards, speed is weave silk under the condition of 20 ~ 65m/s, after weaving silk, wire rod enters Stanermo wind-cooling linear and carries out " delay " type controlled cooling model, i.e. Slow cooling, blower fan Close All when Stanermo wind-cooling linear control is cold, opens insulation shroud above front 3 Fans, and it is 0.25 ~ 0.45m/s that roller table speed controls, collect volume temperature after the air-cooled end of stelmor to control to be 550 ~ 600 DEG C, natural air cooling to room temperature will be coiled afterwards and namely obtain the high intensity non-annealed steel for fastener wire rod of boracic, there is the chemical composition of following weight percents: C0.20 ~ 0.24wt%, Si≤0.04wt%, Mn0.50 ~ 0.70wt%, Cr0.25 ~ 0.35wt%, Ti0.035 ~ 0.055wt%, Als0.035 ~ 0.055wt%, B0.0045 ~ 0.0060wt%, S≤0.004wt%, P≤0.012wt%, O≤0.0015wt%, H≤0.00015wt%, all the other are Fe and inevitable impurity, there is following technologic mechanics performance, as shown in Table 1 and Table 2:

Table 1 boracic high-intensity fasteners steel coil rod technologic mechanics performance

Table 2 boracic high-intensity fasteners steel coil rod microstructure and inclusion

The wire rod cleanliness factor that the present invention produces is apparently higher than existing production technique, and hazardous elements S in steel, P content are low, P≤0.012wt%, S≤0.005wt%, oxygen level≤0.0015wt%, hydrogen richness≤0.00015wt%, non-metallic inclusion≤0.5 grade; Wire rod has good hardening capacity, the plasticity and toughness of suitable intensity and hardness and excellence and cold-heading forge ability, do not need Spheroidizing Annealing process can direct cold upset forming process for producing 10.9 grades of high-level standardized component, reduce manufacturing procedure and steel consumption, reduce production cost.

The present invention adds the effect that Al plays crystal grain thinning and improves intensity in steel; Add micro-B and a small amount of nitrogen killer Ti, be conducive to the hardening capacity giving full play to B, reach the rational Match of intensity, plasticity and toughness; Molten steel, by VD vacuum refinement treatment process, makes gas content and inclusion in steel significantly reduce, P≤0.012wt%, S≤0.005wt%, oxygen level≤0.0015wt%, hydrogen richness≤0.0002wt%, non-metallic inclusion≤0.5 grade, is conducive to the improvement of steel plasticity and toughness; Steel rolling process controls lower start rolling temperature, enters final rolling temperature and laying temperature, facilitate the refinement of ferrite crystal grain, it is cold that wire rod after having weaved silk adopts delaying type stelmor cooling mode to carry out control, stelmor roller-way completes phase transformation with cooling rate slowly, obtain close grain ferrite+spheroidizing pearlite microstructure, the forge ability of steel is significantly improved.

The boracic high-intensity fasteners steel wire rod cleanliness factor that the present invention produces is high, inclusion is few, there is good hardening capacity, the plasticity and toughness of suitable intensity and hardness and excellence and cold-heading forge ability, do not need Spheroidizing Annealing process can direct cold upset forming process for producing 10.9 grades of high-level standardized component, reduce manufacturing procedure and steel consumption, reduce production cost.

Embodiment

Below in conjunction with embodiment, the present invention is further illustrated, but limited the present invention never in any form, and any conversion done based on training centre of the present invention or replacement, all belong to protection scope of the present invention.

The high intensity non-annealed steel for fastener wire rod of boracic of the present invention has the chemical composition of following weight percents: C0.20 ~ 0.24wt%, Si≤0.04wt%, Mn0.50 ~ 0.70wt%, Cr0.25 ~ 0.35wt%, Ti0.035 ~ 0.055wt%, Als0.035 ~ 0.055wt%, B0.0045 ~ 0.0060wt%, S≤0.004wt%, P≤0.012wt%, O≤0.0015wt%, H≤0.00015wt%, and all the other are Fe and inevitable impurity.

The preparation method of the high intensity non-annealed steel for fastener wire rod of boracic of the present invention, is characterized in that comprising the following steps:

A, molten iron pretreatment desulfurizing: by chemical composition C4.5 ~ 5.0wt%, Si0.30 ~ 0.50wt%, Mn0.25 ~ 0.50wt%, P0.090 ~ 0.110wt%, S≤0.020wt%, all the other the blast-melted KR of being transported to method molten iron preprocessing units for Fe and inevitable impurity carry out desulfurization process, it is 2200 ~ 2400mm that stirring-head depth of penetration controls, by 15.0 ~ 17.0kg/t _steelamount, add conventional CaO matter sweetening agent and carry out desulfurization process, churning time control be 8 minutes; Carry out after stirring terminates taking off rear slag operation, to ensure in ladle molten iron face exposed>=4/5, scratch clean desulfurization slag; After pre-treatment, hot metal composition control is: C4.5 ~ 4.8wt%, Si0.30 ~ 0.50wt%, Mn0.25 ~ 0.50wt%, P0.090 ~ 0.110wt%, S≤0.004wt%, and all the other are Fe and inevitable impurity;

B, smelting molten steel: by chemical composition C4.5-4.8wt%, Si0.30-0.50wt%, Mn0.25-0.50wt%, P0.090-0.110wt%, S≤0.004wt%, all the other are the dark desulphurised hot metal of step A pre-treatment of Fe and inevitable impurity, chemical composition C0.16-0.25wt%, Si0.12-0.25wt%, Mn0.45-0.70wt%, P0.015-0.030wt%, S0.018-0.035wt%, all the other are high-quality steel scrap and the chemical composition C3.2-3.4wt% of Fe and inevitable impurity, Si0.30-0.50wt%, Mn0.30-0.50wt%, P0.070-0.090wt%, S0.020-0.035wt%, all the other low phosphorus and sulphur pig irons for Fe and inevitable impurity add in LD converter, carry out conventional top bottom blowing, respectively by 40.0 ~ 45.0kg/t _steel, 18.0 ~ 22.0kg/t _steel, 3.0 ~ 5.0kg/t _steeladd-on, add lime, light dolomite, the slag making of magnesite ball, control endpoint carbon content>=0.08wt%, tapping temperature≤1640 DEG C, tapping forward direction ladle bottom adds quickened lime and carries out wash heat, and lime adding amount is 2.5kg/t _steel, adopt omnidistance bottom argon blowing technology during tapping, it is 20 ~ 35NL/min that argon flow amount controls,

C, deoxidation alloying: step B is smelted complete molten steel tapping, when the molten steel amount in ladle is greater than 1/4, by following deoxidation alloying order: ferro-aluminum → high carbon ferro-chrome → high carbon ferromanganese, adds following material: successively by 2.2 ~ 3.0kg/t in ladle _steelamount, add the ferro-aluminum of following masses ratio: Al70.5wt%, all the other are Fe and inevitable impurity; By 4.1 ~ 5.8kg/t _steelamount, add the high carbon ferro-chrome of following masses ratio: Cr56.7wt%, C7.2wt%, all the other are Fe and inevitable impurity; By 5.4 ~ 8.1kg/t _steelamount, add the high carbon ferromanganese of following masses ratio: Mn75.6wt%, C6.7wt%, all the other are Fe and inevitable impurity; Above-mentioned alloy is added when ladle molten steel amount reaches 4/5; After tapping, molten steel is hung and delivers to LF stove refining procedure;

D, the refining of molten steel LF stove: complete molten steel of step C being tapped winches to LF stove refining station and connects argon gas band, the little argon amount Argon of unlatching argon gas employing 20 ~ 30NL/min 2 minutes, then lower electrode adopts gear 7 ~ 9 grades to change slag; Be energized after 3 minutes, lift electrode and observe stove internalization slag situation, thermometric, sampling afterwards; If slag condition is rarer, add lime 4.0 ~ 6.0kg/t _steel, then add calcium carbide 0.5kg/t _steelresidue adjustment, controlling basicity of slag is 5.5 ~ 7.0; According to steel sample analysis result, add alloy, aluminum shot adjustment molten steel component, control molten steel oxygen activity≤5ppm; Suitably strengthening argon flow amount is afterwards 40 ~ 50NL/min, by 1.9 ~ 2.9kg/t _steelamount, add the ferrotianium of following masses ratio: Ti33.5wt%, all the other are Fe and inevitable impurity, soft blow argon 3 minutes; Afterwards by 0.3 ~ 0.4kg/t _steelamount, add the ferro-boron of following masses ratio: B21.5wt%, all the other are Fe and inevitable impurity, soft blow argon 2 minutes; Carry out wire feeding process after afterwards liquid steel temperature being heated to 1665 ~ 1675 DEG C, feeding has the aluminium calcium line of following masses ratio: Ca57.2wt%, Al36.5wt%, all the other are Fe and inevitable impurity, and wire-feeding velocity is 2.5m/s, and line feeding amount is 150m; Line feeding terminates to adopt flow to be that the little argon gas amount of 20 ~ 30NL/min carries out soft blow argon to molten steel, and the soft blow time is 2 minutes, adds conventional large bag molten steel covering agent afterwards, and add-on controls, for 1.0kg/t steel, then molten steel to be winched to VD stove vacuum refinement station;

E, the vacuum refinement of molten steel VD stove: after D step molten steel is winched to VD vacuum refining furnace, connect Argon pipe, and the little argon amount Argon of unlatching argon gas employing 20 ~ 30NL/min 2 minutes, determines oxygen to molten steel afterwards and determine hydrogen, thermometric sampling simultaneously; After sampling, vacuum container cover car is opened to working position, close vacuum container cover, vacuumize, when vacuum is evacuated to 60Pa, starts to carry out guarantor's Fruit storage, carry out BOTTOM ARGON BLOWING process simultaneously, it is 40 ~ 60NL/min that argon flow amount controls, 15 minutes liquid steel degassing treatment times under vacuum tightness 60Pa condition; Close vacuum main valve after Fruit storage, promote cover, to liquid steel sampling with determine oxygen and determine hydrogen; Carry out the process of little argon gas amount soft blow argon to molten steel afterwards, argon flow amount is 20 ~ 30NL/min, and soft argon blowing time is 2 minutes; After molten steel soft blow argon terminates, add conventional large bag molten steel covering agent, add-on controls as 1.0kg/t _steel, then molten steel is winched to casting station;

F, molten steel casting: be 1525 ~ 1535 DEG C at tundish temperature, pulling rate is 2.1 ~ 2.3m/min, two cold specific waters are 1.1 ~ 1.3L/kg, M-EMS Current intensity is 300A, running frequency is under the condition of 2.5HZ, adopts R9m straight arc continuous straightening 5 machine 5 to flow the steel billet that the molten steel whole process protection continuous casting of step B is become section 150mm × 150mm by small billet casting machine;

G, heating steel billet: it is in the process furnace of 1080 ~ 1120 DEG C that F step steel billet is sent into soaking zone furnace temperature, heat 50 ~ 70 minutes, steel billet tapping temperature is 940 ~ 980 DEG C, squama is gone out by high pressure water, push to 5 base positions before inlet of rolling mill and treat that warm area carries out the naturally cooling of 3 ~ 5 minutes, finally enter mill milling with the start rolling temperature of 900 ~ 920 DEG C;

H, controlled rolling and controlled cooling: be rolled by the high-speed rod-rolling mill that 28 frames sent into by the steel billet of G step are under the rolling condition of 0.15 ~ 0.25m/s in speed, roughing 6 passages, be under the rolling condition of 10.0 ~ 15.0m/s afterwards in speed, in roll 12 passages, before carrying out finish rolling afterwards, pre-water-cooled control is cold, is 120 ~ 150m at cooling water inflow ³cold 2 ~ 3 seconds are controlled under/h, be 840 ~ 860 DEG C at final rolling temperature afterwards, speed is under the rolling condition of 20 ~ 65m/s, finish rolling 5 ~ 10 passages, be 820 ~ 835 DEG C in temperature afterwards, speed is weave silk under the condition of 20 ~ 65m/s, after weaving silk, wire rod enters Stanermo wind-cooling linear and carries out " delay " type controlled cooling model, i.e. Slow cooling, blower fan Close All when Stanermo wind-cooling linear control is cold, opens insulation shroud above front 3 Fans, and it is 0.25 ~ 0.45m/s that roller table speed controls, collect volume temperature after the air-cooled end of stelmor to control to be 550 ~ 600 DEG C, natural air cooling to room temperature will be coiled afterwards and namely obtain the high intensity non-annealed steel for fastener wire rod of boracic, there is the chemical composition of following weight percents: C0.20 ~ 0.24wt%, Si≤0.04wt%, Mn0.50 ~ 0.70wt%, Cr0.25 ~ 0.35wt%, Ti0.035 ~ 0.055wt%, Als0.035 ~ 0.055wt%, B0.0045 ~ 0.0060wt%, S≤0.004wt%, P≤0.012wt%, O≤0.0015wt%, H≤0.00015wt%, all the other are Fe and inevitable impurity, there is following technologic mechanics performance, as shown in Table 1 and Table 2:

Table 1 boracic high-intensity fasteners steel coil rod technologic mechanics performance

Table 2 boracic high-intensity fasteners steel coil rod microstructure and inclusion

Specific embodiment of the invention method is as follows:

A, molten iron pretreatment desulfurizing: by blast-melted (chemical composition C4.5-5.0wt%, Si0.30-0.50wt%, Mn0.25-0.50wt%, P0.090-0.110wt%, S≤0.020wt%, all the other are Fe and inevitable impurity) be transported to KR method molten iron preprocessing unit and carry out desulfurization process, stirring-head depth of penetration controls as 2200-2400mm, by 15.0 ~ 17.0kg/t _steelamount, add conventional CaO matter sweetening agent and carry out desulfurization process, churning time control be 8 minutes; Carry out after stirring terminates taking off rear slag operation, to ensure in ladle molten iron face exposed>=4/5, scratch clean desulfurization slag; After pre-treatment, hot metal composition control is: C4.5-4.8wt%, Si0.30-0.50wt%, Mn0.25-0.50wt%, P0.090-0.110wt%, S≤0.004wt%, and all the other are Fe and inevitable impurity.

B, smelting molten steel: by dark for the pre-treatment of step A desulphurised hot metal (chemical composition C4.5-4.8wt%, Si0.30-0.50wt%, Mn0.25-0.50wt%, P0.090-0.110wt%, S≤0.004wt%, all the other are Fe and inevitable impurity), high-quality steel scrap (chemical composition C0.16-0.25wt%, Si0.12-0.25wt%, Mn0.45-0.70wt%, P0.015-0.030wt%, S0.018-0.035wt%, all the other are Fe and inevitable impurity) and low phosphorus and sulphur pig iron (chemical composition C3.2-3.4wt%, Si0.30-0.50wt%, Mn0.30-0.50wt%, P0.070-0.090wt%, S0.020-0.035wt%, all the other are Fe and inevitable impurity) add in LD converter, carry out conventional top bottom blowing, respectively by 40.0 ~ 45.0kg/t _steel, 18.0 ~ 22.0kg/t _steel, 3.0 ~ 5.0kg/t _steeladd-on, add lime, light dolomite, the slag making of magnesite ball, control endpoint carbon content>=0.08wt%, tapping temperature≤1640 DEG C, tapping forward direction ladle bottom adds quickened lime and carries out wash heat, and lime adding amount is 2.5kg/t _steel, adopt omnidistance bottom argon blowing technology during tapping, it is 20 ~ 35NL/min that argon flow amount controls.

C, deoxidation alloying: step B is smelted complete molten steel tapping, when the molten steel amount in ladle is greater than 1/4, by following deoxidation alloying order: ferro-aluminum → high carbon ferro-chrome → high carbon ferromanganese, adds following material: successively by 2.2 ~ 3.0kg/t in ladle _steelamount, add the ferro-aluminum of following masses ratio: Al70.5wt%, all the other are Fe and inevitable impurity; By 4.1 ~ 5.8kg/t _steelamount, add the high carbon ferro-chrome of following masses ratio: Cr56.7wt%, C7.2wt%, all the other are Fe and inevitable impurity; By 5.4 ~ 8.1kg/t _steelamount, add the high carbon ferromanganese of following masses ratio: Mn75.6wt%, C6.7wt%, all the other are Fe and inevitable impurity; Above-mentioned alloy is added when ladle molten steel amount reaches 4/5; After tapping, molten steel is hung and delivers to LF stove refining procedure.

D, the refining of molten steel LF stove: complete molten steel of step C being tapped winches to LF stove refining station and connects argon gas band, open argon gas and adopt little argon amount (20 ~ 30NL/min) Argon 2 minutes, and then lower electrode adopts gear 7 ~ 9 grades to change slag; Be energized after 3 minutes, lift electrode and observe stove internalization slag situation, thermometric, sampling afterwards; If slag condition is rarer, add lime 4.0 ~ 6.0kg/t _steel, then add calcium carbide 0.5kg/t _steelresidue adjustment, controlling basicity of slag is 5.5 ~ 7.0; According to steel sample analysis result, add alloy, aluminum shot adjustment molten steel component, control molten steel oxygen activity≤5ppm; Suitably strengthen argon flow amount (40 ~ 50NL/min) afterwards, by 1.9 ~ 2.9kg/t _steelamount, add the ferrotianium of following masses ratio: Ti33.5wt%, all the other are Fe and inevitable impurity, soft blow argon 3 minutes; Afterwards by 0.3 ~ 0.4kg/t _steelamount, add the ferro-boron of following masses ratio: B21.5wt%, all the other are Fe and inevitable impurity, soft blow argon 2 minutes; Carry out wire feeding process after afterwards liquid steel temperature being heated to 1665 ~ 1675 DEG C, feeding has the aluminium calcium line of following masses ratio: Ca57.2wt%, Al36.5wt%, all the other are Fe and inevitable impurity, and wire-feeding velocity is 2.5m/s, and line feeding amount is 150m; Line feeding terminates to adopt flow to be that the little argon gas amount of 20 ~ 30NL/min carries out soft blow argon to molten steel, and the soft blow time is 2 minutes, adds conventional large bag molten steel covering agent afterwards, and add-on controls, for 1.0kg/t steel, then molten steel to be winched to VD stove vacuum refinement station.

E, the vacuum refinement of molten steel VD stove: after D step molten steel is winched to VD vacuum refining furnace, connect Argon pipe, opens argon gas and adopt little argon amount (20 ~ 30NL/min) Argon 2 minutes, determine oxygen afterwards determine hydrogen to molten steel, thermometric sampling simultaneously; After sampling, vacuum container cover car is opened to working position, close vacuum container cover, vacuumize, when vacuum is evacuated to 60Pa, starts to carry out guarantor's Fruit storage, carry out BOTTOM ARGON BLOWING process simultaneously, it is 40 ~ 60NL/min that argon flow amount controls, 15 minutes liquid steel degassing treatment times under vacuum tightness 60Pa condition; Close vacuum main valve after Fruit storage, promote cover, to liquid steel sampling with determine oxygen and determine hydrogen; Carry out the process of little argon gas amount soft blow argon to molten steel afterwards, argon flow amount is 20 ~ 30NL/min, and soft argon blowing time is 2 minutes; After molten steel soft blow argon terminates, add conventional large bag molten steel covering agent, add-on controls as 1.0kg/t _steel, then molten steel is winched to casting station.

F, molten steel casting: be 1525 ~ 1535 DEG C at tundish temperature, pulling rate is 2.1 ~ 2.3m/min, two cold specific waters are 1.1 ~ 1.3L/kg, M-EMS Current intensity is 300A, running frequency is under the condition of 2.5HZ, adopts R9m straight arc continuous straightening 5 machine 5 to flow the steel billet that the molten steel whole process protection continuous casting of step B is become section 150mm × 150mm by small billet casting machine;

G, heating steel billet: it is in the process furnace of 1080 ~ 1120 DEG C that F step steel billet is sent into soaking zone furnace temperature, heat 50 ~ 70 minutes, steel billet tapping temperature is 940 ~ 980 DEG C, squama is gone out by high pressure water, push to 5 base positions before inlet of rolling mill and treat that warm area carries out the naturally cooling of 3 ~ 5 minutes, finally enter mill milling with the start rolling temperature of 900 ~ 920 DEG C;

H, controlled rolling and controlled cooling: be rolled by the high-speed rod-rolling mill that 28 frames sent into by the steel billet of G step are under the rolling condition of 0.15 ~ 0.25m/s in speed, roughing 6 passages; Be under the rolling condition of 10.0 ~ 15.0m/s afterwards in speed, in roll 12 passages; Before carrying out finish rolling afterwards, pre-water-cooled control is cold, is 120 ~ 150m at cooling water inflow ³cold 2 ~ 3 seconds are controlled under/h; Be 840 ~ 860 DEG C at final rolling temperature afterwards, speed is under the rolling condition of 20 ~ 65m/s, finish rolling 5 ~ 10 passages; Be 820 ~ 835 DEG C in temperature afterwards, speed is weave silk under the condition of 20 ~ 65m/s; After weaving silk, wire rod enters Stanermo wind-cooling linear and carries out " delay " type controlled cooling model (i.e. Slow cooling); Blower fan Close All when Stanermo wind-cooling linear control is cold, opens insulation shroud above front 3 Fans, and it is 0.25 ~ 0.45m/s that roller table speed controls; Collect volume temperature after the air-cooled end of stelmor to control to be 550 ~ 600 DEG C, will coil natural air cooling to room temperature afterwards and namely obtain the high intensity non-annealed steel for fastener coil rod of a kind of boracic, the temperature control of steel, roller table speed require specifically to determine depending on different size.

The high intensity non-annealed steel for fastener coil rod of a kind of boracic provided by the invention has the chemical composition of following weight percents: C0.20 ~ 0.24wt%, Si≤0.04wt%, Mn0.50 ~ 0.70wt%, Cr0.25 ~ 0.35wt%, Ti0.035 ~ 0.055wt%, Als0.035 ~ 0.055wt%, B0.0045 ~ 0.0060wt%, S≤0.004wt%, P≤0.012wt%, O≤0.0015wt%, H≤0.00015wt%, and all the other are Fe and inevitable impurity.

The present invention has following advantages and beneficial effect:

The preparation method of the high intensity non-annealed steel for fastener wire rod of boracic provided by the invention, adds the effect that Al plays crystal grain thinning and improves intensity in steel; Add micro-B and a small amount of nitrogen killer Ti, be conducive to the hardening capacity giving full play to B, reach the rational Match of intensity, plasticity and toughness; Molten steel, by VD vacuum refinement treatment process, makes gas content and inclusion in steel significantly reduce, P≤0.012wt%, S≤0.005wt%, oxygen level≤0.0015wt%, hydrogen richness≤0.00015wt%, non-metallic inclusion≤0.5 grade, is conducive to the improvement of steel plasticity and toughness; Steel rolling process controls lower start rolling temperature, enters final rolling temperature and laying temperature, facilitate the refinement of ferrite crystal grain, it is cold that wire rod after having weaved silk adopts delaying type stelmor cooling mode to carry out control, stelmor roller-way completes phase transformation with cooling rate slowly, obtain close grain ferrite+spheroidizing pearlite microstructure, the forge ability of steel is significantly improved.

The boracic high-intensity fasteners steel wire rod cleanliness factor that the present invention produces is high, inclusion is few, there is good hardening capacity, the plasticity and toughness of suitable intensity and hardness and excellence and cold-heading forge ability, do not need Spheroidizing Annealing process can direct cold upset forming process for producing 10.9 grades of high-level standardized component, reduce manufacturing procedure and steel consumption, reduce production cost.

With concrete case study on implementation, the present invention will be further described below:

Embodiment 1

A, molten iron pretreatment desulfurizing: by blast-melted (chemical composition C4.5wt%, Si0.30wt%, Mn0.25wt%, P0.090wt%, S0.012wt%, all the other are Fe and inevitable impurity) be transported to KR method molten iron preprocessing unit and carry out desulfurization process, stirring-head depth of penetration controls as 2200-2400mm, by 15.0kg/t _steelamount, add conventional CaO matter sweetening agent and carry out desulfurization process, churning time control be 8 minutes; Carry out after stirring terminates taking off rear slag operation, to ensure in ladle molten iron face exposed>=4/5, scratch clean desulfurization slag; After pre-treatment, hot metal composition control is: C4.5wt%, Si0.30wt%, Mn0.25wt%, P0.090wt%, S0.002wt%, and all the other are Fe and inevitable impurity.

B, smelting molten steel: by dark for the pre-treatment of step A desulphurised hot metal (chemical composition C4.5wt%, Si0.30wt%, Mn0.25wt%, P0.090wt%, S0.002wt%, all the other are Fe and inevitable impurity), high-quality steel scrap (chemical composition C0.16wt%, Si0.12wt%, Mn0.45wt%, P0.015wt%, S0.018wt%, all the other are Fe and inevitable impurity) and low phosphorus and sulphur pig iron (chemical composition C3.2wt%, Si0.30wt%, Mn0.30wt%, P0.070wt%, S0.020wt%, all the other are Fe and inevitable impurity) add in LD converter, carry out conventional top bottom blowing, press 40.0kg/t respectively _steel, 18.0kg/t _steel, 3.0kg/t _steeladd-on, add lime, light dolomite, the slag making of magnesite ball, control endpoint carbon content 0.08wt%, tapping temperature 1625 DEG C, tapping forward direction ladle bottom adds quickened lime and carries out wash heat, and lime adding amount is 2.5kg/t _steel, adopt omnidistance bottom argon blowing technology during tapping, argon flow amount controls as 20NL/min.

C, deoxidation alloying: step B is smelted complete molten steel tapping, when the molten steel amount in ladle is greater than 1/4, by following deoxidation alloying order: ferro-aluminum → high carbon ferro-chrome → high carbon ferromanganese, adds following material: successively by 2.2kg/t in ladle _steelamount, add the ferro-aluminum of following masses ratio: Al70.5wt%, all the other are Fe and inevitable impurity; By 4.1kg/t _steelamount, add the high carbon ferro-chrome of following masses ratio: Cr56.7wt%, C7.2wt%, all the other are Fe and inevitable impurity; By 5.4kg/t _steelamount, add the high carbon ferromanganese of following masses ratio: Mn75.6wt%, C6.7wt%, all the other are Fe and inevitable impurity; Above-mentioned alloy is added when ladle molten steel amount reaches 4/5; After tapping, molten steel is hung and delivers to LF stove refining procedure.

D, the refining of molten steel LF stove: complete molten steel of step C being tapped winches to LF stove refining station and connects argon gas band, open argon gas and adopt little argon amount (20NL/min) Argon 2 minutes, and then lower electrode adopts gear 7 ~ 9 grades to change slag; Be energized after 3 minutes, lift electrode and observe stove internalization slag situation, thermometric, sampling afterwards; If slag condition is rarer, add lime 4.0kg/t _steel, then add calcium carbide 0.5kg/t _steelresidue adjustment, controlling basicity of slag is 5.5; According to steel sample analysis result, add alloy, aluminum shot adjustment molten steel component, control molten steel oxygen activity 5ppm; Suitably strengthen argon flow amount (40NL/min) afterwards, by 1.9kg/t _steelamount, add the ferrotianium of following masses ratio: Ti33.5wt%, all the other are Fe and inevitable impurity, soft blow argon 3 minutes; Press 0.3kg/t afterwards _steelamount, add the ferro-boron of following masses ratio: B21.5wt%, all the other are Fe and inevitable impurity, soft blow argon 2 minutes; Carry out wire feeding process after afterwards liquid steel temperature being heated to 1675 DEG C, feeding has the aluminium calcium line of following masses ratio: Ca57.2wt%, Al36.5wt%, all the other are Fe and inevitable impurity, and wire-feeding velocity is 2.5m/s, and line feeding amount is 150m; Line feeding terminates to adopt flow to be that the little argon gas amount of 20NL/min carries out soft blow argon to molten steel, and the soft blow time is 2 minutes, adds conventional large bag molten steel covering agent afterwards, and add-on controls, for 1.0kg/t steel, then molten steel to be winched to VD stove vacuum refinement station.

E, the vacuum refinement of molten steel VD stove: after D step molten steel is winched to VD vacuum refining furnace, connect Argon pipe, opens argon gas and adopt little argon amount (20NL/min) Argon 2 minutes, determine oxygen afterwards determine hydrogen to molten steel, thermometric sampling simultaneously; After sampling, vacuum container cover car is opened to working position, close vacuum container cover, vacuumize, when vacuum is evacuated to 60Pa, starts to carry out guarantor's Fruit storage, carry out BOTTOM ARGON BLOWING process simultaneously, it is 40 ~ 60NL/min that argon flow amount controls, 15 minutes liquid steel degassing treatment times under vacuum tightness 60Pa condition; Close vacuum main valve after Fruit storage, promote cover, to liquid steel sampling with determine oxygen and determine hydrogen; Carry out the process of little argon gas amount soft blow argon to molten steel afterwards, argon flow amount is 20NL/min, and soft argon blowing time is 2 minutes; After molten steel soft blow argon terminates, add conventional large bag molten steel covering agent, add-on controls as 1.0kg/t _steel, then molten steel is winched to casting station.

F, molten steel casting: be 1535 DEG C at tundish temperature; pulling rate is 2.3m/min; two cold specific waters are 1.3L/kg; M-EMS Current intensity is 300A, running frequency is under the condition of 2.5HZ, adopts R9m straight arc continuous straightening 5 machine 5 to flow the steel billet that the molten steel whole process protection continuous casting of step B is become section 150mm × 150mm by small billet casting machine.

G, heating steel billet: it is in the process furnace of 1120 DEG C that F step steel billet is sent into soaking zone furnace temperature, heat 70 minutes, steel billet tapping temperature is 980 DEG C, squama is gone out by high pressure water, push to 5 base positions before inlet of rolling mill and treat that warm area carries out the naturally cooling of 3 minutes, finally enter mill milling with the start rolling temperature of 920 DEG C.

H, controlled rolling and controlled cooling: be rolled by the high-speed rod-rolling mill that 28 frames sent into by the steel billet of G step are under the rolling condition of 0.25m/s in speed, roughing 6 passages; Be under the rolling condition of 15.0m/s afterwards in speed, in roll 12 passages; Before carrying out finish rolling afterwards, pre-water-cooled control is cold, is 120m at cooling water inflow ³cold 2 seconds are controlled under/h; Be 860 DEG C at final rolling temperature afterwards, speed is under the rolling condition of 65m/s, finish rolling 10 passages; Be 835 DEG C in temperature afterwards, speed is weave silk under the condition of 65m/s; After weaving silk, wire rod enters Stanermo wind-cooling linear and carries out " delay " type controlled cooling model (i.e. Slow cooling); Blower fan Close All when Stanermo wind-cooling linear control is cold, opens insulation shroud above front 3 Fans, and it is 0.25 ~ 0.45m/s that roller table speed controls; Collect volume temperature after the air-cooled end of stelmor to control to be 600 DEG C, natural air cooling to room temperature will be coiled afterwards and namely obtain the high intensity non-annealed steel for fastener coil rod of a kind of boracic, have the chemical composition of following weight percents: C0.20wt%, Si0.04wt%, Mn0.50wt%, Cr0.25wt%, Ti0.035wt%, Als0.035wt%, B0.0045wt%, S0.002wt%, P0.007wt%, O0.0015wt%, H0.00015wt%, all the other are Fe and inevitable impurity.

The inspection of the boracic that the present embodiment prepares high intensity non-annealed steel for fastener coil rod technologic mechanics performance, microstructure and inclusion is in shown in table 3, table 4.

The boracic high-intensity fasteners steel coil rod technologic mechanics performance that table 3 the present embodiment is produced

Boracic high-intensity fasteners steel coil rod microstructure and inclusion that table 4 the present embodiment is produced

Embodiment 2

A, molten iron pretreatment desulfurizing: by blast-melted (chemical composition C4.8wt%, Si0.40wt%, Mn0.38wt%, P0.102wt%, S0.017wt%, all the other are Fe and inevitable impurity) be transported to KR method molten iron preprocessing unit and carry out desulfurization process, stirring-head depth of penetration controls as 2200-2400mm, by 16.0kg/t _steelamount, add conventional CaO matter sweetening agent and carry out desulfurization process, churning time control be 8 minutes; Carry out after stirring terminates taking off rear slag operation, to ensure in ladle molten iron face exposed>=4/5, scratch clean desulfurization slag; After pre-treatment, hot metal composition control is: C4.6wt%, Si0.40wt%, Mn0.38wt%, P0.102wt%, S0.003wt%, and all the other are Fe and inevitable impurity.

B, smelting molten steel: by dark for the pre-treatment of step A desulphurised hot metal (chemical composition C4.6wt%, Si0.40wt%, Mn0.38wt%, P0.102wt%, S0.003wt%, all the other are Fe and inevitable impurity), high-quality steel scrap (chemical composition C0.20wt%, Si0.18wt%, Mn0.58wt%, P0.021wt%, S0.026wt%, all the other are Fe and inevitable impurity) and low phosphorus and sulphur pig iron (chemical composition C3.3wt%, Si0.40wt%, Mn0.40wt%, P0.080wt%, S0.028wt%, all the other are Fe and inevitable impurity) add in LD converter, carry out conventional top bottom blowing, press 42.0kg/t respectively _steel, 20.0kg/t _steel, 4.0kg/t _steeladd-on, add lime, light dolomite, the slag making of magnesite ball, control endpoint carbon content 0.10wt%, tapping temperature 1635 DEG C, tapping forward direction ladle bottom adds quickened lime and carries out wash heat, and lime adding amount is 2.5kg/t _steel, adopt omnidistance bottom argon blowing technology during tapping, argon flow amount controls as 28NL/min.

C, deoxidation alloying: step B is smelted complete molten steel tapping, when the molten steel amount in ladle is greater than 1/4, by following deoxidation alloying order: ferro-aluminum → high carbon ferro-chrome → high carbon ferromanganese, adds following material: successively by 2.6kg/t in ladle _steelamount, add the ferro-aluminum of following masses ratio: Al70.5wt%, all the other are Fe and inevitable impurity; By 5.4kg/t _steelamount, add the high carbon ferro-chrome of following masses ratio: Cr56.7wt%, C7.2wt%, all the other are Fe and inevitable impurity; By 6.7kg/t _steelamount, add the high carbon ferromanganese of following masses ratio: Mn75.6wt%, C6.7wt%, all the other are Fe and inevitable impurity; Above-mentioned alloy is added when ladle molten steel amount reaches 4/5; After tapping, molten steel is hung and delivers to LF stove refining procedure.

D, the refining of molten steel LF stove: complete molten steel of step C being tapped winches to LF stove refining station and connects argon gas band, open argon gas and adopt little argon amount (25NL/min) Argon 2 minutes, and then lower electrode adopts gear 7 ~ 9 grades to change slag; Be energized after 3 minutes, lift electrode and observe stove internalization slag situation, thermometric, sampling afterwards; If slag condition is rarer, add lime 5.0kg/t _steel, then add calcium carbide 0.5kg/t _steelresidue adjustment, controlling basicity of slag is 6.2; According to steel sample analysis result, add alloy, aluminum shot adjustment molten steel component, control molten steel oxygen activity 3ppm; Suitably strengthen argon flow amount (46NL/min) afterwards, by 2.4kg/t _steelamount, add the ferrotianium of following masses ratio: Ti33.5wt%, all the other are Fe and inevitable impurity, soft blow argon 3 minutes; Press 0.36kg/t afterwards _steelamount, add the ferro-boron of following masses ratio: B21.5wt%, all the other are Fe and inevitable impurity, soft blow argon 2 minutes; Carry out wire feeding process after afterwards liquid steel temperature being heated to 1670 DEG C, feeding has the aluminium calcium line of following masses ratio: Ca57.2wt%, Al36.5wt%, all the other are Fe and inevitable impurity, and wire-feeding velocity is 2.5m/s, and line feeding amount is 150m; Line feeding terminates to adopt flow to be that the little argon gas amount of 25NL/min carries out soft blow argon to molten steel, and the soft blow time is 2 minutes, adds conventional large bag molten steel covering agent afterwards, and add-on controls, for 1.0kg/t steel, then molten steel to be winched to VD stove vacuum refinement station.

E, the vacuum refinement of molten steel VD stove: after D step molten steel is winched to VD vacuum refining furnace, connect Argon pipe, opens argon gas and adopt little argon amount (25NL/min) Argon 2 minutes, determine oxygen afterwards determine hydrogen to molten steel, thermometric sampling simultaneously; After sampling, vacuum container cover car is opened to working position, close vacuum container cover, vacuumize, when vacuum is evacuated to 60Pa, starts to carry out guarantor's Fruit storage, carry out BOTTOM ARGON BLOWING process simultaneously, argon flow amount controls as 50NL/min, 15 minutes liquid steel degassing treatment times under vacuum tightness 60Pa condition; Close vacuum main valve after Fruit storage, promote cover, to liquid steel sampling with determine oxygen and determine hydrogen; Carry out the process of little argon gas amount soft blow argon to molten steel afterwards, argon flow amount is 25NL/min, and soft argon blowing time is 2 minutes; After molten steel soft blow argon terminates, add conventional large bag molten steel covering agent, add-on controls as 1.0kg/t _steel, then molten steel is winched to casting station.

F, molten steel casting: be 1530 DEG C at tundish temperature, pulling rate is 2.2m/min, two cold specific waters are 1.2L/kg, M-EMS Current intensity is 300A, running frequency is under the condition of 2.5HZ, adopts R9m straight arc continuous straightening 5 machine 5 to flow the steel billet that the molten steel whole process protection continuous casting of step B is become section 150mm × 150mm by small billet casting machine;

G, heating steel billet: it is in the process furnace of 1100 DEG C that F step steel billet is sent into soaking zone furnace temperature, heat 60 minutes, steel billet tapping temperature is 960 DEG C, squama is gone out by high pressure water, push to 5 base positions before inlet of rolling mill and treat that warm area carries out the naturally cooling of 4 minutes, finally enter mill milling with the start rolling temperature of 910 DEG C;

H, controlled rolling and controlled cooling: be rolled by the high-speed rod-rolling mill that 28 frames sent into by the steel billet of G step are under the rolling condition of 0.20m/s in speed, roughing 6 passages; Be under the rolling condition of 13.0m/s afterwards in speed, in roll 12 passages; Before carrying out finish rolling afterwards, pre-water-cooled control is cold, is 135m at cooling water inflow ³cold 3 seconds are controlled under/h; Be 850 DEG C at final rolling temperature afterwards, speed is under the rolling condition of 48m/s, finish rolling 8 passages; Be 828 DEG C in temperature afterwards, speed is weave silk under the condition of 48m/s; After weaving silk, wire rod enters Stanermo wind-cooling linear and carries out " delay " type controlled cooling model (i.e. Slow cooling); Blower fan Close All when Stanermo wind-cooling linear control is cold, opens insulation shroud above front 3 Fans, and it is 0.25 ~ 0.45m/s that roller table speed controls; Collect volume temperature after the air-cooled end of stelmor to control to be 580 DEG C, natural air cooling to room temperature will be coiled afterwards and namely obtain the high intensity non-annealed steel for fastener coil rod of a kind of boracic, have the chemical composition of following weight percents: C0.22wt%, Si0.03wt%, Mn0.60wt%, Cr0.30wt%, Ti0.046wt%, Als0.045wt%, B0.0052wt%, S0.003wt%, P0.010wt%, O0.0013wt%, H0.00012wt%, all the other are Fe and inevitable impurity.

A kind of boracic high intensity non-annealed steel for fastener coil rod technologic mechanics performance, microstructure and the inclusion inspection that the present embodiment provides is in shown in table 5, table 6.

The boracic high-intensity fasteners steel coil rod technologic mechanics performance that table 5 the present embodiment is produced

Boracic high-intensity fasteners steel coil rod microstructure and inclusion that table 6 the present embodiment is produced

Embodiment 3

A, molten iron pretreatment desulfurizing: by blast-melted (chemical composition C5.0wt%, Si0.50wt%, Mn0.50wt%, P0.110wt%, S0.020wt%, all the other are Fe and inevitable impurity) be transported to KR method molten iron preprocessing unit and carry out desulfurization process, stirring-head depth of penetration controls as 2200-2400mm, by 17.0kg/t _steelamount, add conventional CaO matter sweetening agent and carry out desulfurization process, churning time control be 8 minutes; Carry out after stirring terminates taking off rear slag operation, to ensure in ladle molten iron face exposed>=4/5, scratch clean desulfurization slag; After pre-treatment, hot metal composition control is: C4.8wt%, Si0.50wt%, Mn0.50wt%, P0.110wt%, S0.004wt%, and all the other are Fe and inevitable impurity.

B, smelting molten steel: by dark for the pre-treatment of step A desulphurised hot metal (chemical composition C4.8wt%, Si0.50wt%, Mn0.50wt%, P0.110wt%, S0.004wt%, all the other are Fe and inevitable impurity), high-quality steel scrap (chemical composition C0.25wt%, Si0.25wt%, Mn0.70wt%, P0.030wt%, S0.035wt%, all the other are Fe and inevitable impurity) and low phosphorus and sulphur pig iron (chemical composition C3.4wt%, Si0.50wt%, Mn0.50wt%, P0.090wt%, S0.035wt%, all the other are Fe and inevitable impurity) add in LD converter, carry out conventional top bottom blowing, press 45.0kg/t respectively _steel, 22.0kg/t _steel, 5.0kg/t _steeladd-on, add lime, light dolomite, the slag making of magnesite ball, control endpoint carbon content 0.12wt%, tapping temperature 1640 DEG C, tapping forward direction ladle bottom adds quickened lime and carries out wash heat, and lime adding amount is 2.5kg/t _steel, adopt omnidistance bottom argon blowing technology during tapping, argon flow amount controls as 35NL/min.

C, deoxidation alloying: step B is smelted complete molten steel tapping, when the molten steel amount in ladle is greater than 1/4, by following deoxidation alloying order: ferro-aluminum → high carbon ferro-chrome → high carbon ferromanganese, adds following material: successively by 3.0kg/t in ladle _steelamount, add the ferro-aluminum of following masses ratio: Al70.5wt%, all the other are Fe and inevitable impurity; By 5.8kg/t _steelamount, add the high carbon ferro-chrome of following masses ratio: Cr56.7wt%, C7.2wt%, all the other are Fe and inevitable impurity; By 8.1kg/t _steelamount, add the high carbon ferromanganese of following masses ratio: Mn75.6wt%, C6.7wt%, all the other are Fe and inevitable impurity; Above-mentioned alloy is added when ladle molten steel amount reaches 4/5; After tapping, molten steel is hung and delivers to LF stove refining procedure.

D, the refining of molten steel LF stove: complete molten steel of step C being tapped winches to LF stove refining station and connects argon gas band, open argon gas and adopt little argon amount (30NL/min) Argon 2 minutes, and then lower electrode adopts gear 7 ~ 9 grades to change slag; Be energized after 3 minutes, lift electrode and observe stove internalization slag situation, thermometric, sampling afterwards; If slag condition is rarer, add lime 6.0kg/t _steel, then add calcium carbide 0.5kg/t _steelresidue adjustment, controlling basicity of slag is 7.0; According to steel sample analysis result, add alloy, aluminum shot adjustment molten steel component, control molten steel oxygen activity 2ppm; Suitably strengthen argon flow amount (50NL/min) afterwards, by 2.9kg/t _steelamount, add the ferrotianium of following masses ratio: Ti33.5wt%, all the other are Fe and inevitable impurity, soft blow argon 3 minutes; Press 0.4kg/t afterwards _steelamount, add the ferro-boron of following masses ratio: B21.5wt%, all the other are Fe and inevitable impurity, soft blow argon 2 minutes; Carry out wire feeding process after afterwards liquid steel temperature being heated to 1665 DEG C, feeding has the aluminium calcium line of following masses ratio: Ca57.2wt%, Al36.5wt%, all the other are Fe and inevitable impurity, and wire-feeding velocity is 2.5m/s, and line feeding amount is 150m; Line feeding terminates to adopt flow to be that the little argon gas amount of 30NL/min carries out soft blow argon to molten steel, and the soft blow time is 2 minutes, adds conventional large bag molten steel covering agent afterwards, and add-on controls, for 1.0kg/t steel, then molten steel to be winched to VD stove vacuum refinement station.

E, the vacuum refinement of molten steel VD stove: after D step molten steel is winched to VD vacuum refining furnace, connect Argon pipe, opens argon gas and adopt little argon amount (30NL/min) Argon 2 minutes, determine oxygen afterwards determine hydrogen to molten steel, thermometric sampling simultaneously; After sampling, vacuum container cover car is opened to working position, close vacuum container cover, vacuumize, when vacuum is evacuated to 60Pa, starts to carry out guarantor's Fruit storage, carry out BOTTOM ARGON BLOWING process simultaneously, argon flow amount controls as 60NL/min, 15 minutes liquid steel degassing treatment times under vacuum tightness 60Pa condition; Close vacuum main valve after Fruit storage, promote cover, to liquid steel sampling with determine oxygen and determine hydrogen; Carry out the process of little argon gas amount soft blow argon to molten steel afterwards, argon flow amount is 30NL/min, and soft argon blowing time is 2 minutes; After molten steel soft blow argon terminates, add conventional large bag molten steel covering agent, add-on controls as 1.0kg/t _steel, then molten steel is winched to casting station.

F, molten steel casting: be 1525 DEG C at tundish temperature; pulling rate is 2.1m/min; two cold specific waters are 1.1L/kg; M-EMS Current intensity is 300A, running frequency is under the condition of 2.5HZ, adopts R9m straight arc continuous straightening 5 machine 5 to flow the steel billet that the molten steel whole process protection continuous casting of step B is become section 150mm × 150mm by small billet casting machine.

G, heating steel billet: it is in the process furnace of 1080 DEG C that F step steel billet is sent into soaking zone furnace temperature, heat 50 minutes, steel billet tapping temperature is 940 DEG C, squama is gone out by high pressure water, push to 5 base positions before inlet of rolling mill and treat that warm area carries out the naturally cooling of 5 minutes, finally enter mill milling with the start rolling temperature of 900 DEG C.

H, controlled rolling and controlled cooling: be rolled by the high-speed rod-rolling mill that 28 frames sent into by the steel billet of G step are under the rolling condition of 0.15m/s in speed, roughing 6 passages; Be under the rolling condition of 10.0m/s afterwards in speed, in roll 12 passages; Before carrying out finish rolling afterwards, pre-water-cooled control is cold, is 150m at cooling water inflow ³cold 3 seconds are controlled under/h; Be 840 DEG C at final rolling temperature afterwards, speed is under the rolling condition of 20m/s, finish rolling 5 passages; Be 820 DEG C in temperature afterwards, speed is weave silk under the condition of 20m/s; After weaving silk, wire rod enters Stanermo wind-cooling linear and carries out " delay " type controlled cooling model (i.e. Slow cooling); Blower fan Close All when Stanermo wind-cooling linear control is cold, opens insulation shroud above front 3 Fans, and it is 0.25 ~ 0.45m/s that roller table speed controls; Collect volume temperature after the air-cooled end of stelmor to control to be 550 DEG C, natural air cooling to room temperature will be coiled afterwards and namely obtain the high intensity non-annealed steel for fastener coil rod of a kind of boracic, have the chemical composition of following weight percents: C0.24wt%, Si0.02wt%, Mn0.70wt%, Cr0.35wt%, Ti0.055wt%, Als0.055wt%, B0.0060wt%, S0.004wt%, P0.012wt%, O0.0012wt%, H≤0.0001wt%, all the other are Fe and inevitable impurity.

A kind of boracic high intensity non-annealed steel for fastener coil rod technologic mechanics performance, microstructure and the inclusion inspection that the present embodiment provides is in shown in table 7, table 8.

The boracic high-intensity fasteners steel coil rod technologic mechanics performance that table 7 the present embodiment is produced

Boracic high-intensity fasteners steel coil rod microstructure and inclusion that table 8 the present embodiment is produced

Claims (2)

1. the high intensity non-annealed steel for fastener wire rod of boracic, it is characterized in that the high intensity non-annealed steel for fastener wire rod of described boracic has the chemical composition of following weight percents: C0.20 ~ 0.24wt%, Si≤0.04wt%, Mn0.50 ~ 0.70wt%, Cr0.25 ~ 0.35wt%, Ti0.035 ~ 0.055wt%, Als0.035 ~ 0.055wt%, B0.0045 ~ 0.0060wt%, S≤0.004wt%, P≤0.012wt%, O≤0.0015wt%, H≤0.00015wt%, all the other are Fe and inevitable impurity.

2. a preparation method for the high intensity non-annealed steel for fastener wire rod of boracic according to claim 1, is characterized in that comprising the following steps:

A, molten iron pretreatment desulfurizing: by chemical composition C4.5 ~ 5.0wt%, Si0.30 ~ 0.50wt%, Mn0.25 ~ 0.50wt%, P0.090 ~ 0.110wt%, S≤0.020wt%, all the other the blast-melted KR of being transported to method molten iron preprocessing units for Fe and inevitable impurity carry out desulfurization process, it is 2200 ~ 2400mm that stirring-head depth of penetration controls, by 15.0 ~ 17.0kg/t _steelamount, add conventional CaO matter sweetening agent and carry out desulfurization process, churning time control be 8 minutes; Carry out after stirring terminates taking off rear slag operation, to ensure in ladle molten iron face exposed>=4/5, scratch clean desulfurization slag; After pre-treatment, hot metal composition control is: C4.5 ~ 4.8wt%, Si0.30 ~ 0.50wt%, Mn0.25 ~ 0.50wt%, P0.090 ~ 0.110wt%, S≤0.004wt%, and all the other are Fe and inevitable impurity;

B, smelting molten steel: by chemical composition C4.5-4.8wt%, Si0.30-0.50wt%, Mn0.25-0.50wt%, P0.090-0.110wt%, S≤0.004wt%, all the other are the dark desulphurised hot metal of step A pre-treatment of Fe and inevitable impurity, chemical composition C0.16-0.25wt%, Si0.12-0.25wt%, Mn0.45-0.70wt%, P0.015-0.030wt%, S0.018-0.035wt%, all the other are high-quality steel scrap and the chemical composition C3.2-3.4wt% of Fe and inevitable impurity, Si0.30-0.50wt%, Mn0.30-0.50wt%, P0.070-0.090wt%, S0.020-0.035wt%, all the other low phosphorus and sulphur pig irons for Fe and inevitable impurity add in LD converter, carry out conventional top bottom blowing, respectively by 40.0 ~ 45.0kg/t _steel, 18.0 ~ 22.0kg/t _steel, 3.0 ~ 5.0kg/t _steeladd-on, add lime, light dolomite, the slag making of magnesite ball, control endpoint carbon content>=0.08wt%, tapping temperature≤1640 DEG C, tapping forward direction ladle bottom adds quickened lime and carries out wash heat, and lime adding amount is 2.5kg/t _steel, adopt omnidistance bottom argon blowing technology during tapping, it is 20 ~ 35NL/min that argon flow amount controls,

C, deoxidation alloying: step B is smelted complete molten steel tapping, when the molten steel amount in ladle is greater than 1/4, by following deoxidation alloying order: ferro-aluminum → high carbon ferro-chrome → high carbon ferromanganese, adds following material: successively by 2.2 ~ 3.0kg/t in ladle _steelamount, add the ferro-aluminum of following masses ratio: Al70.5wt%, all the other are Fe and inevitable impurity; By 4.1 ~ 5.8kg/t _steelamount, add the high carbon ferro-chrome of following masses ratio: Cr56.7wt%, C7.2wt%, all the other are Fe and inevitable impurity; By 5.4 ~ 8.1kg/t _steelamount, add the high carbon ferromanganese of following masses ratio: Mn75.6wt%, C6.7wt%, all the other are Fe and inevitable impurity; Above-mentioned alloy is added when ladle molten steel amount reaches 4/5; After tapping, molten steel is hung and delivers to LF stove refining procedure;

D, the refining of molten steel LF stove: complete molten steel of step C being tapped winches to LF stove refining station and connects argon gas band, the little argon amount Argon of unlatching argon gas employing 20 ~ 30NL/min 2 minutes, then lower electrode adopts gear 7 ~ 9 grades to change slag; Be energized after 3 minutes, lift electrode and observe stove internalization slag situation, thermometric, sampling afterwards; If slag condition is rarer, add lime 4.0 ~ 6.0kg/t _steel, then add calcium carbide 0.5kg/t _steelresidue adjustment, controlling basicity of slag is 5.5 ~ 7.0; According to steel sample analysis result, add alloy, aluminum shot adjustment molten steel component, control molten steel oxygen activity≤5ppm; Suitably strengthening argon flow amount is afterwards 40 ~ 50NL/min, by 1.9 ~ 2.9kg/t _steelamount, add the ferrotianium of following masses ratio: Ti33.5wt%, all the other are Fe and inevitable impurity, soft blow argon 3 minutes; Afterwards by 0.3 ~ 0.4kg/t _steelamount, add the ferro-boron of following masses ratio: B21.5wt%, all the other are Fe and inevitable impurity, soft blow argon 2 minutes; Carry out wire feeding process after afterwards liquid steel temperature being heated to 1665 ~ 1675 DEG C, feeding has the aluminium calcium line of following masses ratio: Ca57.2wt%, Al36.5wt%, all the other are Fe and inevitable impurity, and wire-feeding velocity is 2.5m/s, and line feeding amount is 150m; Line feeding terminates to adopt flow to be that the little argon gas amount of 20 ~ 30NL/min carries out soft blow argon to molten steel, and the soft blow time is 2 minutes, adds conventional large bag molten steel covering agent afterwards, and add-on controls, for 1.0kg/t steel, then molten steel to be winched to VD stove vacuum refinement station;

E, the vacuum refinement of molten steel VD stove: after D step molten steel is winched to VD vacuum refining furnace, connect Argon pipe, and the little argon amount Argon of unlatching argon gas employing 20 ~ 30NL/min 2 minutes, determines oxygen to molten steel afterwards and determine hydrogen, thermometric sampling simultaneously; After sampling, vacuum container cover car is opened to working position, close vacuum container cover, vacuumize, when vacuum is evacuated to 60Pa, starts to carry out guarantor's Fruit storage, carry out BOTTOM ARGON BLOWING process simultaneously, it is 40 ~ 60NL/min that argon flow amount controls, 15 minutes liquid steel degassing treatment times under vacuum tightness 60Pa condition; Close vacuum main valve after Fruit storage, promote cover, to liquid steel sampling with determine oxygen and determine hydrogen; Carry out the process of little argon gas amount soft blow argon to molten steel afterwards, argon flow amount is 20 ~ 30NL/min, and soft argon blowing time is 2 minutes; After molten steel soft blow argon terminates, add conventional large bag molten steel covering agent, add-on controls as 1.0kg/t _steel, then molten steel is winched to casting station;

F, molten steel casting: be 1525 ~ 1535 DEG C at tundish temperature, pulling rate is 2.1 ~ 2.3m/min, two cold specific waters are 1.1 ~ 1.3L/kg, M-EMS Current intensity is 300A, running frequency is under the condition of 2.5HZ, adopts R9m straight arc continuous straightening 5 machine 5 to flow the steel billet that the molten steel whole process protection continuous casting of step B is become section 150mm × 150mm by small billet casting machine;

G, heating steel billet: it is in the process furnace of 1080 ~ 1120 DEG C that F step steel billet is sent into soaking zone furnace temperature, heat 50 ~ 70 minutes, steel billet tapping temperature is 940 ~ 980 DEG C, squama is gone out by high pressure water, push to 5 base positions before inlet of rolling mill and treat that warm area carries out the naturally cooling of 3 ~ 5 minutes, finally enter mill milling with the start rolling temperature of 900 ~ 920 DEG C;

H, controlled rolling and controlled cooling: be rolled by the high-speed rod-rolling mill that 28 frames sent into by the steel billet of G step are under the rolling condition of 0.15 ~ 0.25m/s in speed, roughing 6 passages, be under the rolling condition of 10.0 ~ 15.0m/s afterwards in speed, in roll 12 passages, before carrying out finish rolling afterwards, pre-water-cooled control is cold, is 120 ~ 150m at cooling water inflow ³cold 2 ~ 3 seconds are controlled under/h, be 840 ~ 860 DEG C at final rolling temperature afterwards, speed is under the rolling condition of 20 ~ 65m/s, finish rolling 5 ~ 10 passages, be 820 ~ 835 DEG C in temperature afterwards, speed is weave silk under the condition of 20 ~ 65m/s, after weaving silk, wire rod enters Stanermo wind-cooling linear and carries out " delay " type controlled cooling model, i.e. Slow cooling, blower fan Close All when Stanermo wind-cooling linear control is cold, opens insulation shroud above front 3 Fans, and it is 0.25 ~ 0.45m/s that roller table speed controls, collect volume temperature after the air-cooled end of stelmor to control to be 550 ~ 600 DEG C, natural air cooling to room temperature will be coiled afterwards and namely obtain the high intensity non-annealed steel for fastener wire rod of boracic, there is the chemical composition of following weight percents: C0.20 ~ 0.24wt%, Si≤0.04wt%, Mn0.50 ~ 0.70wt%, Cr0.25 ~ 0.35wt%, Ti0.035 ~ 0.055wt%, Als0.035 ~ 0.055wt%, B0.0045 ~ 0.0060wt%, S≤0.004wt%, P≤0.012wt%, O≤0.0015wt%, H≤0.00015wt%, all the other are Fe and inevitable impurity, there is following technologic mechanics performance, as shown in Table 1 and Table 2:

Table 1 boracic high-intensity fasteners steel coil rod technologic mechanics performance

Table 2 boracic high-intensity fasteners steel coil rod microstructure and inclusion

。