Production method of hot-rolled, whole-coil annealed and pickled steel strip with high alloy content

文档序号:112691 发布日期:2021-10-19 浏览:38次 中文

阅读说明:本技术 一种高合金含量的热轧、整卷退火、酸洗钢带的生产方法 (Production method of hot-rolled, whole-coil annealed and pickled steel strip with high alloy content ) 是由 乔治明 牛树林 俞飞 刘莹 宋燕燕 花艳侠 顾凤义 田志鹏 乔治平 于 2021-07-16 设计创作,主要内容包括:本发明属于热轧钢带的生产领域,尤其提供一种高合金含量的热轧、整卷退火、酸洗钢带的生产方法,该生产方法对应钢带的质量成分范围为:C:0.25-0.35%;Mn≤1.2%;P≤0.005%;S≤0.003%;Si:0.15-0.35%;Cr:3.5-4.5%;Ni:0.65-1.00%;Mo:1.00-1.45%;V:0.25-0.45%;Al:0.035-0.075%;Cu≤0.04%;其它为Fe及不可避免的残余元素;所述生产方法包括铁水炉外脱硫、转炉+LF+RH冶炼、连铸、热轧、冷却、整卷退火、推拉式酸洗;经过该方法生产的钢带表面洁净、强度也可以满足下游工序使用要求。(The invention belongs to the production field of hot rolled steel strips, and particularly provides a production method of hot rolled, whole-coil annealed and pickled steel strips with high alloy content, which corresponds to the following mass component ranges of the steel strips: 0.25-0.35% of C; mn is less than or equal to 1.2 percent; p is less than or equal to 0.005 percent; s is less than or equal to 0.003 percent; 0.15 to 0.35 percent of Si; 3.5 to 4.5 percent of Cr; 0.65 to 1.00 percent of Ni; 1.00 to 1.45 percent of Mo; 0.25 to 0.45 percent of V; 0.035 to 0.075 percent of Al; cu is less than or equal to 0.04 percent; the others are Fe and inevitable residual elements; the production method comprises the steps of molten iron external desulphurization, converter + LF + RH smelting, continuous casting, hot rolling, cooling, whole coil annealing and push-pull type acid pickling; the steel strip produced by the method has clean surface and strength, and can meet the use requirements of downstream processes.)

1. A production method of hot rolled, whole-coil annealed and pickled steel strip with high alloy content is characterized by comprising the following steps: the production method corresponds to the steel strip and comprises the following mass component ranges: 0.25-0.35% of C; mn is less than or equal to 1.2 percent; p is less than or equal to 0.005 percent; s is less than or equal to 0.003 percent; 0.15 to 0.35 percent of Si; 3.5 to 4.5 percent of Cr; 0.65 to 1.00 percent of Ni; 1.00 to 1.45 percent of Mo; 0.25 to 0.45 percent of V; 0.035 to 0.075 percent of Al; cu is less than or equal to 0.04 percent; the others are Fe and inevitable residual elements;

the production method comprises the steps of molten iron external desulphurization, converter + LF + RH smelting, continuous casting, hot rolling, cooling, whole coil annealing and push-pull type acid pickling;

after being taken off line, the smelted and continuously cast steel billet must be slowly cooled and air-cooled by a heat preservation pit, and then is cold-loaded into a heating furnace for heating after being peeled on the surface layer; the billet steel is heated in a heating furnace in 3 stages: the heating speed of the first heating section is controlled to be 1-2 ℃/min, the heating speed of the second heating section is controlled to be 0.5-1.5 ℃/min, and the heating speed of the third heating section is controlled to be 0.15-0.20 ℃/min; the discharging temperature of the steel billet is 1240-1270 ℃;

the method comprises the following steps that (1) after a steel billet is discharged from a furnace, the surface of the steel billet is dephosphorized by a dephosphorizing machine, the steel billet is rolled for 6 times by two blooming mills to obtain an intermediate billet, the intermediate billet is fed into a hot coil box to perform mandrel-free coiling on the rough-rolled intermediate billet, then the rough-rolled intermediate billet is uncoiled to realize end-to-end reversal, the upper surface and the lower surface of the rough-rolled intermediate billet are reversed, the rough-rolled intermediate billet is fed into a finishing mill group to be rolled, and after uncoiling, the rough-rolled intermediate billet is subjected to end cutting and dephosphorization and then fed into a 7-stand finishing mill to roll a steel strip with required thickness; controlling the finishing temperature of the steel strip to be 860-880 ℃; the curling temperature is controlled between 660 ℃ and 680 ℃;

the front section cooling mode of the laminar cooling line adopts an XOXO on-off weak cooling mode;

annealing the whole coil of steel by using a well-type annealing furnace; heating the steel coil in an annealing furnace at 885-905 ℃ for 40-60 minutes, and then cooling along with the furnace;

the push-pull type pickling process refers to: uncoiling, 9-roller straightening, 6-section pickling, 5-section rinsing, drying, discharging a loop, oiling and coiling; the pickling solution is prepared by adopting high-concentration hydrochloric acid to prepare a certain proportion of dilute nitric acid and a proper amount of slow release agent; in the push-pull type pickling process, 6 pickling tanks are adopted to continuously pickle the steel strip; wherein the content of the first and second substances,

the No. 1 pickling tank comprises 15-18% of hydrochloric acid and 2.8-3% of nitric acid; the pickling temperature is 75-85 ℃;

the No. 2 pickling tank comprises 16-18% of hydrochloric acid and 2.5-3% of nitric acid; the pickling temperature is 76-84 ℃;

the 3# pickling tank comprises 15-18% of hydrochloric acid and 2.5-2.8% of nitric acid; the pickling temperature is 77-83 ℃;

the No. 4 pickling tank comprises 15-17% of hydrochloric acid and 2-2.8% of nitric acid; the pickling temperature is 72-84 ℃;

the No. 5 pickling tank comprises 16-18% of hydrochloric acid and 0.8-2.7% of nitric acid; the pickling temperature is 73-85 ℃;

the No. 6 pickling tank comprises 16.5-17.5% of hydrochloric acid and 0.8-2.7% of nitric acid; the pickling temperature is 74-84 ℃;

2-3% of the slow release agent of the milrins hydrochloric acid is added into each pickling tank.

2. The method of producing a high alloy content hot rolled, coil annealed, pickled steel strip as claimed in claim 1, characterized in that: after the steel billets are taken off line after smelting and continuous casting, the steel billets need to enter a steel billet heat preservation pit, the bottom of the heat preservation pit is firstly paved with high-temperature common carbon continuous casting steel billets, then the steel type continuous casting billets are loaded, and the heat preservation pit is provided with a heat preservation cover; when the billet does not enter or exit the heat preservation pit, the heat preservation cover needs to be closed; after the temperature of the steel billet in the heat preservation pit is lower than 150 ℃, the steel billet can be lifted out of the heat preservation pit and stacked and cooled; and (4) after the continuous casting billet is discharged from the heat preservation pit and naturally cooled to normal temperature, peeling the surface layer of the casting billet by using a billet peeling machine.

3. The method of claim 1 wherein the pickling means comprises acid tanks and piping resistant to dilute nitric acid corrosion, and the material is acid-resistant stainless steel or glass reinforced plastic.

4. The method of producing a high alloy content hot rolled, coil annealed, pickled steel strip as claimed in claim 1, characterized in that: the acid washing speed in the push-pull acid washing process is 20-40 m/min.

Technical Field

The invention belongs to the production field of hot-rolled pickled steel strips, and particularly provides a production method of hot-rolled, whole-coil annealed and pickled steel strips with high alloy content, which is a production method of hot-rolled whole-coil annealed steel strips with special surface scale structures formed by 'diffusing' multiple alloy elements into surface scale in the whole-coil annealing process after plate coils are rolled.

Background

In a cold rolling plant, deep processing such as pickling, rolling, whole-coil annealing, galvanizing and the like is carried out on a hot rolled steel strip, and the general process flow is adopted. The scale structure of the cold-rolled material represented by SPHC conforms to a typical three-layer scale structure. Formation of scaleThe process is also a diffusion process of two elements, oxygen and iron, oxygen diffusing from the surface to the inside of the iron, and iron diffusing from the inside to the outside. The outer layer has high oxygen concentration and low iron concentration, and generates iron higher oxides; the inner iron layer has a high concentration and the oxygen has a low concentration, and forms a low-valence oxide of oxygen, so that the iron scale generally has three layers: the outermost layer is Fe2O3The iron scale accounts for about 10 percent of the thickness of the whole iron scale, and has the properties of fineness, luster, crispness and easy shedding; and has the function of preventing the interior from continuing to be oxidized violently; the second layer being Fe2O3And FeO, usually written as Fe3O4About 50% of the total thickness; the third layer connected with the metal body is FeO which accounts for about 40% of the thickness of the iron scale, and the FeO has sticky property and is not easy to remove when being stuck on the steel material. The pickling line of the cold rolling plant is mainly used for pickling the iron scales of common steel in a hydrochloric acid pickling mode, and the iron scales on the surface of the steel strip can be thoroughly cleaned by pickling.

For a certain grade of high-alloy hot rolled steel, because the strength of the coiled plate after hot rolling and curling exceeds 1000MP, a user can not uncoil the plate directly, so that the strength of the hot rolled steel strip needs to be reduced by using a whole coil steel strip annealing method, the tensile strength of the whole coil annealed steel strip is between 600 and 700MP, the yield strength is less than 400MP, and the extension A50 is not less than 23%. The purpose of this is to enable the subsequent pickling process to be uncoiled normally, and to be coiled after pickling, and downstream processing enterprises can cut and deep process. However, the whole coil annealing of the steel strip causes great difference between the scale structure on the surface of the steel strip and the scale structure of the conventional hot rolled steel strip, and the hydrochloric acid pickling is difficult. The industrial trial production shows that no matter how long the pickling time is, the pickling concentration and the acid temperature are high (the industrial production allowable range), the surface layer 'oxide scale' of the steel strip cannot be cleaned by using the traditional hydrochloric acid. Specifically, the surface scale structure of the grade steel has a great difference from the traditional steel scale shown in fig. 1, mainly including a mixed structure of the scale and the matrix caused by the fact that high-content alloy elements permeate to the surface in the annealing process, and the mixed structure and the matrix form a close staggered relationship shown in fig. 2, and the mixed structure of the matrix and the scale is difficult to wash away by conventional hydrochloric acid pickling; the main difference between the scale in fig. 1 and fig. 2 is that the scale in fig. 1 is clearly demarcated from the substrate, and fig. 2 is clearly distinguished from fig. 1 in that the surface region does not have the conventional scale form, and the substrate and the surface are fused with each other. Fig. 3(a, b) is the scanning electron microscope analysis of the steel grade, it can be seen that the main body of the scale outer layer structure is mainly the matrix, and the spot-network local oxidation phenomenon is distributed, and the electron microscope and energy spectrum analysis show that the manganese, chromium, molybdenum, silicon and other elements which are easy to be enriched at the grain boundary and a small amount of iron are oxidized to form a spot-network and form a mutually-infiltrated surface layer structure with the matrix.

As shown by the above comparative analysis, the same pickling effect as that of the pickling process for pickling common raw materials cannot be achieved, and the test of various limit process production is also carried out in the production line, and the surface effect of the pickled steel strip is shown in FIG. 4, and the pickling effect of the common plate cannot be achieved. Therefore, a set of hot rolling, whole coil annealing and pickling processes aiming at the steel grade is needed.

Disclosure of Invention

Aiming at the technical problems in the prior art, the invention provides a production method of hot-rolled, whole-coil annealed and pickled steel strips with high alloy content.

The technical scheme adopted by the invention for solving the technical problems in the prior art is as follows:

a production method of hot rolled, whole-coil annealed and pickled steel strip with high alloy content comprises the following steps of: 0.25-0.35% of C; mn is less than or equal to 1.2 percent; p is less than or equal to 0.005 percent; s is less than or equal to 0.003 percent; 0.15 to 0.35 percent of Si; 3.5 to 4.5 percent of Cr; 0.65 to 1.00 percent of Ni; 1.00 to 1.45 percent of Mo; 0.25 to 0.45 percent of V; 0.035 to 0.075 percent of Al; cu is less than or equal to 0.04 percent; the others are Fe and inevitable residual elements;

the production method comprises the steps of molten iron external desulphurization, converter + LF + RH smelting, continuous casting, hot rolling, cooling, whole coil annealing and push-pull type acid pickling;

after being taken off line, the smelted and continuously cast steel billet must be slowly cooled and air-cooled by a heat preservation pit, and then is cold-loaded into a heating furnace for heating after being peeled on the surface layer; the billet steel is heated in a heating furnace in 3 stages: the heating speed of the first heating section is controlled to be 1-2 ℃/min, the heating speed of the second heating section is controlled to be 0.5-1.5 ℃/min, and the heating speed of the third heating section is controlled to be 0.15-0.20 ℃/min; the discharging temperature of the steel billet is 1240-1270 ℃. The steel billet is heated slowly at the heating speed, so that the phenomenon that the steel billet is heated too fast to crack due to high alloy content is avoided.

The method comprises the following steps that (1) after a steel billet is discharged from a furnace, the surface of the steel billet is dephosphorized by a dephosphorizing machine, the steel billet is rolled for 6 times by two blooming mills to obtain an intermediate billet, the intermediate billet is fed into a hot coil box to perform mandrel-free coiling on the rough-rolled intermediate billet, then the rough-rolled intermediate billet is uncoiled to realize end-to-end reversal, the upper surface and the lower surface of the rough-rolled intermediate billet are reversed, the rough-rolled intermediate billet is fed into a finishing mill group to be rolled, and after uncoiling, the rough-rolled intermediate billet is subjected to end cutting and dephosphorization and then fed into a 7-stand finishing mill to roll a steel strip with required thickness; controlling the finishing temperature of the steel strip to be 860-880 ℃; the curling temperature is controlled between 660 ℃ and 680 ℃, so that the problem that the strength is too high and the curling of the curling machine is difficult due to too high cooling speed of the laminar cooling section is avoided.

The front section cooling mode of the laminar cooling line adopts an XOXO on-off weak cooling mode, because of high alloy content, the low cooling rate enters a bainite and martensite region, the lower cooling rate is adopted, the proportion of the martensite content of the strip steel with high alloy content is reduced, the strength of the strip steel is reduced to the maximum extent, and the hot rolled strip steel can be coiled by utilizing the capacity of the existing coiling machine.

Annealing the whole coil of steel by using a well-type annealing furnace; the heating temperature of the steel coil in the annealing furnace is 885-905 ℃, the heating time is 40-60 minutes, and then the steel coil is cooled along with the furnace, so that the strength of the steel coil is reduced from more than 1000MPa to 600-700MPa, and the subsequent deep processing is facilitated.

The push-pull type pickling process refers to: uncoiling, 9-roller straightening, 6-section pickling, 5-section rinsing, drying, discharging a loop, oiling and coiling; the acid washing solution is different from the traditional single acid solvent, and adopts high-concentration hydrochloric acid and a certain proportion of dilute nitric acid and a proper amount of slow release agent. In the push-pull type pickling process, 6 pickling tanks are adopted to continuously pickle the steel strip; wherein, the No. 1 pickling tank comprises 15 to 18 percent of hydrochloric acid and 2.8 to 3 percent of nitric acid; the pickling temperature is 75-85 ℃;

the No. 2 pickling tank comprises 16-18% of hydrochloric acid and 2.5-3% of nitric acid; the pickling temperature is 76-84 ℃;

the 3# pickling tank comprises 15-18% of hydrochloric acid and 2.5-2.8% of nitric acid; the pickling temperature is 77-83 ℃;

the No. 4 pickling tank comprises 15-17% of hydrochloric acid and 2-2.8% of nitric acid; the pickling temperature is 72-84 ℃;

the No. 5 pickling tank comprises 16-18% of hydrochloric acid and 0.8-2.7% of nitric acid; the pickling temperature is 73-85 ℃;

the No. 6 pickling tank comprises 16.5-17.5% of hydrochloric acid and 0.8-2.7% of nitric acid; the pickling temperature is 74-84 ℃;

2-3% of the slow release agent of the milrins hydrochloric acid is added into each pickling tank. Both production and laboratory tests prove that only surface layer mixed tissues generated by mutual 'penetration' of iron scales generated in the whole roll annealing process and matrix alloy elements can be cleaned by acid washing by matching a certain proportion of nitric acid.

As a preferred technical scheme, after steel billets are smelted and continuously cast, the steel billets need to enter a steel billet heat preservation pit firstly after being taken off line, the bottom of the heat preservation pit is firstly paved with high-temperature common carbon continuous casting steel billets, then the steel type continuous casting billets are loaded, and the heat preservation pit is provided with a heat preservation cover; when the billet does not enter or exit the heat preservation pit, the heat preservation cover needs to be closed; after the temperature of the steel billet in the heat preservation pit is lower than 150 ℃, the steel billet can be lifted out of the heat preservation pit and stacked and cooled; and (4) after the continuous casting billet is discharged from the heat preservation pit and naturally cooled to normal temperature, peeling the surface layer of the casting billet by using a billet peeling machine. If the steel billet on the lower line does not enter the heat preservation pit, because the alloy content is high and the temperature sensitivity is strong, microcracks are formed inside the steel billet after the steel billet is naturally cooled in the air, the steel billet can be rolled and cracked in the finish rolling stage when the steel billet is charged and rolled again, steel piling accidents occur, the microcracks in the steel billet can be detected by flaw detection equipment when the steel billet is in a cold state, and the change inside the steel billet can be found. The surface of the casting blank is cleaned by the peeling machine because the surface of the casting blank is easy to form surface microcracks due to high alloy content, and the surface defects of the strip steel can be formed by direct rolling and must be cleaned.

As the preferred technical scheme, the pickling equipment adopts an acid tank and a pipeline which are resistant to dilute nitric acid corrosion and is made of acid-resistant stainless steel and glass fiber reinforced plastic.

As a preferred technical scheme, the acid washing speed in the push-pull acid washing process is 20-40 m/min. The pickling speed is too low, so that the pickling yield is influenced; the pickling speed is too high, the chemical reaction time of the acid liquor and the surface layer of the strip steel is insufficient, and the effect of completely cleaning mixed tissues generated by mutual 'penetration' of iron scales and alloy elements and the iron scales cannot be achieved.

The invention has the advantages and positive effects that:

the invention aims at a high-alloy-content hot rolled steel strip which is high in strength and difficult to acid wash by common hydrochloric acid, and the tensile strength of the steel strip after hot rolling exceeds 1000MP by hot rolling due to the addition of high-content alloy elements such as chromium, molybdenum, vanadium and nickel. The purposes of high strength and high hardness are achieved, but downstream users cannot deeply process the high-strength strip steel, and then whole-roll annealing is carried out, so that the tensile strength of the whole-roll annealed strip steel is reduced to 600-670 MP, and the strip steel can be uncoiled for the downstream users. Through the pickling of a special process, the surface quality of the steel strip after pickling can meet the use requirement of deep processing of a downstream procedure. Because the high-content alloy elements of chromium, molybdenum, vanadium and nickel diffuse to the iron oxide layer, uneven mixed tissues of iron oxide scales and metal layers can be generated on the surface layer of the steel plate.

Drawings

FIG. 1 shows the scale microstructure of a conventional steel grade;

FIG. 2 shows the scale microstructure of a steel grade according to the invention;

FIG. 3(a, b) is a scanning electron microscope analysis of the scale of the steel grade of the present invention;

FIG. 4 is a graph showing the effect of pickling the steel of the present invention with a hydrochloric acid solution;

FIG. 5 is a graph showing the pickling effect of example 1;

FIG. 6 is a graph showing the pickling effect of example 2;

FIG. 7 is a graph showing the pickling effect of example 3;

FIG. 8 is a graph showing the pickling effect of example 4;

FIG. 9 is a graph showing the pickling effect of example 5.

Detailed Description

For a further understanding of the invention, its nature and utility, reference should be made to the following examples, which are set forth in the following detailed description, taken in conjunction with the accompanying drawings, in which:

the invention relates to a production method of a hot-rolled, whole-coil annealed and pickled steel strip with high alloy content, which comprises the following components in percentage by mass:

C:0.25-0.35%;Mn≤1.2%;P≤0.005%;S≤0.003%;Si:0.15-0.35%;Cr:3.5-4.5%;

0.65 to 1.00 percent of Ni; 1.00 to 1.45 percent of Mo; 0.25 to 0.45 percent of V; 0.035 to 0.075 percent of Al; cu is less than or equal to 0.04 percent, and the balance is Fe and inevitable residual elements.

The production method comprises the steps of molten iron external desulphurization, smelting (converter + LF + RH), continuous casting, hot rolling, cooling, whole coil annealing and push-pull type acid pickling;

wherein: after the smelting continuous casting of the steel billet is taken off line, the steel billet needs to enter a steel billet heat preservation pit firstly, the bottom of the heat preservation pit is paved with a high-temperature common carbon continuous casting steel billet firstly, then the steel type continuous casting billet is filled, the heat preservation pit is provided with a heat preservation cover, and when the steel billet does not enter the heat preservation pit, the heat preservation cover needs to be closed; after the temperature of the steel billet in the heat preservation pit is lower than 150 ℃, the steel billet can be lifted out of the heat preservation pit and stacked and cooled; and (4) after the continuous casting billet is discharged from the heat preservation pit and naturally cooled to normal temperature, peeling the surface layer of the casting billet by using a billet peeling machine. The steel billet must be slowly cooled and air-cooled by a heat preservation pit, and then the steel billet is cold-loaded into a heating furnace after being peeled on the surface layer, the heating speed of the heating section of the heating furnace is less than that of the common steel billet, the heating speed of the first heating section is controlled to be 1-2 ℃/min, the heating speed of the second heating section is controlled to be 0.5-1.5 ℃/min, and the heating speed of the third heating section is controlled to be 0.15-0.20 ℃/min, so that the high alloy steel billet is prevented from being heated too fast to generate burst; the discharging temperature of the steel billet is 1240-1270 ℃, the atmosphere in the furnace is strictly controlled, and the surface layer of the steel billet is prevented from further deep oxidation.

After the steel billet is discharged from the furnace, the surface of the steel billet is dephosphorized by a dephosphorizing machine, and after the steel billet is rolled for 6 times by two blooming mills, a heat-insulating cover is required to cover on a roller way between the roughing mill and the finishing mill, so that the intermediate billet is prevented from being rapidly cooled; the steel coil enters a hot coil box and is turned upside down, and the steel coil is uncoiled, then enters a 7-stand finishing mill through head cutting and dephosphorization to be rolled out into a steel strip with required thickness; the final rolling temperature is controlled to be 860-880 ℃, and the curling temperature is controlled to be 660-680 ℃; the front section cooling mode of the laminar cooling line adopts an on-off weak cooling mode of 'XOXO'.

By calculation, the AC3 temperature of the steel grade is 852.77 ℃, a well-type annealing furnace is adopted to anneal the whole coil of steel, the heating temperature is 885-905 ℃, the heating time is 40-60 minutes, then the steel is cooled along with the furnace, nitrogen protection is adopted in the furnace, the aim is to reduce the tensile strength of the steel strip to 600-670 MP, so that the subsequent processing procedures can be uncoiled,

the push-pull type pickling process refers to: uncoiling, 9-roller straightening, 6-section pickling, 5-section rinsing, drying, discharging a loop, oiling and coiling; the pickling solution is prepared by adopting high-concentration hydrochloric acid to prepare a certain proportion of dilute nitric acid and a proper amount of slow release agent; the acid washing equipment must use acid tank and pipeline which are resistant to dilute nitric acid corrosion, the main materials are acid-resistant stainless steel and glass fiber reinforced plastic reinforced plastics, and a general marble bottom structure for hydrochloric acid washing cannot be adopted.

Example 1

The method for producing the hot-rolled, whole-coil annealed and pickled steel strip with high alloy content comprises the following steps:

s1, after molten iron desulphurization and converter + LF + RH smelting, molten steel components are controlled as follows: 0.32 wt% of C, 1.12 wt% of Mn, 0.001 wt% of P, 0.002 wt% of S, 0.18 wt% of Si, 4.00 wt% of Cr, 1.00 wt% of Ni, 1.22 wt% of Mo, 0.45 wt% of V, 0.035 wt% of Al, 0.04 wt% of Cu, and the balance of Fe and unavoidable residual elements.

S2, continuously casting molten steel meeting the component requirements into a steel billet with the thickness of 180mm, slowly cooling the hot steel billet in a heat preservation pit to 150 ℃, discharging the hot steel billet out of the heat preservation pit, and stacking and naturally cooling the steel billet to the normal temperature; peeling the surface of the steel billet by using a billet peeling machine to clean the surface defects;

s3, slowly heating the cold steel billet in a heating furnace to 1240 ℃ and discharging, removing phosphorus by 24MP high-pressure water, rolling by 2 roughing mills for 6 times to obtain an intermediate billet with the thickness of 40mm, and feeding the intermediate billet into a hot coil box; the hot rolling box mainly has the functions of reversing the head and the tail of the rough rolling intermediate blank, reversing the surface under the mountain and enabling the temperature of the whole rolled strip steel to be uniform. The steel is uncoiled and then sent to a finishing mill group for rolling, and the steel is characterized in that the head-tail temperature difference can be eliminated, the product quality is ensured, the stability of thin specifications and varieties with larger deformation resistance is improved, the influence of secondary iron scale on the surface quality is improved, and the descaling effect is improved.

Keeping the temperature uniform, reversing the head and the tail of the intermediate blank in a hot rolling box, and cutting the head after uncoiling; removing phosphorus by using high-pressure water before finish rolling, and rolling the steel strip into a steel strip with the thickness of 4.0mm by using a 7-stand finishing mill, wherein the finish rolling temperature is 857-870 ℃;

s4, cooling the finish-rolled steel strip, specifically: adopting a cooling mode of opening and closing one by XOXO for water cooling 30m in front of the laminar cooling line, and automatically fine-adjusting a rear cooling section;

s5, curling the water-cooled steel strip, and the specific process is as follows: the curling temperature is 665-678 ℃; bundling the steel coils and stacking for slow cooling, wherein the steel coils of other steel types are stacked around the steel coil of the steel type to form an enclosing wall, and the stacking is cooled to room temperature in air;

s6, feeding the steel coil into an annealing furnace, slowly heating to 890 ℃, stopping heating after heating for 50 minutes, cooling to 150 ℃ along with the furnace, discharging, and air cooling to room temperature;

s7, pickling the steel coil on a dilute nitric acid pickling line according to the pickling process shown in the table 1, and specifically, uncoiling, straightening, pickling at 6 sections, rinsing at 5 sections, drying and curling until the surface quality of the pickled steel strip is qualified.

Table 1 pickling process in example 1

After pickling, the sample is taken from the tail of the steel coil, and the mechanical properties are shown in Table 2.

TABLE 2 mechanical Properties of the pickled steel strip in example 1

Tensile Strength Range (MP) Yield strength Range (MP) Elongation Range (A50,%) Direction of sample
615 345 30 Transverse direction

After pickling, sampling is carried out, the pickling surface is observed under an optical microscope, the pickling effect is shown in figure 5, and the steel strip surface is favorably improved to a great extent compared with figure 4 and only has a few oxidation spots.

Example 2:

the method for producing the hot-rolled, whole-coil annealed and pickled steel strip with high alloy content comprises the following steps:

s1, after molten iron desulphurization and converter + LF + RH smelting, molten steel components are controlled as follows:

0.31 wt% of C, 1.00 wt% of Mn; 0.004 wt% of P; 0.001 wt% of S; 0.23 wt% of Si; 3.93 wt% of Cr; 0.76 wt% of Ni; 1.29 wt% of Mo; 0.35 wt% of V; 0.065% of AL; 0.03 wt% of Cu. The others are Fe and inevitable residual elements;

s2, continuously casting molten steel meeting the component requirements into a steel billet with the thickness of 180mm, slowly cooling the hot steel billet in a heat preservation pit to 150 ℃, discharging the hot steel billet out of the heat preservation pit, and stacking and naturally cooling the steel billet to the normal temperature; peeling the surface of the steel billet by using a billet peeling machine to clean the surface defects;

s3, slowly heating the cold steel billet in a heating furnace to 1240 ℃ and discharging, removing phosphorus by 24MP high-pressure water, rolling by 2 roughing mills for 6 times to obtain an intermediate billet with the thickness of 40mm, and feeding the intermediate billet into a hot coil box; keeping the temperature uniform, reversing the head and the tail of the intermediate blank in a hot rolling box, and cutting the head after uncoiling; removing phosphorus by using high-pressure water before finish rolling, and rolling the steel strip into a steel strip with the thickness of 3.0mm by using a 7-stand finishing mill, wherein the finish rolling temperature is 857-870 ℃;

s4, cooling the finish-rolled steel strip, specifically: adopting a cooling mode of opening and closing one by XOXO for water cooling 30m in front of the laminar cooling line, and automatically fine-adjusting a rear cooling section;

s5, curling the water-cooled steel strip, and the specific process is as follows: the curling temperature is 665-678 ℃; bundling the steel coils and stacking for slow cooling, wherein the steel coils of other steel types are stacked around the steel coil of the steel type to form an enclosing wall, and the stacking is cooled to room temperature in air;

s6, feeding the steel coil into an annealing furnace, slowly heating to 890 ℃, stopping heating after heating for 50 minutes, cooling to 150 ℃ along with the furnace, discharging, and air cooling to room temperature;

s7, pickling the steel coil on a dilute nitric acid pickling line according to the pickling process shown in the table 3, specifically, uncoiling, straightening, pickling at 6 sections, rinsing at 5 sections, drying and curling until the surface quality of the pickled steel strip is qualified.

Table 3 pickling process in example 2

After pickling, sampling is carried out at the tail part of the steel coil, and the mechanical properties are shown in a table 4:

TABLE 4 mechanical Properties of the pickled steel strip in example 2

Tensile Strength Range (MP) Yield strength Range (MP) Elongation Range (A50,%) Direction of sample
645 360 28 Transverse direction

After pickling, a sample was taken and the pickled surface was observed under an optical microscope, and it was seen from FIG. 6 that the surface of the steel strip was pickled very cleanly.

Example 3:

the method for producing the hot-rolled, whole-coil annealed and pickled steel strip with high alloy content comprises the following steps:

s1, after molten iron desulphurization and converter + LF + RH smelting, molten steel components are controlled as follows:

0.35 wt% of C, 0.98 wt% of Mn, 0.005 wt% of P, 0.003 wt% of S, 0.22 wt% of Si, 4.50 wt% of Cr, 0.88 wt% of Ni, 1.15 wt% of Mo, 0.25 wt% of V, 0.056 wt% of AL and 0.03 wt% of Cu. The others are Fe and inevitable residual elements.

S2, continuously casting molten steel meeting the component requirements into a steel billet with the thickness of 180mm, slowly cooling the hot steel billet in a heat preservation pit to 150 ℃, discharging the hot steel billet out of the heat preservation pit, and stacking and naturally cooling the steel billet to the normal temperature; peeling the surface of the steel billet by using a billet peeling machine to clean the surface defects;

s3, slowly heating the cold steel billet in a heating furnace to 1240 ℃ and discharging, removing phosphorus by 24MP high-pressure water, rolling by 2 roughing mills for 6 times to obtain an intermediate billet with the thickness of 35mm, and feeding the intermediate billet into a hot coil box; keeping the temperature uniform, reversing the head and the tail of the intermediate blank in a hot rolling box, and cutting the head after uncoiling; removing phosphorus by using high-pressure water before finish rolling, and rolling the steel strip into a steel strip with the thickness of 2.5mm by using a 7-stand finishing mill, wherein the finish rolling temperature is 857-870 ℃;

s4, cooling the finish-rolled steel strip, specifically: adopting a cooling mode of opening and closing one by XOXO for water cooling 30m in front of the laminar cooling line, and automatically fine-adjusting a rear cooling section;

s5, curling the water-cooled steel strip, and the specific process is as follows: the curling temperature is 665-678 ℃; bundling the steel coils and stacking for slow cooling, wherein the steel coils of other steel types are stacked around the steel coil of the steel type to form an enclosing wall, and the stacking is cooled to room temperature in air;

s6, feeding the steel coil into an annealing furnace, slowly heating to 890 ℃, stopping heating after heating for 50 minutes, cooling to 150 ℃ along with the furnace, discharging, and air cooling to room temperature;

s7, pickling the steel coil on a dilute nitric acid pickling line according to the pickling process shown in the table 5, and specifically, uncoiling, straightening, pickling at 6 sections, rinsing at 5 sections, drying and curling until the surface quality of the pickled steel strip is qualified.

Table 5 pickling process in example 3

After pickling, sampling is carried out at the tail part of the steel coil, and the mechanical properties are shown in a table 6:

TABLE 6 mechanical Properties of the pickled steel strip in example 3

Tensile Strength Range (MP) Yield strength Range (MP) Elongation Range (A50,%) Direction of sample
650 365 27 Transverse direction

After pickling, a sample was taken and the pickled surface was observed under an optical microscope, and it was seen from FIG. 7 that the surface layer of the steel strip was pickled well.

Example 4:

the method for producing the hot-rolled, whole-coil annealed and pickled steel strip with high alloy content comprises the following steps:

s1, after molten iron desulphurization and converter + LF + RH smelting, molten steel components are controlled as follows:

0.25 wt% of C, 1.15 wt% of Mn, 0.002 wt% of P, 0.002 wt% of S, 0.35 wt% of Si, 3.50 wt% of Cr, 0.65 wt% of Ni, 1.45 wt% of Mo, 0.30 wt% of V, 0.042 wt% of AL and 0.03 wt% of Cu. The others are Fe and inevitable residual elements;

s2, continuously casting molten steel meeting the component requirements into a steel billet with the thickness of 180mm, slowly cooling the hot steel billet in a heat preservation pit to 150 ℃, discharging the hot steel billet out of the heat preservation pit, and stacking and naturally cooling the steel billet to the normal temperature; peeling the surface of the steel billet by using a billet peeling machine to clean the surface defects;

s3, slowly heating the cold steel billet in a heating furnace to 1240 ℃ and discharging, removing phosphorus by 24MP high-pressure water, rolling by 2 roughing mills for 6 times to obtain an intermediate billet with the thickness of 33mm, and feeding the intermediate billet into a hot coil box; keeping the temperature uniform, reversing the head and the tail of the intermediate blank in a hot rolling box, and cutting the head after uncoiling; removing phosphorus by using high-pressure water before finish rolling, and rolling the steel strip into a steel strip with the thickness of 1.8mm by using a 7-stand finishing mill, wherein the finish rolling temperature is 857-870 ℃;

s4, cooling the finish-rolled steel strip, specifically: adopting a cooling mode of opening and closing one by XOXO for water cooling 30m in front of the laminar cooling line, and automatically fine-adjusting a rear cooling section;

s5, curling the water-cooled steel strip, and the specific process is as follows: the curling temperature is 665-678 ℃; bundling the steel coils and stacking for slow cooling, wherein the steel coils of other steel types are stacked around the steel coil of the steel type to form an enclosing wall, and the stacking is cooled to room temperature in air;

s6, feeding the steel coil into an annealing furnace, slowly heating to 890 ℃, stopping heating after heating for 50 minutes, cooling to 150 ℃ along with the furnace, discharging, and air cooling to room temperature;

s7, pickling the steel coil on a dilute nitric acid pickling line according to the pickling process shown in the table 7, specifically, uncoiling, straightening, pickling at 6 sections, rinsing at 5 sections, drying and curling until the surface quality of the pickled steel strip is qualified.

Table 7 pickling process in example 4

After pickling, sampling is carried out at the tail part of the steel coil, and the mechanical properties are shown in a table 8:

TABLE 8 mechanical Properties of the pickled steel strip in example 4

Tensile Strength Range (MP) Yield strength Range (MP) Elongation Range (A50,%) Direction of sample
630 350 29 Transverse direction

After pickling, a sample was taken and the pickled surface was observed under an optical microscope, and it was seen from FIG. 8 that the surface layer of the steel strip was pickled well.

Example 5:

s1, after molten iron desulphurization and converter + LF + RH smelting, molten steel components are controlled as follows:

0.28 wt% of C, 1.20 wt% of Mn, 0.003 wt% of P, 0.002 wt% of S, 0.15 wt% of Si, 3.80 wt% of Cr, 0.71 wt% of Ni, 1.00 wt% of Mo, 0.40 wt% of V, 0.075 wt% of Al and 0.02 wt% of Cu; the others are Fe and inevitable residual elements;

s2, continuously casting molten steel meeting the component requirements into a steel billet with the thickness of 180mm, slowly cooling the hot steel billet in a heat preservation pit to 150 ℃, discharging the hot steel billet out of the heat preservation pit, and stacking and naturally cooling the steel billet to the normal temperature; peeling the surface of the steel billet by using a billet peeling machine to clean the surface defects;

s3, slowly heating the cold steel billet in a heating furnace to 1240 ℃ and discharging, removing phosphorus by 24MP high-pressure water, rolling by 2 roughing mills for 6 times to obtain an intermediate billet with the thickness of 30mm, and feeding the intermediate billet into a hot coil box; keeping the temperature uniform, reversing the head and the tail of the intermediate blank in a hot rolling box, and cutting the head after uncoiling; removing phosphorus by using high-pressure water before finish rolling, and rolling the steel strip into a steel strip with the thickness of 1.2mm by using a 7-stand finishing mill, wherein the finish rolling temperature is 857-870 ℃;

s4, cooling the finish-rolled steel strip, specifically: adopting a cooling mode of opening and closing one by XOXO for water cooling 30m in front of the laminar cooling line, and automatically fine-adjusting a rear cooling section;

s5, curling the water-cooled steel strip, and the specific process is as follows: the curling temperature is 665-678 ℃; bundling the steel coils and stacking for slow cooling, wherein the steel coils of other steel types are stacked around the steel coil of the steel type to form an enclosing wall, and the stacking is cooled to room temperature in air;

s6, feeding the steel coil into an annealing furnace, slowly heating to 890 ℃, stopping heating after heating for 50 minutes, cooling to 150 ℃ along with the furnace, discharging, and air cooling to room temperature;

s7, pickling the steel coil on a dilute nitric acid pickling line according to the pickling process shown in the table 9, and specifically, uncoiling, straightening, pickling at 6 sections, rinsing at 5 sections, drying and curling until the surface quality of the pickled steel strip is qualified.

Table 9 pickling process in example 5

After pickling, sampling is carried out at the tail part of the steel coil, and the mechanical properties are shown in a table 10:

TABLE 10 mechanical Properties of the pickled steel strip in example 5

Tensile Strength Range (MP) Yield strength Range (MP) Elongation Range (A50,%) Direction of sample
640 350 28 Transverse direction

After pickling, a sample was taken and the pickled surface was observed under an optical microscope, and it was found from FIG. 9 that the surface of the steel strip was pickled cleanly.

The embodiments described herein are only some, and not all, embodiments of the invention. Based on the above explanations and guidance, those skilled in the art can make modifications, improvements, substitutions, and the like on the embodiments based on the present invention and examples, but all other embodiments obtained without innovative research fall within the scope of the present invention.

16页详细技术资料下载
上一篇:一种医用注射器针头装配设备
下一篇:一种复合稀土增强粉末冶金高速钢的制备方法

网友询问留言

已有0条留言

还没有人留言评论。精彩留言会获得点赞!

精彩留言,会给你点赞!