CN114086061B - 6.8-grade corrosion-resistant cold forging steel and production method thereof - Google Patents

6.8-grade corrosion-resistant cold forging steel and production method thereof Download PDF

Info

Publication number
CN114086061B
CN114086061B CN202111259371.8A CN202111259371A CN114086061B CN 114086061 B CN114086061 B CN 114086061B CN 202111259371 A CN202111259371 A CN 202111259371A CN 114086061 B CN114086061 B CN 114086061B
Authority
CN
China
Prior art keywords
steel
percent
corrosion
grade
equal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN202111259371.8A
Other languages
Chinese (zh)
Other versions
CN114086061A (en
Inventor
姜婷
汪开忠
郭湛
张晓瑞
尹德福
丁雷
何峰
石践
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Maanshan Iron and Steel Co Ltd
Original Assignee
Maanshan Iron and Steel Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Maanshan Iron and Steel Co Ltd filed Critical Maanshan Iron and Steel Co Ltd
Priority to CN202111259371.8A priority Critical patent/CN114086061B/en
Publication of CN114086061A publication Critical patent/CN114086061A/en
Application granted granted Critical
Publication of CN114086061B publication Critical patent/CN114086061B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/005—Continuous casting of metals, i.e. casting in indefinite lengths of wire
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10—Supplying or treating molten metal
    • B22D11/108—Feeding additives, powders, or the like
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10—Supplying or treating molten metal
    • B22D11/11—Treating the molten metal
    • B22D11/114—Treating the molten metal by using agitating or vibrating means
    • B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
    • B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

The invention discloses 6.8-grade corrosion-resistant cold forging steel and a production method thereof, belonging to the technical field of production of acid corrosion resistant reinforcing steel bars. The invention comprises the following chemical components in percentage by weight: 0.10 to 0.20 percent of C, 0.40 to 0.60 percent of Si, 0.60 to 0.80 percent of Mn, 0.020 to 0.030 percent of Alt, 0.008 to 0.015 percent of La, 0.008 to 0.015 percent of Nd, 0.010 to 0.020 percent of Y, less than or equal to 0.015 percent of P, less than or equal to 0.015 percent of S, and the balance of Fe and other inevitable impurities. In order to solve the problems in the prior art, the invention provides 6.8-grade corrosion-resistant cold forging steel and a production method thereof, the cold forging steel with excellent corrosion resistance is obtained through a specific chemical component proportion and a production method, and the cold forging steel is suitable for manufacturing 6.8-grade fasteners resistant to corrosion of industrial atmospheric environment and other workpieces with the same strength grade, and the preparation cost of steel is lower.

Description

6.8-grade corrosion-resistant cold forging steel and production method thereof
Technical Field
The invention belongs to the technical field of cold forging steel, and particularly relates to 6.8-grade corrosion-resistant cold forging steel and a production method thereof.
Background
The cold heading steel is mainly used for producing fasteners such as bolts, screws, nuts and the like, railway construction in China keeps developing rapidly, not only new railways and transformation of existing lines provide new market demands for high-speed motor train units, high-power locomotives and heavy-duty trucks, but also market space is provided for the fasteners due to updating and upgrading of in-service equipment. The Chinese territory is wide, the natural climate environment is complex, with the development of the rail transit industry, higher requirements are put forward on cold forging steel for the fastener, the cold forging steel material with excellent corrosion resistance is urgently needed to be developed, and the steel for the fastener with the corrosion resistance is urgently needed in the fields of wind power, bridges and the like in China. At present, corrosion-resistant construction steel such as plates and section steel in China is researched more, products are relatively mature, but corrosion-resistant cold forging steel is researched less. With the complication of the application environment of the fastener, the development of low-cost cold heading steel material with corrosion resistance is urgently needed.
Through retrieval, a large number of patent documents are disclosed in the research on the acid corrosion resistance of the steel bar, such as Chinese patent publication numbers: CN 10139634B discloses a 08CrNiCu low-alloy high-strength annealing-free cold forging steel with atmospheric corrosion resistance and a production process thereof, wherein the chemical components in percentage by weight are as follows: 0.05 to 0.90%, si:0.15 to 0.25%, mn:0.55 to 0.65%, P:0.005 to 0.025%, S: 0.005-0.02%, cr:0.65 to 0.75%, ni:0.25 to 0.30%, cu:0.35 to 0.40 percent, and the balance of Fe and inevitable impurities; can be used for processing 8.8-grade bolts and matched nuts. The defects that the steel of the invention is added with noble alloy elements such as Ni, cr and the like, and the cost is higher.
And as Chinese patent publication No. is: CN108070796A discloses a 1040 MPa-grade weather-resistant bolt with delayed fracture resistance, which comprises the following chemical components in percentage by mass: c:0.21 to 0.32, si:0.10 to 0.50, mn:0.60 to 1.00, P:0.008 to 0.020, S: less than or equal to 0.005, cr:0.82 to 1.20, ni:0.25 to 0.50, cu:0.25 to 0.50, mo:0.05 to 0.20, nb:0.015 to 0.060, V:0.015 to 0.090, ti:0.008 to 0.035, B:0.0008 to 0.0035, al:0.015 to 0.040, ca:0.003 to 0.007, zr:0.015 to 0.045, re:0.010 to 0.045, and the balance of Fe and inevitable impurities; the preparation method of the bolt mainly adopts the conventional high-purity melting-continuous casting-rolling technology, and the manufactured bolt is resistant to delayed fracture and atmospheric corrosion. However, in this method, ti and Zr elements are added, nitride inclusions are formed, which are detrimental to the toughness of the material, and the alloy addition amount in the steel is large, and the strength level is also 1000MPa or more.
Disclosure of Invention
1. Problems to be solved
In order to solve the problems in the prior art, the invention provides 6.8-grade corrosion-resistant cold forging steel and a production method thereof, the cold forging steel with excellent corrosion resistance is obtained through a specific chemical component proportion and a production method, and the cold forging steel is suitable for manufacturing 6.8-grade fasteners resistant to corrosion of industrial atmospheric environment and other workpieces with the same strength grade, and the steel preparation cost is lower.
2. Technical scheme
In order to solve the above problems, the present invention adopts the following technical solutions.
The invention relates to 6.8-grade corrosion-resistant cold forging steel which comprises the following chemical components in percentage by weight: 0.10 to 0.20 percent of C, 0.40 to 0.60 percent of Si, 0.60 to 0.80 percent of Mn, 0.020 to 0.030 percent of Alt, 0.008 to 0.015 percent of La, 0.008 to 0.015 percent of Nd, 0.010 to 0.020 percent of Y, less than or equal to 0.015 percent of P, less than or equal to 0.015 percent of S, and the balance of Fe and other inevitable impurities.
Furthermore, the corrosion resistance index W of the 6.8-grade corrosion-resistant cold forging steel is more than or equal to 0.26, the unit of W value is wt%, and W =0.3Si +3.6La +4.5Nd +3.9Y.
Furthermore, the molten steel fluidity index L of the 6.8-grade corrosion-resistant cold forging steel is less than or equal to 0.045, the L value unit is wt%, and L =1.12Nd +0.95Y +1.20La.
The components of the 6.8-grade corrosion-resistant cold forging steel provided by the invention are controlled as follows:
c: c is the most effective reinforcing element in steel, but ductility decreases as the content thereof increases, and therefore the C content needs to be controlled within a range of 0.10% to 0.20%, and more preferably 0.12% to 0.18%.
Si: si is an important element for strengthening in steel, the strength of the steel is improved through solid solution, the Si is mainly enriched on the surface of the steel, the stability of a rust layer in the steel is improved, and the corrosion resistance is improved. However, the increase of the Si element increases the diffusion of carbon in the steel, and thus the decarburization of the steel is promoted. Therefore, the Si content is controlled to be in the range of 0.40% to 0.60%, and more preferably 0.44% to 0.56% of Si.
Mn: mn and Fe form a solid solution, increasing the hardness and strength of ferrite and austenite in steel, but excessive Mn reduces the plasticity of steel, increases the notch sensitivity of the material, and increases grain boundary segregation, resulting in a decrease in grain boundary strength. The addition of Mn is simultaneously beneficial to forming a rust layer on the surface of steel, the corrosion resistance of steel is improved, excessive Mn can cause the growth of corrosion product particles, and the corrosion rate is improved. Therefore, the Mn content is controlled to be in the range of 0.60% to 0.80%, and more preferably 0.63% to 0.75%.
Al: al is a strong deoxidizing element and improves the oxidation resistance of steel, but the amount of coarse carbonitride-based inclusions increases with the increase in Al content. Therefore, the content of Alt is controlled to be within the range of 0.020% to 0.030%, and more preferably 0.022% to 0.029%.
La: la modifies inclusions in the steel, promotes the dispersion distribution of fine spherical inclusions, and improves the toughness of the steel. La is also effective in improving pitting corrosion and intergranular corrosion in steel; however, when the La content is too high, the formation of nodules is liable to occur during the casting of molten steel, and the La content is controlled to be in the range of 0.008% to 0.015%, and more preferably 0.010% to 0.013%.
Nd: nd and La form a composite modifier, and the composite modifier is more effective in modifying the inclusion than single La. Nd increases the resistance of the rust layer on the surface of the substrate and the reaction resistance of the joint of the substrate and the Nd, and enhances the protection of the rust layer on steel. The content of Nd is controlled within the range of 0.008% to 0.015%, and more preferably 0.009% to 0.013%.
Y: the effect of Y in steel is similar to that of Nd, and the Y and Nd and La form a composite modifier, so that inclusion can be refined, and the strength and toughness of the steel can be improved through dispersion strengthening. Y can significantly improve the corrosion resistance of the steel by increasing the potential in the rust layer of the steel. The content of Y is controlled to be in the range of 0.010 to 0.020%, and more preferably 0.013 to 0.018%.
S and P: sulfur easily forms MnS inclusions with manganese in steel, and is harmful to the processability of steel; p is an element with a strong segregation tendency and usually also causes co-segregation of sulphur and manganese, which is detrimental to the homogeneity of the product structure and properties. Therefore, P is required to be controlled to be less than or equal to 0.015 percent and S is required to be controlled to be less than or equal to 0.015 percent.
The invention relates to a production method of 6.8-grade corrosion-resistant cold heading steel, which comprises the following production steps: molten iron pretreatment → molten steel smelting → LF furnace refining → square billet continuous casting → square billet heating → wire rod rolling → stelmor cooling line cooling → finished product, in the continuous casting step, la line, nd line and Nd line are added in a crystallizer to adjust the contents of La, nd and Y to the target range, and meanwhile, electromagnetic stirring and argon protection casting are adopted, and the flow of primary cooling water is 100m 3 /h～120m 3 The water amount of the secondary cooling is 1.0-1.2 l/kg.
Further, the billet obtained after the continuous casting enters a heating furnace for heating treatment, wherein the soaking temperature in the heating furnace is controlled within the range of 1000-1100 ℃, the tapping temperature is controlled within the range of 900-1000 ℃, the billet discharged from the heating furnace is subjected to rolling treatment by a high-speed wire rod rolling mill, and the spinning temperature in the rolling process is controlled within the range of 780-830 ℃.
Furthermore, in the LF furnace refining step, argon is blown from the bottom of the steel ladle in the whole process, premelted refining slag and lime are added for slagging, the white slag holding time is more than or equal to 15 minutes, and according to the component analysis result before entering the LF furnace, alloy is added in the early stage and the middle stage of refining to adjust the contents of Si and Mn to the target range.
Furthermore, the converter end point in the molten steel smelting step is controlled to be less than or equal to 0.04 percent of C and less than or equal to 0.006 percent of P; and (3) slag stopping and tapping, wherein about 1/5 of molten steel is tapped, refining slag and lime are added, about 1/3 of tapping is tapped, deoxidizing agent and alloy are added, about 3/4 of tapping is tapped, aluminum cakes are added, and a proper amount of aluminum particles are uniformly thrown to the steel slag surface according to the slag amount after tapping.
Furthermore, the metallographic structure of the finished cold heading steel wire rod is ferrite and pearlite, the mechanical property Rm is more than or equal to 520MPa, A is more than or equal to 38 percent, Z is more than or equal to 70 percent, and one fifth of the cold heading is qualified.
Further, naHSO compares favorably with cold heading steel 1022 of the same grade 3 The relative corrosion rate of the weekly soaking test is less than or equal to 40 percent.
3. Advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
(1) The 6.8-grade corrosion-resistant cold forging steel is different from the traditional corrosion-resistant steel added with Cu, cr and Ni noble alloy elements, and the manufacturing cost of steel can be effectively reduced by adding La, nd and Y rare earth elements with low cost. Wherein Y can remarkably improve the corrosion resistance of the rust layer of the steel by increasing the potential; la modifies inclusions in the steel, promotes dispersion and distribution of fine spherical inclusions, and improves the toughness of the steel; nd raises the rust layer resistance on the surface of the matrix and the reaction resistance of the joint of the matrix, and enhances the protection of the rust layer on steel. In addition, la, nd and Y form a composite modifier, so that the modification of inclusions is realized, the inclusions can be refined, the dispersion distribution effect is realized in the middle stage of steel, and the toughness of the steel is effectively improved. When Nd is added singly, the effect is not significant any more when the amount is too large, and Y increases the potential in the rust layer of the steel, thereby significantly improving the corrosion resistance of the steel.
(2) In order to obtain a sufficient corrosion resistant effect, the chemical component proportion of the 6.8-grade corrosion resistant cold forging steel needs to ensure that the corrosion resistant performance index W of the cold forging steel is more than or equal to 0.26, the W value unit is wt%, and W =0.3Si +3.6La +4.5Nd +3.9Y. In the invention, because Si, la, nd and Y are main corrosion-resistant elements, in order to ensure that the cold forging steel achieves sufficient corrosion resistance, the elements need to be matched according to the contribution of the corrosion resistance of the elements so as to strengthen and generate a compact and strong-adhesion rust layer and better increase the corrosion resistance. The steel is easier to corrode due to the higher C content, and the corrosion resistance index W value is higher to ensure the corrosion resistance of the cold forging steel.
(3) According to the 6.8-grade corrosion-resistant cold forging steel and the production method thereof, in the continuous casting step, la lines, nd lines and Nd lines are added into a crystallizer to adjust the contents of La, nd and Y to the target range, the added La, nd and Y elements are linear, molten steel nodulation can be effectively prevented through dissolution, and meanwhile, electricity is adopted to prevent the molten steel from nodulationMagnetic stirring and argon protection casting in the whole process, so that the risk of molten steel nodulation is further reduced. The invention adopts strong cooling, increases the cooling solidification coefficient, shortens the solidification time and improves the production efficiency, and the key parameters are as follows: primary cooling water flow of 100m 3 /h～120m 3 The water amount of the secondary cooling is 1.0-1.2 l/kg. If the maximum value is exceeded, the casting blank cracks can occur, and the columnar crystal grows to cause coarse crystals, and if the minimum value is lower than the maximum value, the pulling speed is low, and the production efficiency is insufficient.
(4) The invention relates to a production method of 6.8-grade corrosion-resistant cold heading steel, which comprises the steps of feeding a billet obtained after continuous casting into a heating furnace for heating treatment, wherein the soaking temperature in the heating furnace is controlled within the range of 1000-1100 ℃, the tapping temperature is controlled within the range of 900-1000 ℃, the billet discharged from the heating furnace is subjected to rolling treatment by a high-speed wire rod rolling mill, and the spinning temperature in the rolling process is controlled within the range of 780-830 ℃.
Drawings
FIG. 1 is a graph showing a change trend between the molten steel fluidity and the molten steel fluidity index L of a grade 6.8 corrosion-resistant cold forging steel according to the present invention.
Detailed Description
The invention is further described with reference to specific embodiments and the accompanying drawings.
Example 1
As shown in fig. 1, the grade 6.8 corrosion-resistant cold forging steel of the present embodiment comprises the following chemical components by weight percent: 0.10% of C, 0.40% of Si, 0.80% of Mn, 0.030% of Alt, 0.008% of La, 0.015% of Nd, 0.010% of Y, 0.012% of P, 0.003% of S, and the balance of Fe and other inevitable impurities. Compared with the traditional corrosion-resistant steel added with Cu, cr and Ni noble alloy elements, the invention can effectively reduce the manufacturing cost of steel by adding La, nd and Y rare earth elements with low cost. Wherein Y can remarkably improve the corrosion resistance of the steel by increasing the potential in the rust layer of the steel; la modifies inclusions in the steel, promotes dispersion and distribution of fine spherical inclusions, and improves the toughness of the steel; nd increases the resistance of the rust layer on the surface of the substrate and the reaction resistance of the joint of the substrate and the Nd, and enhances the protection of the rust layer on steel. In addition, la, nd and Y form a composite modifier, so that the modification of inclusions is realized, the inclusions can be refined, the dispersion distribution effect is realized in the middle stage of steel, and the toughness of the steel is effectively improved. If Nd is added alone, the effect is not significant any more when the amount is too large, and Y increases the potential in the rust layer of the steel, thereby significantly improving the corrosion resistance of the steel.
In order to obtain a sufficient corrosion resistant effect, the chemical composition ratio needs to ensure that the corrosion resistant performance index W of the 6.8-grade corrosion resistant cold forging steel is more than or equal to 0.26, the W value unit is wt%, and W =0.3Si +3.6La +4.5Nd +3.9Y. In the invention, because Si, la, nd and Y are main corrosion-resistant elements, in order to ensure that the cold forging steel achieves sufficient corrosion resistance, the elements need to be matched according to the contribution of the corrosion resistance of the elements so as to strengthen and generate a compact and strong-adhesion rust layer and better increase the corrosion resistance. The steel is easier to corrode due to the higher C content, and the corrosion resistance index W value is higher to ensure the corrosion resistance of the cold forging steel.
Meanwhile, in order to ensure the fluidity of the molten steel, the chemical composition proportion needs to ensure that the molten steel fluidity index L of the 6.8-grade corrosion-resistant cold forging steel is less than or equal to 0.045, the L value unit is wt%, and L =1.12Nd +0.95Y +1.20La. The fluidity of molten steel was tested by conducting a pilot steel production and casting in a simulated industrial production environment, and it was found that the L value was required to be maintained at 0.045 or less for sufficient fluidity of molten steel. Specifically, in this embodiment, the value of W is 0.26 and the value of L is 0.036.
The production method of the 6.8-grade corrosion-resistant cold heading steel comprises the following production steps: molten iron pretreatment → molten steel smelting → LF furnace refining → square billet continuous casting → square billet heating → wire rod rolling → stelmor cooling line cooling → finished product of wire rod of phi 5.5-30 mm. Wherein, the desulfurization target value S is less than or equal to 0.006 percent through pretreatment desulfurization. In the step of smelting molten steel, the end point of the converter is controlled to be 0.04 percent of C and 0.005 percent of P; and (3) slag stopping and tapping, wherein about 1/5 of molten steel is tapped, refining slag and lime are added, about 1/3 of tapping is tapped, deoxidizing agent and alloy are added, about 3/4 of tapping is tapped, aluminum cakes are added, and a proper amount of aluminum particles are uniformly thrown to the steel slag surface according to the slag amount after tapping.
In the LF furnace refining step, argon is blown from the bottom of the ladle in the whole process, argon flow is based on that molten steel does not splash to the ladle, premelted refining slag and lime are added for slagging, the white slag holding time is more than or equal to 15 minutes, and according to the component analysis result before entering the LF furnace, alloy is added in the early stage and the middle stage of refining to adjust the contents of Si and Mn to a target range. Specifically, in the embodiment, the converter end point control C is 0.03%, and the P is 0.005%; the white slag retention time was 15 minutes.
In the continuous casting step of this embodiment, the La line, the Nd line, and the Nd line are added to the mold to adjust the La, nd, and Y contents to the target ranges, and the three elements added are linear, so that the La, nd, and Y can be effectively dissolved to prevent the molten steel from nodulating, and meanwhile, electromagnetic stirring and argon protection casting are adopted to further reduce the risk of the molten steel nodulating. In this embodiment, the forced cooling is adopted, the cooling solidification coefficient is increased, the solidification time is shortened, the production efficiency is improved, and the key parameters are as follows: primary cooling water flow of 100m 3 /h～120m 3 The water amount of the secondary cooling is 1.0-1.2 l/kg. If the maximum value is exceeded, the casting blank cracks can occur, and the columnar crystal grows to cause coarse crystals, and if the minimum value is lower than the maximum value, the pulling speed is low, and the production efficiency is insufficient. Specifically, the primary cooling water flow rate in the present embodiment is 110m 3 The secondary cooling specific water amount was 1.20l/kg.
And (2) putting the billet obtained after the continuous casting into a heating furnace for heating treatment, wherein the soaking temperature in the heating furnace is controlled within the range of 1000-1100 ℃, the tapping temperature is controlled within the range of 900-1000 ℃, the billet discharged from the heating furnace is subjected to rolling treatment by a high-speed wire rod rolling mill, and the spinning temperature in the rolling process is controlled within the range of 780-830 ℃. Specifically, in the embodiment, the soaking temperature in the heating furnace is 1100 ℃, and the tapping temperature is 1000 ℃; the spinning temperature during rolling was 822 ℃.
The metallographic structure of the finished cold heading steel wire rod product of the embodiment is ferrite and pearlite, rm is more than or equal to 520MPa, A is more than or equal to 38%, Z is more than or equal to 70%, and one fifth of the cold heading is qualified. And (3) performing cold upset forging on the finished product of the cold upset steel wire rod according to the following requirements, wherein after a cold upset forging test, the defects of cracks, cracks and hairlines which can be seen by naked eyes cannot be obtained on the surface of a sample. Simulating an industrial atmospheric environment in NaHSO 3 The relative corrosion rate of the solution is the same as that of the solution in a week immersion testCompared with cold forging steel 1022, naHSO of the 6.8-grade corrosion-resistant cold forging steel of the embodiment 3 The relative corrosion rate of the weekly leaching test is less than or equal to 40 percent. Specifically, the tensile property Rm of the finished cold heading steel wire rod in the embodiment is 536MPa, A is 38%, Z is 71%, and one fifth of the cold heading steel wire rod is qualified; naHSO of 6.8-grade corrosion-resistant cold heading steel 3 The relative corrosion rate of the weekly soaking test is 38.35 percent.
Wherein NaHSO 3 The test procedure of 72-hour soaking of the solution is as follows: sampling on the square billet, and processing the sample according to TB/T2375-1993 periodic infiltration corrosion test method for weathering steel for railways to finish NaHSO 3 The solution is subjected to 72-hour week immersion test, the corrosion weight loss rate is calculated, each group is numbered 10, and the average value is calculated, and the specific result is shown in table 3. Wherein the corrosion weight loss ratio (W) is calculated according to the following formula:
Figure BDA0003324979620000061
in the formula: w-weight loss ratio, g/(m) 2 ·h)；G 0 -sample original weight, g; g 1 -the post-test weight of the sample, g; a-specimen length, mm; b-specimen width, mm; c-specimen thickness, mm; t-test time, h.
The cold heading steel manufactured by the method for manufacturing the 6.8-grade corrosion-resistant cold heading steel has excellent corrosion resistance and cold heading performance, can be used for manufacturing fasteners with large deformation, is suitable for manufacturing 6.8-grade fasteners resistant to corrosion of industrial atmospheric environment, can also be used for manufacturing other workpieces with the same strength grade, such as rods and the like, and has low steel cost. The chemical composition and the production method of the cold forging steel are properly controlled, the hot rolled mechanical property is high in strength, the plasticity is good, the corrosion resistance is higher than that of the 6.8-grade cold forging steel 1022 universally used in the market by more than 2.5 times, the cold forging steel has excellent cold forging performance, and is easy to process by users and low in steel cost.
Table 1 shows chemical compositions (wt%) in examples 1 to 7 and comparative examples 1 to 3
Steel grade C Si Mn Alt La Nd Y P S Value of W Value of L
Example 1 0.10 0.40 0.80 0.030 0.008 0.015 0.010 0.012 0.003 0.26 0.036
Example 2 0.20 0.57 0.60 0.020 0.013 0.008 0.020 0.013 0.002 0.33 0.044
Example 3 0.12 0.44 0.75 0.029 0.010 0.013 0.013 0.011 0.003 0.28 0.039
Example 4 0.18 0.56 0.63 0.022 0.013 0.009 0.018 0.009 0.001 0.33 0.043
Example 5 0.17 0.60 0.69 0.028 0.008 0.008 0.010 0.012 0.003 0.28 0.028
Example 6 0.13 0.51 0.73 0.023 0.011 0.011 0.015 0.009 0.001 0.30 0.040
Example 7 0.15 0.49 0.65 0.025 0.015 0.010 0.014 0.010 0.001 0.26 0.032
Comparative example 1 0.16 0.40 0.73 0.025 0.008 0.008 0.010 0.011 0.002 0.22 0.028
Comparative example 2 0.14 0.53 0.77 0.026 0.015 0.015 0.014 0.012 0.001 0.34 0.048
Comparative example 3 0.21 0.28 0.93 0.028 / / / 0.013 0.002 / /
TABLE 2 production Process parameters of cold heading steels in examples 1 to 7 and comparative examples 1 to 3
Figure BDA0003324979620000071
TABLE 3 List of specific process parameters and performance measurements for inventive and comparative examples
Figure BDA0003324979620000072
Example 2
The grade 6.8 corrosion-resistant cold forging steel of the embodiment is basically consistent with the example 1, except that the embodiment comprises the following chemical components in percentage by weight: 0.20% of C, 0.57% of Si, 0.60% of Mn, 0.020% of Alt, 0.013% of La, 0.008% of Nd, 0.020% of Y, 0.013% of P, 0.002% of S and the balance of Fe and other unavoidable impurities.
The corrosion resistance index W of the grade 6.8 corrosion-resistant cold forging steel of the embodiment is 0.33, and the fluidity index L of the molten steel is 0.044.
The production method of the 6.8-grade corrosion-resistant cold heading steel comprises the following production steps: molten iron pretreatment → molten steel smelting → LF furnace refining → square billet continuous casting → square billet heating → wire rod rolling → stelmor cooling line cooling → wire rod finished product of phi 5.5-30 mm. Wherein, the desulfurization target value S is less than or equal to 0.006 percent through pretreatment desulfurization. In the molten steel smelting step, the converter end point control C is 0.04 percent, the converter end point control P is 0.005 percent, and the white slag retention time is 17 minutes.
Adding La line, nd line and Nd line into the crystallizer to adjust the contents of La, nd and Y to the target range, and simultaneously adopting electromagnetic stirring and argon protection casting in the whole process. In this embodiment, the forced cooling is adopted, the cooling solidification coefficient is increased, the solidification time is shortened, the production efficiency is improved, and the key parameters are as follows: primary cooling water flow rate of 130m 3 The secondary cooling specific water amount was 1.26l/kg.
In the embodiment, the soaking temperature in the heating furnace is 1085 ℃, and the tapping temperature is 900 ℃; the spinning temperature in the rolling process is 830 ℃.
In the embodiment, the tensile property Rm of the finished cold heading steel wire rod is 542MPa, A is 38.5 percent, Z is 71 percent, and one fifth of cold heading is qualified; naHSO of 6.8-grade corrosion-resistant cold heading steel 3 The relative corrosion rate of the weekly immersion test is 39.1%.
Example 3
The grade 6.8 corrosion-resistant cold forging steel of the embodiment is basically consistent with the example 1, except that the embodiment comprises the following chemical components in percentage by weight: 0.12% of C, 0.44% of Si, 0.75% of Mn, 0.029% of Alt, 0.010% of La, 0.013% of Nd, 0.013% of Y, 0.011% of P, 0.003% of S, and the balance of Fe and other unavoidable impurities.
The corrosion resistance index W of the grade 6.8 corrosion-resistant cold forging steel of the embodiment is 0.28, and the fluidity index L of the molten steel is 0.039.
The production method of the 6.8-grade corrosion-resistant cold heading steel comprises the following production steps: molten iron pretreatment → molten steel smelting → LF furnace refining → square billet continuous casting → square billet heating → wire rod rolling → stelmor cooling line cooling → wire rod finished product of phi 5.5-30 mm. Wherein, the desulfurization target value S is less than or equal to 0.006 percent through pretreatment desulfurization. In the smelting step of molten steel, the converter end point control C is 0.03%, the converter end point control P is 0.005%, and the white slag retention time is 17 minutes.
And adding La lines, nd lines and Nd lines into the crystallizer to adjust the contents of La, nd and Y to the target range, and simultaneously adopting electromagnetic stirring and argon protection casting in the whole process. In the embodiment, strong cooling is adopted to increase the coolingBut the solidification coefficient shortens the solidification time, improves production efficiency, and key parameter is as follows: primary cooling water flow of 115m 3 The secondary cooling specific water amount was 1.30l/kg.
In the embodiment, the soaking temperature in the heating furnace is 1000 ℃, and the tapping temperature is 906 ℃; the spinning temperature in the rolling process is 780 ℃.
In the embodiment, the tensile property Rm of the finished cold heading steel wire rod is 543MPa, A is 39%, Z is 73%, and one fifth of cold heading is qualified; naHSO of 6.8-grade corrosion-resistant cold heading steel 3 The relative corrosion rate of the weekly leaching test is 36.09%.
Example 4
The grade 6.8 corrosion-resistant cold forging steel of the embodiment is basically consistent with the grade 1, and is different from the grade 1 corrosion-resistant cold forging steel in that the chemical components in percentage by weight are included in the embodiment: 0.18% of C, 0.56% of Si, 0.63% of Mn, 0.022% of Alt, 0.013% of La, 0.009% of Nd, 0.018% of Y, 0.009% of P, 0.001% of S and the balance of Fe and other unavoidable impurities.
The corrosion resistance index W of the grade 6.8 corrosion-resistant cold forging steel of the embodiment is 0.33, and the fluidity index L of the molten steel is 0.043.
The production method of the 6.8-grade corrosion-resistant cold heading steel comprises the following production steps: molten iron pretreatment → molten steel smelting → LF furnace refining → square billet continuous casting → square billet heating → wire rod rolling → stelmor cooling line cooling → wire rod finished product of phi 5.5-30 mm. Wherein, the desulfurization target value S is less than or equal to 0.006 percent through pretreatment desulfurization. In the smelting step of molten steel, the converter end point is controlled to be 0.05 percent of C, 0.004 percent of P and 17 minutes of white slag holding time.
And adding La lines, nd lines and Nd lines into the crystallizer to adjust the contents of La, nd and Y to the target range, and simultaneously adopting electromagnetic stirring and argon protection casting in the whole process. In the embodiment, strong cooling is adopted, the cooling solidification coefficient is increased, the solidification time is shortened, the production efficiency is improved, and the key parameters are as follows: primary cooling water flow of 122m 3 The secondary cooling specific water amount was 1.23l/kg.
In the embodiment, the soaking temperature in the heating furnace is 1056 ℃, and the tapping temperature is 984 ℃; the spinning temperature in the rolling process is 796 ℃.
In the embodiment, the cold heading steel wire rod finished product has tensile property Rm of 538MPa, A of 39%, Z of 72% and one fifth of qualified cold heading; naHSO of 6.8-grade corrosion-resistant cold heading steel 3 The relative corrosion rate of the weekly leaching test is 36.09%.
Example 5
The grade 6.8 corrosion-resistant cold forging steel of the embodiment is basically consistent with the grade 1, and is different from the grade 1 corrosion-resistant cold forging steel in that the chemical components in percentage by weight are included in the embodiment: 0.17% of C, 0.60% of Si, 0.69% of Mn, 0.028% of Alt, 0.008% of La, 0.008% of Nd, 0.010% of Y, 0.012% of P, 0.003% of S, and the balance of Fe and other inevitable impurities.
The corrosion resistance index W of the grade 6.8 corrosion-resistant cold forging steel of the present example was 0.28, and the fluidity index L of the molten steel was 0.028.
The production method of the 6.8-grade corrosion-resistant cold heading steel comprises the following production steps: molten iron pretreatment → molten steel smelting → LF furnace refining → square billet continuous casting → square billet heating → wire rod rolling → stelmor cooling line cooling → finished product of wire rod of phi 5.5-30 mm. Wherein the desulfurization target value S is less than or equal to 0.006 percent through pretreatment desulfurization. In the molten steel smelting step, the converter end point control C is 0.03 percent, the P is 0.005 percent, and the white slag retention time is 17 minutes.
And adding La lines, nd lines and Nd lines into the crystallizer to adjust the contents of La, nd and Y to the target range, and simultaneously adopting electromagnetic stirring and argon protection casting in the whole process. In this embodiment, the forced cooling is adopted, the cooling solidification coefficient is increased, the solidification time is shortened, the production efficiency is improved, and the key parameters are as follows: primary cooling water flow of 123m 3 The secondary cooling specific water amount was 1.26l/kg.
In the embodiment, the soaking temperature in the heating furnace is 1023 ℃, and the tapping temperature is 956 ℃; the spinning temperature in the rolling process is 793 ℃.
The tensile property Rm of the finished cold heading steel wire rod in the embodiment is 529MPa, A is 38.5 percent, Z is 71 percent, and one fifth of the cold heading steel wire rod is qualified; naHSO of 6.8-grade corrosion-resistant cold heading steel 3 The relative corrosion rate of the weekly soaking test is 34.59 percent.
Example 6
The grade 6.8 corrosion-resistant cold forging steel of the embodiment is basically consistent with the example 1, except that the embodiment comprises the following chemical components in percentage by weight: 0.13% of C, 0.51% of Si, 0.73% of Mn, 0.023% of Alt, 0.011% of La, 0.011% of Nd, 0.015% of Y, 0.009% of P, 0.001% of S and the balance of Fe and other inevitable impurities.
The corrosion resistance index W of the grade 6.8 corrosion-resistant cold forging steel of this example was 0.30, and the fluidity index L of molten steel was 0.040.
The production method of the 6.8-grade corrosion-resistant cold heading steel comprises the following production steps: molten iron pretreatment → molten steel smelting → LF furnace refining → square billet continuous casting → square billet heating → wire rod rolling → stelmor cooling line cooling → finished product of wire rod of phi 5.5-30 mm. Wherein, the desulfurization target value S is less than or equal to 0.006 percent through pretreatment desulfurization. In the smelting step of molten steel, the converter end point is controlled to be 0.03 percent of C, 0.004 percent of P and 18 minutes of white slag holding time.
Adding La line, nd line and Nd line into the crystallizer to adjust the contents of La, nd and Y to the target range, and simultaneously adopting electromagnetic stirring and argon protection casting in the whole process. In the embodiment, strong cooling is adopted, the cooling solidification coefficient is increased, the solidification time is shortened, the production efficiency is improved, and the key parameters are as follows: primary cooling water flow of 112m 3 The secondary cooling specific water amount was 1.21l/kg.
In the embodiment, the soaking temperature in the heating furnace is 1029 ℃, and the tapping temperature is 927 ℃; the spinning temperature in the rolling process is 816 ℃.
The tensile property Rm of the cold heading steel wire rod finished product in the embodiment is 547MPa, A is 38%, Z is 70%, and one fifth of cold heading is qualified; naHSO of 6.8-grade corrosion-resistant cold heading steel 3 The relative corrosion rate of the weekly immersion test is 37.59 percent.
Example 7
The grade 6.8 corrosion-resistant cold forging steel of the embodiment is basically consistent with the example 1, except that the embodiment comprises the following chemical components in percentage by weight: 0.15% of C, 0.49% of Si, 0.65% of Mn, 0.025% of Alt, 0.015% of La, 0.010% of Nd, 0.014% of Y, 0.010% of P, 0.001% of S, and the balance of Fe and other inevitable impurities.
The corrosion resistance index W of the grade 6.8 corrosion-resistant cold forging steel of this example was 0.26, and the fluidity index L of molten steel was 0.032.
The production method of the 6.8-grade corrosion-resistant cold heading steel comprises the following production steps: molten iron pretreatment → molten steel smelting → LF furnace refining → square billet continuous casting → square billet heating → wire rod rolling → stelmor cooling line cooling → wire rod finished product of phi 5.5-30 mm. Wherein, the desulfurization target value S is less than or equal to 0.006 percent through pretreatment desulfurization. In the smelting step of molten steel, the converter end point is controlled to be 0.04 percent C, 0.004 percent P and the white slag retention time is 16 minutes.
And adding La lines, nd lines and Nd lines into the crystallizer to adjust the contents of La, nd and Y to the target range, and simultaneously adopting electromagnetic stirring and argon protection casting in the whole process. In this embodiment, the forced cooling is adopted, the cooling solidification coefficient is increased, the solidification time is shortened, the production efficiency is improved, and the key parameters are as follows: primary cooling water flow rate is 126m 3 The secondary cooling specific water amount was 1.28l/kg.
In the embodiment, the soaking temperature in the heating furnace is 1049 ℃, and the tapping temperature is 933 ℃; the spinning temperature during the rolling process is 821 ℃.
The tensile property Rm of the cold heading steel wire rod finished product in the embodiment is 547MPa, A is 39.5%, Z is 73%, and one fifth of cold heading is qualified; naHSO of 6.8-grade corrosion-resistant cold heading steel 3 The relative corrosion rate of the weekly soaking test is 38.35 percent.
Comparative example 1
The cold heading steel of the comparative example comprises the following chemical components in percentage by weight: 0.16% of C, 0.40% of Si, 0.73% of Mn, 0.025% of Alt, 0.008% of La, 0.008% of Nd, 0.010% of Y, 0.011% of P, 0.002% of S and the balance of Fe and other inevitable impurities.
The cold forging steel of this comparative example had a corrosion resistance index W value of 0.22 and a molten steel fluidity index L of 0.028.
The production method of the cold heading steel comprises the following production steps: molten iron pretreatment → molten steel smelting → LF furnace refining → square billet continuous casting → square billet heating → wire rod rolling → stelmor cooling line cooling → wire rod finished product of phi 5.5-30 mm. Wherein, the desulfurization target value S is less than or equal to 0.006 percent through pretreatment desulfurization. In the smelting step of molten steel, the converter end point control C is 0.03%, the converter end point control P is 0.005%, and the white slag retention time is 18 minutes.
Adding La wires, ce wires and Yb wires into the crystallizer to adjust the contents of La, ce and Yb to a target range, and simultaneously adopting electromagnetic stirring and argon protection casting in the whole process. In this embodiment, the forced cooling is adopted, the cooling solidification coefficient is increased, the solidification time is shortened, the production efficiency is improved, and the key parameters are as follows: primary cooling water flow of 120m 3 The secondary cooling specific water amount was 1.25l/kg.
In the comparative example, the soaking temperature in the heating furnace is 1084 ℃, and the tapping temperature is 945 ℃; the spinning temperature during the rolling process is 803 ℃.
Although the chemical compositions of the comparative example are within the ranges and the production method is proper, the value of the corrosion resistance index W is not properly controlled to be less than 0.26, and the corrosion resistance index W has certain corrosion resistance compared with 1022, but only reaches 1.4 times, and the corrosion resistance index W is insufficient.
Comparative example 2
The cold forging steel of the comparative example comprises the following chemical components in percentage by weight: 0.14% of C, 0.53% of Si, 0.77% of Mn, 0.026% of Alt, 0.015% of La, 0.015% of Nd, 0.014% of Y, 0.012% of P, 0.001% of S, and the balance of Fe and other unavoidable impurities.
The cold heading steel of this comparative example had a corrosion resistance index W of 0.34 and a molten steel fluidity index L of 0.048.
The production method of the cold heading steel comprises the following production steps: molten iron pretreatment → molten steel smelting → LF furnace refining → square billet continuous casting → square billet heating → wire rod rolling → stelmor cooling line cooling → finished product of wire rod of phi 5.5-30 mm. Wherein, the desulfurization target value S is less than or equal to 0.006 percent through pretreatment desulfurization. In the molten steel smelting step, the converter end point control C is 0.04 percent, the converter end point control P is 0.005 percent, and the white slag retention time is 18 minutes.
Adding La wires, ce wires and Yb wires into the crystallizer to adjust the contents of La, ce and Yb to a target range, and simultaneously adopting electromagnetic stirring and argon protection casting in the whole process. In this embodiment, strong cooling and enlargement are adoptedThe cooling solidification coefficient shortens the solidification time, improves production efficiency, and key parameters are as follows: primary cooling water flow of 121m 3 The secondary cooling specific water amount was 1.25l/kg.
The chemical components of the comparative example are in the required range, but the fluidity index L of the molten steel is too high, so that the nodulation occurs in the continuous casting process, the casting is stopped, and the further production cannot be realized.
Comparative example 3
The cold forging steel of the comparative example comprises the following chemical components in percentage by weight: 0.21% of C, 0.28% of Si, 0.93% of Mn, 0.028% of Alt, 0.013% of P, 0.002% of S and the balance of Fe and other inevitable impurities.
The production method of the cold heading steel comprises the following production steps: molten iron pretreatment → molten steel smelting → LF furnace refining → square billet continuous casting → square billet heating → wire rod rolling → stelmor cooling line cooling → wire rod finished product of phi 5.5-30 mm. Wherein, the desulfurization target value S is less than or equal to 0.006 percent through pretreatment desulfurization. In the smelting step of molten steel, the converter end point is controlled to be 0.04 percent C, 0.004 percent P and 17 minutes of white slag retention time.
Adding La wire, ce wire and Yb wire into the crystallizer to adjust the La, ce and Yb content to the target range, and simultaneously adopting electromagnetic stirring and argon protection casting in the whole process. In this embodiment, the forced cooling is adopted, the cooling solidification coefficient is increased, the solidification time is shortened, the production efficiency is improved, and the key parameters are as follows: primary cooling water flow of 119m 3 The secondary cooling specific water amount was 1.25l/kg.
In the comparative example, the soaking temperature in the heating furnace is 1088 ℃, and the tapping temperature is 967 ℃; the spinning temperature in the rolling process is 813 ℃.
The comparative example is 1022 grade 6.8 cold heading steel for fasteners, which has excellent mechanical properties but no corrosion resistance.
The examples described herein are merely illustrative of the preferred embodiments of the present invention and do not limit the spirit and scope of the invention, and various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the design concept of the present invention should fall within the protection scope of the present invention.

Claims (6)

1. The 6.8-grade corrosion-resistant cold forging steel is characterized in that: comprises the following chemical components in percentage by weight: 0.10 to 0.20 percent of C, 0.40 to 0.60 percent of Si, 0.60 to 0.80 percent of Mn, 0.020 to 0.030 percent of Alt, 0.008 to 0.015 percent of La, 0.008 to 0.015 percent of Nd, 0.010 to 0.020 percent of Y, less than or equal to 0.015 percent of P, less than or equal to 0.015 percent of S, and the balance of Fe and other inevitable impurities; the corrosion resistance index W of the 6.8-grade corrosion-resistant cold forging steel is more than or equal to 0.26, the W value unit is wt%, and W =0.3Si +3.6La +4.5Nd +3.9Y; the molten steel fluidity index L of the 6.8-grade corrosion-resistant cold forging steel is less than or equal to 0.045, the L value unit is wt%, and L =1.12Nd +0.95Y +1.20La.
2. The production method of the grade 6.8 corrosion-resistant cold heading steel according to claim 1, characterized by comprising the following steps: comprises the following production steps: molten iron pretreatment → molten steel smelting → LF furnace refining → square billet continuous casting → square billet heating → wire rod rolling → stelmor cooling line cooling → finished product, wherein in the continuous casting step, la line, nd line and Nd line are added in the crystallizer to adjust the La, nd and Y contents to the target range, and meanwhile, electromagnetic stirring and whole-process argon protection casting are adopted, and the flow of primary cooling water is 100m 3 /h～120m 3 The water amount of the secondary cooling is 1.0-1.2 l/kg; the metallographic structure of the finished cold heading steel wire rod is ferrite and pearlite, the mechanical property Rm is more than or equal to 520MPa, A is more than or equal to 38 percent, Z is more than or equal to 70 percent, and one fifth of the cold heading is qualified.
3. The production method of the grade 6.8 corrosion-resistant cold heading steel according to claim 2, characterized by comprising the following steps: and (2) putting the billet obtained after the continuous casting into a heating furnace for heating treatment, wherein the soaking temperature in the heating furnace is controlled within the range of 1000-1100 ℃, the tapping temperature is controlled within the range of 900-1000 ℃, the billet discharged from the heating furnace is subjected to rolling treatment by a high-speed wire rod rolling mill, and the spinning temperature in the rolling process is controlled within the range of 780-830 ℃.
4. The production method of the grade 6.8 corrosion-resistant cold heading steel according to claim 2, characterized by comprising the following steps: in the LF furnace refining step, bottom blowing argon is performed on the steel ladle in the whole process, premelted refining slag and lime are added for slagging, the white slag holding time is more than or equal to 15 minutes, and according to the composition analysis result before entering the LF furnace, alloy is added in the early stage and the middle stage of refining to adjust the contents of Si and Mn to a target range.
5. The production method of grade 6.8 corrosion-resistant cold heading steel according to claim 4, wherein: in the step of smelting molten steel, the converter end point is controlled to have C less than or equal to 0.04 percent and P less than or equal to 0.006 percent; and (3) slag stopping and tapping, wherein refining slag and lime are added when 1/5 molten steel is tapped, deoxidizing agent and alloy are added when 1/3 molten steel is tapped, aluminum cakes are added when 3/4 molten steel is tapped, and a proper amount of aluminum particles are uniformly thrown to the steel slag surface according to the slag amount after tapping.
6. The production method of grade 6.8 corrosion-resistant cold heading steel according to claim 5, wherein the production method comprises the following steps: compared with the same grade of cold forging steel 1022, naHSO 3 The relative corrosion rate of the weekly soaking test is less than or equal to 40 percent.
CN202111259371.8A 2021-10-28 2021-10-28 6.8-grade corrosion-resistant cold forging steel and production method thereof Active CN114086061B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202111259371.8A CN114086061B (en) 2021-10-28 2021-10-28 6.8-grade corrosion-resistant cold forging steel and production method thereof

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202111259371.8A CN114086061B (en) 2021-10-28 2021-10-28 6.8-grade corrosion-resistant cold forging steel and production method thereof

Publications (2)

Publication Number Publication Date
CN114086061A CN114086061A (en) 2022-02-25
CN114086061B true CN114086061B (en) 2023-03-03

Family

ID=80298248

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202111259371.8A Active CN114086061B (en) 2021-10-28 2021-10-28 6.8-grade corrosion-resistant cold forging steel and production method thereof

Country Status (1)

Country Link
CN (1) CN114086061B (en)

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1410582A (en) * 2002-11-29 2003-04-16 莱芜钢铁集团有限公司 Rare earth series easy cutting steel
CN1456699A (en) * 2003-06-02 2003-11-19 北京科技大学 Calcium-rare earth-tin series composite easily machined steel
CN102449177A (en) * 2009-05-29 2012-05-09 住友电气工业株式会社 Linear object, bolt, nut and washer each comprising magnesium alloy
CN103710609A (en) * 2013-12-12 2014-04-09 山西新泰钢铁有限公司 High-quality high-strength cold heading steel and production method thereof
JP2016222970A (en) * 2015-05-29 2016-12-28 新日鐵住金株式会社 Superclean steel and method of refining the same
CN110923545A (en) * 2019-12-09 2020-03-27 马鞍山钢铁股份有限公司 High-weather-resistance cold forging steel for 12.9-grade fastener and production method thereof
CN110923546A (en) * 2019-12-09 2020-03-27 马鞍山钢铁股份有限公司 High-weather-resistance cold forging steel for 10.9-grade fastener and production method thereof
CN112813346A (en) * 2020-12-29 2021-05-18 河钢股份有限公司 Cold heading steel suitable for 6.8 and 8.8-grade weather-resistant fasteners and production method thereof

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1410582A (en) * 2002-11-29 2003-04-16 莱芜钢铁集团有限公司 Rare earth series easy cutting steel
CN1456699A (en) * 2003-06-02 2003-11-19 北京科技大学 Calcium-rare earth-tin series composite easily machined steel
CN102449177A (en) * 2009-05-29 2012-05-09 住友电气工业株式会社 Linear object, bolt, nut and washer each comprising magnesium alloy
CN103710609A (en) * 2013-12-12 2014-04-09 山西新泰钢铁有限公司 High-quality high-strength cold heading steel and production method thereof
JP2016222970A (en) * 2015-05-29 2016-12-28 新日鐵住金株式会社 Superclean steel and method of refining the same
CN110923545A (en) * 2019-12-09 2020-03-27 马鞍山钢铁股份有限公司 High-weather-resistance cold forging steel for 12.9-grade fastener and production method thereof
CN110923546A (en) * 2019-12-09 2020-03-27 马鞍山钢铁股份有限公司 High-weather-resistance cold forging steel for 10.9-grade fastener and production method thereof
CN112813346A (en) * 2020-12-29 2021-05-18 河钢股份有限公司 Cold heading steel suitable for 6.8 and 8.8-grade weather-resistant fasteners and production method thereof

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
控轧控冷对低碳铆螺钢力学性能的影响;李壮等;《东北大学学报(自然科学版)》;20080415(第04期);第525-528页 *

Also Published As

Publication number Publication date
CN114086061A (en) 2022-02-25

Similar Documents

Publication Publication Date Title
CN110923546B (en) High-weather-resistance cold forging steel for 10.9-grade fastener and production method thereof
CN110923545B (en) High-weather-resistance cold forging steel for 12.9-grade fastener and production method thereof
CN100422373C (en) Air corrosion resisting high strength low alloy metal and its production process
CN109957707B (en) Weather-resistant cold-heading steel wire rod for 1000 MPa-level fastener and production method thereof
CN107419191A (en) Ultra-thin weathering steel and its production method
CN110791715A (en) Niobium-titanium-containing atmospheric corrosion-resistant 14.9-grade high-strength bolt steel and production method thereof
CN111041356B (en) Niobium-containing atmospheric corrosion-resistant 14.9-grade high-strength bolt steel and production method thereof
CN102719749B (en) Steel for railway axle and production process for steel
CN105624562B (en) Steel for ultra-high-strength sucker rod and production method thereof
CN111363976B (en) Microalloyed steel with long service life, high strength and toughness for high-speed rail plate spring and production process thereof
CN110938732A (en) Titanium-containing atmospheric corrosion-resistant 14.9-grade high-strength bolt steel and production method thereof
CN112813346A (en) Cold heading steel suitable for 6.8 and 8.8-grade weather-resistant fasteners and production method thereof
CN109957728B (en) Weather-resistant cold heading steel wire rod for 800 MPa-level fastener and production method thereof
CN111206190B (en) Non-quenched and tempered cold heading steel for weather-resistant fastener, weather-resistant fastener and production methods of non-quenched and tempered cold heading steel and weather-resistant fastener
CN114836686A (en) HRB600E normal speed hot rolled ribbed steel bar with yield ratio more than 1.26
CN114058974B (en) 15.9-grade corrosion-resistant high-strength bolt steel and production method and heat treatment method thereof
CN114672605A (en) Corrosion-resistant steel bar mechanical connection sleeve, wire rod and production method of wire rod
CN114058956B (en) 4.8-grade corrosion-resistant cold forging steel and production method thereof
CN114086061B (en) 6.8-grade corrosion-resistant cold forging steel and production method thereof
CN107236906B (en) Corrosion-resistant conduit and its production method
CN116065083A (en) Smelting method of thick high-strength weather-proof anti-seismic H-shaped steel
CN115404399B (en) Homogeneous high-strength durable bolt steel and preparation method thereof
CN112111690B (en) Thin-specification high-strength container plate and preparation method thereof
CN114752847B (en) Annealing-free high-strength cold forging steel and manufacturing method thereof
CN115466905A (en) Non-quenched and tempered steel with good corrosion resistance for 10.9-grade large-size wind power bolt and production method thereof

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant