CN105624580A - Duplex stainless steel wire and preparation method thereof - Google Patents

Abstract

The present invention aims at the problem that the steel wire alloy used in the tension compensation device for the catenary of electrified railways contains too much manganese, which is not conducive to the improvement of corrosion resistance, and the total amount of alloy elements is low, so the strength of the steel wire is difficult to guarantee. A duplex stainless steel wire, the chemical composition of which is calculated by mass percentage: C: 0.008-0.016%, Cr: 20-28%, Ni: 3-8%, Mo: 1-6%, Mn: 0.1-1%, Si: 0.1-1%, Cu: 0.1-0.6%, N: 0.05-0.5%, Ce: 0.03-0.2%, B: 0.001-0.005%, P≤0.03%, S≤0.01%, O≤0.01%, Balance: Fe and unavoidable impurities; the preparation steps are: medium frequency induction melting - electroslag remelting - hot rolling - wire drawing, solid solution - surface pickling and cleaning - cold drawing; the steel wire obtained in this way has high resistance Tensile strength, excellent corrosion resistance and excellent fatigue resistance. Through process design and implementation, the duplex stainless steel wire can meet the performance requirements of the tension compensation rope, and solve the technical problem of the duplex stainless steel wire being difficult to form by cold drawing.

Description

A kind of duplex stainless steel wire and its preparation method

technical field

The invention relates to the technical field of metal materials, in particular to a duplex stainless steel wire and a preparation method thereof.

Background technique

The safety and reliability of the catenary system is an important guarantee for the safe and reliable operation of electrified railways. The tension compensation rope with superior performance plays an important role in supporting the safe and reliable operation of the catenary system. The tension compensation rope has been exposed above the railway for many years and is subject to pollution. , corrosion and long-term tensile stress, once the tension compensation rope fails and breaks, it will directly affect the working efficiency of the contact line and catenary cable, and then affect the normal operation of the electric locomotive. Duplex stainless steel wire with excellent comprehensive performance is used as raw material for steel wire rope preparation.

Duplex stainless steel with austenitic + ferritic structure has the characteristics of both austenitic stainless steel and ferritic stainless steel, and has been widely used because of its excellent corrosion resistance and toughness. Since the hardening rate of the austenite phase is higher than that of the ferrite when the duplex stainless steel wire is drawn, a strength difference occurs between the two phases, that is, a high-strength austenite phase and a low-strength ferrite phase are formed. The dual-phase fiber structure of the phase makes the duplex stainless steel wire have a strong and tough fit. Compared with SUS304 steel wire, duplex stainless steel wire has a higher fatigue life, which is related to the formation of fibrous structure after drawing, and the duplex fibrous structure prevents the expansion of fatigue cracks; , hindering the crack propagation. Therefore, duplex stainless steel has very good comprehensive performance.

Domestic patents on duplex stainless steel are mainly concentrated in the fields of smelting and molding preparation. Patents on duplex stainless steel wire, such as: a method for manufacturing duplex stainless steel braided hose wire, authorized publication number: CN103103457B, however, the patented alloy contains If the manganese content is too high, it is not conducive to the improvement of corrosion resistance; and the total amount of alloying elements is too low, so it is difficult to guarantee the strength of the steel wire.

Contents of the invention

The present invention provides a duplex stainless steel wire for the steel wire rope used for the tension compensation device of the electrified railway catenary. Through composition design, the steel wire obtained is expected to have high tensile strength, excellent corrosion resistance and excellent fatigue resistance. Through process design and implementation, the duplex stainless steel wire can meet the performance requirements of the tension compensation rope, and solve the technical problem that the duplex stainless steel wire is difficult to form by cold drawing.

The technical scheme that technical problem of the present invention adopts is:

A kind of duplex stainless steel wire, its chemical composition is as follows by mass percentage:

C: 0.008-0.016%, Cr: 20-28%, Ni: 3-8%, Mo: 1-6%, Mn: 0.1-1%, Si: 0.1-1%, Cu: 0.1-0.6%, N : 0.05-0.5%, Ce: 0.03-0.2%, B: 0.001-0.005%, P≤0.03%, S≤0.01%, O≤0.01%, balance: Fe and unavoidable impurities.

The composition of the alloy of the present invention should satisfy that the Ni equivalent: Cr equivalent ratio is ≥ 0.28, and the Ni equivalent is ≤ 16, the optimal ratio of elements is carried out, and the content of ferrite in the duplex stainless steel is guaranteed by optimizing and limiting the elements Control within the preferred range of 40-45%, wherein: Ni equivalent = Ni + 30C + 25N + 0.5Mn + 0.25Cu + 40B, Cr equivalent = Cr + 2Si + 1.5Mo.

Preferably, the chemical composition of the duplex stainless steel wire is as follows by mass percentage:

C: 0.010-0.013%, Cr: 22-26%, Ni: 5-7%, Mo: 2-5%, Mn: 0.2-0.5%, Si: 0.2-0.5%, Cu: 0.1-0.3%, N : 0.1-0.3%, Ce: 0.04-0.08%, B: 0.002-0.004%, balance: Fe and unavoidable impurities.

C is the forming element of austenite, which can improve the strength of steel wire, but too high C content is easy to produce various carbides, which affects the processing technology of steel, especially the cold drawing performance. In order to control the formation of carbides, C The content of 0.008-0.016%, preferably 0.010-0.013%.

Si is an effective deoxidizing element, but if the Si content is too high, it will show a tendency to reduce the corrosion resistance and formability. Therefore, the Si content in the steel is 0.5% or less, and there is no lower limit for the Si content. It is particularly limited, but if it is less than 0.01%, deoxidation may be insufficient. The content of Si is 0.1-1%, preferably 0.2-0.5%.

Mn is an effective element for stabilizing the austenite phase. It can play a role in desulfurization and deoxidation in steel smelting. When the Mn content is below 2.0%, the higher the Mn content, the more stable the austenite phase, but too high content Mn will lead to a decrease in corrosion resistance; therefore, the content of Mn is in the range of 0.1-1%, preferably 0.2-0.5%.

P impurity elements, in order to avoid the higher P content from affecting the plasticity and toughness of the steel, the P content in the steel should be less than 0.03%, and the lower the P content, the better.

S is the most harmful impurity, so the lower the S content, the better. According to the types of coexisting elements in the steel, the content of the above elements and the content of S, S in the steel is basically Mn sulfide, Cr sulfide , Fe sulfide and other metal inclusions are precipitated, and the inclusions all play a role as the starting point of corrosion. In the steel of the present invention, the content of S is controlled below 0.01%, and the content of S is preferably 0.005%. below, and the lower the better.

Cr is the most basic alloying element in stainless steel. Its main function is to improve the corrosion resistance of steel. In the oxidizing medium, a layer of firm and dense chromium oxide is formed on the surface of the steel to protect the steel. As a ferrite stabilizer, chromium is also the main additive used to create a proper phase balance between the austenite phase and the ferrite phase, and is one of the main constituent elements of the passivation film. Therefore, in terms of ensuring corrosion resistance It is a relatively important element. If the content of Cr is too small, the corrosion resistance will decrease. Therefore, the content of Cr should be 20-28%. Preferably 23-26%.

Ni is a forming element of austenite. Nickel can increase the strength of steel while maintaining good plasticity and toughness. However, if the content of Ni is high, the manufacturing cost will be increased. In order to have good ductility and stable dual-phase structure, The content of Ni is 3-8%, preferably 5-7%.

As an element forming austenite, N is effective in adjusting the balance of austenite phase. In addition, N also helps to improve corrosion resistance and can replace the role of nickel in steel. However, if N is excessive, there will be Nitrides are produced to deteriorate the workability, so the N content is made 0.01-0.5%, preferably 0.1-0.3%.

Mo is a forming element of ferrite and is an alloy component that improves corrosion resistance, especially pitting corrosion resistance in duplex stainless steel. Molybdenum can also improve the strength of steel, but high molybdenum content increases the tendency of σ phase precipitation. At the same time, high molybdenum content will also increase the difficulty of cold working, therefore, the Mo content is 1-6%, preferably 2-5%.

Cu is an austenite stabilizer used to improve corrosion resistance. When used together with molybdenum, it can significantly increase corrosion resistance in acidic environments. Copper also causes displacement type solid solution hardening, thereby improving tensile strength and Yield strength, and reduce the tendency of σ phase precipitation, but when the copper content is too high, it is easy to produce brittle phase; therefore, the Cu content is 0.1-0.6%, preferably 0.1-0.3%.

O impurity elements, oxygen elements have adverse effects on hot ductility, the presence of oxide inclusions can reduce the corrosion resistance of steel, high oxygen content also reduces impact toughness; the oxygen content must be strictly controlled, high oxygen content Also reduces the toughness of the steel; thus, the O content is less than 0.01%, preferably less than 0.005%.

Ce is an austenite forming element that can refine the structure, purify molten steel, have strong desulfurization and deoxidation capabilities, improve the toughness, plasticity and anisotropy of steel, and improve the processability of steel, but high content of cerium , It is easy to produce large spherical oxides, which will affect the corrosion performance and impact toughness of steel. Therefore, the Ce content is 0.03-0.2%, preferably 0.06-0.12%.

Trace boron element B can refine grains and improve intergranular corrosion resistance. The addition of trace boron can also improve the thermoplasticity of valve alloy and improve hot workability, but excessive B element will easily cause brittleness and produce abnormal Metal inclusions, therefore, the B content is 0.001-0.005%, preferably 0.002-0.003%.

Due to the existence of the duplex structure, the duplex stainless steel causes local uneven deformation and affects the deformation behavior. Compared with the austenitic stainless steel, the cold work hardening effect of the duplex stainless steel is greater, especially in the initial stage of deformation, when the thick steel wire is cold-drawn Among them, the initial deformation resistance is relatively large, and the elongation is lower than that of austenitic stainless steel. Considering comprehensively, the ferrite phase in the steel accounts for 35-50% of the two-phase structure, and the amount of ferrite is preferably 40-45%. While ensuring the comprehensive performance of the duplex stainless steel, the cold-drawn machinability of the steel wire is improved as much as possible, so as to improve the cold-drawn processing efficiency and yield of the steel wire.

A method for preparing duplex stainless steel wire, the preparation steps of which are: medium frequency induction smelting-electroslag remelting-hot rolling-wire drawing, solid solution-surface pickling and cleaning-cold drawing;

Among them, during the intermediate frequency induction smelting process, the raw materials are heated and dried to keep the raw materials dry and pure, and reduce the gas content in the steel. In order to ensure the purity of duplex stainless steel, the selected raw materials are metals with high purity, and the intermediate alloys are For ultra-low carbon alloys, the order of adding elements during medium-frequency induction melting is as follows: pure iron, nickel plate and slag are put into the induction furnace. Stand still, add electrolytic copper and cerium-iron intermediate alloy, test the nitrogen content in the molten steel, according to the nitrogen content value, after adding manganese nitride, according to the manganese content in the molten steel, add electrolytic manganese to supplement the manganese element, the steel The boron element in the slag is obtained through the borax in the slag, and the boron element in the steel is calculated as 0.3% of the borax content;

The slag material is lime, fluorite, borax and a small amount of calcium silicate. The mass ratio of lime to fluorite is 3:1. Lime is added as 2kg per 100Kg of molten steel. Calcium silicon is added as a deoxidizer. 1-5% of the total mass, just keep the white residue;

After medium-frequency induction melting, the molten steel is poured into ingots for electroslag remelting to further purify the ingots and reduce steel impurities. After electroslag remelting, the ingots are hot-rolled into thick steel wires with a diameter of 5 mm for wire drawing;

In the wire drawing process, when the total diameter reduction reaches 70-80%, solution treatment must be carried out, and the intermediate solution temperature is 1060°C, so as to reduce the hardness of the steel wire as much as possible, increase the elongation, and facilitate cold drawing deformation. The melting temperature is 1000°C, the purpose is to control the content of ferrite phase to 40-45%. When drawing the steel wire, considering the factor that the initial deformation stress of the duplex stainless steel is large, the diameter reduction coefficient is appropriately reduced to avoid broken ends, For broken wires, after the first two steps of drawing, the steel wires are reduced in diameter with a constant reduction coefficient. The diameter reduction coefficient of thick wire drawing is 1.1, and the diameter reduction coefficient of thin wire is 1.07.

(1) The first solid solution treatment

Hot-rolled thick steel wire with a diameter of 5mm, after solution treatment at 1060℃ for 0.5h, quickly water-cooled after coming out of the furnace, pickled and dried, the diameter of the first wire drawing was reduced by a coefficient of 1.06, and the diameter was 4.7mm, and the second The diameter of the first wire drawing is reduced by a coefficient of 1.09, and the diameter is 4.3mm. The diameter of the third wire drawing is reduced by a coefficient of 1.1, and the diameter is 3.9mm. The diameter of the fourth and subsequent wire drawing is reduced by a coefficient of 1.1 until the diameter is 2.4mm. The total diameter reduction is 70-80%.

(2) Second solid solution treatment

Steel wire with a diameter of 2.4mm, solid solution treatment at 1060°C for 0.4h, rapid water cooling after being released from the furnace, pickling and drying, the diameter of the first wire drawing is reduced by a factor of 1.06, the diameter is 2.26mm, and the diameter of the second wire drawing is 1.09 The diameter is reduced by a factor of 2.1mm, the third drawing is reduced by a factor of 1.1, and the diameter is 1.9mm, the fourth and subsequent drawing are reduced by a factor of 1.1 until the diameter is 1.1mm, and the total diameter reduction is in 70-80%.

(3) The third solid solution treatment

Steel wire with a diameter of 1.1mm, solid solution treatment at 1000℃ for 0.3h, rapid water cooling after being released from the furnace, pickling and drying, the diameter of the first wire drawing is reduced by a factor of 1.03, the diameter is 1.068mm, and the diameter of the second wire drawing is 1.05 The diameter is reduced by the coefficient, the diameter is 1.017mm, the third drawing is reduced by the coefficient of 1.07, and the diameter is 0.95mm, the fourth and subsequent drawing are all reduced by the coefficient of 1.07, until the diameter is 0.5mm.

The present invention has the following advantages and positive effects:

1. Through the design of the composition, according to the Ni equivalent: Cr equivalent ratio ≥ 0.28, and the Ni equivalent ≤ 16, the element optimization and ratio are carried out to ensure that the ferrite content in the duplex stainless steel is controlled within the preferred range of 40-45% , where: Ni equivalent = Ni+30C+25N+0.5Mn+0.25Cu+40B, Cr equivalent = Cr+2Si+1.5Mo, so that the duplex stainless steel wire with optimized ratio has excellent tensile strength and stress corrosion resistance , Anti-fatigue performance.

2. Duplex stainless steel is produced by medium frequency induction melting plus electroslag remelting process, which solves the composition control of small-scale production of duplex stainless steel. This process method is easy to implement and is more suitable for the manufacture of small batches of steel wire for steel wire rope.

3. Design wire drawing matching mold and intermediate heat treatment process, adjust and control the content ratio of α phase and γ phase in duplex stainless steel wire, solve the problem of high deformation resistance of duplex stainless steel wire and difficult cold drawing plastic forming, and greatly improve the duplex stainless steel wire. Silk yield.

detailed description

Embodiment one:

A duplex stainless steel wire whose chemical composition is calculated by mass percentage: C: 0.011%, Cr: 23%, Ni: 5.5%, Mo: 3%, Mn: 0.4%, Si: 0.4%, Cu: 0.2% , N: 0.15%, Ce: 0.05%, B: 0.003%, balance: Fe and unavoidable impurities.

The preparation method of the duplex stainless steel wire is: medium frequency induction smelting-electroslag remelting-hot rolling-wire drawing, solid solution-surface pickling and cleaning-cold drawing.

Among them, during the intermediate frequency induction smelting process, the raw materials are heated and dried to keep the raw materials dry and pure, and reduce the gas content in the steel. In order to ensure the purity of duplex stainless steel, the selected raw materials are metals with high purity, and the intermediate alloys are For ultra-low carbon alloys, the order of adding elements during medium-frequency induction melting is as follows: pure iron, nickel plate and slag are put into the induction furnace. Stand still, add electrolytic copper and cerium-iron intermediate alloy, test the nitrogen content in the molten steel, according to the nitrogen content value, after adding manganese nitride, according to the manganese content in the molten steel, add electrolytic manganese to supplement the manganese element, the steel The boron element in the slag is obtained through the borax in the slag, and the boron element in the steel is calculated as 0.3% of the borax content;

The slag material is lime, fluorite, borax and a small amount of calcium silicate. The mass ratio of lime to fluorite is 3:1. Lime is added as 2kg per 100Kg of molten steel. Calcium silicon is added as a deoxidizer. 1-5% of the total mass, just keep the white residue;

After medium-frequency induction melting, the molten steel is poured into ingots for electroslag remelting to further purify the ingots and reduce steel impurities. After electroslag remelting, the ingots are hot-rolled into thick steel wires with a diameter of 5 mm for wire drawing;

When the wire drawing process is carried out, when the total diameter reduction reaches 70-80%, solution treatment must be carried out. The specific operation process is as follows:

(1) The first solid solution treatment

Thick steel wire with a diameter of 5mm is hot-rolled, solution treated at 1060°C for 0.5h, quickly water-cooled after being released from the furnace, pickled and passivated with 20% nitric acid and 5% hydrofluoric acid, and then dried. The first wire drawing diameter The diameter is reduced according to the coefficient of 1.06, and the diameter is 4.7mm. The diameter of the second wire drawing is reduced according to the coefficient of 1.09, and the diameter is 4.3mm. The diameter of the third wire drawing is reduced according to the coefficient of 1.1, and the diameter is 3.9mm. The diameter of the wire drawing is reduced by a factor of 1.1 until the diameter is 2.4mm, and the total diameter reduction is 76.96%.

(2) Second solid solution treatment

Steel wire with a diameter of 2.4mm, solid solution treatment at 1060℃ for 0.4h, rapid water cooling after being out of the furnace, pickling passivation and drying after mixing 20% nitric acid and 5% hydrofluoric acid, the diameter of the first drawing wire is reduced by a factor of 1.06 Diameter, the diameter is 2.26mm, the diameter of the second wire drawing is reduced by a coefficient of 1.09, the diameter is 2.1mm, the diameter of the third wire drawing is reduced by a coefficient of 1.1, and the diameter is 1.9mm, the fourth and subsequent wire drawing are all according to a coefficient of 1.1 The diameter is reduced until the diameter is 1.1mm, and the total diameter reduction is 78.99%.

(3) The third solid solution treatment

Steel wire with a diameter of 1.1mm, solid solution treatment at 1000℃ for 0.3h, rapid water cooling after being released from the furnace, pickling and drying, the diameter of the first wire drawing is reduced by a factor of 1.03, the diameter is 1.068mm, and the diameter of the second wire drawing is 1.05 The diameter is reduced by a factor of 1.017mm. The third drawing is reduced by a factor of 1.07, and the diameter is 0.95mm. The fourth and subsequent drawing are all reduced by a factor of 1.07 until the diameter is 0.5mm. The total diameter reduction is 79.33%.

Embodiment two

A duplex stainless steel wire as in Example 1, the difference is that its chemical composition is calculated by mass percentage: C: 0.013%, Cr: 24%, Ni: 6.5%, Mo: 4.4%, Mn: 0.39 %, Si: 0.43%, Cu: 0.3%, N: 0.18%, Ce: 0.07%, B: 0.004%, balance: Fe and unavoidable impurities.

Embodiment Three

A duplex stainless steel wire as in Example 1, the difference is that its chemical composition is calculated by mass percentage: C: 0.010%, Cr: 22%, Ni: 5.2%, Mo: 2.4%, Mn: 0.36 %, Si: 0.35%, Cu: 0.18%, N: 0.12%, Ce: 0.04%, B: 0.002%, balance: Fe and unavoidable impurities.

Embodiment Four

A duplex stainless steel wire as in Example 1, the difference is that its chemical composition is calculated by mass percentage: C: 0.012%, Cr: 23%, Ni: 5.8%, Mo: 3.7%, Mn: 0.23 %, Si: 0.28%, Cu: 0.25%, N: 0.14%, Ce: 0.06%, B: 0.003%, balance: Fe and unavoidable impurities.

The duplex stainless steel wire obtained in the first, second, third and fourth examples of the present invention is mechanically tested, and a duplex stainless steel braided hose wire with the authorized publication number CN103103457B is used as a comparative example for mechanical testing. Test, the test results are as follows:

The description and application of the present invention here are illustrative, and are not intended to limit the scope of the present invention to the above-mentioned embodiments. Therefore, the present invention is not limited by this embodiment, and any technical solutions obtained by adopting equivalent replacement are included in this within the scope of invention protection.

Claims (5)

1. a dual-phase stainless steel wire, is characterized by, and its chemical composition is as follows by mass percentage:

C:0.008-0.016%, Cr:20-28%, Ni:3-8%, Mo:1-6%, Mn:0.1-1%, Si:0.1-1%, Cu:0.1-0.6%, N:0.05-0.5%, Ce:0.03-0.2%, B:0.001-0.005%, P��0.03%, S��0.01%, O��0.01%, surplus: Fe and inevitable impurity.

2. a kind of dual-phase stainless steel wire as claimed in claim 1, is characterized by, and its chemical composition is as follows by mass percentage:

C:0.010-0.013%, Cr:22-26%, Ni:5-7%, Mo:2-5%, Mn:0.2-0.5%, Si:0.2-0.5%, Cu:0.1-0.3%, N:0.1-0.3%, Ce:0.04-0.08%, B:0.002-0.004%, surplus: Fe and inevitable impurity.

3. a kind of dual-phase stainless steel wire as claimed in claim 1 or 2, is characterized by, and the composition of alloy is pressed, Ni equivalent: Cr equivalent ratio >=0.28 and Ni equivalent��16, carry out element proportioning, wherein, Ni equivalent=Ni+30C+25N+0.5Mn+0.25Cu+40B, Cr equivalent=Cr+2Si+1.5Mo.

4. a kind of dual-phase stainless steel wire as claimed in claim 1 or 2, is characterized by, and the ferritic phase in steel accounts for the 35-50% of two phase constitutions, and ferrite content is preferably 40-45%.

5. the preparation method of a kind of dual-phase stainless steel wire as claimed in claim 1 or 2, is characterized by, and its preparation process is: Medium frequency induction melting, and------wire drawing, solid solution--surface acid-washing is also cleaned--are cold drawn in hot rolling for esr;

Wherein, in Medium frequency induction fusion process, raw material is through heating, drying, keep raw material drying pure, reduce the gas content in steel, during Medium frequency induction melting, the addition sequence of each element is: pure iron, nickel plate puts into induction furnace together with slag material, after chemical conversion molten iron fusion, add ferrochrome master alloy, ferrosilicon, molybdenum-iron, leave standstill after fusing, add electrolytic copper and ferrocerium master alloy, nitrogen content in test molten steel, according to nitrogen content value, after adding nitrogenized manganese, according to the Fe content in molten steel, add electrolytic manganese to be supplemented by manganese element, boron in steel is obtained by the borax in slag material, boron acquisition rate in steel is by the 0.3% of borax amount,

Described slag material is lime, fluorite, borax and a small amount of silicon calcium, and the mass ratio of lime and fluorite is 3:1, and lime adds 2kg by every 100Kg molten steel, and silicon calcium adds as reductor, and the quality of silicon calcium accounts for the 1-5% of slag material total mass, keeps white slag just may be used;

Molten steel pouring into after Medium frequency induction melting base ingot and carries out esr, purify steel ingot further, reduce the impurity of steel, after esr, slab hot-rolling becomes diameter to be the heavy wire of 5mm, carries out wire drawing;

When carrying out drawing process, always subtracting footpath amount when reaching 70-80%, must carry out solution treatment, concrete operating process is:

(1) first solution treatment

The heavy wire of hot rolling diameter 5mm, through 1060 DEG C of �� 0.5h solution treatment, quick water-cooled after coming out of the stove, carry out pickling and dry, first wire drawing diameter is undertaken subtracting footpath by 1.06 coefficients, and diameter is 4.7mm, and second wire drawing diameter is undertaken subtracting footpath by 1.09 coefficients, diameter is 4.3mm, 3rd road wire drawing is undertaken subtracting footpath by 1.1 coefficients, and diameter is 3.9mm, and the 4th road and wire drawing below all are undertaken subtracting footpath by 1.1 coefficients, until 2.4mm diameter, always subtract footpath and measure at 70-80%;

(2) second solution treatment

Diameter 2.4mm steel wire, 1060 DEG C of �� 0.4h solution treatment, quick water-cooled after coming out of the stove, carry out pickling and dry, first wire drawing diameter is undertaken subtracting footpath by 1.06 coefficients, and diameter is 2.26mm, and second wire drawing diameter is undertaken subtracting footpath by 1.09 coefficients, diameter is 2.1mm, 3rd road wire drawing is undertaken subtracting footpath by 1.1 coefficients, and diameter is 1.9mm, and the 4th road and wire drawing below all are undertaken subtracting footpath by 1.1 coefficients, until 1.1mm diameter, always subtract footpath and measure at 70-80%;

(3) the 3rd road solution treatment

Diameter 1.1mm steel wire, 1000 DEG C of �� 0.3h solution treatment, after coming out of the stove, quick water-cooled, carries out pickling and dries, first wire drawing diameter is undertaken subtracting footpath by 1.03 coefficients, diameter is 1.068mm, and second wire drawing diameter is undertaken subtracting footpath by 1.05 coefficients, and diameter is 1.017mm, 3rd road wire drawing is undertaken subtracting footpath by 1.07 coefficients, diameter is 0.95mm, and the 4th road and wire drawing below all are undertaken subtracting footpath by 1.07 coefficients, until 0.5mm diameter.