CN112091473A

CN112091473A - Wire rod for Cr-Mo steel submerged arc welding wire and manufacturing method

Info

Publication number: CN112091473A
Application number: CN202011020546.5A
Authority: CN
Inventors: 陈海燕; 张奇毅; 张剑锋; 刘海; 何佳锋; 刘振伟
Original assignee: Jiangyin Xingcheng Alloy Material Co ltd
Current assignee: Jiangyin Xingcheng Alloy Material Co ltd
Priority date: 2020-09-25
Filing date: 2020-09-25
Publication date: 2020-12-18

Abstract

The invention relates to a wire rod for a Cr-Mo steel submerged arc welding wire and a manufacturing method thereof, wherein the wire rod comprises the following chemical components in percentage by mass: c: 0.10 to 0.20%, Si: 0.10 to 0.60%, Mn: 1.0-1.5%, Cr: 2.0-3.0%, Mo: 0.95-1.15%, V: 0.3 to 0.5%, Nb: 0.01-0.05%, Ni: 0.01-0.20%, Cu: 0.01-0.20%, and the balance of Fe and inevitable impurity elements. The wire produced by steel making, refining, continuous casting, controlled rolling and controlled cooling and annealing can be used for welding for manufacturing high-strength Cr and Mo steel, and the component design and the high purity requirement of the invention ensure that the welded metal has good temper brittleness resistance and better high-temperature durability.

Description

Wire rod for Cr-Mo steel submerged arc welding wire and manufacturing method

Technical Field

The invention belongs to the technical field of metallurgy, and particularly relates to a wire rod for a Cr-Mo steel submerged arc welding wire and a manufacturing method thereof.

Background

The hot wall hydrogenation reactor is the key equipment for oil refining and coal liquefaction engineering. The reactor works at a certain high temperature and high pressure, and petroleum, residual oil, heavy oil and the like are cracked, refined and purified through hydrogenation catalysis and cracking. The complete manufacturing technology of the hot wall hydrogenation reactor in China is mature day by day, and the localization of main materials and internal components is realized. However, the narrow-gap submerged arc welding and the inner wall surfacing welding material of the cylinder mainly depend on the inlet.

The key technical requirements are as follows: the working temperature of the pressure vessel is 320-550 ℃, which is the tempering and embrittlement temperature range of the metal material of the shell. In order to prevent tempering embrittlement under long-term high-temperature and high-pressure working conditions, the tempering embrittlement sensitivity coefficients J and X of the material are strictly controlled, so that the chemical composition of the material is required to reach extremely low P, S content, trace control of 'five harmful elements', and extremely low residual element content and gas content in steel; in order to realize excellent structure performance and good weldability of the material, main alloy elements are ensured to reach specific indexes, and the contents of harmful elements such as Ni, Cu and the like and [ H ] and [ O ] in the steel are strictly limited. Due to the strict technical index limit, the metallurgical manufacturing difficulty of the welding materials is high, and the welding materials mainly depend on import at present.

The welding metal forming the invention disclosed in the patent publication No. CN 101249592B is mainly obtained by a shielded arc welding rod and a welding slag generating agent coated on the surface of the welding rod, and the welding metal finally obtained in the invention is mainly obtained by adding a welding flux to an automatic submerged arc welding wire, and the welding mode is different, the invention mainly explains a wire rod for producing the automatic submerged arc welding wire and a manufacturing method of the wire rod, and has essential difference with the patent No. CN 101249592B.

Among the inevitable impurity components of patent No. CN 101249592B, Cu and Ni are effective elements for securing toughness of the weld metal, but have components for promoting temper embrittlement on the other hand. Therefore, the contents of Cu and Ni in the inevitable impurity elements in the weld metal are limited to less than 0.05 mass%, and more preferably less than 0.03 mass%, respectively.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a wire rod for a Cr-Mo steel submerged arc welding wire and a manufacturing method thereof aiming at the prior art, wherein the tempering brittleness resistance of welding metal is improved by controlling X and J coefficients influencing the tempering brittleness of the welding metal in the wire rod and adding a reasonable process, and the uniform spheroidized annealing structure is obtained after the wire rod is annealed.

The technical scheme adopted by the invention for solving the problems is as follows: a wire rod for a Cr-Mo steel submerged arc welding wire comprises the following chemical components in percentage by mass: c: 0.10 to 0.20%, Si: 0.10 to 0.60%, Mn: 1.0-1.5%, Cr: 2.0-3.0%, Mo: 0.95-1.15%, V: 0.3 to 0.5%, Nb: 0.01-0.05%, Ni: 0.01-0.20%, Cu: 0.01-0.20%, and the balance of Fe and inevitable impurity elements.

Among the above inevitable impurities, P: less than or equal to 0.006 percent, S: less than or equal to 0.003 percent, less than or equal to 0.002 percent of Sb, less than or equal to 0.003 percent of Sn and less than or equal to 0.005 percent of As. And the tempering embrittlement sensitivity coefficient X is not more than 12, X is (10P +5Sb +4Sn + As) × 10, calculated by the following formula²Wherein P, Sb, Sn and As represent the mass percent of the elements in the steel. Residual elements such As P, Sb, Sn and As in the steel are easy to segregate in grain boundaries, the influence of the element P is the largest, the elements cause the brittle transition temperature to rise at the tempering temperature, and the low-temperature impact toughness of the weld metal is reduced. The temper embrittlement resistance of the weld metal can be improved by reducing temper embrittlement sensitive elements in the steel.

In addition, P among the above residual elements is most likely to segregate at grain boundaries, and the presence of Mn and Si in steel promotes segregation of P element to increase embrittlement, so that the tempering embrittlement sensitivity coefficient J of the following formula is required to be not more than 120, J ═ (Si + Mn) × (P + Sn) × 10 ×, where J is calculated by the following formula⁴Wherein Si, Mn, P and Sn represent the mass percent of the above elements in the steel.

The action mechanism of the chemical elements is as follows:

c is a main strengthening element of the weld metal, the tensile strength and the yield strength of the weld metal are improved along with the increase of the carbon content, but the low-temperature impact toughness is reduced along with the increase of the carbon content, in order to ensure that the weld metal has good impact toughness, the C is controlled to be 0.10-0.20%, excessive C is added to precipitate excessive carbides to influence the tempering brittleness, and researches show that a certain amount of carbon content can play a role in improving the high-temperature creep property, so that the more excellent C is controlled to be 0.10-0.15%.

Si is used as an alloy element to play a role in solid solution strengthening in steel, the strength of the steel is improved, meanwhile, Si in a welding wire can also be used as a deoxidizing agent to deoxidize in the welding process, when more strongly acidic oxide SiO2 exists in submerged arc welding slag, the Si and FeO are easy to form a compound, the activity of FeO in the slag is reduced, FeO in liquid metal continuously diffuses into the slag, and the acidic slag is favorable for deoxidation; the toughness and the temper brittleness resistance of the welding material are improved, the Si of the invention is controlled to be 0.10-0.60%, but the over high Si causes the strength to be improved and the temper brittleness resistance to be reduced in the welding metal, so the Si of the invention is more preferably controlled to be 0.10-0.20%.

Mn in the Mn welding wire can be used as a deoxidizer to deoxidize in a welding process, and can be used as a solid solution strengthening element to improve the strength of weld metal, meanwhile, Mn can promote the acicular formation of the weld metal and improve the impact toughness of the weld metal, but Mn can obviously reduce the brittle transition temperature of the weld metal and reduce the temper-resistant brittleness, so that Mn in the Mn welding wire is controlled to be 1.0-1.5%, and more preferably Mn is controlled to be 1.2-1.3%.

The Cr can improve the strength and the hardness of the weld metal and play a role in precipitation strengthening, but if the Cr content is too high, reheat cracking tendency exists, the toughness of the weld metal is reduced, and the temper brittleness resistance of the material is reduced, wherein the Cr content is controlled to be 2.0-3.0%, and more preferably 2.40-2.50%

Mo and Cr can improve the strength and hardness of the weld metal together and play a role in precipitation strengthening, and Mo is matched with Mn% in the invention to promote the precipitation of acicular ferrite and improve the temper brittleness resistance. Mo is a refined crystal grain element, so that the crack resistance of a welding seam can be improved; however, too high Mo increases hardenability of the metal material, decreases toughness of the weld metal, and also tends to reheat cracking; in the present invention, Mo is controlled to be 0.95 to 1.15%, and more preferably 1.0 to 1.1%.

V can be precipitated and strengthened in CrMo steel; tiny and dispersed VC compounds are separated out in the subsequent heat treatment process, so that the crack resistance of the welding line can be improved; and meanwhile, the high-temperature durability of the welding metal is improved. The V content of the invention is controlled to be 0.3-0.5%, and more preferably 0.3-0.4%.

In steel, Nb tends to precipitate a fine Nb (C, N) compound at grain boundaries, to refine grains, and to improve the normal temperature and high temperature durability of weld metal, but if the Nb content is too high, a ferrite phase or other brittle phases are generated, and the toughness is lowered. The Nb content of the invention is controlled to be 0.01-0.05%, and the more preferable Nb content is controlled to be 0.01-0.03%. .

Ni can improve the strength of steel and maintain good plasticity and toughness, Ni can promote the precipitation of acicular ferrite and can improve the low-temperature toughness of materials in a low-temperature environment, but Ni can influence the temper brittleness of welding metals when being high, so that the addition of a small amount of Ni in the invention is 0.01-0.2%, and the addition of Ni in the invention is more preferably 0.06-0.15%, and can ensure the low-temperature toughness of the welding metals but not influence the temper brittleness.

Cu can improve the strength and toughness of the material to a certain extent, but has the defect that the hot brittleness is easily generated when the Cu exceeds 0.5 percent, so that the toughness of the welding metal can be effectively improved without influencing the temper brittleness by adding a small amount of Cu of 0.01 to 0.2 percent and more preferably 0.06 to 0.15 percent.

P is a harmful element, and increases the strength and hardness of steel, but causes a significant decrease in plasticity and impact toughness. Particularly, at low temperature, the wire material can obviously embrittle the steel, and P is easy to segregate at grain boundaries to promote the tempering embrittlement of the welding metal.

S is also a harmful element in steel, is easy to form a compound of S, generates hot brittleness in the hot working process of steel, and is easy to segregate at grain boundaries in weld metal to cause temper brittleness.

Sb antimony has a bad influence on the properties of steel, generally causes the strength of the steel to be reduced and the brittleness to be increased,

sn can greatly reduce the high-temperature mechanical properties of steel and alloy and is very harmful to the processing property of the steel.

As and P have similar influence on the performance of steel, arsenic can improve the tensile strength and yield point of steel and enhance the corrosion resistance and oxidation resistance, but when the content of arsenic is higher, the brittleness of steel is increased, the elongation, the reduction of area and the impact toughness are reduced, and the welding performance is influenced.

In addition, in order to improve the temper brittleness resistance of the welding metal, the inclusion of the welding wire steel wire rod is required to be controlled at the following level: A. b, C, D, the maximum levels of non-metallic inclusions are respectively less than or equal to 1.5 levels, the maximum level of DS is respectively less than or equal to 2.0 levels, and the sum of A + C is less than or equal to 1.5 levels, B + D is less than or equal to 1.5 levels, and the sum of A coarse + B coarse + C coarse + D coarse + DS is less than or equal to 4 levels. The tempering brittleness resistance of the finished welding metal is improved by controlling the high purity of the welding wire steel.

In order to improve the temper brittleness resistance of the welding metal, the inclusion of the welding wire steel wire rod is required to be 25mm according to the scanning of an electron microscope²And in the area, the inclusion index is less than or equal to 2.0, and the inclusion index is the area of the inclusion/the scanned area multiplied by a scanning electron microscope.

The invention also provides a manufacturing method for manufacturing the wire rod for the Cr-Mo steel submerged arc welding wire, which comprises the following specific production process flows: the method comprises the steps of KR molten iron pretreatment, converter smelting, LF and RH furnace refining, slab continuous casting, slab heating, rolling and annealing treatment which are sequentially carried out.

Wherein:

smelting molten steel conforming to the composition design of the invention, smelting the steel in a converter, wherein the converter is equipped with special molten iron for ensuring that harmless elements such As P, S, Sn, Sb, As and the like in the steel are low enough, smelting in 100% full molten iron, and adding a special desulfurizer into the molten iron through KR pretreatment, wherein the main component is CaO, and S% of the molten iron is reduced to be below 0.002%; in order to ensure that the P percent is low enough and reaches below the ideal 0.003 percent, the special P removing agent for the converter is added with CaO as the main component, and the steel ladle is subjected to slag skimming treatment after the converter taps, so that the P return in the refining process is prevented.

The refining furnace adopts high-performance special refining slag (the main components are CaO, SiO2 and Al2O3), the refining and smelting time is ensured to be more than or equal to 50min, the soft argon blowing time is ensured to be more than or equal to 50min, and Al is added into molten steel to fully deoxidize and remove impurities. And (3) carrying out RH vacuum degassing treatment on the molten steel, wherein the vacuum circulation time is more than 20min, the H is determined to be less than 2.0ppm after RH is finished, and the soft blowing time is ensured to be more than 15min after RH is finished, so that impurities are further removed, and the purity of the molten steel is ensured.

The continuous casting adopts a small square billet, the superheat degree of a tundish is controlled at 15-30 ℃, an electromagnetic stirring device is arranged, the homogeneity of a casting blank is ensured, the uniformity of the carbon segregation of a wire rod is good, the special low-carbon alloy steel crystallizer casting powder is adopted, the surface quality of the blank is effectively ensured, and the problems of surface crust and pits of the blank are solved.

The blank rolling selects a proper heating temperature, specifically, the temperature of a high-temperature section in a heating furnace before rolling is more than 1050 ℃, more preferably more than 1080 ℃, the total heating time is more than 120min, and the high-temperature time is more than 60min, so that the enough temperature and time diffusion of the casting blank is ensured, and the important function of the diffusion and homogenization of C, Mn, Cr and Mo elements in the casting blank is played. And continuously rolling by 36 rolling mills after descaling by high pressure water, wherein the initial rolling temperature is 1000-1100 ℃, the final rolling temperature is controlled to be above 960 ℃, the rolling speed is set to be 95-120 m/s, the spinning temperature is 900-960 ℃, considering that the austenitizing temperature of the steel is higher, the spinning temperature is more preferably above 930 ℃, the wire rod immediately enters a heat-preserving cover for slow cooling after spinning, the retention time of the wire rod in the heat-preserving cover is fully prolonged, the speed of a roller way is set to be 0.15m/s at a constant speed, the structure of the slow cooling cover of the wire rod is bainite + martensite, the temperature of the wire rod in the heat-preserving cover is reduced to be below 500 ℃, the wire rod begins to be transformed from austenite to bainite and martensite, the retention time of the wire rod in the heat-preserving cover is more than 10min, and the structure of the slow cooling.

In order to ensure that the hardness of the finished wire rod is below 200HBW, the hot rolled wire rod needs to be annealed, a hood-type annealing furnace is adopted for annealing, surface pickling is carried out to remove oxide skin before the wire rod is annealed, H2 gas protection is adopted to prevent full decarburization in the annealing furnace, the annealing temperature is 720 and 760 ℃, the temperature is kept for more than 4 hours, the hardness of the wire rod can be ensured to be below 200HBW, and the requirement of the subsequent drawing of the welding wire steel is met.

The wire rod for the Cr-Mo steel submerged arc welding wire produced by the method has good component uniformity, extremely low P, S residual elements and high purity, and can meet the requirements of inclusions of coarse A, coarse B, coarse C, coarse D and DS which are not more than 4 grade. In addition, after the blank is rolled and annealed by the process, the wire rod is a uniform carbide spheroidized structure, the requirement that the hardness of the wire rod is less than or equal to 200HBW can be met, and the smooth drawing of a submerged arc welding wire produced by a user in the next process can be ensured.

Compared with the prior art, the invention has the advantages that:

1. according to the invention, the X coefficient and the J coefficient which influence the tempering brittleness of the weld metal in the wire rod are strictly controlled, the X coefficient is required to be below 12, the J coefficient is required to be below 120, the segregation of impurity elements is substantially reduced, the embrittlement of the material is reduced, the tempering brittleness of the weld metal can be obviously improved, the influence of Cu and Ni on the tempering brittleness is weakened, and the toughness of the weld metal can be effectively improved by adding a small amount of Cu and Ni.

2. According to the invention, the inclusion grade of the hot-rolled wire rod produced by the high-purity steel smelting method is 2.0 grade of A coarse grade, B coarse grade, C coarse grade, D coarse grade and DS grade, the purity of the hot-rolled wire rod is higher, and the high-temperature tempering brittleness of weld metal is ensured.

3. The Cr and Mo steel submerged arc welding wire has high austenitizing temperature, wire rod rolling preferably adopts wire spinning at the temperature of over 930 ℃, and the key point is to ensure that the final rolling temperature is over 960 ℃, and a uniform spheroidizing annealing structure is obtained after wire rod annealing.

Drawings

FIG. 1 is a photograph of the microstructure of a wire rod of example 1 of the present invention.

FIG. 2 is a photograph of the microstructure of a wire rod of example 2 of the present invention.

FIG. 3 is an illustration of the temper embrittlement resistance of the weld metal of the present invention.

Detailed Description

The present invention will be described in further detail with reference to examples.

Smelting 150 tons of molten steel with two different chemical compositions:

example 1:

C：0.13％，Si：0.18％，Mn：1.2％，P：0.003，S：0.002％，Cr：2.4％，Mo：1.05％，V：0.38％，Nb：0.015％，Ni：0.08％，Cu：0.08％，Sb：0.0012％，Sn：0.0023％，As：0.0062％，X＝(10P+5Sb+4Sn+As)×10²＝5.14，J＝(Si+Mn)×(P+Sn)×10⁴73.14, the balance being Fe and inevitable impurity elements.

Example 2:

C：0.12％，Si：0.17％，Mn：1.22％，P：0.004，S：0.002％，Cr：2.4％，Mo：1.05％，V：0.38％，Nb：0.015％，Ni：0.08％，Cu：0.08％，Sb：0.0015％，Sn：0.0020％，As：0.0052％，X＝(10P+5Sb+4Sn+As)×10²＝6.07，J＝(Si+Mn)×(P+Sn)×10⁴83.4, and the balance of Fe and inevitable impurity elements.

The molten steel of the two components is respectively lifted to be continuously cast to manufacture a continuous casting billet with the section size of 200mm multiplied by 200mm, and the continuous casting ensures that the superheat degree of a tundish is 15-30 ℃. The crystallizer adopts special low-carbon alloy steel covering slag, and adopts crystallizer electromagnetic stirring and tail end electromagnetic stirring to ensure the uniformity of casting blank structures. The casting blank is subjected to full peeling treatment before high-speed wire rolling, the peeling depth is more than or equal to 1.0mm, and the surface quality of the blank is ensured.

Heating the continuous casting billet to more than 1110 ℃, controlling the residual oxygen content in the furnace to be less than 4%, keeping the temperature for 3 hours, discharging the continuous casting billet from the furnace, and rolling the continuous casting billet after descaling by high-pressure water: the initial rolling temperature is 1000-1100 ℃, the rolling process is divided into 39 passes of rolling, the rolling speed is set to be 100m/s, the final rolling temperature is controlled to be above 960 ℃, and the spinning temperature is controlled to be 930-950 ℃; after rolling is finished, the wire rod immediately enters the heat-preserving cover for slow cooling after spinning, the retention time of the wire rod in the heat-preserving cover is fully prolonged, the roller way speed is set to be 0.15m/s at a constant speed, and the structure of the wire rod out of the slow cooling cover is bainite and martensite.

The grade of inclusions of the hot-rolled wire rod is 2.0 grades including A coarse grade, B coarse grade, C coarse grade, D coarse grade and DS grade through metallographic detection, and the purity of the hot-rolled wire rod is high.

In order to ensure that the wire rod is successfully drawn into the welding wire, the back process of the hot rolled wire rod adopts a hood-type annealing furnace for annealing, the surface of the wire rod is pickled to remove oxide skin before annealing, H2 gas protection is adopted to prevent the full decarburization in the annealing furnace, the annealing temperature is 720 plus 760 ℃, the heat preservation is carried out for more than 4 hours, the hardness of the wire rod can be ensured to be below 200HBW, the tensile strength of the wire rod is ensured to be below 670Mpa, and the requirement that the back process of the wire rod of the welding wire steel is directly drawn from phi 5.5mm to 4.0mm is.

The annealing temperature is 720-760 ℃, the heat preservation is carried out for more than 4 hours, the hardness of the wire rod can be ensured to be below 200HBW, the tensile strength of the wire rod is ensured to be 560-600MPa, the surface shrinkage is 70-80%, and the requirement that the wire rod is directly drawn from phi 5.5mm to 4.0mm in the subsequent process is met.

The wire rod is drawn to be made into a welding wire, and the welding performance evaluation of deposited metal detects the low-temperature impact toughness at minus 20 ℃ from different tempering temperature ranges of 350-750 ℃, the impact value is ensured to stably rise above 85J, and the impact value is stable and does not fluctuate in the brittle range of 400-650 ℃. See in particular fig. 3.

In addition to the above embodiments, the present invention also includes other embodiments, and any technical solutions formed by equivalent transformation or equivalent replacement should fall within the scope of the claims of the present invention.

Claims

1. A wire rod for a Cr-Mo steel submerged arc welding wire is characterized in that: the wire comprises the following chemical components in percentage by mass: c: 0.10 to 0.20%, Si: 0.10 to 0.60%, Mn: 1.0-1.5%, Cr: 2.0-3.0%, Mo: 0.95-1.15%, V: 0.3 to 0.5%, Nb: 0.01-0.05%, Ni: 0.01-0.20%, Cu: 0.01-0.20%, and the balance of Fe and inevitable impurity elements.

2. The wire rod for a submerged arc welding wire of Cr-Mo steel according to claim 1, wherein: the wire comprises the following chemical components in percentage by mass: c: 0.10 to 0.15%, Si: 0.10-0.20%, Mn: 1.2-1.3%, Cr: 2.40-2.50%, Mo: 1.0-1.1%, V: 0.3-0.4%, Nb: 0.01-0.03%, Ni: 0.06-0.15%, Cu: 0.06-0.15%, and the balance of Fe and inevitable impurity elements.

3. The wire rod for a submerged arc welding wire of Cr-Mo steel according to claim 2, characterized in that: among the above inevitable impurities, P: less than or equal to 0.006 percent, S: 0.003% or less, 0.002% or less Sb, 0.003% or less Sn, 0.005% or less As, and a tempering embrittlement sensitivity coefficient X of 12 or less, X ═ 10P +5Sb +4Sn + As) X10²In the formula, P, Sb, Sn, As represents the mass percent content of the elements in the steel; the sensitive coefficient J of temper embrittlement is less than or equal to 120, J is (Si + Mn) × (P + Sn) × 10⁴Wherein Si, Mn, P and Sn represent the mass percent of the above elements in the steel.

4. The wire rod for a submerged arc welding wire of Cr-Mo steel according to claim 2, characterized in that: the wire rod inclusion for the welding wire is controlled in the following grades: A. b, C, D, the maximum levels of non-metallic inclusions are respectively less than or equal to 1.5 levels, the maximum level of DS is respectively less than or equal to 2.0 levels, and the sum of A + C is less than or equal to 1.5 levels, B + D is less than or equal to 1.5 levels, and the sum of A coarse + B coarse + C coarse + D coarse + DS is less than or equal to 4 levels.

5. The wire rod for a submerged arc welding wire of Cr-Mo steel according to claim 2, characterized in that: the inclusions of the welding wire steel wire rod are 25mm according to the scanning of an electron microscope²And in the area, the inclusion index is less than or equal to 2.0, and the inclusion index is the area of the inclusion/the scanned area multiplied by a scanning electron microscope.

6. A method for producing a wire rod for a submerged arc welding wire of Cr-Mo steel according to claim 1, characterized in that: the method comprises the steps of KR molten iron pretreatment, converter smelting, LF and RH furnace refining, slab continuous casting, slab heating, rolling and annealing treatment which are sequentially carried out.

7. The method for manufacturing a wire rod for a submerged arc welding wire of Cr-Mo steel according to claim 6, wherein: the slab continuous casting adopts small square billets, the superheat degree of a tundish is controlled at 15-30 ℃, and the slab continuous casting is provided with electromagnetic stirring equipment.

8. The method for manufacturing a wire rod for a submerged arc welding wire of Cr-Mo steel according to claim 6, wherein: when the plate blank is heated, the temperature of a high-temperature section in the heating furnace is more than 1050 ℃, the total heating time is more than 120min, and the high-temperature time is more than 60 min.

9. The method for manufacturing a wire rod for a submerged arc welding wire of Cr-Mo steel according to claim 6, wherein: and (2) descaling by high-pressure water, rolling, wherein the initial rolling temperature is 1000-1100 ℃, the final rolling temperature is controlled to be above 960 ℃, the rolling speed is set to be 95-120 m/s, the spinning temperature is 900-960 ℃, the wire rod immediately enters a heat-preserving cover for slow cooling after spinning, the roller way speed is set to be 0.15m/s at a constant speed, and the structure of the wire rod out of the slow cooling cover is bainite and martensite.

10. The method for manufacturing a wire rod for a submerged arc welding wire of Cr-Mo steel according to claim 6, wherein: the hot-rolled wire rod is annealed by adopting a hood-type annealing furnace, the surface of the hot-rolled wire rod is pickled to remove oxide skin before annealing, H2 gas is adopted for protection to prevent the full decarburization in the annealing furnace, the annealing temperature is 720-760 ℃, the heat preservation is carried out for more than 4 hours, the hardness of the wire rod is ensured to be below 200HBW, and the requirement of the subsequent drawing of the welding wire steel is met.