CN112547825A

CN112547825A - Heating method and heating furnace for gas shielded welding wire steel casting blank

Info

Publication number: CN112547825A
Application number: CN202011446904.9A
Authority: CN
Inventors: 陈涛; 孙齐松; 易敏; 徐兵伟; 黄昌洪; 罗洪金; 吕迺冰; 徐士新; 佟倩; 马跃; 罗志俊; 李舒笳
Original assignee: Shougang Corp
Current assignee: Shougang Group Co Ltd; Shougang Corp
Priority date: 2020-12-08
Filing date: 2020-12-08
Publication date: 2021-03-26

Abstract

The invention provides a heating method and a heating furnace for a gas shielded wire steel casting blank, wherein the method comprises the steps of preheating and first heating the gas shielded wire steel casting blank with the mass fraction of Si being more than or equal to 0.7% to obtain a first heated casting blank; secondly heating the first heated casting blank to the temperature of less than or equal to 1000 ℃ within the time of less than or equal to 60min to obtain a second heated casting blank; and thirdly, heating the second heated casting blank to the temperature of less than or equal to 1120 ℃ within the time of less than or equal to 60min to finish heating the gas shielded wire steel casting blank. According to the heating method provided by the invention, the embedded depth of the iron scale of the produced wire rod is not more than 25 mu m, and the drawing fracture rate is not more than 0.5 times per ton when the welding wire is manufactured by cold drawing, so that the wire rod has good processing performance, and the copper coating is uniformly and firmly adhered, thereby ensuring that the welding wire has good surface quality.

Description

Heating method and heating furnace for gas shielded welding wire steel casting blank

Technical Field

The invention belongs to the technical field of heating furnaces, and particularly relates to a heating method of a gas shielded wire steel casting blank and a heating furnace.

Background

The gas shield welding wire steel is a raw material of a gas shield welding wire, and in order to ensure the quality of a welded seam, such as strength, cleanliness and the like, the gas shield welding wire steel contains high silicon content which can reach 0.7-1.2%. During the heating process of the gas shielded wire steel casting blank before rolling, the surface of the gas shielded wire steel casting blank is oxidized.

The preparation process of the gas-shielded welding wire steel comprises the steps of heating a casting blank, drawing to obtain a wire rod, drawing the wire rod to the specification of phi 0.8-phi 1.6mm, and carrying out surface copper plating to obtain the welding wire. However, in the prior art, the problem of drawing fracture is easy to occur in the process of preparing the welding wire, and meanwhile, the copper plating layer is discontinuous and easy to fall off, so that the production efficiency of the welding wire is greatly reduced, and the quality of a finished product is also influenced.

Disclosure of Invention

The embodiment of the invention provides a heating method and a heating furnace for a gas shielded wire steel casting blank, which aim to solve the technical problems that the gas shielded wire steel casting blank is drawn into a wire rod, and the wire rod is easy to break in drawing and the surface of a finished welding wire is plated with copper and falls off in the process of preparing the welding wire by drawing the wire rod.

In a first aspect, the present invention provides a method of heating a gas shielded wire steel billet, the method comprising,

preheating and first heating a gas shielded wire steel casting blank with the mass fraction of Si being more than or equal to 0.7% to obtain a first heated casting blank;

secondly heating the first heated casting blank to the temperature of less than or equal to 1000 ℃ within the time of less than or equal to 60min to obtain a second heated casting blank;

and thirdly, heating the second heated casting blank to the temperature of less than or equal to 1120 ℃ within the time of less than or equal to 60min to finish heating the gas shielded wire steel casting blank.

Further, the first heated casting blank is heated to the temperature of less than or equal to 1000 ℃ within the time of less than or equal to 60min for the second time, comprising,

and secondly heating the first heated casting blank to 980-1000 ℃ within 25-60 min.

Further, the second heated casting blank is heated to the temperature of less than or equal to 1120 ℃ within the time of less than or equal to 60min for the third time, comprising,

and thirdly heating the second heated casting blank to 1080-1120 ℃ within 25-60 min.

Further, the preheating temperature is 700-780 ℃, and the preheating time is 5-12 min.

Further, the first heating temperature is 770-800 ℃, and the first heating time is 20-48 min.

Further, the total time of the preheating, the first heating, the second heating and the third heating is 75-180 min.

Further, in the casting blank, the mass fraction of Si is 0.7-1.2%, and the mass fraction of Mn is more than or equal to 1.4%.

Further, the mass fraction ratio of the Si and the Mn is > 0.5.

Further, the casting blank heating is carried out in a heating furnace, and the charging system of the heating furnace is any one of the following air-step charging systems: and (4) entering a first empty part and entering a second empty part, wherein the heating of the heating furnace adopts reversing heating, and the reversing period is 40-80 seconds.

In a second aspect, the invention provides a heating furnace, wherein the heating furnace is adopted to complete the heating of the gas shielded wire steel casting blank, the heating furnace comprises a preheating section, a heating section, a soaking section and a retaining wall, the preheating section, the heating section and the soaking section are sequentially arranged, the preheating is carried out in the preheating section of the heating furnace, the first heating is carried out in the heating section of the heating furnace, the second heating is carried out in the heating section of the heating furnace, and the third heating is carried out in the soaking section of the heating furnace;

the barricade has two, two the barricade set up respectively in one section of heating with between the heating two-stage section with between the soaking section, the height of barricade is 1200 ~ 1500 mm.

One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

the embodiment of the invention provides a heating method and a heating furnace for a gas-shielded wire steel casting blank, wherein in the heating process, a temperature curve with sequentially increased second heating temperature and third heating temperature is adopted, the third heating temperature is not more than 1120 ℃, and because the casting blank contains extremely high silicon content, Fe is easily formed in the heating process₂SiO₄。Fe₂SiO₄Solid below 1177 ℃ and Fe after a temperature above 1177 ℃₂SiO₄The melt becomes liquid. Therefore, in one aspect, the maximum heating temperature of the embodiments of the present invention is lower than the conventional maximum heating temperature, and the production of liquid phase Fe is avoided₂SiO₄So that the iron olivine can not be mutually wrapped and combined with FeO with loose structure, an iron olivine layer with complex structure can not be generated, and Fe can be coated at lower temperature₂SiO₄Is in a solid state, and Fe₂SiO₄The bonding force between the steel matrix and the steel matrix is small, and the steel matrix can be removed by the traditional descaling water pressure of 16-25 MPa. Meanwhile, the second heating time and the third heating time are controlled, so that the amount of generated iron scales is reduced on the basis of realizing austenitizing of a casting blank and uniform temperature, and meanwhile, the over-deep oxidation cracks influencing production and quality are eliminated. The invention controls the temperature and time of the second heating and the third heating,the method has the advantages that the generation of an fayalite layer which is difficult to remove is avoided, the iron scale can be removed under the descaling water pressure of 16-25 MPa, the amount of the generated iron scale is reduced, and meanwhile, the problems of drawing breakage caused by the fact that the iron scale cuts into the matrix and poor binding force between a copper plating layer and the matrix are avoided. According to the gas shielded welding wire rod prepared by the heating method provided by the invention, the embedded depth of the iron scale is not more than 25 mu m, the cold-drawing breakage rate is not more than 0.5 times per ton, and the copper coating of the prepared welding wire is uniformly and firmly attached.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

FIG. 1 is a prior art heating profile for a gas shielded wire steel and a heating profile for an embodiment of the present invention;

FIG. 2 is a macroscopic view of the gas shielded wire steel blank after a single descaling, under the prior art heating curve of FIG. 1;

FIG. 3 is a differential thermal experimental plot of gas shielded wire steel ER 70S-G;

4-9 are near surface oxidation characteristic surface morphologies of gas shielded wire steel ER70S-G heated to 1100 ℃ in air, after heat preservation for 1.5h, 2h, 2.5h, 3h, 4h, and 6h, respectively;

FIG. 10 shows the heating times for different open-step charging regimes;

FIG. 11 is the temperature of a heating section under a retaining wall with different amounts and heights;

FIG. 12 is a microstructure of the ingot skin after heating in example 1 of the present invention;

FIG. 13 is a billet subsurface microstructure after heating in example 2 of the present invention;

FIG. 14 is a billet subsurface microstructure after heating in example 3 of the present invention;

FIG. 15 shows the surface morphology of a wire rod prepared from a heated ingot as a raw material according to an embodiment of the present invention;

FIG. 16 shows the surface morphology of a wire rod prepared from a heated casting blank according to an embodiment of the present invention;

FIG. 17 is a macro-scale morphology of a welding wire prepared by using a heated ingot as a raw material according to example (right) and comparative example 1 (left) of the present invention;

FIG. 18 is a microscopic pattern of a near-surface position of a cross section of a wire rod prepared by using a heated casting blank as a raw material in comparative example 1;

FIG. 19 is the appearance and appearance of a copper-plated wire produced from a heated ingot of comparative example 1 as a starting material;

FIG. 20 is a graph of the gas shielded wire rod ER70S-G coil scale maximum depth of the inventive example and comparative example 1.

Detailed Description

The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.

Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

In the present invention, "first", "second", and "third" do not indicate an order, and may be understood as nouns.

In order to solve the technical problems, the embodiment of the invention provides the following general ideas:

in one aspect, the present invention provides a method for heating a gas shielded wire steel casting blank, the method including,

s1, preheating and first heating a gas shielded wire steel casting blank with the mass fraction of Si being more than or equal to 0.7% to obtain a first heated casting blank;

s2, second heating the first heated casting blank to a temperature of less than or equal to 1000 ℃ within 60min to obtain a second heated casting blank;

and S3, thirdly heating the second heated casting blank to a temperature of less than or equal to 1120 ℃ within the time of less than or equal to 60min, and finishing heating the gas shielded wire steel casting blank.

In the prior art, the temperature in a steel rolling heating furnace generally appears in the highest temperature zone (about 1200 ℃) in the heating two sections, and the temperature of a steel billet is uniform by utilizing the heating three sections before discharging, and the heating curve is shown in figure 1. For gas-shielded welding wire steel, the chemical composition of the gas-shielded welding wire steel contains high silicon content, and silicon is easy to generate ion diffusion at an interface at high temperature and is gathered at the interface, so that a silicon-rich region is formed at the interface, a silicon-poor region is formed in an adjacent region, and finally the two regions are alternately formed. After selective oxidation of silicon, the silicon and FeO form fayalite phase Fe₂SiO₄. Fayalite phase Fe₂SiO₄Solid below 1177 ℃ and Fe after a temperature above 1177 ℃₂SiO₄Melting into liquid state, entering into FeO phase with loose structure, wrapping with FeO, and making into liquid Fe₂SiO₄And also tends to infiltrate coarse austenite grain boundaries. Fe solidified after temperature reduction₂SiO₄An iron olivine layer with a complex structure is formed between the matrix and the iron scale and is embedded into the matrix. Fe₂SiO₄The viscosity is high, the scale removing water pressure is 30-40 MPa, the scale removing water pressure configured in the current wire production line is not more than 25MPa, so that the scale is difficult to remove completely by one-time scale removal, FIG. 2 is a macro morphology picture of a casting blank heated under the heating curve process in the prior art in FIG. 1 after one-time scale removal, the part with darker color is unremoved scale, a large amount of scale cannot be removed obviously from FIG. 2, the residual scale on the surface of the casting blank is pressed into a matrix in the subsequent rolling process, and in the subsequent rolling, the hard and brittle scale is broken, the influence range is further expanded, during medium and finish rolling,the scale still cannot be removed, resulting in significant scale-embedded defects on the substrate surface. The conventional heat exchange type heating furnace and the conventional regenerative heating furnace are widely used due to economy, high efficiency and higher heating efficiency, but a local high-temperature area always exists in the furnace, and the defects are aggravated. In use, the steel wire rod of the gas shielded welding wire with the defects is likely to become a main cause of drawing fracture due to iron scale embedding, and the iron scale further enters a welding wire processing procedure to influence the copper plating quality, so that the welding wire quality is damaged.

In the heating process of the embodiment of the invention, the temperature control curves that the heating temperatures of the second heating section and the third heating section are sequentially increased and the third heating temperature is not more than 1120 ℃ are adopted, on one hand, the highest heating temperature of the embodiment of the invention is lower than the traditional highest heating temperature, and the production of liquid-phase Fe is avoided₂SiO₄And thus an iron olivine layer having a complicated structure cannot be produced. Solid phase of Fe₂SiO₄The bonding force between the steel matrix and the steel matrix is small, and the steel matrix can be removed by the traditional descaling water pressure of 16-25 MPa. And meanwhile, the second heating time and the third heating time are controlled, so that the amount of generated iron scales is reduced on the basis of realizing austenitizing of the casting blank and uniform temperature. By controlling the second heating temperature and the third heating time, the generation of an fayalite layer which is difficult to remove is avoided, so that the iron scale can be removed under the descaling water pressure of 16-25 MPa, the amount of the generated iron scale is reduced, and the problems of drawing fracture and poor bonding force between a copper plating layer and a substrate caused by the fact that the iron scale cuts into the substrate are avoided.

The second heating section is used for continuously heating the first heating casting blank to a preset temperature interval. The excessive second heating temperature can increase the thermal stress of the casting blank, increase the risk of breakage of the casting blank, generate serious production accidents and also aggravate the occurrence of related defects such as oxidation loss of the casting blank and the like; and if the second heating time is too long, the heating process time is prolonged, the energy consumption is increased, the defects of oxidation, decarburization and the like are aggravated, and the quality of the casting blank and the rolled material is reduced.

The third heating temperature is too high to cause Fe₂SiO₄And then the solution is changed into liquid phase, so that an iron olivine layer with a complex structure is formed and is difficult to remove. And the third heating time is too long, more iron scale can be generated.

As an implementation manner of the embodiment of the invention, the third heating of the second heated casting blank to the temperature of 1120 ℃ or less in the time of 60min or less comprises,

The third heating temperature is too low to realize austenitization of the casting blank. The third heating time is too short to heat the casting blank uniformly.

As an implementation manner of the embodiment of the invention, the second heating of the first heated casting blank to the temperature of less than or equal to 1000 ℃ within the time of less than or equal to 60min comprises,

If the second heating temperature is too low, the effect of the subsequent heating process of the casting blank cannot be guaranteed, if the second heating time is too short, the heating quality is influenced, the uniform temperature of the surface of the core of the casting blank cannot be guaranteed, and the subsequent process is influenced,

as an implementation manner of the embodiment of the invention, the preheating temperature can be 700-780 ℃, and the preheating time can be 5-12 min.

Preheating is to heat the gas shielded welding wire steel casting blank at room temperature or with residual temperature to 700-780 ℃, so that the casting blank can meet the requirements of subsequent heating and rolling processes. If the preheating temperature is too low, the effect of the subsequent heating process of the casting blank is influenced, uneven temperature in the section is generated, and further the quality indexes such as rolling production, hot rolled material structure and performance and the like are influenced; the preheating temperature is too high or the preheating time is too short, so that the thermal stress of the casting blank is increased rapidly, the risk of breakage of the casting blank is increased, and serious production accidents are caused; the preheating time is too long, so that the subsequent heating process is long, and the heating process effect is not realized easily.

As an implementation manner of the embodiment of the invention, the first heating temperature may be 770-800 ℃, and the first heating time may be 20-48 min.

The first heating section is used for continuously heating the preheated casting blank to a temperature range of 770-800 ℃, and uniform heating of the first stage of the casting blank is realized. If the first heating temperature is too low, the subsequent heating process effect of the casting blank cannot be guaranteed, if the first heating temperature is too high, the thermal stress of the casting blank can be increased rapidly, the risk of breakage of the casting blank is increased, serious production accidents are caused, the time of the surface of the casting blank in a high-temperature area is prolonged, and the oxidation loss and related defects are increased; the first heating time is too short, so that the temperature uniformity of the core surface of the casting blank cannot be guaranteed, the heating quality is influenced, the heating process time is prolonged if the first heating time is too long, the energy consumption is increased, and the defects of oxidization, decarburization and the like are aggravated, so that the quality of the casting blank and the rolled material is reduced.

Fig. 3 shows a differential thermal experimental curve of ER70S-G for gas shielded wire steel, and it can be seen from fig. 3 that the oxidation rate of the gas shielded wire steel is increased after 800 ℃, the oxidation burning loss is severe, and the yield is greatly affected. The total heating time is controlled, so that the amount of generated iron scale can be controlled. FIGS. 4-9 show the near-surface oxidation characteristic surface morphology of a typical gas shielded wire steel ER70S-G observed by a scanning electron microscope SEM after the typical gas shielded wire steel ER70S-G is heated to 1100 ℃ in air and is respectively kept warm for 1.5h, 2h, 2.5h, 3h, 4h and 6 h. As can be seen from fig. 4 to 9, the oxidation reaction of the surface of the gas shielded wire steel continued to occur as the holding time was longer, and the cracks were significantly deepened. The total heating time is too short, so that austenitization and uniform temperature of the casting blank cannot be realized.

As an implementation mode of the embodiment of the invention, the gas shielded wire steel casting blank comprises the following chemical components in percentage by mass: c: less than or equal to 0.15 percent, Si: 0.7-1.2%, Mn is more than or equal to 1.4%, P is less than or equal to 0.035%, S is less than or equal to 0.035%, and the mass fraction ratio of Si to Mn is more than 0.5.

When the mass fraction ratio of Si to Mn is less than or equal to 0.5, Mn can react with partial Si to generate silico-manganese acid salt in the heating process, thereby inhibiting Fe₂SiO₄And (5) generating a phase.

As an implementation manner of the embodiment of the present invention, the gas shielded wire steel casting blank may further include at least one of the following chemical components:

Ti≤0.35％，Ni≤3.0％，Cr≤1.0％，Cu≤0.50％，Mo≤0.80％，V≤0.15％。

ti element can improve the activity of Si, so that the Ti element is easier to form Fe in the heating process₂SiO₄Phase, therefore, Ti is limited to 0.35%.

As an implementation mode of the embodiment of the invention, in the heating of the casting blank, the residual oxygen content is 1-3%.

In an embodiment of the present invention, the heating of the slab is performed in a heating furnace, and a charging schedule of the heating furnace is any one of the following empty-step charging schedules: one empty one and one empty two. In the embodiment of the invention, the first blank entering means that the casting blank passes through one step after entering the furnace for one casting blank, and then enters the next casting blank, and the steps are repeated in such a way, namely, the two casting blanks are separated by one step; the second step of entering into the first step and the second step means that after one casting blank enters into the furnace, the casting blank is empty for two steps and then enters into the furnace for the next casting blank; the first step of entering two empty refers to that the casting blank passes one step after continuously entering two furnaces and then continuously enters two furnaces.

The casting blank is fed into a furnace in a two-empty mode, the heating time can be controlled to be about 120-220 min, the average time is about 150min, and the factors influencing the time are the rolling rhythm; the mode of one-empty-two or one-empty-one-furnace feeding is adopted, the heating time can be basically controlled for about 100min (see figure 10), at the moment, the rolling rhythm is reduced to be below the load of the heating furnace, the heating time is released from the compression of the rolling period, and the active control is realized. Actually, when the furnace is charged in a two-empty-one mode, the preheating temperature is less than 750 ℃, the first heating temperature is 778-782 ℃ for the first heating section, the second heating temperature is 970-1000 ℃ for the second heating section, and the third heating temperature is 1110-1120 ℃ for the soaking section; when the furnace is charged into the one-air-two furnace, the preheating temperature is lower than 780 ℃, the first heating temperature is 790-820 ℃ for the first heating section, the second heating temperature is 980-1000 ℃ for the second heating section, and the third heating temperature is 1090-1110 ℃ for the soaking section. It can be seen that the temperature of each zone is slightly different under different charging systems under the influence of different charging amounts of the heating furnace.

The loading capacity of the existing heating furnace is larger than or equal to 80, a step-by-step loading system is adopted, the step frequency is about 40 seconds, the diameter of a finished wire rod of the gas shielded wire rod is 5.5mm, the rolling period of a single wire rod exceeds 2min according to the rolling rhythm, and therefore if a non-empty close-packed mode is adopted, the processing time of a casting blank in the heating furnace reaches more than 3 hours and is close to 4 hours, and the oxidation behavior is seriously aggravated.

As an implementation manner of the embodiment of the invention, the heating of the heating furnace adopts reversing heating, and the reversing period is 40-80 seconds.

The reversing heating means that the head and the tail of the casting blank are heated circularly and alternately in a heating furnace, namely, the head side is heated firstly, the tail side is in a stop state, after the preset time is reached, the tail side is heated, and the head side is stopped. The time for each transition between the two heating positions described above is the commutation period. For the regenerative heating furnace used in the embodiment of the invention, the reversing period has a large influence on energy consumption, and an optimal value exists. The commutation period affects the thermal field distribution in the furnace by acting on the heating energy consumption. The reversing period is controlled within 40-80 seconds, the temperatures of the air smoke and the soot in the soaking section tend to increase along with the shortening of the reversing period, and the temperature of the heating second section with the reversing period of 40 seconds is obviously higher than that of the heating second section with the reversing period of 80 seconds, which shows that the reversing period is shortened, and the heat storage capacity of the heat accumulator is improved.

In a second aspect, an embodiment of the present invention provides a heating furnace, and the heating furnace is adopted to complete heating of the gas shielded wire steel casting blank.

The heating furnace comprises a preheating section, a heating section, a soaking section and a retaining wall, wherein the preheating section, the heating section and the soaking section are sequentially arranged, the preheating is carried out in the preheating section of the heating furnace, the first heating is carried out in the heating section of the heating furnace, the second heating is carried out in the heating section of the heating furnace, and the third heating is carried out in the soaking section of the heating furnace;

the barricade has two, two the barricade set up respectively in one section of heating with between the heating two-stage section with between the soaking section.

The retaining walls are arranged at the positions where the first heating section and the second heating section are connected and the second heating section and the soaking section are connected, so that the heat of a high-temperature area can be effectively prevented from flowing to a low-temperature area, the main functions of the sections are respectively realized, and the advantages are more remarkable; and the flow field of a section of area can be well and stably heated, the uniformity of heating of the heating section is ensured, and conditions are provided for stably producing the gas shield welding wire steel wire rod.

As an implementation manner of the embodiment of the invention, the height of the retaining wall is 1200-1500 mm.

The height of the retaining walls is controlled to be 1200-1500 mm, the temperature of the first-section heating casting blank can be obviously reduced, different numbers of retaining walls are arranged in figure 11, the temperature of the first-section heating is counted under different heights, as can be seen from figure 11, the retaining walls are respectively arranged between the first-section heating and the second-section heating and between the second-section heating and the soaking section, and the temperature of the first-section heating is the lowest.

When the retaining wall is arranged between the first heating section and the second heating section and the height of the retaining wall is 1000mm, the temperature of the first heating section fluctuates at 880 ℃, the fluctuation range is large, and occasionally the temperature exceeds 950 ℃;

when the retaining wall is arranged between the first heating section and the second heating section and is raised to 1200mm and then to 1500mm, the temperature of the first heating section is obviously reduced, the temperature fluctuates at 800 ℃, and only the individual point temperature on the casting blank exceeds 900 ℃;

when the retaining wall is arranged between the first heating section and the second heating section and between the second heating section and the soaking section, the temperature of the first heating section is continuously reduced to about 780 ℃ and can be reduced to about 750 ℃ at the lowest.

The method and furnace for heating a gas shielded wire steel ingot according to the present invention will be described in detail with reference to examples, comparative examples, and experimental data.

Example 1

The gas shielded welding wire steel casting blank used in the embodiment 1 comprises the following chemical components in percentage by mass: c: 0.07%, Si: 0.89%, Mn: 1.43%, P: 0.012%, S: 0.006%, and the balance Fe and inevitable impurities. The size of the casting blank is 160mm multiplied by 12000 mm.

A heating furnace charging system: enter one empty one.

The heating process of the heating furnace comprises the following steps: the preheating temperature is 730 ℃, the preheating time is 8min, the first-stage heating temperature is 770 ℃, the first-stage heating time is 32min, the second-stage heating temperature is 990 ℃, the second-stage heating time is 40min, the soaking temperature is 1080 ℃, and the soaking time is 40 min. The total heating time is 120 min.

Coke oven gas is used as fuel.

Residual oxygen content: 2 to 3 percent.

Example 2

The gas shielded welding wire steel casting blank used in the embodiment 2 comprises the following chemical components in percentage by mass: c: 0.05%, Si: 0.80%, Mn: 1.46%, P: 0.014%, S: 0.015%, Ti: 0.19%, and the balance of Fe and inevitable impurities. The size of the casting blank is 160mm multiplied by 12000 mm.

A heating furnace charging system: one empty two.

The heating process of the heating furnace comprises the following steps: the preheating temperature is 760 ℃ of the charging temperature, the preheating time is 6min, the first-stage heating temperature is 790 ℃, the first-stage heating time is 24min, the second-stage heating temperature is 990 ℃, the second-stage heating time is 30min, the soaking section temperature is 1090 ℃, and the soaking section heating time is 30 min. The total heating time is 90 min. The size of the casting blank is 160mm multiplied by 12000 mm.

Coke oven gas is used as fuel.

Residual oxygen content: 1 to 2.5 percent.

Example 3

The gas shielded welding wire steel casting blank used in the embodiment 3 comprises the following chemical components in percentage by mass: c: 0.05%, Si: 0.77%, Mn: 1.46%, P: 0.012%, S: 0.015%, Ti: 0.20%, and the balance of Fe and inevitable impurities. The size of the casting blank is 160mm multiplied by 12000 mm.

A heating furnace charging system: one empty two.

The heating process of the heating furnace comprises the following steps: the preheating temperature is 760 ℃, the preheating time is 5min, the first-stage heating temperature is 790 ℃, the first-stage heating time is 21min, the second-stage heating temperature is 1000 ℃, the second-stage heating time is 26min, the soaking section temperature is 1110 ℃, and the soaking section heating time is 26 min. The total heating time was 78 min.

Coke oven gas is used as fuel.

Residual oxygen content: 1 to 2.5 percent.

Example 4

The gas shielded wire steel casting blank used in the embodiment 4 comprises the following chemical components in percentage by mass: c: 0.07%, Si: 0.72%, Mn: 1.35%, P: 0.0075%, S: 0.005% and the balance of Fe and inevitable impurities. The size of the casting blank is 150mm multiplied by 12000 mm.

A heating furnace charging system: enter one empty one.

The heating process of the heating furnace comprises the following steps: the preheating temperature is 750 ℃ of the charging temperature, the preheating time is 10min, the first-stage heating temperature is 780 ℃, the first-stage heating time is 30min, the second-stage heating temperature is 990 ℃, the second-stage heating time is 28min, the soaking temperature is 1100 ℃, and the soaking time is 26 min. The total heating time was 94 min.

Coke oven gas is used as fuel.

Residual oxygen content: 2 to 3 percent.

Comparative example 1

Comparative example 1 provides a method of heating a gas shielded wire steel ingot whose chemical composition is shown in table 1, and the balance being Fe and inevitable impurities.

The charging system of the heating furnace is normal branch-by-branch charging without idle step.

The heating process of the heating furnace comprises the following steps: the preheating temperature is 850 ℃, the preheating time is 12min, the first-stage heating temperature is 920 ℃, the first-stage heating time is 52min, the second-stage heating temperature is 1150 ℃, the second-stage heating time is 64min, the soaking temperature is 1080 ℃, and the soaking time is 64 min. The total heating time was 192 min.

Comparative example 2

Comparative example 2 in contrast to example 1, in which example 1 was referenced, the heating temperature of the second heating stage was 1050 ℃ and the heating time was 80 min; the heating temperature in the soaking section was 1150 ℃ and the heating time in the soaking section was 80min, the rest being the same as in example 1.

TABLE 1

Numbering	C/％	Si/％	Mn/％	P/％	S/％	Ti/％
							Example 1	0.07	0.89	1.43	0.012	0.006	/
Example 2	0.05	0.80	1.46	0.014	0.015	0.19
							Example 3	0.05	0.77	1.46	0.012	0.015	0.20
Example 4	0.07	0.72	1.35	0.007	0.005	/
							Comparative example 1	0.06	0.84	1.45	0.012	0.012	/
Comparative example 2	0.07	0.89	1.43	0.012	0.006	/

TABLE 2

Numbering	Iron scale embedding depth/mum	Adhesion of copper plating
			Example 1	0-25	Is uniform and firm
Example 2	0-25	Is uniform and firm
			Example 3	0-25	Is uniform and firm
Example 4	0-25	Is uniform and firm
			Comparative example 1	0-70	Has obvious falling-off
Comparative example 2	0-120	Has obvious falling-off

Hot rolling the heated casting blanks of examples 1-4 and comparative examples 1-2 to phi 5.5mm to obtain a wire rod, randomly sampling and counting the embedding depth of iron scales, carrying out copper plating treatment after cold drawing the wire rod to obtain a welding wire with phi 0.8-1.6mm, and observing the adhesion condition of a copper coating on the surface of the welding wire, wherein the results are shown in Table 2. In the cold drawing process, the breakage frequency of the welding rod after the casting blank hot rolling of the embodiment 1-4 in the process of preparing the welding wire by cold drawing is less than or equal to 0.5 times/ton, and the breakage frequency of the welding rod after the casting blank hot rolling of the comparative example 1 in the cold drawing process is more than or equal to 5 times/ton.

As is clear from Table 2, the wire rods prepared from the heated ingots of examples 1 to 4 as a raw material had a depth of scale insertion of not more than 25 μm, and the copper plating layer of the wires produced therefrom was uniformly and firmly adhered. The casting blank after being heated in the comparative examples 1-3 is used as a raw material, the upper limit of the embedding depth of the prepared wire rod iron scale is 70-120 mu m, individual samples are even more than 200 mu m, and the copper coating of the further manufactured welding wire also has obvious shedding condition.

FIGS. 12 to 14 show the microstructure of the ingot skin after heating in examples 1 to 3 of the present invention, in which the interface between the ingot matrix and the scale is smooth and regular, and no deep embedded oxide cracks are generated at the edge of the steel matrix. Fig. 15 to 16 are surface appearances of wire rods prepared by using the heated casting blank as a raw material according to the embodiment of the present invention, and it can be seen from fig. 15 and 16 that there is no crack on the surface of the wire rod. FIG. 18 is a microscopic pattern of a cross section near the surface of a wire rod prepared from a heated ingot of comparative example 1, and it can be seen from FIG. 18 that there are microscopic cracks under the skin and the crack length can reach 218.69 μm. FIG. 19 is a drawing showing the appearance of a wire produced from a heated ingot of comparative example 1 after copper plating, in which the copper plating layer was peeled off. Fig. 20 shows the maximum depth of scale insertion of the gas shielded wire rod ER70S-G wire rod in the example of the present invention and the comparative example 1, and it can be seen that the depth of scale insertion of the comparative example 1 is significantly greater than that in the example of the present invention, because the heating process of the comparative example 1 generates a fayalite layer with a complicated structure, which is difficult to remove deep into the matrix and embed into the matrix in the subsequent rolling process.

The invention provides a heating method and a heating furnace for a gas shielded wire steel casting blank, which avoid the surface peroxidation of the gas shielded wire steel casting blank in a high-efficiency heating process of a heat accumulating type heating furnace, effectively control the occurrence of oxidation cracks and improve the removal effect of surface iron oxide scales.

The method has the advantages that under the existing equipment conditions, a one-in-two air step type furnace entering measure and a means for building a retaining wall in the furnace are adopted to optimize the heating process, the heating process breaks through the traditional heating process method, the surface oxidation behavior of the gas shielded welding wire steel is effectively controlled, the problem that a copper plated layer is easy to fall off due to the fact that oxide scales which are difficult to remove are generated is avoided, the problem that the cold drawing breakage is caused by the defect that the oxide scales are embedded into a matrix to form oxide cracks is solved, the surface quality of the welding wire is improved, the use performance of the wire rod is guaranteed, the heating method further exerts an economical and efficient heating mode of a heat accumulating type heating furnace, and the satisfactory guarantee is obtained on the product quality. After the technical measures are implemented and applied, the improvement effect of the oxide scale embedded defects of the gas shielded welding wire steel wire rod is remarkable, the defect depth can be basically and stably controlled to reach the target of less than or equal to 25 mu m, the drawing fracture rate is less than or equal to 0.5 times per ton when the welding wire is manufactured by cold drawing, the wire rod has good processing performance, and meanwhile, the copper plating layer is uniformly and firmly adhered, so that the welding wire has good surface quality.

Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. A method for heating a gas shielded wire steel blank, comprising,

2. The method of claim 1, wherein the first heated ingot is second heated to a temperature of 1000 ℃ or less for a period of 60 minutes or less, comprising,

and secondly heating the first heated casting blank to the temperature of 980-1000 ℃ within 25-60 min.

3. The method of claim 1, wherein the second heated ingot is heated to a temperature of 1120 ℃ or less for a period of 60 minutes or less, comprising,

4. The method for heating the gas shielded wire steel casting blank according to claim 1, wherein the preheating temperature is 700 to 780 ℃ and the preheating time is 5 to 12 min.

5. The method for heating a gas shielded wire steel casting blank according to claim 1, wherein the first heating temperature is 770 to 800 ℃ and the first heating time is 20 to 48 min.

6. The method of claim 1, wherein the total time of the preheating, the first heating, the second heating, and the third heating is 75 to 180 minutes.

7. The method for heating the gas shielded wire steel casting blank according to claim 1, wherein the mass fraction of Si in the gas shielded wire steel casting blank is 0.7-1.2%, the mass fraction of Mn is more than or equal to 1.4%, and the mass fraction ratio of Si to Mn is more than 0.5.

8. The method as claimed in claim 7, wherein the mass fraction of Ti in the gas-shielded wire steel slab is 0.35% or less.

9. The method of heating a gas shielded wire strand according to any one of claims 1 to 8, wherein the strand heating is carried out in a heating furnace, and the charging system of the heating furnace is any one of the following empty hearth charging systems: and (4) entering a first empty part and entering a second empty part, wherein the heating of the heating furnace adopts reversing heating, and the period of the reversing is 40-80 seconds.

10. A heating furnace for heating a gas shielded wire steel ingot as claimed in any one of claims 1 to 9,