Wire rod for gas shielded welding wire and production method thereof
Technical Field
The invention relates to the technical field of welding wires and metallurgy, in particular to a wire rod for a gas shielded welding wire and a component control production method thereof.
Background
The gas shielded welding wire can obtain excellent mechanical property and technological property under various shielding gas atmospheres. The welding method is mainly applied to welding of parts such as a superheater, a reheater and a main steam pipeline in the supercritical thermal power generating unit.
Phosphorus in the welding wire is a harmful element in steel and welding seams, and increases the strength of the steel and reduces the plasticity and toughness. Phosphorus also causes segregation of the steel, i.e., during tempering, phosphorus segregates to grain boundaries, thereby causing temper brittleness of the steel. Phosphorus in the weld also reduces its impact toughness and raises the brittle transition temperature, and also promotes hot cracking. At present, the P content of a welding wire such as P91 in foreign countries can be controlled below 0.02 percent so as to ensure the thermoplasticity of a P91 steel welding seam when the welding seam works in a high-temperature state. However, the control of the P content in the wire is very difficult. And too high P content can cause unstable mechanical property of the welding line and influence the service life of the welding product.
Five harmful chemical elements in the wire rod steel for the welding wire are As, Sn, Sb, Pb and Bi. The presence of five harmful chemical elements in the wire rod steel in the steel lowers the melting point of the steel. The higher the content, the more the melting point decreases. When the content of five harmful chemical elements in the steel exceeds a certain limit, the high-temperature mechanical property of the steel is obviously reduced, and the high-temperature brittleness of the steel is increased. Five harmful chemical elements in steel are often symbiotic with each other, and grain boundaries are separated out at high temperature, so that grain boundary segregation is caused, and the high-temperature toughness of the steel is reduced. Therefore, the control of five harmful chemical elements is particularly important for the wire rod steel for the welding wire with the service temperature of close to 600 ℃ and the pressure of close to 26 MPa.
The inclusion in the steel wire rod can damage the continuity of a steel matrix, cause the nonuniformity of a steel structure and seriously affect the performance of the steel. At the same time, the inclusions can form crack nuclei in the steel in different ways, the inclusions deform at high temperature deformation and are accompanied by crack initiation around the inclusions, and under the action of certain mechanical conditions, the cracks around the inclusions are mutually connected into pieces to form macroscopic cracks. In addition, another hazard of the inclusion is that the steel forms stress concentration during the stress process, which causes the strength of the steel to be reduced. Therefore, the control of inclusions in steel is very important in smelting.
Disclosure of Invention
The invention provides a wire rod for a gas shielded welding wire and a component control production method thereof according to the control problems of P content, non-metallic inclusion distribution, harmful element content and gas content in the production process of the welding wire. The method stably controls the P content in the steel to be below 0.008 percent by adopting a reasonable electric furnace slagging process, electric furnace steel-retaining operation, low-P raw and auxiliary materials and other measures. The sum of the levels of the non-metallic inclusions in the steel is controlled to be less than or equal to 1.0 level by adopting the reasonable electric furnace steel retaining operation, the electric furnace steel tapping and deoxidizing process, the LF refining slagging and deoxidizing process, the vacuum treatment and other means. The total content of harmful elements of As, Sn, Sb, Pb and Bi is controlled to be less than 0.025 percent by adopting high-quality molten iron, scrap steel and high-quality raw and auxiliary materials. By adopting reasonable refining slagging and deoxidation process, vacuum treatment and nitrogen element alloying process control, the gas elements meet the requirements that O is less than or equal to 40ppm, N is 400-600ppm and H is less than or equal to 1.5 ppm. The welding wire rod produced by the method has stable P content and components, uniform distribution of inclusions, lower content of harmful elements and gas elements, and completely meets the component control requirement of the wire rod for the welding wire.
The invention provides a wire rod for a gas shielded welding wire, which comprises the following components in percentage by mass: 0.08 to 0.12 percent of C, 0.20 to 0.30 percent of Si, 0.50 to 0.70 percent of Mn, less than or equal to 0.008 percent of P, less than or equal to 0.006 percent of S, less than or equal to 0.80 to 9.10 percent of Cr8, 0.40 to 0.60 percent of Ni, less than or equal to 0.10 percent of Cu, 0.90 to 1.10 percent of Mo, less than or equal to 0.020 percent of Al, 0.16 to 0.25 percent of V, less than or equal to 0.01 percent of Ti, 0.060 to 0.090 percent of Nb, less than or equal to 0.010 percent of Zr, and the: less than or equal to 0.008 percent of As, less than or equal to 0.005 percent of Sn, less than or equal to 0.005 percent of Sb, less than or equal to 0.005 percent of Pb, less than or equal to 0.005 percent of Bi, and the sum of the total of the contents of As, Sn, Sb and Pb is less than or equal to 0.025 percent; the balance of Fe and inevitable impurities; the gas content is: o is less than or equal to 40ppm, N is 400-600ppm, H is less than or equal to 1.5 ppm. The non-metallic inclusion grade of the wire rod is as follows: the sum of the grades of A-type (sulfide) fine series, B-type (alumina-type) fine series, C-type (silicate-type) fine series, D-type (spherical oxide-type) fine series and Ds (single-particle spherical) inclusions is less than or equal to 1.0 grade; the sum of the grades of A-type (sulfide) coarse series, B-type (alumina-type) coarse series, C-type (silicate-type) coarse series, D-type (spherical oxide-type) coarse series and Ds (single-particle spherical) inclusions is less than or equal to 1.0 grade.
The further optimized welding wire coil rod comprises the following chemical components in percentage by mass: 0.09 to 0.11 percent of C, 0.23 to 0.27 percent of Si, 0.55 to 0.65 percent of Mn, less than or equal to 0.008 percent of P, less than or equal to 0.003 percent of S, 8.80 to 9.10 percent of Cr, 0.52 to 0.58 percent of Ni, less than or equal to 0.08 percent of Cu, 0.95 to 1.05 percent of Mo, less than or equal to 0.012 percent of Al, 0.20 to 0.23 percent of V, less than or equal to 0.008 percent of Ti, 0.070 to 0.080 percent of Nb, less than or equal to 0.008 percent of Zr, less than or equal to 0.005 percent of As, less than or equal to 0.004 percent of Sn, less than or equal to 0.003 percent of Sb; the total weight percentage of As, Sn, Sb, Pb and Bi components is not more than 0.015 percent; the gas content is: o is less than or equal to 35ppm, N is 400-600ppm, H is less than or equal to 1.5 ppm; the non-metallic inclusion grade of the wire rod is as follows: the sum of the grades of A-type (sulfide) fine series, B-type (alumina-type) fine series, C-type (silicate-type) fine series, D-type (spherical oxide-type) fine series and Ds (single-particle spherical) inclusions is less than or equal to 1.0 grade; the sum of the grades of A-type (sulfide) coarse series, B-type (alumina-type) coarse series, C-type (silicate-type) coarse series, D-type (spherical oxide-type) coarse series and Ds (single-particle spherical) inclusions is less than or equal to 0.5 grade.
The invention also provides a production method of the wire rod for the gas shielded welding wire, which can control components and nonmetallic inclusions in production and comprises an electric furnace smelting step, an LF refining step and a VD refining step.
Wherein the weight percentage of P in the molten steel at the end of the electric furnace smelting step is controlled as follows: p is less than or equal to 0.0030 percent; the tapping temperature is 1630-1650 ℃;
the weight percentage of P in the molten steel at the end point in the LF refining step is controlled as follows: p is less than or equal to 0.0075 percent;
the VD refining step adjusts the content of the gas O, N, H to be: o is less than or equal to 40ppm, N is 400-600ppm, H is less than or equal to 1.5 ppm.
Further, in the electric furnace smelting step, the raw material molten iron comprises the following chemical components in percentage by weight: more than or equal to 3.5 percent of C, 0.2 to 0.6 percent of Si, less than or equal to 0.050 percent of S, less than or equal to 0.140 percent of P, less than or equal to 1.00 percent of Mn, less than or equal to 0.05 percent of Cr, less than or equal to 0.05 percent of Ni, less than or equal to 0.05 percent of Cu, less than or equal to 0.05 percent of Mo, less than or equal to 0.005 percent of As, less than or equal to 0.005 percent of Pb, less than or equal to 0.003 percent of Sn, less than or equal to 0.003 percent; the scrap steel adopts electric furnace shearing materials or self-produced scrap steel, and does not adopt pig iron, cast iron and other scrap steel with higher phosphorus content. The invention controls the content of As, Sn, Sb, Pb and Bi five-harmful elements in the steel by adopting high-quality molten iron and waste steel, and avoids the reduction of the high-temperature mechanical property of the welding joint caused by the five-harmful elements. In addition, the raw material molten iron with low P content creates good production conditions for reducing the P content control in the next steelmaking process.
The electric furnace smelting steps of the invention are controlled as follows:
(1) and reserving 25-30 tons of molten steel for a proper amount of molten steel of the electric furnace. The proper steel amount is beneficial to quickly forming a molten pool and producing foam slag, creates good conditions for early dephosphorization and removing inclusions, and is also beneficial to controlling the slag amount of the final tapping, reducing rephosphorization of molten steel and reducing the oxygen content and the inclusion content of the molten steel.
(2) The dephosphorization reaction is facilitated by reducing the temperature of the molten pool. When the temperature of the molten pool reaches 1570-; the steel-making end temperature is 1630-1650 ℃.
(3) The slag quantity is increased, the high alkalinity foam slag is rapidly produced, and the dephosphorization rate is favorably improved. Adding 1250-1300kg lime and 950-1000kg blast furnace return ores during slagging, controlling the alkalinity of the slag to be 4.0-5.0, and controlling the FeO content in the slag to be 25-35%. The blast furnace return ores are added into the slag, so that the slag alkalinity can be improved, a cooling effect is achieved, and the dephosphorization rate is favorably improved.
(4) Before the furnace body tilts to tap, the furnace body is calmed for more than 5s, so that the molten steel in the furnace tends to be stable, slag entrapment in the tapping process is avoided, molten steel rephosphorization is reduced, and the oxygen content and inclusion content of the molten steel are reduced.
(5) The electric furnace tapping adopts strong deoxidizer to carry out precipitation deoxidation, the oxygen content in steel is reduced, the content of molten steel inclusions is further reduced, and aluminum cakes are added when the tapping amount reaches 1/5 and are fully mixed and flushed with steel flow.
(6) In order to reduce the content of phosphorus brought into molten steel by the alloy and consider the alloy cost, the proportion of the low-phosphorus alloy and the common alloy is adjusted according to the content of P in the electric furnace tapping.
(7) The weight percentage of P in molten steel at the end point of the electric furnace smelting step is as follows: p is less than or equal to 0.0030 percent.
The electric furnace steelmaking process controls the electric furnace end point P to be less than or equal to 0.0030% by adopting reasonable slagging process, steel remaining operation, low-P raw and auxiliary materials and other methods, and lays a good foundation for the low-P content control of the subsequent processes; meanwhile, the inclusion content in the steel is reduced by adopting reasonable steel retaining operation, tapping, deoxidation process and other methods, and a foundation is laid for finally obtaining a good inclusion grade.
The LF smelting step control process of the invention is as follows:
(1) in order to reduce the phosphorus content of the molten steel, low-phosphorus alloy and metal manganese are adopted for alloying in the LF refining process.
(2) In order to reduce the oxygen content and the inclusion content of the molten steel, the LF refining process is deoxidized in the whole process. The earlier stage adopts slag surface deoxidation and precipitation deoxidation, and the middle and later stages adopt slag surface deoxidation, wherein the slag surface deoxidation adopts ferrosilicon powder and aluminum bean composite deoxidation.
(3) The high-alkalinity strong-reducing slag system is beneficial to reducing the oxygen content and the sulfur content of the molten steel and floating removal of impurities, wherein the alkalinity of the slag is controlled to be 5.5-6.5, and the content of FeO and MnO is controlled to be 0.45-0.65%.
In the LF refining process, the high-quality low-phosphorus alloy and the reasonable slagging and deoxidizing process are selected to ensure that the P content of molten steel is less than or equal to 0.0075 percent after LF refining is finished, and a foundation is laid for obtaining the P content of the final welding wire rod which is less than 0.008 percent and good inclusion grade.
The VD refining step comprises the following steps:
(1) in order to reduce the oxygen and hydrogen contents of molten steel, the vacuum degree of the VD refining step is less than or equal to 67Pa, and the vacuum degree is kept for 30-45 minutes.
(2) In order to control the nitrogen content of the molten steel finely, the VD vacuum treatment is carried out and then the cored wire of ferrochromium nitride, ferromanganese nitride or ferrosilicon nitride is adopted for alloying.
In the VD step, the gas in the steel is removed by controlling the vacuum time and the vacuum degree, so that O is less than or equal to 40ppm, N is 400-600ppm and H is less than or equal to 1.5 ppm.
The wire rod for the gas shielded welding wire accurately controls the processes of electric furnace smelting, LF refining and VD refining on molten iron and scrap steel, controls the content of P in the molten steel to be less than 0.008 percent, controls the total content of five harmful chemical elements of As, Sn, Sb, Pb and Bi to be less than 0.025 percent, and ensures that the content of gas in steel meets the requirements that O is less than or equal to 40ppm, N is 400-600ppm and H is less than or equal to 1.5 ppm. The non-metallic inclusion grade of the wire rod is as follows: the sum of the grades of A-type (sulfide) fine series, B-type (alumina-type) fine series, C-type (silicate-type) fine series, D-type (spherical oxide-type) fine series and Ds (single-particle spherical) inclusions is less than or equal to 1.0 grade; the sum of the grades of A-type (sulfide) coarse series, B-type (alumina-type) coarse series, C-type (silicate-type) coarse series, D-type (spherical oxide-type) coarse series and Ds (single-particle spherical) inclusions is less than or equal to 1.0 grade.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Detailed Description
The following exemplary examples illustrate specific embodiments of the present invention in detail. The present invention may be variously modified and may include various embodiments.
The invention provides a wire rod for a gas shielded welding wire and a production method for controlling components of the wire rod according to the problems of stable control of P content, inclusion content, harmful element content and gas content in the production process of the welding wire. The method stably controls the P content in the steel to be less than 0.008 percent by adopting a reasonable electric furnace slagging process, electric furnace steel retaining operation, low-P raw and auxiliary materials and other measures; the sum of the levels of the nonmetallic inclusions in the steel is controlled to be less than or equal to 1.0 by adopting the reasonable measures of electric furnace steel retaining operation, electric furnace steel tapping and deoxidizing process, refining slagging and deoxidizing process, vacuum treatment and the like; the total content of harmful elements of As, Sn, Sb, Pb and Bi is controlled to be not more than 0.025 percent by adopting high-quality molten iron and waste steel; the reasonable refining slagging and deoxidizing process, vacuum treatment and nitrogen element alloying process are adopted to control harmful gas elements to meet the requirements that O is less than or equal to 40ppm, N is 400-600ppm and H is less than or equal to 1.5 ppm. The welding wire rod produced by the method has stable P content, uniform distribution of inclusions and stable content of harmful elements and gas elements, and completely meets the quality requirement of the welding wire rod.
The invention provides a wire rod for a gas shielded welding wire, wherein the wire rod comprises the following chemical components in percentage by mass: 0.08 to 0.12 percent of C, 0.20 to 0.30 percent of Si, 0.50 to 0.70 percent of Mn, less than or equal to 0.008 percent of P, less than or equal to 0.006 percent of S, 8.80 to 9.10 percent of Cr, 0.40 to 0.60 percent of Ni, less than or equal to 0.10 percent of Cu, 0.90 to 1.10 percent of Mo, less than or equal to 0.020 percent of Al, 0.16 to 0.25 percent of V, less than or equal to 0.01 percent of Ti, 0.060 to 0.090 percent of Nb, less than or equal to 0.010 percent of Zr, and the five chemical elements in percentage by: less than or equal to 0.008 percent of As, less than or equal to 0.005 percent of Sn, less than or equal to 0.005 percent of Sb, less than or equal to 0.005 percent of Pb, less than or equal to 0.005 percent of Bi, less than or equal to 0.025 percent of the total, and the balance of Fe and inevitable impurities. The gas content is: o is less than or equal to 40ppm, N is 400-600ppm, H is less than or equal to 1.5 ppm. The non-metallic inclusion grade of the wire rod is as follows: the sum of the grades of A-type (sulfide) fine series, B-type (alumina-type) fine series, C-type (silicate-type) fine series, D-type (spherical oxide-type) fine series and Ds (single-particle spherical) inclusions is less than or equal to 1.0 grade; the sum of the grades of A-type (sulfide) coarse series, B-type (alumina-type) coarse series, C-type (silicate-type) coarse series, D-type (spherical oxide-type) coarse series and Ds (single-particle spherical) inclusions is less than or equal to 1.0 grade.
The further optimized welding wire coil rod comprises the following chemical components in percentage by mass: 0.09 to 0.11 percent of C, 0.23 to 0.27 percent of Si, 0.55 to 0.65 percent of Mn, less than or equal to 0.008 percent of P, less than or equal to 0.003 percent of S, 8.80 to 9.10 percent of Cr, 0.52 to 0.58 percent of Ni, less than or equal to 0.08 percent of Cu, 0.95 to 1.05 percent of Mo, less than or equal to 0.012 percent of Al, 0.20 to 0.23 percent of V, less than or equal to 0.008 percent of Ti, 0.070 to 0.080 percent of Nb, less than or equal to 0.008 percent of Zr, less than or equal to 0.005 percent of As, less than or equal to 0.004 percent of Sn, less than or equal to 0.003 percent of Sb. The total weight percentage of As, Sn, Sb, Pb and Bi components is not more than 0.015 percent; the gas content is: o is less than or equal to 35ppm, N is 400-600ppm, H is less than or equal to 1.5 ppm. The non-metallic inclusion grade of the wire rod is as follows: the sum of the grades of A-type (sulfide) fine series, B-type (alumina-type) fine series, C-type (silicate-type) fine series, D-type (spherical oxide-type) fine series and Ds (single-particle spherical) inclusions is less than or equal to 1.0 grade; the sum of the grades of A-type (sulfide) coarse series, B-type (alumina-type) coarse series, C-type (silicate-type) coarse series, D-type (spherical oxide-type) coarse series and Ds (single-particle spherical) inclusions is less than or equal to 0.5 grade.
The invention also provides a method for controlling the components and the inclusions of the wire rod for the gas shielded welding wire, which comprises an electric furnace smelting step, an LF refining step and a VD refining step.
In the electric furnace smelting step, the raw material molten iron comprises the following chemical components in percentage by weight: more than or equal to 3.5 percent of C, 0.2 to 0.6 percent of Si, less than or equal to 0.050 percent of S, less than or equal to 0.140 percent of P, less than or equal to 1.00 percent of Mn, less than or equal to 0.05 percent of Cr, less than or equal to 0.05 percent of Ni, less than or equal to 0.05 percent of Cu, less than or equal to 0.05 percent of Mo, less than or equal to 0.005 percent of As, less than or equal to 0.005 percent of Pb, less than or equal to 0.003 percent of Sn, less than or equal to 0.003 percent. The scrap steel adopts electric furnace shearing materials or self-produced scrap steel, and does not adopt pig iron, cast iron and other scrap steel with higher phosphorus content. The invention controls the content of As, Sn, Sb, Pb and Bi five-harmful elements in the steel by adopting high-quality molten iron and waste steel, and avoids the reduction of the high-temperature mechanical property of the welding joint caused by the five-harmful elements. The raw material molten iron with low P content creates good production conditions for reducing P content control in the next steelmaking process.
Further, the electric furnace control process comprises the following steps: the end point P of the electric furnace is less than or equal to 0.0030 percent, and the tapping temperature is 1630-.
The electric furnace smelting control process comprises the following steps:
(1) and reserving 25-30 tons of molten steel for a proper amount of molten steel of the electric furnace. The proper steel retaining amount is beneficial to quickly forming a molten pool and making foam slag, and good conditions are created for early dephosphorization and impurity removal. The method is also beneficial to controlling the slag discharge amount of the end point tapping, reducing the rephosphorization of the molten steel and reducing the oxygen content and the inclusion content of the molten steel.
(2) The dephosphorization reaction is facilitated by reducing the temperature of the molten pool. When the temperature of the molten pool reaches 1570-. The steel-making end temperature is 1630-1650 ℃.
(3) The slag quantity is increased, the high alkalinity foam slag is rapidly produced, and the dephosphorization rate is favorably improved. And adding 1250-1300kg lime and 950-1000kg blast furnace return ores for slagging, wherein the alkalinity of the slag is controlled to be 4.0-5.0, and the FeO content in the slag is controlled to be 25-35%. The blast furnace return mine can not only improve the slag alkalinity, but also play a cooling role, and is beneficial to improving the dephosphorization rate.
(4) Before the furnace body tilts to tap, the furnace body is calmed for more than 5s, so that the molten steel in the furnace tends to be stable, slag entrapment in the tapping process is avoided, molten steel rephosphorization is reduced, and the oxygen content and the inclusion content of the molten steel are reduced.
(5) The electric furnace tapping adopts a strong deoxidizer for precipitation deoxidation, so that the oxygen content in steel is reduced, and further the inclusion content in molten steel is reduced. When the tapping amount reaches 1/5, aluminum cakes are added and fully mixed with the steel flow.
(6) In order to reduce the content of phosphorus brought into molten steel by the alloy and consider the alloy cost, the proportion of the low-phosphorus alloy and the common alloy is adjusted according to the content of P in the electric furnace tapping.
(7) The weight percentage of P in molten steel at the end point of the electric furnace smelting step is as follows: p is less than or equal to 0.0030 percent.
The electric furnace steelmaking process controls the electric furnace end point P to be less than or equal to 0.0030% by adopting reasonable slagging process, steel remaining operation, low-P raw and auxiliary materials and other methods, and lays a good foundation for the low-P content control of the subsequent processes. Meanwhile, the inclusion content in the steel is reduced by adopting reasonable steel retaining operation, tapping, deoxidation process and other methods, and a foundation is laid for finally obtaining a good inclusion grade.
Further, the weight percentage of the molten steel P at the end point of the LF refining step is as follows: p is less than or equal to 0.0075 percent.
The LF smelting control process is as follows:
(1) in order to reduce the phosphorus content of the molten steel, the LF refining process adopts metal chromium (P is less than or equal to 0.005%) and metal manganese (P is less than or equal to 0.01%) for alloying.
(2) In order to reduce the oxygen content and the inclusion content of the molten steel, the LF refining process is deoxidized in the whole process. The earlier stage adopts slag surface deoxidation and precipitation deoxidation, and the middle and later stages adopt slag surface deoxidation.
(3) The high-alkalinity strong-reducing slag system is beneficial to reducing the oxygen content and the sulfur content of the molten steel and floating removal of impurities, wherein the alkalinity of the slag is controlled to be 5.5-6.5, and the content of FeO and MnO is controlled to be 0.45-0.65%.
In the LF refining process, the high-quality low-phosphorus alloy and the reasonable slagging and deoxidizing process are selected to ensure that the P content of molten steel is less than or equal to 0.0075 percent after LF refining is finished, and a foundation is laid for obtaining the P content of the final welding wire rod which is less than 0.008 percent and good inclusion grade.
Further, the VD refining step adjusts the content of the gas O, N, H to be: o is less than or equal to 40ppm, N is 400-600ppm, H is less than or equal to 1.5 ppm.
The VD refining step comprises the following steps:
(1) in order to reduce the oxygen and hydrogen contents of molten steel, the vacuum degree of the VD refining step is less than or equal to 67Pa, and the vacuum degree is kept for 30-45 minutes.
(2) In order to control the nitrogen content of the molten steel finely, the VD vacuum treatment is carried out and then the cored wire of ferrochromium nitride, ferromanganese nitride or ferrosilicon nitride is adopted for alloying.
In the VD step, the gas in the steel is removed by controlling the vacuum time and the vacuum degree, so that O is less than or equal to 40ppm, N is 400-600ppm and H is less than or equal to 1.5 ppm.
According to the wire rod for the gas shielded welding wire, provided by the invention, the processes of electric furnace smelting, LF refining and VD refining are accurately controlled on molten steel and scrap steel, the content of P in the molten steel is controlled to be below 0.008%, the total content of five harmful chemical elements of As, Sn, Sb, Pb and Bi is controlled to be below 0.025%, the gas content in the steel meets the requirements that O is less than or equal to 40ppm, N is 400-600ppm, and H is less than or equal to 1.5 ppm. The non-metallic inclusion grade of the wire rod is as follows: the sum of the grades of A-type (sulfide) fine series, B-type (alumina-type) fine series, C-type (silicate-type) fine series, D-type (spherical oxide-type) fine series and Ds (single-particle spherical) inclusions is less than or equal to 1.0 grade; the sum of the grades of A-type (sulfide) coarse series, B-type (alumina-type) coarse series, C-type (silicate-type) coarse series, D-type (spherical oxide-type) coarse series and Ds (single-particle spherical) inclusions is less than or equal to 1.0 grade.
Example 1
The electric furnace smelting raw material molten iron of the wire rod for the gas shielded welding wire comprises the following components in percentage by weight: 3.5% of C, 0.2% of Si, 0.030% of S, 0.130% of P, 0.60% of Mn, 0.02% of Cr, 0.02% of Ni, 0.04% of Cu, 0.03% of Mo, 0.005% of As, 0.004% of Pb, 0.003% of Sn, 0.003% of Sb, 0.004% of Bi, 0.040% of Ti, and the balance of Fe and inevitable impurities. The content of As, Sn, Sb, Pb and Bi in steel is controlled by adopting high-quality molten iron and steel scraps, so that the reduction of the high-temperature mechanical property of a welding joint caused by five-harmful elements is avoided. In addition, the low P content of the raw material molten iron creates good production conditions for low P control in the next steelmaking process.
Electric furnace smelting:
(1) the weight of the reserved molten steel in the electric furnace is 25 tons;
(2) adding 1250kg of lime and 950kg of blast furnace return ores for slagging, wherein the slag alkalinity is 4.0, and the FeO content in the slag is 25 percent;
(3) the electrifying power is reduced when the temperature of a molten pool in the electric furnace is 1570 ℃; the tapping temperature of the electric furnace is 1635 ℃;
(4) precipitating and deoxidizing the electric furnace steel tapping, and adding aluminum cakes when the steel tapping amount reaches 1/5;
(5) before the furnace body tilts to tap, the furnace body is calmed for 5 s;
(6) the weight percentage of P in molten steel at the end point of the electric furnace smelting step is as follows: p is 0.0027%.
The process controls the end point P content of the electric furnace to be 0.0027% by adopting a reasonable slagging process, steel remaining operation and low-P raw material method, and lays a good foundation for the low-P content control of the subsequent process; meanwhile, the inclusion content in the steel is reduced by adopting reasonable steel retaining operation, tapping, deoxidation process and other methods, and a foundation is laid for finally obtaining a good inclusion grade.
The LF smelting control process comprises the following steps:
(1) the LF refining is performed by alloying low-phosphorus chromium metal with 0.005% of P content and low-phosphorus manganese metal with 0.01% of P content.
(2) And deoxidizing in the whole LF refining process. The earlier stage adopts slag surface deoxidation and precipitation deoxidation, and the middle and later stages adopt slag surface deoxidation.
(3) The alkalinity of the high-alkalinity strong-reducing slag is controlled to be 5.5, and the content of FeO and MnO is 0.45 percent.
The process ensures that the P content of molten steel after LF refining is 0.0073% by selecting high-quality low-phosphorus alloy and reasonable slagging and deoxidizing processes, and lays a foundation for obtaining the P content of the final welding wire rod which is lower than 0.008% and good inclusion grade.
The VD refining step comprises the following steps:
(1) the vacuum degree of the VD refining step is 67Pa, and the vacuum degree is kept for 30 minutes.
(2) And alloying by adopting ferrochromium nitride after VD vacuum treatment.
In the VD step, the gas in the steel is removed by controlling the vacuum time and the vacuum degree, so that the gas content O: 30ppm, N: 580ppm, H: 0.5 ppm.
The molten steel discharged from the VD refining furnace is cast into a billet, and the components measured by rolling a final welding wire rod are as follows in percentage by weight: 0.08% of C, 0.20% of Si, 0.50% of Mn, 0.008% of P, 0.0038% of S, 8.80% of Cr, 0.40% of Ni, 0.10% of Cu0.90% of Mo, 0.020% of Al, 0.16% of V, 0.01% of Ti, 0.060% of Nb, 0.010% of Zr, 0.0050% of As0, 0.0047% of Sn, 0.0045% of Sb, 0.0040% of Pb, 0.0050% of Bi, and the balance of Fe and inevitable impurities. Gas content O: 30ppm, N: 580ppm, H: 0.5 ppm. Steel billet sampling inclusion detection, and wire rod inclusion grade: the sum of the grades of A-type (sulfide) fine system, B-type (alumina-type) fine system, C-type (silicate-type) fine system, D-type (spherical oxide-type) fine system, and Ds (single-particle spherical-type) inclusions is 1.0 grade; class A (sulfide) coarse series, class B (alumina) coarse series, class C (silicate) coarse series, class D (spherical oxide) coarse series, and Ds (single-particle spherical) inclusion grade, and 1.0 grade.
In the embodiment, the processes of electric furnace smelting, LF refining and VD refining are accurately controlled for molten iron and scrap steel, the weight percentage of P in the wire rod billet for the gas shielded welding wire is controlled to be 0.008%, the total weight percentage of five harmful chemical elements of As, Sn, Sb, Pb and Bi is controlled to be below 0.025%, the level of inclusions is 1.0, and the gas content meets the requirement of O: 30ppm, N: 580ppm, H: 0.5 ppm.
The phosphorus content of the wire rod for the gas shielded welding wire produced in the embodiment is 0.008% and is lower than P0.02% of the P91 welding wire. In addition, the inclusion particles in the embodiment are fine and uniformly distributed, and the content of harmful elements and gases is strictly controlled, so that the requirement of the steel for the welding wire on component control is met.
Example 2
The electric furnace smelting raw material molten iron of the wire rod for the gas shielded welding wire comprises the following components in percentage by weight: 3.5% of C, 0.3% of Si, 0.02% of S, 0.12% of P, 0.85% of Mn, 0.04% of Cr, 0.03% of Ni, 0.02% of Cu, 0.04% of Mo, 0.005% of As, 0.001% of Pb, 0.002% of Sn, 0.001% of Sb, 0.001% of Bi, 0.03% of Ti, and the balance of Fe and inevitable impurities.
Electric furnace smelting:
(1) the reserved molten steel weight of the electric furnace is 27 tons;
(2) 1270kg of lime and 970kg of blast furnace return ores are added for slagging, the slag alkalinity is 4.5, and the FeO content in the slag is 27 percent;
(3) the electrifying power is reduced when the temperature of a molten pool in the electric furnace is 1575 ℃; the tapping temperature of the electric furnace is 1638 ℃;
(4) precipitating and deoxidizing the electric furnace steel tapping, and adding aluminum cakes when the steel tapping amount reaches 1/5;
(5) before the furnace body tilts to tap, the furnace body is calmed for 6 s;
(6) the weight percentage of P in molten steel at the end point of the electric furnace smelting step is as follows: p is 0.0023%.
The LF smelting control process comprises the following steps:
(1) the LF refining is performed by alloying low-phosphorus chromium metal with the P content of 0.003 percent and low-phosphorus manganese metal with the P content of 0.007 percent.
(2) And deoxidizing in the whole LF refining process. The earlier stage adopts slag surface deoxidation and precipitation deoxidation, and the middle and later stages adopt slag surface deoxidation.
(3) The alkalinity of the high-alkalinity strong-reducing slag is 6.0, and the content of FeO and MnO is 0.50 percent.
(4) And the P content of the molten steel is 0.0065% after LF refining.
The VD refining step comprises the following steps:
(1) the vacuum degree of the VD refining step is 65Pa, and the vacuum degree is kept for 40 minutes.
(2) And carrying out VD vacuum treatment and alloying by adopting manganese iron nitride.
Gas content O after VD step: 25ppm, N: 550ppm, H: 0.5 ppm.
The molten steel discharged from the VD refining furnace is cast into a billet and is rolled to obtain a final welding wire rod, and the components in percentage by weight are respectively: 0.10% of C, 0.22% of Si, 0.58% of Mn, 0.007% of P, 0.002% of S, 9.02% of Cr, 0.54% of Ni, 0.02% of Cu, 0.98% of Mo, 0.008% of Al, 0.20% of V, 0.002% of Ti, 0.077% of Nb, 0.001% of Zr, 0.005% of As0.005%, 0.003% of Sn, 0.001% of Sb, 0.001% of Pb, 0.001% of Bi, and the balance of Fe and inevitable impurities. Gas content O: 25ppm, N: 550ppm, H: 0.5 ppm. Steel billet sampling inclusion detection, and wire rod inclusion grade: class A (sulfide) fines, class B (alumina) fines, class C (silicate) fines, class D (spherical oxide) fines, and class Ds (single-particle spherical inclusions) grade 1.0; class A (sulfide) coarse series, class B (alumina) coarse series, class C (silicate) coarse series, class D (spherical oxide) coarse series, and class Ds (single-particle spherical) inclusion grade sum 0.5 grade.
The coil rod for the gas shielded welding wire produced by the embodiment is precisely controlled by carrying out electric furnace smelting, LF refining and VD refining processes on molten iron and scrap steel, the weight percentage of P in a billet of the coil rod for the gas shielded welding wire is controlled to be 0.007%, the total weight percentage of five harmful chemical elements of As, Sn, Sb, Pb and Bi is controlled to be below 0.015%, and the gas content meets the requirement of O: 25ppm, N: 550ppm, H: 0.5 ppm.
The phosphorus content of the wire rod for the gas shielded welding wire produced by the embodiment is controlled to be 0.007 percent and is lower than P0.02 percent of the welding wire P91, the inclusion particles are fine and uniformly distributed, the content of harmful elements and gas is strictly controlled, and the requirement of the steel for the welding wire on component control is met.
Example 3
The electric furnace smelting raw material molten iron of the wire rod for the gas shielded welding wire comprises the following components in percentage by weight: 3.6% of C, 0.6% of Si, 0.040% of S, 0.130% of P, 0.95% of Mn, 0.05% of Cr, 0.05% of Ni, 0.03% of Cu, 0.05% of Mo, 0.004% of As, 0.003% of Pb, 0.003% of Sn, 0.003% of Sb, 0.004% of Bi, 0.030% of Ti, and the balance of Fe and inevitable impurities.
Electric furnace smelting:
(1) the reserved molten steel weight of the electric furnace is 30 tons;
(2) adding 1300kg of lime and 1000kg of blast furnace return ores for slagging, wherein the slag alkalinity is 5.0, and the FeO content in the slag is 35 percent;
(3) the power is reduced when the temperature of a molten pool in the electric furnace is 1590 ℃; the tapping temperature of the electric furnace is 1650 ℃;
(4) precipitating and deoxidizing the electric furnace steel tapping, and adding aluminum cakes when the steel tapping amount reaches 1/5;
(5) before the furnace body tilts to tap, the furnace body is calmed for 6 s;
(6) the weight percentage of P in molten steel at the end point of the electric furnace smelting step is as follows: p is 0.0026%.
The LF smelting control process comprises the following steps:
(1) the LF refining adopts low-phosphorus chromium metal with 0.004 percent of P content and low-phosphorus manganese metal with 0.008 percent of P content for alloying.
(2) And deoxidizing in the whole LF refining process. The earlier stage adopts slag surface deoxidation and precipitation deoxidation, and the middle and later stages adopt slag surface deoxidation.
(3) The alkalinity of the high-alkalinity strong-reducing slag is 6.5, and the content of FeO and MnO is 0.65%. And the P content of the molten steel is 0.0070% after LF refining.
The VD refining step comprises the following steps:
(1) the vacuum degree of the VD refining step is 66Pa, and the vacuum degree is kept for 45 minutes.
(2) And alloying by ferrosilicon nitride after VD vacuum treatment.
Gas content O after VD step: 28ppm, N: 560ppm, H: 0.5 ppm.
The molten steel discharged from the VD refining furnace is cast into a billet and is rolled to obtain a final welding wire rod, and the components in percentage by weight are respectively: 0.12% of C, 0.30% of Si, 0.70% of Mn, 0.0075% of P, 0.0045% of S, 9.10% of Cr, 0.60% of Ni, 0.08% of Cu0.08%, 1.10% of Mo, 0.015% of Al, 0.25% of V, 0.008% of Ti, 0.090% of Nb, 0.008% of Zr, 0.004% of As0.004%, 0.0045% of Sn, 0.004% of Sb, 0.003% of Pb, 0.004% of Bi, and the balance of Fe and inevitable impurities. Gas content O: 28ppm, N: 560ppm, H: 0.5 ppm. Steel billet sampling inclusion detection, and wire rod inclusion grade: class A (sulfide) fines, class B (alumina) fines, class C (silicate) fines, class D (spherical oxide) fines, and class Ds (single-particle spherical inclusions) grade 1.0; class A (sulfide) coarse series, class B (alumina) coarse series, class C (silicate) coarse series, class D (spherical oxide) coarse series, and class Ds (single-particle spherical) inclusion grade, and 1.0 grade.
In the embodiment, the electric furnace smelting, the LF refining and the VD refining processes are accurately controlled on molten iron and scrap steel, the weight percentage of P in the wire rod steel billet for the gas shielded welding wire is controlled to be 0.0075%, the total weight percentage of five harmful chemical elements of As, Sn, Sb, Pb and Bi is controlled to be below 0.025%, and the gas content meets the requirement of O: 28ppm, N: 560ppm, H: 0.5 ppm; the phosphorus content of the wire rod for the gas shielded welding wire is controlled to be 0.0075 percent and is lower than P0.02 percent of the welding wire P91, the particles of inclusions are fine and are uniformly distributed, the content of harmful elements and gas is strictly controlled, and the requirement of steel for the welding wire on component control is met.
The above-described embodiments of the present invention are merely exemplary, and various modifications may be made to the embodiments by others. Such variations are not to be regarded as a departure from the spirit and scope of the invention.