Rolling process for preparing ER50-6E welding wire steel with tensile strength not larger than 1360 MPa and application of ER50-6E welding wire steel

Abstract

The invention belongs to the technical field of rolling, and relates to a rolling process for preparing ER50-6E welding wire steel with the tensile strength not larger than 1360 MPa and application of the ER50-6E welding wire steel. Billet steel is continuously fed, the in-furnace time is controlled to be not shorter than 110 minutes, the heating temperature is 1100-1150 DEG C, and the soaking temperature is 1170-1220 DEG C; the initial rolling temperature is 1070 DEG C to 1120 DEG C; the finish rolling temperature is not lower than 960 DEG C; and the water amount of finish rolling cooling water is reduced so that the finish rolling outlet temperature can be increased to be not lower than 1050 DEG C, the spinning temperature can be 920-950 DEG C, a heat preservation cover is completely closed, the roller way speed is low, and the cover outlet temperature is controlled to be 650 DEG C or below. The tensile strength of a hot-rolled wire rod does not exceed 500 MPa, the yield strength does not exceed 310 MPa, the yield ratio does not exceed 0.63, the hot-rolled wire rod is suitable for drawing a 0.8 mm welding wire from a phi 6.5 mm wire rod, the tensile strength of the welding wire is not larger than 1360 MPa, and the hot-rolled wire rod has good wire feeding performance.

Description

Technical Field

[0001] The invention relates to the technical field of rolling, in particular to a rolling process of a gas-shielded welding wire steel ER50-6E wire rod, in particular to a rolling process of a drawing thin wire welding wire steel wire rod. Background Art

[0002] With the continuous development of welding technology, the demand for gas shielded welding wire ER50-6E has increased significantly. CO2 gas shielded welding and CO2+Ar mixed gas shielded welding are welding methods vigorously promoted by my country's welding industry, and the main one used is ER50-6 solid wire. This welding wire not only has good arc stability and high welding performance, but also has stable arc, high deposition efficiency, less spatter, beautiful weld formation, strong resistance to oxidation and corrosion, low sensitivity of weld metal pores, and convenient operation. In addition, the annealing process can be omitted during the processing of the welding wire to reduce the manufacturing cost. It is widely used in various fields such as petrochemical, pressure vessels, electricity, automobiles, ships, power stations, etc.

[0003] At present, the specifications of ER50-6 welding wire steel for CO2 gas shielded welding and CO2+Ar mixed gas shielded welding in China are Φ0.8mm~Φ1.2mm, and are generally produced by drawing Φ5.5mm wire rods. The relevant patents are also for drawing Φ5.5mm wire rods to produce welding wires. In recent years, in order to reduce costs, welding wire steel has begun to use Φ6.5mm wire rods to produce welding wires, but it has only been able to draw Φ1.0mm~Φ1.2mm welding wires.

[0004] In the previous ER50-6E wire rod patent, the conventional rolling of the wire rod adopts controlled rolling, with three modes: two-phase controlled rolling, non-recrystallized controlled rolling, and recrystallized controlled rolling. The two-phase controlled rolling is carried out in the two-phase region of ferrite and austenite, and the temperature is very low; the non-recrystallized controlled rolling is carried out in the range of Ar3 to 950℃; the recrystallized controlled rolling is carried out in the range of 950 to 1000℃. The purpose of the three controlled rolling modes is to refine the austenite grains, move the C curve to the left, and transform austenite into ferrite as soon as possible, so as to control the tensile strength of the wire rod within an appropriate range.

[0005] The three controlled rolling modes must first control the start rolling temperature, which is mainly controlled by the heating process. The higher the heating temperature and the longer the heating time, the larger the austenite size of the high-temperature billet. Therefore, in order to finally refine the austenite grain size, the three controlled rolling modes require that the start rolling temperature should not be too high, and the billet can be heated through, so the start rolling temperature is generally controlled at 960-1050℃. Due to the low start rolling temperature, the rough rolling and pre-finishing rolling are basically in the recrystallization type controlled rolling, and the austenite grains are refined to a certain extent. The main control points of the three controlled rolling modes are all in the finishing mill, because the entire rolling line only has cooling water tanks before and after the finishing mill. The finishing mill has 10 stands, and the final rolling speed exceeds 100m / s. The rolling deformation heat is large and the material heats up rapidly. Therefore, the amount of cooling water inside the finishing mill is large to control the outlet temperature of each stand of the finishing rolling, thereby controlling the outlet temperature of the finishing mill. The ER50-6E wire rod patent generally requires a finishing rolling temperature of 900-950℃, which belongs to the non-recrystallization type controlled rolling temperature. However, since the material heats up rapidly during the rolling process, most of the rolling process is within the recrystallization type controlled rolling temperature range, that is, the 10 stands inside the finishing rolling are mainly in a controlled rolling mode dominated by recrystallization type controlled rolling.

[0006] Patent CN202210065495.0 is a rolling process for high-speed drawing welding wire steel, which controls the temperature entering the finishing mill at 920-960°C and the temperature leaving the finishing mill is less than 1050°C. It is a typical finishing rolling mode in which the 10 stands inside are mainly recrystallization-type controlled rolling, with the main purpose of refining austenite grains. The patent does not specifically explain the cooling water control inside the finishing mill, and does not study the mechanical properties and wire feeding performance of wire rod drawing production.

[0007] The reason why users do not use Φ6.5mm wire rod drawing to produce Φ0.8mm welding wire is that the drawing reduction rate is increased, the work hardening ability is improved, and the Φ0.8mm welding wire is easy to break, especially the welding wire tensile strength is still very high, reaching about 1350-1420MPa, the welding wire rigidity is high, which seriously affects the wire feeding performance (according to the experience of the welding wire factory, the tensile strength exceeds 1360MPa, and the wire feeding performance of Φ0.8mm welding wire is greatly reduced.)

[0008] So far, there is no relevant technical information on the drawing of Φ0.8mm welding wire from Φ6.5mm wire rod, and there is no report on how to achieve low work hardening performance by appropriately coarsening the austenite grains and pursuing a uniform and relatively coarse ferrite structure. Summary of the invention

[0009] The object of the present invention is to provide an ER50-6E welding wire steel rolling process for drawing fine wires. The Φ6.5mm wire rod produced by the process has low work hardening when drawing Φ0.8mm welding wire, the tensile strength of the welding wire will not exceed 1360MPa, and the wire feeding performance is good.

[0010] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present invention is as follows: a welding wire steel rolling process for drawing thin wires, including heating by a heating furnace, rolling by a roughing and intermediate rolling and pre-finishing mill group, rolling by a finishing mill group, wire laying, and cooling by a Stelmor fan and a heat preservation cover. The steps are as follows:

[0011] (1) After the continuous casting billet is heated and discharged from the furnace, it is descaled with high-pressure water. The descaling pressure is greater than 20 MPa. After descaling, no iron oxide scale remains on the surface of the billet;

[0012] (2) During the rolling process, the temperature entering the finishing mill is controlled by the two water tanks in front of the finishing mill, and the temperature at the final rolling outlet is controlled by controlling the water volume of the finishing mill;

[0013] (3) The wire rod is formed into a circle and the wire is evenly piled. After passing through the finishing mill, the wire is controlled by 5 water tanks;

[0014] (4) All Stelmor insulation covers and Stelmor fans are turned off, the roller inlet section speed is 6 m / min, the Stelmor outlet section speed is 23 m / min, and the hood outlet temperature does not exceed 650°C;

[0015] Furthermore, the chemical composition of the welding wire steel is calculated by mass percentage, and the composition ratio is C: 0.06-0.10, Si: 0.80-0.90, Mn: 1.40-1.51, P≤0.025, S≤0.025, Cr≤0.10, Ni≤0.10, Cu≤0.10, Al≤0.004, Ca≤0.001, and the rest is iron and unavoidable impurities.

[0016] Furthermore, in the step (1), the continuously cast billet is a rectangular billet of 142 mm×166 mm.

[0017] Furthermore, in the step (1), in the continuous casting billet heating process, the heating temperature is 1100°C to 1150°C, the soaking temperature is 1170°C to 1220°C, the billets are continuously fed, and the time in the furnace is not less than 110 minutes.

[0018] Furthermore, in the step (2), the temperature of the ingot rolling is controlled at 1070℃~1120℃; the temperature of the pre-finishing mill is controlled to be not less than 960℃ during the rolling process; the temperature of the finishing mill is controlled to be not less than 960℃, the water volume of the finishing mill cooling water is controlled to be 30-40%, and the outlet temperature of the finishing mill is controlled to be not less than 1050℃. As a preferred embodiment: the temperature of the finishing mill is controlled to be 975℃~985℃; the outlet temperature of the finishing mill is controlled to be 1060~1073℃.

[0019] Furthermore, the spinning temperature in step (3) is 920-950°C.

[0020] Furthermore, in step (4), the roller speed from the 1st section to the 8th section in step (4) remains unchanged, the cooling time in the hood is extended, and the roller speed from the 9th section to the 11th section is gradually increased by 5%.

[0021] The beneficial effects of the present invention are as follows: the process controls the tensile strength of the hot-rolled wire rod to be no more than 500MPa, and the yield strength to be no more than 310MPa, and is suitable for drawing 0.8mm welding wire from Φ6.5mm wire rod, the tensile strength of the welding wire is no more than 1360MPa, and has good wire feeding performance.

[0022] The present invention is different from the traditional technical principle of pursuing the refinement of austenite grains through three controlled rolling modes. Instead, it pursues uniform and slightly coarse austenite grains before the ferrite phase transformation of the wire rod, reduces the dynamic recrystallization and static recrystallization efficiency, and generates a uniform and relatively coarse ferrite structure after the transformation, thereby obtaining wire rod performance with low yield strength and low tensile strength, thereby achieving the purpose of low work hardening ability. The billet should be fully heated in the heating furnace first, and the temperature of the cross section of the billet should be uniform and high, so that the austenite grains can grow appropriately and the effect of austenite grain refinement during rough rolling and pre-finishing rolling can be weakened; the temperature entering the final rolling unit (finishing mill, MINI mill or sizing unit) should be controlled above 960℃, and the amount of cooling water for finishing rolling should be controlled so that the red steel is rolled above the temperature of the recrystallization controlled rolling mode most of the time, and the final rolling outlet temperature should be above 1050℃, that is, there is basically no recrystallization controlled rolling with the main purpose of refining the austenite grains in the finishing rolling area. The purpose is to make the austenite grains of the steel uniform and slightly coarse before the phase transformation. Taking into account the strong hardenability of this steel and the small size of the wire rod, if the wire drawing temperature is too low, the wire rod will be undercooled to a large extent, that is, the cooling rate will be very fast, and the ferrite crystallization will be refined when the wire rod transforms from austenite to ferrite. In addition, there is a need to control the oxide scale of the wire rod, so the wire drawing temperature is controlled at the upper limit temperature at which the oxide scale will not be powdered, that is, relatively high temperature is put into the hood to continue to coarsen the austenite grains and extend the transformation time in the ferrite area. The ferrite grains generated in this way are relatively larger and the work hardening is relatively small. DETAILED DESCRIPTION

[0023] The present invention combines the production example of welding wire steel 142mm×166mm rectangular continuous casting billet and rolling it into Φ6.5mm wire rod

[0024] Further details are given below in conjunction with embodiments:

[0025] The present invention is not limited to the following specific embodiments. A person skilled in the art can implement the present invention in various other specific embodiments according to the contents disclosed in the present invention, or any simple changes or modifications made to the design structure and ideas of the present invention fall within the protection scope of the present invention. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0026] Example 1

[0027] The composition of the welding wire steel continuous casting billet is calculated by mass percentage (wt%), and the components are C: 0.07, Si: 0.85, Mn: 1.51, P: 0.012, S: 0.012, Cr: 0.02, Ni: 0.01, Cu: 0.02, Al: 0.002, Ca: 0.0004, and the rest are iron and unavoidable impurities.

[0028] The continuous casting billet heating temperature is 1120℃~1140℃, the soaking temperature is 1180℃~1210℃, the material is continuously fed, and the furnace time is 125 minutes; after the continuous casting billet is taken out of the furnace, it is descaled by high-pressure water, and the descaling pressure is 25MPa. After descaling, there is no iron oxide scale remaining on the surface of the billet;

[0029] The starting rolling temperature of the ingot before entering the rolling mill is controlled at 1080℃~1110℃; during the rolling process, the temperature entering the finishing mill is controlled at 975℃~985℃; the opening degree of the cooling water of the finishing mill unit is controlled at 36%, and the outlet temperature of the finishing mill is controlled at 1060~1072℃.

[0030] After the wire rod is coiled and spun, it enters the Stelmor roller table for cooling, and the spinning temperature is 935-945℃.

[0031] All Stelmor insulation hoods are closed, all Stelmor fans are closed, the speed of the Stelmor roller entrance section is 6 m / min, the roller speed from the entrance section to the 8th section remains unchanged, the cooling time in the hood is extended, the roller speed from the 9th section to the 11th section is increased by 5% step by step, the Stelmor exit section speed is 23 m / min; the hood outlet temperature is 620℃~630℃.

[0032] Example 2

[0033] On the basis of Example 1, the continuous casting billet is heated to a temperature of 1125°C to 1135°C, the soaking temperature is 1180°C to 1210°C, the material is continuously fed, and the furnace time is 130 minutes; after the continuous casting billet is discharged from the furnace, high-pressure water descaling is performed, and the descaling pressure is 25 MPa. After descaling, no iron oxide scale remains on the surface of the billet;

[0034] The starting rolling temperature of the ingot before entering the rolling mill is controlled at 1080℃~1110℃; during the rolling process, the temperature entering the finishing mill is controlled at 975℃~985℃; the opening degree of the cooling water of the finishing mill unit is controlled at 36%, and the outlet temperature of the finishing mill is controlled at 1062~1073℃.

[0035] After the wire rod is coiled and spun, it enters the Stelmor roller table for cooling, and the spinning temperature is 935-945℃.

[0036] All Stelmor insulation hoods are closed, all Stelmor fans are closed, the speed of the Stelmor roller entrance section is 6 m / min, the roller speed from the entrance section to the 8th section remains unchanged, the cooling time in the hood is extended, the roller speed from the 9th section to the 11th section is increased by 5% step by step, the Stelmor exit section speed is 23 m / min; the hood outlet temperature is 620℃~630℃.

[0037] Example 3

[0038] On the basis of Example 1, the continuous casting billet is heated to a temperature of 1130°C to 1150°C, the soaking temperature is 1190°C to 1220°C, the material is continuously fed, and the furnace time is 120 minutes; after the continuous casting billet is discharged from the furnace, high-pressure water descaling is performed, and the descaling pressure is 25 MPa. After descaling, no iron oxide scale remains on the surface of the billet;

[0039] The starting rolling temperature of the ingot before entering the rolling mill is controlled at 1090℃~1120℃; during the rolling process, the temperature entering the finishing mill is controlled at 975℃~985℃; the opening degree of the cooling water of the finishing mill unit is controlled at 36%, and the outlet temperature of the finishing mill is controlled at 1060~1072℃.

[0040] After the wire rod is coiled and spun, it enters the Stelmor roller table for cooling, and the spinning temperature is 935-945℃.

[0041] All Stelmor insulation hoods are closed, all Stelmor fans are closed, the entrance section speed of the Stelmor roller is 6 m / min, the roller speed from the entrance section to the 8th section remains unchanged, the cooling time in the hood is extended, the roller speed from the 9th section to the 11th section is increased by 5% step by step, the Stelmor exit section speed is 23 m / min; the hood outlet temperature is 620℃-630℃.

[0042] Comparative Example 1

[0043] On the basis of Example 1, the continuous feeding of the blanks with a furnace time of 120 minutes was adjusted to the intermittent feeding of the blanks with a furnace time of 93 minutes; other parameters remained unchanged and were the same as in Example 1.

[0044] Comparative Example 2

[0045] On the basis of Example 1, the continuous casting billet heating temperature of 1120°C to 1140°C and the average heating temperature of 1180°C to 1210°C were adjusted to a heating temperature of 970°C to 1040°C and an average heating temperature of 1130°C to 1180°C.

[0046] Comparative Example 3

[0047] On the basis of Example 1, "the temperature entering the finishing mill during rolling is controlled at 975°C~985°C" is replaced by "the temperature entering the finishing mill during rolling is controlled at 865°C~895°C"; "the opening of the cooling water of the finishing mill is controlled at 36%, and the outlet temperature of the finishing mill is controlled at 1060~1072°C" is replaced by "the opening of the cooling water of the finishing mill is controlled at 44%, and the outlet temperature of the finishing mill is controlled not to exceed 970°C"; other parameters remain unchanged and are the same as in Example 1.

[0048] The Φ6.5 mm hot-rolled wire rods of the embodiments of the present invention and the comparative examples are directly drawn to 0.8 mm after rust removal and abrasive belt treatment. The properties of the hot-rolled wire rods and welding wires are shown in Table 1 below.

[0049] Table 1

[0050]

[0051] It can be seen from the data in the above table that the yield strength and yield strength ratio of the wire rod of the embodiment are relatively small, the tensile strength of the welding wire after drawing does not exceed 1360MPa, and the wire feeding performance is good; the yield strength and yield strength ratio of the wire rod of the comparison example are much higher than those of the embodiment. Although the tensile strength of the comparison example 3 does not exceed 500MPa, the yield strength and yield strength ratio are not low, so the tensile strength of the welding wire after drawing exceeds the requirement of 1360MPa, the welding wire has high rigidity, and the wire feeding performance is poor.

[0052] The above-mentioned ideal embodiments of the present invention are for inspiration. Through the above-mentioned description, relevant staff can make various changes and modifications without departing from the technical idea of ​​the present invention. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A rolling process for preparing ER50-6E welding wire steel with a tensile strength of no more than 1360 MPa, characterized in that: The steps include: (1) The continuous casting billet is heated to a temperature of 1100°C to 1150°C, and the soaking temperature is 1170°C to 1220°C. The billet is continuously fed, and the time in the furnace is not less than 110 minutes. After being discharged from the furnace, high-pressure water descaling is performed; (2) During the rolling process, the temperature of the finishing mill is not less than 960°C, and the final rolling outlet temperature is controlled to be not less than 1050°C; (3) The wire rod is coiled and the spinning temperature is 920-950°C; (4) All Stelmor insulation covers and Stelmor fans are closed, and the hood outlet temperature does not exceed 650° C. to obtain ER50-6E welding wire steel; The chemical composition of the ER50-6E welding wire steel is calculated by mass percentage, and the composition ratio is C: 0.06-0.10%, Si: 0.80-0.90%, Mn: 1.40-1.51%, P≤0.025%, S≤0.025%, Cr≤0.10%, Ni≤0.10%, Cu≤0.10%, Al≤0.004%, Ca≤0.001%, and the rest is iron and unavoidable impurities.

2. The rolling process for preparing ER50-6E welding wire steel with a tensile strength of no more than 1360 MPa according to claim 1, characterized in that: In step (1), the high-pressure water descaling has a descaling pressure greater than 20 MPa, and no iron oxide scale remains on the surface of the ingot after descaling.

3. The rolling process for preparing ER50-6E welding wire steel with a tensile strength of no more than 1360 MPa according to claim 1, characterized in that: During the rolling process of step (2), the finishing rolling temperature is controlled by the two water tanks in front of the finishing rolling mill, the water flow opening of the finishing rolling mill group cooling water is reduced to 30-40%, and the final rolling outlet temperature is controlled to be not less than 1050°C.

4. The rolling process for preparing ER50-6E welding wire steel with a tensile strength of no more than 1360 MPa according to claim 1, characterized in that: In step (4), all Stelmor insulation covers and Stelmor fans are turned off, the speed of the roller inlet section is 6 m / min, and the speed of the Stelmor outlet section is 23 m / min; the roller speed from the 1st section to the 8th section remains unchanged, the cooling time in the cover is extended, and the roller speed from the 9th section to the 11th section is increased by 5% step by step.

5. Use of ER50-6E welding wire steel rolled according to any one of claims 1 to 4 in preparing welding wire with a tensile strength not greater than 1360 MPa, characterized in that: The tensile strength of hot-rolled wire rod shall not exceed 500MPa, and the yield strength shall not exceed 310MPa. It is used to draw 0.8mm welding wire from Φ6.5mm wire rod, and the tensile strength of the welding wire shall not exceed 1360MPa.

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