Wire rod for 55kg-grade gas shielded welding wire and preparation method

Abstract

The invention provides a wire rod for a 55kg-grade gas shielded welding wire and a preparation method, and belongs to the field of wire rod production. The method comprises the following steps: obtaining a blank with set chemical components; the blank is subjected to spinning at the set temperature, and a scattered coil is obtained; and the loose coil is subjected to Stelmor cooling, then coil collecting and cooling are conducted, and a wire rod is obtained. Wherein the Stelmor cooling comprises the following parameters: the temperature of a scattered coil non-lap joint entering a heat preservation cover, the temperature of the scattered coil non-lap joint exiting the heat preservation cover, the temperature of a scattered coil lap joint exiting the heat preservation cover, the cooling rate of the scattered coil non-lap joint and the speed of a segmented control roller way. A process thought of relatively high spinning temperature and proper improvement of roller speed is adopted, phase change from austenite to ferrite and bainite structures is completed in a non-lap joint point in a heat preservation cover, ferrite phase change is completed when the lap joint point is taken out of the heat preservation cover, and phase change from the remaining austenite to the bainite structure is completed when the remaining austenite is slowly cooled after coil collection; therefore, the same-circle performance of the wire rod for the 55kg-level gas shielded welding wire is improved.

Description

Technical Field

[0001] The present application relates to the technical field of wire rod production, and in particular to a wire rod for 55kg-grade gas shielded welding wire and a preparation method thereof. Background Art

[0002] The main production process of wire rod for gas shielded welding wire is: molten iron → converter (electric furnace) smelting → LF refining → VD (RH) vacuum smelting → tundish → continuous casting → continuous casting billet → high-speed wire workshop → heating → rough rolling → medium rolling → finishing rolling (RSM) → wire laying → Stelmor delayed cooling line → coiling → inspection → packaging → storage. The main production process of gas shielded welding wire is: (annealing) → wire rod → mechanical shelling → pickling → rough drawing → (annealing) → fine drawing → washing copper plating → polishing → spooling → inspection → packaging → storage. or The wire rods are roughly drawn and finely drawn to the finished wire specifications. The total reduction rate of drawing deformation reaches 92-98%. Therefore, the wire rod is required to have good drawing performance (plasticity). In order to ensure a smooth drawing process, the high-strength welding wire production process needs to be annealed and softened before or during drawing according to the strength of the wire rod or welding wire.

[0003] During the preparation process of 55kg-grade gas shielded welding wire, the wire rod falls on the Stelmor cooling line in a loose coil in the shape of a ring. The thickness of the wire rod accumulation at the overlap point and the non-overlap point is different, and the cooling rate is different, resulting in different proportions of ferrite + bainite structures and different strengths. The metallographic structures corresponding to the different strengths of the overlap point and the non-overlap point are different, and the same-circle performance (the difference between the maximum strength value and the minimum strength value obtained by sampling at different positions of the same circle of wire rod for tensile mechanical properties) is greater than 100MPa. Due to the poor same-circle performance of the wire rod, users must anneal it before use. Therefore, how to improve the same-circle performance of the wire rod for 55kg-grade gas shielded welding wire so that it can be used without annealing and drawing is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application provides a 55kg-level gas shielded welding wire wire rod and a preparation method thereof, so as to solve the following technical problem: how to improve the same-turn performance of the 55kg-level gas shielded welding wire wire rod.

[0005] In a first aspect, the present application provides a method for preparing a 55kg-grade gas shielded welding wire wire rod, the method comprising:

[0006] A blank with a set chemical composition is obtained;

[0007] Spinning the blank at a set temperature to obtain loose coils; and

[0008] The loose coils are subjected to Stelmor cooling, and then are rolled and cooled to obtain wire rods; wherein the Stelmor cooling includes the following parameters: the temperature of the non-overlapping points of the loose coils entering the insulation hood, the temperature of the non-overlapping points of the loose coils exiting the insulation hood, the temperature of the overlapping points of the loose coils exiting the insulation hood, the cooling rate of the non-overlapping points of the loose coils, and the segmented control of the roller speed.

[0009] Optionally, the setting temperature of the spinning is 950°C to 980°C.

[0010] Optionally, the temperature of the non-overlapping points of the loose coils entering the heat preservation cover is ≥800°C, and the temperature of the non-overlapping points of the loose coils exiting the heat preservation cover is ≤450°C.

[0011] Optionally, the temperature of the heat preservation cover at the overlap point of the loose coil is 580°C to 680°C.

[0012] Optionally, the cooling rate of the non-overlapping points of the loose coil is ≤0.6°C / s.

[0013] Optionally, the segmented control of the roller speed includes: the roller speeds of the first to thirteenth sections of Stelmor cooling are 0.15m / s, 0.16m / s, 0.16m / s, 0.17m / s, 0.17m / s, 0.18m / s, 0.18m / s, 0.19m / s, 0.19m / s, 0.20m / s, 0.27m / s, 0.38m / s and 0.53m / s respectively.

[0014] Optionally, the coiling includes the following parameters: the coiling temperature of the overlapping points of the loose coils is ≥550°C, and the cooling rate is ≤0.4°C / s.

[0015] Optionally, the set chemical composition includes: C, Si, Mn, P, S, Cr, Mo, and Fe; in terms of mass fraction, the C content is 0.06% to 0.10%, the Si content is 0.50% to 0.70%, the Mn content is 1.35% to 1.55%, the P content is ≤0.015%, the S content is ≤0.012%, the Cr content is 1.25% to 1.50%, and the Mo content is 0.40% to 0.60%.

[0016] In a second aspect, the present application provides a wire rod prepared by a method as described in any one of the embodiments of the first aspect, wherein the metallographic structure of the wire rod comprises: ferrite and bainite, and the content of the ferrite is ≥60% by volume, and the microhardness of the bainite is ≤500HV.

[0017] Optionally, the wire rod meets the following properties: tensile strength of 650Mpa to 720Mpa, same-turn performance ≤50MPa, and can be used without annealing and drawing.

[0018] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0019] The present application provides a method for preparing a wire rod for a 55kg-level gas shielded welding wire, comprising: obtaining a blank with a set chemical composition; spinning the blank at a set temperature to obtain a loose coil; and performing Stelmor cooling on the loose coil, followed by coiling and cooling to obtain a wire rod; wherein the Stelmor cooling includes the following parameters: the temperature of the non-overlapping point of the loose coil entering the insulation cover, the temperature of the non-overlapping point of the loose coil exiting the insulation cover, the temperature of the overlapping point of the loose coil exiting the insulation cover, the cooling rate of the non-overlapping point of the loose coil, and the segmented control of the roller speed. A process idea of ​​adopting a higher spinning temperature and appropriately increasing the roller speed is adopted, and the non-overlapping point completes the phase transformation of austenite to ferrite and bainite structure in the insulation cover; at the same time, the ferrite phase transformation is completed when the overlapping point position exits the insulation cover, and the remaining austenite completes the phase transformation to bainite structure under the condition of slow cooling after coiling, which is conducive to reducing the strength difference between the overlapping point and the non-overlapping point of the wire rod, and thus improving the same-circle performance of the wire rod for the 55kg-level gas shielded welding wire. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0022] Figure 1 The CCT curve of the 55kg-grade gas shielded welding wire provided in the embodiment of the present application;

[0023] Figure 2 A schematic flow chart of a method for preparing a 55kg-grade gas shielded welding wire wire rod provided in an embodiment of the present application;

[0024] Figure 3 The metallographic structure diagram of the non-overlapping point (a) and the overlapping point (b) of the wire rod provided in Example 1 of the present application;

[0025] Figure 4 The metallographic structure diagram of the non-overlapping point (a) and the overlapping point (b) of the wire rod provided in Comparative Example 1 of the present application;

[0026] Figure 5 The metallographic structure diagrams of the non-overlapping point (a) and the overlapping point (b) of the wire rod provided for Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0028] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0029] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "the following at least one item (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc or abc, where a, b, c can be single or plural, respectively.

[0030] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0031] The creative ideas of this application are:

[0032] The 55kg-grade gas shielded welding wire wire of the present invention is a high-strength heat-resistant welding wire steel with high content of alloy elements such as Cr, Mn, and Mo, high hardenability of steel, and high content of bainite structure. After the high-speed wire rod is spun, the wire rod is piled on the moving roller in a ring shape, and the stacking density and cooling speed of the wire rod on the roller can be adjusted by adjusting the roller speed. The cooling speed can also be adjusted by covering the cooling roller with a heat preservation cover. After the coil is spun, it is scattered on the slow cooling roller in a ring shape, forming overlapping points on both sides of the roller and non-overlapping points in the middle of the roller. The overlapping point temperature is high and the cooling speed is slow, while the non-overlapping point temperature is low and the cooling speed is fast. Different positions on the same circle of wire rod have different cooling speeds, and the metallographic structure and strength properties are also different. For welding wire steel, the traditional production process is low spinning temperature, low roller speed, and covering all heat preservation covers to reduce the cooling speed of the wire rod, so as to obtain as many ferrite structures with good plasticity as possible and as few bainite structures as possible. However, for the high-strength heat-resistant welding wire steel of the present invention, in order to obtain as much ferrite structure content as possible, a lower roller speed is used under the traditional process, but the temperature of the overlap point is high when it leaves the insulation cover, and it is in the bainite phase transformation temperature zone (580℃~450℃). Under the condition of air cooling (cooling rate greater than 1℃ / s) before coiling, bainite phase transformation occurs, resulting in bainite strengthening. Although the ferrite structure content at the overlap point and non-overlap point is greater than 60%, due to the difference in bainite hardness, the tensile strength of the wire rod is poor, and the same-turn performance is poor. The metallographic structures corresponding to different strengths of overlap points and non-overlap points are different, and the same-turn performance is greater than 100MPa. Due to the poor same-turn performance of the wire rod, users must anneal it before use.

[0033] The CCT curve of the thermal simulation test of the steel grade according to the present invention is shown in the attached Figure 1 It can be seen that the ferrite + bainite phase transformation temperature range of the 55kg-grade gas shielded welding wire wire rod of the Cr, Mn, Mo system of the present invention is relatively wide, the ferrite phase transformation temperature range is 800°C to 680°C, and the bainite phase transformation temperature range is 580°C to 450°C. In order to obtain a metallographic structure with better plasticity, it is hoped that the ferrite and bainite structures will undergo phase transformation in the insulation cover (the average cooling rate is less than 0.6°C / s). However, under the condition of the existing equipment limit capacity, due to the temperature difference between the overlap point and the non-overlap point, it is difficult to achieve the ferrite and bainite phase transformation in the insulation cover at both the overlap point and the non-overlap point. If you want the ferrite and bainite phase transformations at the overlap points to occur inside the insulation cover, the temperature of the non-overlap points entering the insulation cover may be too low, resulting in excessive bainite structure or even full bainite structure; if you want the ferrite and bainite phase transformations at the non-overlap points to occur inside the insulation cover, the temperature of the overlap points exiting the insulation cover will be high, so that the bainite phase transformation at the overlap points may be completed under air cooling conditions (cooling rate greater than 1°C / s) after exiting the insulation cover and before rolling.

[0034] Based on the above technical problems, the production method provided by the embodiment of the present invention is different from the traditional process concept of low spinning temperature to reduce hardenability and extremely slow roller speed, and adopts a higher spinning temperature and appropriately increases the roller speed. The non-overlapping points are controlled to complete the phase transformation of austenite to ferrite and bainite structures in the insulation cover (temperature range is 800-450°C); at the same time, the temperature of the overlapping point position is controlled to be lower than 680°C when it leaves the insulation cover (to complete the ferrite phase transformation), and the temperature of the overlapping point coiling is higher than 550°C. The remaining austenite completes the phase transformation to bainite structure under the condition of slow cooling after coiling. This application solves the problem that the phase transformation temperature range of 55kg-grade heat-resistant gas shielded welding wire steel is wide, the temperature difference between the overlapping points and the non-overlapping points is large, and the existing Stelmor cooling process cannot achieve the problem that the entire circle of wire rod is completed in the insulation cover. The ferrite bainite structure phase transformation. The present invention is beneficial to reducing the strength difference between the overlapping points and the non-overlapping points of the wire rod, and the same-circle performance is ≤50MPa, which can meet the needs of subsequent users to use the wire without annealing during the drawing process of the gas shielded welding wire.

[0035] Please see attached Figure 2 The present application provides a method for preparing a 55kg-grade gas shielded welding wire wire rod, the method comprising:

[0036] S1, obtaining a blank with a set chemical composition;

[0037] In some embodiments, the set chemical composition includes: C, Si, Mn, P, S, Cr, Mo, and Fe; in terms of mass fraction, the C content is 0.06% to 0.10%, the Si content is 0.50% to 0.70%, the Mn content is 1.35% to 1.55%, the P content is ≤0.015%, the S content is ≤0.012%, the Cr content is 1.25% to 1.50%, and the Mo content is 0.40% to 0.60%.

[0038] The chemical composition of the blank needs to be precisely controlled to ensure the performance and quality of the final product. The specific components include: Carbon (C): 0.06% to 0.10%. Carbon is the main strengthening element in steel and has an important influence on the hardenability and strength of steel. Silicon (Si): 0.50% to 0.70%. Silicon, as a deoxidizing element and strengthening element, can improve the strength and hardness of the weld. Manganese (Mn): 1.35% to 1.55%. Manganese can significantly improve the hardenability of steel and promote the formation of bainite structure. Phosphorus (P): ≤0.015%. Phosphorus is a harmful element in steel and its content needs to be strictly controlled. Sulfur (S): ≤0.012%. Sulfur is also a harmful element and has an adverse effect on the welding performance of steel. Chromium (Cr): 1.25% to 1.50%. Chromium can improve the corrosion resistance and hardness of steel and promote the formation of bainite structure. Molybdenum (Mo): 0.40% to 0.60%. Molybdenum can enhance the hardenability and heat resistance of steel, and improve the strength and toughness of welds. In the present invention, the content of alloying elements such as Cr, Mn, and Mo is high, the hardenability of steel is high, and the obtained bainite structure content is high. Exemplarily, the C content can be 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, etc., the Si content can be 0.50%, 0.55%, 0.60%, 0.65%, 0.70%, etc., the Mn content can be 1.35%, 1.40%, 1.45%, 1.50%, 1.55%, etc., and the P content can be 0.005%, 0.007%, 0.009%, The content of S can be 0.005%, 0.007%, 0.009%, 0.010%, 0.012%, etc., the content of Cr can be 1.25%, 1.30%, 1.35%, 1.40%, 1.45%, 1.50%, etc., the content of Mo can be 0.40%, 0.45%, 0.50%, 0.55%, 0.60%, etc.

[0039] S2, spinning the blank at a set temperature to obtain a loose coil; and

[0040] In some embodiments, the setting temperature of spinning is 950°C to 980°C.

[0041] The positive effect of limiting the spinning temperature to 950℃~980℃: With high spinning temperature, the temperature of non-overlapping points entering the hood is relatively high, which can ensure that the non-overlapping points complete the ferrite phase transformation completely in the insulation hood, obtain coarse ferrite grains, and help reduce the strength of the wire rod. At the same time, it is beneficial to increase the temperature of the overlapping points out of the hood, avoid the bainite phase transformation when leaving the hood, and postpone the phase transformation process to after the coiling. The spinning temperature can be 950℃, 955℃, 960℃, 970℃, 975℃, 980℃, etc.

[0042] S3. The loose coils are subjected to Stelmor cooling, followed by coiling and cooling to obtain wire rods; wherein the Stelmor cooling includes the following parameters: the temperature of the non-overlapping points of the loose coils entering the insulation hood, the temperature of the non-overlapping points of the loose coils exiting the insulation hood, the temperature of the overlapping points of the loose coils exiting the insulation hood, the cooling rate of the non-overlapping points of the loose coils and the segmented control of the roller speed.

[0043] The present invention arranges heat preservation covers on the Stellmore cooling slow cooling line, realizes controlled cooling by controlling the number of heat preservation covers on the Stellmore cooling slow cooling line, and opens the first one, two or three heat preservation covers depending on the temperature entering the cover (seasonal factor), and closes the remaining heat preservation covers.

[0044] In the embodiment of the present application, the non-overlap point entry temperature also represents the "non-overlap point insulation start temperature", the overlap point exit temperature also represents the "overlap point insulation end temperature", and the non-overlap point cooling rate inside the cover also represents the "non-overlap point cooling rate".

[0045] In some embodiments, the temperature of the non-overlapping points of the loose coils entering the heat preservation cover is ≥ 800°C, and the temperature of the non-overlapping points of the loose coils exiting the heat preservation cover is ≤ 450°C.

[0046] The positive effect of limiting the temperature of the non-overlapping points of the loose coils entering the insulation cover to ≥800℃ and the temperature of the non-overlapping points of the loose coils exiting the insulation cover to ≤450℃ is as follows: According to the CCT curve, within this temperature range, the non-overlapping points can complete the ferrite and bainite phase transformation in the insulation cover. The temperature of the non-overlapping points of the loose coils entering the insulation cover can be 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, etc., and the temperature of the non-overlapping points of the loose coils exiting the insulation cover can be 450℃, 440℃, 430℃, 420℃, 410℃, 400℃, etc.

[0047] In some embodiments, the temperature of the heat preservation cover at the overlap point of the loose coil is 580°C to 680°C.

[0048] The positive effect of limiting the end temperature of the insulation at the overlap point to 580-680℃ is that the ferrite phase transformation is completed before the overlap point leaves the cover, and the bainite phase transformation has not started before the roll is collected after leaving the cover. Otherwise, the bainite phase transformation will occur immediately during the air cooling process after leaving the cover, and the bainite hardness will increase, the strength will be too high, and the performance of the same circle will be poor. The temperature of the overlap point of the loose roll leaving the insulation cover can be 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃, etc.

[0049] In some embodiments, the cooling rate of the non-overlapping points of the loose coil is ≤ 0.6° C. / s.

[0050] The positive effect of limiting the cooling rate of the non-overlap point to ≤ 0.6°C / s is that a lower cooling rate can obtain more ferrite and less bainite structure, and the hardness of the bainite structure is also lower. The adjustment of the cooling rate can be achieved by adding a heat preservation cover and adjusting the roller speed on the cooling line. Specifically, the cooling rate of the non-overlap point can be 0.6°C / s, 0.55°C / s, 0.5°C / s, 0.45°C / s, 0.40°C / s, 0.35°C / s, 0.30°C / s, etc.

[0051] In some embodiments, the segmented control of the roller speed includes: the roller speeds of the first to thirteenth sections of Stelmor cooling are 0.15m / s, 0.16m / s, 0.16m / s, 0.17m / s, 0.17m / s, 0.18m / s, 0.18m / s, 0.19m / s, 0.19m / s, 0.20m / s, 0.27m / s, 0.38m / s and 0.53m / s respectively.

[0052] The positive effect of segmented control of roller speed and the technical effect of the above roller parameter settings: This application has achieved accurate cooling of the wire rod through a large number of process parameter adjustment tests, combined with the spinning temperature, the start and end temperatures of the insulation cover. Compared with the traditional process, the spinning temperature and the hood entry temperature are increased. In order to prevent the hood exit temperature from being too high, this application proposes a technical solution to appropriately increase the roller speed in the insulation cover to achieve a non-overlap point hood exit temperature below 450°C.

[0053] In some embodiments, the coiling includes the following parameters: the coiling temperature of the loose coil overlap point is ≥550°C, and the cooling rate is ≤0.4°C / s.

[0054] The positive effect of limiting the overlap point coiling temperature to ≥550℃ is that the overlap point undergoes bainite transformation after coiling. If the temperature is too low, the bainite transformation will occur during the air cooling process before coiling. The overlap point coiling temperature can be 550℃, 555℃, 560℃, 565℃, 570℃, 575℃, 580℃, etc.

[0055] The positive effect of limiting the cooling rate of the wire rod after coiling to ≤0.4℃ / s is that a low cooling rate after coiling is conducive to obtaining a low hardness bainite structure. The cooling rate after coiling ≤0.4℃ / s can be 0.4℃ / s, 0.35℃ / s, 0.3℃ / s, 0.25℃ / s, 0.2℃ / s, 0.15℃ / s, etc.

[0056] Based on a general inventive concept, the present application provides a wire rod prepared by a method as described in any one of the above embodiments, wherein the metallographic structure of the wire rod includes: ferrite and bainite, and the content of the ferrite is ≥60% by volume, and the microhardness of the bainite is ≤500HV.

[0057] The present invention controls the non-overlapping points to complete the phase transformation from austenite to ferrite and bainite in the heat preservation cover (temperature range is 800℃~450℃); at the same time, the temperature of the overlapping point is controlled to be lower than 680℃ (to complete the ferrite phase transformation) when it leaves the heat preservation cover, and the temperature of the overlapping point coiling is higher than 550℃, and the remaining austenite completes the phase transformation from austenite to bainite when slowly cooled after coiling. Exemplarily, the ferrite content can be 60%, 62%, 65%, 67%, 70%, 72%, 75%, etc., and the microhardness of bainite can be 440HV, 450HV, 460HV, 470HV, 480HV, 490HV, 500HV, etc.

[0058] In some embodiments, the wire rod meets the following properties: tensile strength is 650Mpa to 720Mpa, same-circle performance is ≤50MPa, and annealing-free drawing is required.

[0059] The present application is conducive to reducing the strength difference between the overlapped and non-overlapped points of the wire rod, and the same-circle performance is ≤50MPa, which can meet the needs of subsequent users for annealing-free use during the drawing process of gas shielded welding wire. For example, the tensile strength of the wire rod can be 650Mpa, 660Mpa, 670Mpa, 680Mpa, 690Mpa, 700Mpa, 710Mpa, 720Mpa, etc., and the same-circle performance is 40Mpa, 42Mpa, 44Mpa, 46Mpa, 48Mpa, 50MPa, etc.

[0060] The wire rod is realized based on the preparation method of the wire rod mentioned above. The specific steps of the preparation method of the wire rod can refer to the above embodiment. Since the wire rod adopts part or all of the technical solutions of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment, which will not be described one by one here.

[0061] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0062] Example 1

[0063] The present embodiment provides a 55kg-grade wire rod for gas shielded welding wire, which contains, by mass percentage, the following chemical elements: C: 0.06%, Si: 0.50%, Mn: 1.35%, P: 0.013%, S: 0.011%, Cr: 1.25%, Mo: 0.40%, and the remainder is Fe.

[0064] This embodiment also provides a method for preparing a 55kg-grade gas shielded welding wire wire rod, including: high-speed wire plant heating furnace → rough rolling → flying shear head → intermediate rolling → pre-finishing rolling → high-speed finishing rolling → water cooling → clamping and wire laying → temperature-controlled loose coil cooling → coiling → wire rod inspection. Specifically, the following steps are included:

[0065] The blank is spun to obtain loose coils; the spinning temperature is 950°C;

[0066] The loose coils are Stelmor cooled, then rolled and cooled to obtain wire rods; wherein, the Stelmor cooling process is as follows: after spinning, on the Stelmor cooling line, the first two insulation covers are opened, the remaining insulation covers are closed, and all fans are turned off. The non-overlap point entry temperature is controlled at 800°C, the exit temperature at 430°C, the overlap point exit temperature at 580°C, and the cooling rate of the non-overlap point is 0.5°C / s; the roller speeds of the first to thirteenth sections of Stelmor cooling are 0.15m / s, 0.16m / s, 0.16m / s, 0.17m / s, 0.17m / s, 0.18m / s, 0.18m / s, 0.19m / s, 0.19m / s, 0.20m / s, 0.27m / s, 0.38m / s, 0.53m / s respectively. The coiling temperature of the overlap point is 550℃, and the cooling rate of the wire rod after coiling is 0.4℃ / s. Figure 3 shown.

[0067] Example 2

[0068] The present embodiment provides a 55kg-grade wire rod for gas shielded welding wire, which contains, by mass percentage, the following chemical elements: C: 0.08%, Si: 0.60%, Mn: 1.45%, P: 0.012%, S: 0.010%, Cr: 1.35%, Mo: 0.50%, and the remainder is Fe.

[0069] This embodiment also provides a method for preparing a 55kg-grade gas shielded welding wire wire rod, including: high-speed wire plant heating furnace → rough rolling → flying shear head → intermediate rolling → pre-finishing rolling → high-speed finishing rolling → water cooling → clamping and wire laying → temperature-controlled loose coil cooling → coiling → wire rod inspection. Specifically, the following steps are included:

[0070] The blank is spun to obtain loose coils; the spinning temperature is 970°C;

[0071] The loose coils are Stelmor cooled, then rolled and cooled to obtain wire rods; wherein, the Stelmor cooling process is as follows: after spinning, on the Stelmor cooling line, the first two insulation covers are opened, the remaining insulation covers are closed, and all fans are turned off. The non-overlap point entry temperature is controlled to be 810°C, and the exit temperature is 440°C. At this time, the overlap point exit temperature is 620°C, and the cooling rate of the non-overlap point is 0.45°C / s; the roller speeds of the first to thirteenth sections of Stelmor cooling are 0.15m / s, 0.16m / s, 0.16m / s, 0.17m / s, 0.17m / s, 0.18m / s, 0.18m / s, 0.19m / s, 0.19m / s, 0.20m / s, 0.27m / s, 0.38m / s, 0.53m / s respectively. The coiling temperature at the overlap point is 560°C, and the cooling rate of the wire rod after coiling is 0.35°C / s.

[0072] Example 3

[0073] The present embodiment provides a 55kg-grade wire rod for gas shielded welding wire, which contains, by mass percentage, the following chemical elements: C: 0.10%, Si: 0.70%, Mn: 1.55%, P: 0.015%, S: 0.012%, Cr: 1.50%, Mo: 0.60%, and the remainder is Fe.

[0074] This embodiment also provides a method for preparing a 55kg-grade gas shielded welding wire wire rod, including: high-speed wire plant heating furnace → rough rolling → flying shear head → intermediate rolling → pre-finishing rolling → high-speed finishing rolling → water cooling → clamping and wire laying → temperature-controlled loose coil cooling → coiling → wire rod inspection. Specifically, the following steps are included:

[0075] The blank is spun to obtain loose coils; the spinning temperature is 980°C;

[0076] The loose coils are Stelmor cooled, then rolled and cooled to obtain wire rods; wherein, the Stelmor cooling process is as follows: after spinning, on the Stelmor cooling line, the first two insulation covers are opened, the remaining insulation covers are closed, and all fans are turned off. The non-overlap point entry temperature is controlled to be 820°C, the exit temperature is 450°C, the overlap point exit temperature is 680°C, and the cooling rate of the non-overlap point is 0.4°C / s; the roller speeds of the first to thirteenth sections of Stelmor cooling are 0.15m / s, 0.16m / s, 0.16m / s, 0.17m / s, 0.17m / s, 0.18m / s, 0.18m / s, 0.19m / s, 0.19m / s, 0.20m / s, 0.27m / s, 0.38m / s, and 0.53m / s, respectively. The coiling temperature at the overlap point is 580°C, and the cooling rate of the wire rod after coiling is 0.35°C / s.

[0077] The metallographic structure, tensile strength, and coil performance of the wire rods obtained in Examples 1 to 3 are shown in Table 1.

[0078] Table 1 Metallographic structure, tensile strength and same-circle performance of the wire rod obtained in Examples 1 to 3

[0079]

[0080] Comparative Example

[0081] This comparative example provides a wire rod for gas shielded welding wire, and the chemical elements and contents of the wire rod are the same as those in Example 1.

[0082] This comparative example also provides a wire rod for gas shielded welding wire, comprising the following steps:

[0083] After the final rolling, the wire is laid, and the laying temperature is controlled at 820℃~840℃. The cooling line roller speed adopts the lowest roller speed (the first section roller speed is 0.1m / s), and all the insulation covers are closed. The temperature of the wire rod entering the cover at the overlapping point is 780℃~720℃, the temperature of the non-overlapping point entering the cover is 720℃~660℃, the temperature of the overlapping point leaving the cover is 580℃~500℃, and the temperature of the non-overlapping point leaving the cover is 480℃~400℃. After leaving the cover, it is air-cooled on the roller and then rolled. The specific process parameters of the preparation method of the comparative wire rod are shown in Table 2, and the metallographic structure, tensile strength, and same-circle performance of the wire rod prepared in the comparative example are shown in Table 3.

[0084] Table 2 Specific process parameters of the preparation method of the wire rod of the comparative example

[0085]

[0086] Table 3 Metallographic structure, tensile strength and same-circle performance of wire rods prepared in comparative example

[0087]

[0088] From Tables 2, 3 and Figure 4 , 5 It can be seen that it is difficult to take into account the performance of both overlapping points and non-overlapping points using traditional technology.

[0089] When the temperature of the wire rod in the comparative example 1 is 720℃ at the lap joint point, the temperature out of the hood is 500℃, and a large amount of ferrite content of 60% is obtained. When it is out of the hood at 500℃, it is close to the bainite phase transformation temperature range. Bainite phase transformation occurs under air cooling conditions. The microhardness of bainite is 530HV, and the strength of the wire rod is 710MPa. At the same time, the temperature of the non-lap joint point entering the hood and the temperature of the hood exiting the hood are 660℃ and 400℃ respectively. When it is out of the hood, the bainite structure basically completes the phase transformation in the hood, the microhardness of bainite is low at 328HV, and the strength of the wire rod is 820MPa. The same circle performance of the wire rod is 110MPa. When the temperature of the wire rod in the hood at the overlap point of the comparative example 2 is 780℃, the temperature out of the hood is 560℃, and a large amount of ferrite content of 65% is obtained. However, when it is out of the hood at 560℃, it is close to the bainite phase transformation temperature range. Bainite phase transformation occurs under air cooling conditions before coiling. The microhardness of bainite is 558HV, and the strength of the wire rod is 750MPa. At the same time, the temperature of the non-overlap point entering the hood and the temperature of the hood exiting the hood are 720℃ and 500℃ respectively. When it is out of the hood, the bainite structure basically completes the phase transformation in the hood, the microhardness of bainite is low at 488HV, and the strength of the wire rod is 650MPa. The same-circle performance of the wire rod is 100MPa.

[0090] With traditional technology, it is difficult to achieve ferrite and bainite transformation at both overlap points and non-overlap points in the insulation cover due to the temperature difference between overlap points and non-overlap points. If you want the ferrite and bainite transformation at overlap points to occur in the insulation cover, the temperature of non-overlap points entering the insulation cover may be too low, resulting in excessive bainite structure or even full bainite structure. Figure 4 (a) As shown; if the ferrite-bainite phase transformation of non-overlapping points is to occur in the insulation cover, the temperature of the overlapping points is high when leaving the insulation cover, so that the bainite phase transformation of the overlapping points may be completed under air cooling conditions (cooling rate greater than 1℃ / s) after leaving the insulation cover and before rolling, as shown in the attached figure. Figure 5 (b) as shown.

[0091] In addition, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0092] In the embodiment of the present invention, the tensile strength of the wire rod for gas shielded welding wire is 650Mpa-720Mpa, and the same-circle performance is ≤50MPa.

[0093] In the embodiment of the present invention, it is helpful to reduce the strength difference between the overlapping points and the non-overlapping points of the wire rod, and the same-circle performance is ≤50MPa, which can meet the needs of subsequent users to use the gas shielded welding wire without annealing during drawing.

[0094] In the embodiment of the present invention, unlike the traditional process idea of ​​using low spinning temperature to reduce hardenability and extremely slow roller speed, a process idea of ​​using higher spinning temperature and appropriately increasing roller speed is adopted. The non-overlapping points are controlled to complete the phase transformation from austenite to ferrite and bainite in the heat preservation cover (temperature range is 800℃~450℃); at the same time, the temperature of the overlapping points is controlled to be lower than 680℃ (complete the ferrite phase transformation) when they leave the heat preservation cover, and the temperature of the overlapping points is higher than 550℃. The remaining austenite completes the phase transformation from austenite to bainite when slowly cooled after rolling.

[0095] In the embodiments of the present invention, the problems that the phase transformation temperature range of 55kg-grade heat-resistant gas shielded welding wire steel is wide, the temperature difference between overlap points and non-overlap points is large, and the existing Stelmor cooling process cannot achieve the ferrite-bainite microstructure phase transformation of the entire circle of wire rod in the insulation cover are solved.

[0096] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing a 55kg-grade gas shielded welding wire wire rod, characterized in that: The method comprises: A blank with a set chemical composition is obtained; Spinning the blank at a set temperature to obtain loose coils; and The loose coils are subjected to Stelmor cooling, and then are rolled and cooled to obtain wire rods; wherein the Stelmor cooling includes the following parameters: the temperature of the non-overlapping points of the loose coils entering the insulation hood, the temperature of the non-overlapping points of the loose coils exiting the insulation hood, the temperature of the overlapping points of the loose coils exiting the insulation hood, the cooling rate of the non-overlapping points of the loose coils, and the segmented control of the roller speed.

2. The method according to claim 1, characterized in that The setting temperature of the spinning is 950°C to 980°C.

3. The method according to claim 1, characterized in that The temperature of the non-overlapping points of the loose coils entering the heat preservation cover is ≥800°C, and the temperature of the non-overlapping points of the loose coils exiting the heat preservation cover is ≤450°C.

4. The method according to claim 1, characterized in that: The temperature of the heat preservation cover at the overlap point of the loose coil is 580°C to 680°C.

5. The method according to claim 1, characterized in that The cooling rate of the non-overlapping points of the loose coil is ≤0.6°C / s.

6. The method according to claim 1, characterized in that The segmented control of the roller speed includes: the roller speeds of the first to thirteenth sections of Stelmor cooling are 0.15m / s, 0.16m / s, 0.16m / s, 0.17m / s, 0.17m / s, 0.18m / s, 0.18m / s, 0.19m / s, 0.19m / s, 0.20m / s, 0.27m / s, 0.38m / s and 0.53m / s respectively.

7. The method according to claim 1, characterized in that The coiling includes the following parameters: the coiling temperature of the overlapping points of the loose coils is ≥550°C, and the cooling rate is ≤0.4°C / s.

8. The method according to claim 1, characterized in that The set chemical composition includes: C, Si, Mn, P, S, Cr, Mo, and Fe; in terms of mass fraction, the C content is 0.06% to 0.10%, the Si content is 0.50% to 0.70%, the Mn content is 1.35% to 1.55%, the P content is ≤0.015%, the S content is ≤0.012%, the Cr content is 1.25% to 1.50%, and the Mo content is 0.40% to 0.60%.

9. A wire rod prepared by the method according to any one of claims 1 to 8, characterized in that: The metallographic structure of the wire rod includes: ferrite and bainite. Calculated by volume fraction, the content of the ferrite is ≥60%, and the microhardness of the bainite is ≤500HV.

10. The wire rod according to claim 9, characterized in that The wire rod meets the following properties: tensile strength is 650Mpa-720Mpa, same-circle performance is ≤50MPa, and annealing-free drawing is required.

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