Steel-making deoxidation process for titanium-containing high-strength gas shield welding wire

Abstract

The invention belongs to the technical field of steelmaking processes, and discloses a steelmaking deoxidation process for titanium-containing high-strength gas shielded welding wire steel. Comprising the following working procedures: a KR desulfurization working procedure, a converter smelting working procedure, an LF refining working procedure and a continuous casting working procedure. In the converter smelting process, silicon-aluminum-barium and silicon-barium-manganese-calcium are adopted as deoxidizing agents, and the LF station entering oxygen content is controlled to be smaller than or equal to 0.0080 wt%; in the LF refining process, lime and fluorite are adopted for slagging, SiC and a calcined coal carburant are adopted for diffusion deoxidation, silicon barium manganese calcium is adopted for precipitation deoxidation, the oxygen level of molten steel is adjusted to be smaller than or equal to 0.0020 wt%, and the content of unstable oxides FeO + MnO in steel ladle top slag is smaller than or equal to 1.5 wt%. The two deoxidizing agents, namely the silicon-aluminum-barium composite deoxidizing agent and the silicon-barium-manganese-calcium composite deoxidizing agent, are used for conducting composite deoxidizing and two-phase promoting, it can be stably guaranteed that Al in the steel for the welding wire is smaller than or equal to 0.0070 wt%, the deoxidizing effect is good, the machining performance and the mechanical performance of the steel can be improved, the welding performance of the steel for the welding wire is further improved, and the welding production efficiency is improved; and compared with single use of one deoxidizing agent, the deoxidizing agent is less in dosage and low in deoxidizing cost.

Description

Technical Field

[0001] The invention relates to the technical field of steelmaking technology, and in particular to a steelmaking and deoxidation process for steel used for titanium-containing high-strength gas shielded welding wire. Background Art

[0002] The high-strength titanium-containing gas shielded welding wire is made of wire rods. The wire rods are drawn from φ5.5mm wire rods to φ0.8-1.2mm and then copper-plated. The wire rods are required to have good wire feeding performance and weld quality, and to ensure welding strength and less welding spatter after welding. Excessive oxygen content and large inclusions in the steel can easily cause spatter in the molten pool during welding, seriously affecting welding performance and reducing welding productivity. At the same time, since the welding wire steel wire must be drawn to 0.8mm-1.2mm, the inclusions in the steel, especially the non-ductile inclusions, are inconsistent with the deformation of the matrix during the drawing process, which is one of the reasons for wire breakage during drawing.

[0003] According to production experience and customer suggestions, it is necessary to control Alt≤0.010% or Alt≤0.0050%, Ca≤0.0010%, and total oxygen T[O]≤0.0015% in steel during production. Therefore, the production process of titanium-containing high-strength gas shielded welding wire steel needs to adopt aluminum-controlled and calcium-controlled deoxidation processes. The smelting process path of titanium-containing high-strength gas shielded welding wire steel is KR-BOF-LF-CC, and the chemical composition weight percentage is C0.05-0.09%, Si 0.50-0.80%, Mn 1.50-1.70%, P≤0.018%, S≤0.015%, Ti 0.05-0.12%, Cr 0.25-0.40%, Alt≤0.010%, Ni, Cu≤0.100%, N<0.0070%, and the others are iron or impurity elements. The carbon content in welding wire steel is low, and the converter terminal needs low carbon and high oxygen steel (the converter terminal oxygen control target is 300-700ppm, and the terminal carbon is 0.03-0.06%). For high-strength welding wire steel or other purpose steels containing titanium or other easily burnt alloy elements, in order to ensure the alloy yield, aluminum deoxidizers are generally used to deoxidize and reduce the dissolved oxygen in the steel before adding the easily burnt elements. However, the aluminum in the steel will be secondary oxidized to cause clustered Al2O3 high-melting point inclusions to gather at the nozzle, causing nozzle nodule defects. Therefore, it is necessary to feed a certain amount of calcium wire before the end of LF refining to denature the inclusions to generate low-melting point 12CaO·7AlO2 liquid inclusions to ensure the castability of the molten steel. However, the aluminum and calcium content in the steel is too high, which will cause large spatter defects in the welding process of the welding wire for gas shielded welding wire steel, and cannot meet user requirements. If a deoxidizer that does not contain aluminum is used, it is difficult to reduce the dissolved oxygen in molten steel to below 0.0020%, or a new type of deoxidizer needs to be specially developed, and the deoxidation cost is high. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a steelmaking and deoxidation process for steel containing titanium high-strength gas shielded welding wire.

[0005] The specific technical solutions are as follows:

[0006] A steelmaking and deoxidation process for titanium-containing high-strength gas shielded welding wire steel, comprising the following steps: a KR desulfurization step, a converter smelting step, a LF refining step, and a continuous casting step;

[0007] In the converter smelting process, the deoxidizers are silicon aluminum barium and silicon barium manganese calcium, and the oxygen content of the LF inlet is controlled to be ≤0.0080wt%;

[0008] The LF refining process adopts lime and fluorite to make slag, adopts SiC and calcined coal carburizer to carry out diffusion deoxidation, adopts silicon, barium, manganese and calcium to carry out precipitation deoxidation, adjusts the oxygen level of molten steel to ≤0.0020wt%, and the unstable oxide FeO+MnO in the ladle top slag is ≤1.5wt%.

[0009] In the converter smelting process, the ladle bottom blowing system is opened before the converter taps steel, Ar is blown at the bottom, and charging starts at 1 / 4 of the tapping and ends at 3 / 4, and the charging order is: lime → low carbon ferromanganese → low aluminum ferrosilicon → low carbon ferrochrome → deoxidizer;

[0010] The weight ratio of silicon aluminum barium to silicon barium manganese calcium in the deoxidizer is 1:1, and the added amount per ton of steel is 0.56-0.62 kg.

[0011] The converter smelting process adopts a top and bottom combined blowing converter and bottom blowing argon throughout the whole process. The converter is at position 0 before steel tapping, and bottom blowing argon for 1-5 minutes reduces the dissolved oxygen in the molten steel, so as to control the dissolved oxygen in the steel at the end of smelting to be less than or equal to 0.0700wt%.

[0012] In the LF refining process, the amount of lime added is 5.7-6.1 kg / furnace, the amount of fluorite added is 1.6-2.3 kg / ton of steel, the amount of SiC added is 0.3-0.4 kg / ton of steel, the amount of calcined coal carburizer added is 0.07-0.16 kg / ton of steel, and the amount of silicon-barium-manganese-calcium composite deoxidizer added is 0.3-0.45 kg / ton of steel.

[0013] The silicon-aluminum-barium is FeAll5Ba12Si30, wherein Si≥30.0wt%, Ba≥12.0wt%, Al≥15.0wt%, Mn≤0.30wt%, C≤0.20wt%, P≤0.040wt%, and S≤0.03wt%; the silicon-barium-manganese-calcium composite deoxidizer contains Si: 40-45wt%, Ba: 10-15wt%, Ca: 5-10wt%, and Mn: 5-10wt%.

[0014] Silicon aluminum barium deoxidizer not only reduces the total amount of inclusions in steel, but also changes the shape, size and distribution of inclusions, improves the impact toughness and elongation of steel, and reduces the amount of steel inclusions by more than 30%. The product after deoxidation of silicon aluminum barium calcium alloy is easy to float and easy to discharge, and the steel liquid deoxidized by silicon aluminum barium calcium alloy is relatively pure. The two deoxidizers of the present invention carry out composite deoxidation, and the calcium deoxidizer and the aluminum deoxidizer promote each other. At the same time, they can generate spherical calcium aluminate with a lower melting point, which has a smaller specific surface area and a fast floating speed, so that the amount of inclusions in steel is significantly reduced. The small amount of calcium aluminate inclusions remaining in the steel will not deform during rolling, and will not form the sharp-angle chain distribution of Al2O3 inclusions, which can improve the isotropy of steel, have good processing performance and mechanical properties, further improve the welding performance of steel for welding wire, and improve welding productivity.

[0015] The present invention can stably control the dissolved oxygen of molten steel before adding titanium to be below 0.0020%, and the total oxygen of the wire rod to be ≤0.0015% under the condition of ensuring Alt≤0.0100% or even Alt≤0.0050% and Ca≤0.0010% in the wire rod steel, thereby achieving good castability of molten steel for continuous casting of small square billets, high steel cleanliness and low deoxidation cost.

[0016] The LF outlet oxygen of the present invention is controlled at 0.0010-0.0030%. Under good conditions of LF and continuous casting protection, especially for gas-shielded high-strength welding wire steel that requires aluminum and calcium control and contains easily burnt metal elements such as Ti, the yield of 70 titanium-iron alloy (Ti content 66.24%) can be stably achieved to 57% or above.

[0017] By using special protective slag containing titanium steel, the continuous casting molten steel has good castability and no sprue nodule phenomenon. It can control Alt≤0.0100%, Ca≤0.0010%, and T(O)≤0.0015% in the steel. It can ensure the titanium alloy yield and smooth continuous casting of small square billets on the basis of controlling aluminum (Alt≤0.0100%) and calcium (Ca≤0.0010%) to reduce welding spatter of welding wire. The total oxygen in the steel is controlled at ≤0.0020%, the inclusion content is low, and the cleanliness is high. It can improve the drawing processability of wire rod to a certain extent and reduce welding spatter of welding wire.

[0018] The beneficial effects of the present invention are:

[0019] 1. The present invention uses two deoxidizers, silicon-aluminum-barium and silicon-barium-manganese-calcium composite deoxidizer, for composite deoxidation. The two phases promote each other, which can stably ensure that Al≤0.0070% in the steel for welding wire. The deoxidation effect is good, and the processing performance and mechanical properties of the steel can be improved, and the welding performance of the steel for welding wire can be further improved, and the welding production efficiency can be improved. In addition, the amount of deoxidizer used is less than that of a single deoxidizer, and the deoxidation cost is low.

[0020] 2. Under the condition of good continuous casting protection pouring, the molten steel has good castability, and there will be no problems affecting the castability of the molten steel such as water inlet blockage, rod plugging, and rod expansion, and the surface quality of the continuous casting billet is good. DETAILED DESCRIPTION

[0021] The steelmaking and deoxidation process for titanium-containing high-strength gas shielded welding wire includes the following steps: KR desulfurization step, converter smelting step, LF refining step, and continuous casting step;

[0022] After KR desulfurization, it enters the converter smelting process. The top and bottom combined converter adopts the bottom blowing of argon throughout the process. The converter is at 0 position before tapping. The bottom blowing of argon reduces the dissolved oxygen in the molten steel for 1-5 minutes, and the dissolved oxygen in the steel at the end of smelting is controlled to be ≤0.0700%. The sliding plate + positioning slag cone is used to strictly block the slag during tapping, and the thickness of the slag layer of the ladle is controlled to be ≤50mm. Before tapping, the ladle bottom blowing system is opened, and Ar is blown at the bottom. The feeding starts from 1 / 4 of the tapping and ends at 3 / 4. The feeding order is: lime → low carbon ferromanganese → low aluminum ferrosilicon → low carbon ferrochrome → deoxidizer; the deoxidizer adopts silicon aluminum barium and silicon barium manganese calcium composite deoxidizer for composite deoxidation (the weight ratio of the two deoxidizers is 1:1, and the amount added to ton of steel is 0.56-0.62kg). The silicon-aluminum-barium is FeAll5Ba12Si30, wherein Si≥30.0wt%, Ba≥12.0wt%, Al≥15.0wt%, Mn≤0.30wt%, C≤0.20wt%, P≤0.040wt%, S≤0.03wt%; the silicon-barium-manganese-calcium composite deoxidizer contains Si: 40-45wt%, Ba: 10-15wt%, Ca: 5-10wt%, and Mn: 5-10wt%.

[0023] The target LF steel liquid oxygen entering the station is ≤0.0080%, and a certain amount of ladle top slag lime (300kg). LF enters the station and is stirred for 1min to determine the oxygen, lime and fluorite are added to make slag (lime 5.7-6.1kg / ton steel, fluorite 1.60-2.30kg / ton steel), SiC (0.3-0.4kg / ton steel) and calcined coal carburizer (0.07-0.16kg / ton steel) are used for diffusion deoxidation, and silicon-barium-manganese-calcium composite deoxidizer (0.30-0.45kg / ton steel) is used for precipitation deoxidation, and the steel liquid oxygen is controlled to be ≤0.0020wt%, and FeO+MnO in the slag is ≤1.5wt%. After the other components and temperature of the steel liquid are suitable, 70 titanium iron is added to match titanium. After adding titanium iron, it is strictly forbidden to heat it again with electricity, and the bottom blowing flow is controlled. Soft blowing for 15min is hoisted to continuous casting and pouring steel.

[0024] Strict protective pouring measures are implemented during continuous casting, and special protective slag containing titanium steel is used.

[0025] Production Example

[0026] Table 1 shows the amount of converter deoxidizer and slag and deoxidation raw materials added in the LF refining process when producing ER55-Ti high-strength titanium-containing gas shielded welding wire wire rod in four batches. Among them, the silicon aluminum barium is FeAll5Ba12Si30, wherein Si≥30.0wt%, Ba≥12.0wt%, Al≥15.0wt%, Mn≤0.30wt%, C≤0.20wt%, P≤0.040wt%, S≤0.03wt%; the silicon barium manganese calcium composite deoxidizer contains Si: 40-45wt%, Ba: 10-15wt%, Ca: 5-10wt%, Mn: 5-10wt%.

[0027] Table 1 Amount of raw materials added for slag making and deoxidation in converter deoxidation and LF refining process (kg / ton steel)

[0028]

[0029] Table 2-4 shows the composition of LF refined slag and continuous casting ladle slag in the production process of ER55-Ti high-strength titanium-containing gas shielded welding wire wire rod in furnace 3 and the chemical composition of the smelting process.

[0030] Table 2 Composition of refined slag and tundish slag

[0031]

[0032]

[0033] Table 3 Molten steel composition during production (%)

[0034] Process C Mn S P Si Ti Cr Al Ca Dissolved O Spectrum N end 0.058 0.034 0.011 0.005 - - - - - 0.0510 - Ladle 0.05 1.41 0.007 0.009 0.68 - 0.31 - - - 0.0014 Slag 0.06 1.5 0.0075 0.0087 0.71 0.004 0.308 0.003 0.0005 0.0021 0.0034 Exit 0.065 1.56 0.006 0.009 0.72 0.0899 0.309 0.005 0.0005 0.0008 0.0035 Continuous Casting 0.065 1.56 0.006 0.009 0.72 0.08 0.0305 0.0034 0.0006 - 0.0036

[0035] Table 4 Mechanical properties, chemical composition and oxygen and nitrogen content of 5.5mmER55-Ti wire rod produced

[0036]

[0037] The continuous casting of the present invention adopts strict protection pouring, the molten steel has good castability, and there is no problem of water inlet plugging, plugging rod expansion, etc. that affects the castability of the molten steel. As shown in Table 4, the surface quality of the continuous casting billet is good, and it has good processing performance and mechanical properties.

[0038] The present invention uses two deoxidizers, silicon-aluminum-barium and silicon-barium-manganese-calcium composite deoxidizer, for composite deoxidation, the two phases promote each other, the deoxidation effect is good, and the Al content in the welding wire steel can be stably guaranteed to be less than or equal to 0.0070%, thereby further improving the welding performance of the welding wire steel and improving the welding production efficiency.

[0039] The final oxygen of the converter is 0.0510%, the output of the converter is calculated as 128 tons, 75kg of silicon aluminum barium, 125kg of silicon barium manganese calcium composite deoxidizer are added, the price of silicon aluminum barium is 9600 yuan / ton, and the silicon barium manganese calcium composite deoxidizer is 7699 yuan / ton, and the total deoxidation cost per ton of steel is 13.14 yuan. Under the same output, aluminum manganese titanium iron is used for deoxidation, the amount of aluminum manganese titanium iron is 250-270kg, and the aluminum manganese titanium iron deoxidizer is calculated at 13805 yuan / ton, and the total cost per ton of steel is (250+270) / 2 / 128×13805 / 1000=28 yuan. The use of silicon aluminum barium and silicon barium calcium manganese deoxidizer composite deoxidation can save about 15 yuan / ton of deoxidation cost. It can be seen that the present invention uses less deoxidizer than using a single deoxidizer, has low deoxidation cost, and greatly reduces production costs.

Claims

1. A steelmaking and deoxidation process for titanium-containing high-strength gas shielded welding wire, characterized in that: It includes the following processes: KR desulfurization process, converter smelting process, LF refining process, and continuous casting process; In the converter smelting process, the deoxidizers are silicon aluminum barium and silicon barium manganese calcium, and the oxygen content of LF entering the station is controlled to be ≤0.0080wt%; The LF refining process adopts lime and fluorite to make slag, adopts SiC and calcined coal carburizer to carry out diffusion deoxidation, adopts silicon, barium, manganese and calcium to carry out precipitation deoxidation, adjusts the oxygen level of molten steel to ≤0.0020wt%, and the unstable oxide FeO+MnO in the ladle top slag is ≤1.5wt%.

2. The steelmaking and deoxidation process for titanium-containing high-strength gas shielded welding wire according to claim 1 is characterized in that: In the converter smelting process, the ladle bottom blowing system is opened before the converter taps steel, Ar is blown at the bottom, and charging starts from 1 / 4 of the tapping and ends at 3 / 4. The charging sequence is: lime → low carbon ferromanganese → low aluminum ferrosilicon → low carbon ferrochrome → deoxidizer.

3. The steelmaking and deoxidation process for titanium-containing high-strength gas shielded welding wire according to claim 1 is characterized in that: The weight ratio of silicon aluminum barium to silicon barium manganese calcium in the deoxidizer is 1:1, and the added amount per ton of steel is 0.56-0.62 kg.

4. The steelmaking and deoxidation process for titanium-containing high-strength gas shielded welding wire according to claim 1 is characterized in that: The converter smelting process adopts a top and bottom combined blowing converter and bottom blowing argon throughout the whole process. The converter is at position 0 before steel tapping, and bottom blowing argon for 1-5 minutes reduces the dissolved oxygen in the molten steel, so as to control the dissolved oxygen in the steel at the end point of smelting to be ≤0.0700wt%.

5. The steelmaking and deoxidation process for titanium-containing high-strength gas shielded welding wire according to claim 1 is characterized in that: In the LF refining process, the amount of lime added is 5.7-6.1 kg / ton of steel, the amount of fluorite added is 1.60-2.30 kg / ton of steel, the amount of SiC added is 0.3-0.4 kg / ton of steel, the amount of calcined coal carburizer added is 0.07-0.16 kg / ton of steel, and the amount of silicon-barium-manganese-calcium composite deoxidizer added is 0.30-0.45 kg / ton of steel.

6. The steelmaking and deoxidation process for titanium-containing high-strength gas shielded welding wire according to claim 1, characterized in that: The silicon-aluminum-barium is FeAll5Ba12Si30, wherein Si≥30.0wt%, Ba≥12.0wt%, Al≥15.0wt%, Mn≤0.30wt%, C≤0.20wt%, P≤0.040wt%, and S≤0.03wt%; the silicon-barium-manganese-calcium composite deoxidizer contains Si:40-45wt%, Ba:10-15wt%, Ca:5-10wt%, and Mn:5-10wt%.

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