Production method of novel rare earth submerged arc welding wire steel wire rod for pipeline steel

Abstract

The invention discloses a production method of a novel rare earth submerged arc welding wire steel wire rod for pipeline steel. The specific technological process is as follows. Blast furnace molten iron preparation, molten iron pretreatment, converter top and bottom combined blowing smelting, LF refining, VD vacuum treatment, small square billet continuous casting, steel billet heating, high-pressure water descaling, rough rolling, flying shearing, intermediate rolling, kick shearing, finish rolling, controlled cooling water tank, spinning, stelmor cooling, coil collecting, trimming, sampling inspection, collecting and bundling and weighing -a finished wire. According to the novel production method of the rare earth submerged arc welding wire steel wire rod for the pipeline steel, by adding rare earth elements and novel alloy elements, the comprehensive performance, including but not limited to the low-temperature toughness impact performance, strength, toughness, corrosion resistance and the like, of welding wire steel is improved. Meanwhile, the rare earth element and the nickel element are added, the smelting process is optimized, composition segregation and inclusions are reduced, the porosity is reduced, and the strength and toughness of the welding wire steel are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of welding materials, and particularly relates to a production method of a new rare earth submerged arc welding wire steel wire rod for pipeline steel. BACKGROUND

[0002] As a high-efficiency and stable welding method, submerged arc welding has been widely used in oil and gas pipeline construction. With the continuous growth of global energy demand and the adjustment of energy structure, the construction of oil and gas pipelines has entered a period of rapid development. In particular, in China, the implementation of large projects such as the "West-East Gas Transmission" has put forward higher requirements for the quality of pipeline steel and welding materials. In order to meet the construction needs of long-distance, high-pressure and large-diameter oil and gas pipelines, it is necessary to ensure that the pipeline steel has excellent mechanical properties and welding performance. However, the traditional submerged arc welding wire steel cannot meet the requirements of new pipeline steel for the performance of welded joints in some specific application scenarios, such as extreme weather and complex geological conditions. Therefore, the development of new submerged arc welding wire steel for pipeline steel has become the key to solving this problem. With the continuous progress of material science and welding technology, the addition of new alloy elements and the improvement of welding process make it possible to develop high-performance submerged arc welding wire steel. By optimizing the chemical composition and rolling and controlled cooling process of the welding wire steel, a weld with excellent strength and toughness, hydrogen-induced cracking resistance and low-temperature toughness can be obtained, thereby meeting the high requirements of new pipeline steel for welding materials. SUMMARY

[0003] The purpose of the present application is to provide a production method of a new rare earth submerged arc welding wire steel wire rod for pipeline steel. By adding rare earth elements and new alloy elements, the comprehensive performance of the welding wire steel is improved, including but not limited to low-temperature toughness impact performance, strength, toughness, corrosion resistance and the like. At the same time, by adding rare earth elements and nickel elements and optimizing the smelting process, the composition segregation and inclusions are reduced, the porosity is reduced, and the strength and toughness of the welding wire steel are improved.

[0004] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0005] The production method of the new rare earth submerged arc welding wire steel wire rod for pipeline steel according to the present application has the following specific process flow: blast furnace molten iron - molten iron pretreatment - top and bottom combined blowing smelting of converter - LF refining - VD vacuum treatment - small billet continuous casting - billet heating - high-pressure water descaling - rough rolling - flying shear - medium rolling - shear cutting - finish rolling - controlled cooling water tank - wire drawing - Stelmor cooling - coil collecting - trimming - sampling inspection - collecting and bundling - weighing - finished wire rod. The specific features are as follows:

[0006] Smelting:

[0007] The pre-processed molten iron and scrap steel are charged into the converter in a certain proportion, which is adjusted according to the specific production requirements; the end-point control target is C≥0.03% and T≥1620℃;

[0008] Slagging and blowing: slagging materials are added for slagging, and the slagging materials are added in batches; during the blowing process, the gun position and the bottom blowing stirring intensity are controlled, low-high-low gun position control is adopted, the gun position is 1.1-1.5 m, and the bottom blowing stirring intensity is 100-400 NL / min, so as to ensure the stability and high efficiency of the smelting process; tapping operation: after the smelting reaches the end point, the tapping operation is carried out; before tapping, alloy is added for deoxidization and alloying; the slag is blocked by the slag blocking cone during tapping, so as to reduce the influence of impurities in the slag on the molten steel; at the same time, the tapping temperature is controlled to be ≥1610℃, so as to ensure the smooth progress of the subsequent refining process; slagging and deoxidization: in the LF refining process, lime and fluorite slagging materials are added for slagging, and silicon iron deoxidizer is added for deoxidization; alloy fine adjustment: according to the analysis results of the molten steel composition, silicon iron, medium-carbon ferromanganese, nickel plate, ferromolybdenum and ferrotitanium alloy are added for fine adjustment, so as to ensure that the composition of the molten steel meets the target requirements; soft blowing and temperature measurement: after the refining is completed, soft blowing operation is required to further remove inclusions and gases in the molten steel; at the same time, temperature measurement operation is required to ensure that the temperature of the molten steel meets the requirements of the subsequent continuous casting process; the molten steel is subjected to VD vacuum degassing treatment, the vacuum degree is ≤0.10 KPa, the deep vacuum time is ≥10 min, after breaking the vacuum, 200 mSiCa wire is fed; the soft blowing time is ensured to be greater than 13 min, and the molten steel shall not be exposed during soft blowing; rare earth is added in the later stage of VD vacuum degassing, and appropriate means are adopted to ensure uniform distribution of rare earth elements;

[0009] The molten steel after VD vacuum treatment is subjected to continuous casting operation to obtain the required submerged arc welding wire steel billet; during continuous casting, the pulling speed and cooling intensity parameters need to be controlled to ensure that the quality and size of the billet meet the requirements. Continuous casting ensures constant pulling speed operation, the pulling speed control target is 2.1 m / min, and the secondary cooling water table adopts gas mist intensive cooling (K values of 1-4 zones are 1.5, 1.3, 1.3 and 1.3 respectively); the billet shall not have serious squareness deviation, bulging, center shrinkage, the hot acid macroscopic sample of each billet is taken for inspection, the skin crack, skin bubble, corner crack and intermediate crack defect levels shall not be greater than 1.5 level, and the remaining defects shall not be greater than 2.0 level, and the over-standard billet is changed to another one; the continuous casting billet is put into the slow cooling pit for slow cooling, and after slow cooling for 36 hours, it is sent to the next plant for rolling;

[0010] Rolling:

[0011] After the continuous casting billet is heated to the appropriate temperature, a rolling operation is performed; through multi-pass rolling, the continuous casting billet is rolled into a required specification of a rod; in the rolling process, the rolling temperature and the deformation amount need to be strictly controlled to ensure the structure and performance of the rod; before rolling, the long material factory inspects the surface quality of the casting billet and picks out the casting billet with surface defects. The casting billet heating system and the rolling process parameters are shown in the following table:

[0012] Casting billet heating system:

[0013]

[0014] Rolling process parameters:

[0015] The temperature control parameters are as shown in the following table, the starting roller speed is 0.1 m / s, the time on the roller is ensured to be more than 5 min, and the tempering effect is realized.

[0016]

[0017]

[0018] Further, the chemical composition includes the following weight percentages: C: 0.05%~0.10%; Mn: 1.55%~1.80%; Si: 0.08%~0.20%; P: ≤0.012%; S: ≤0.003%; Ni: 0.30%~0.50%; Mo: 0.30%~0.45%; B: 0.004%~0.008%; Ti: 0.06%~0.12%; rare earth elements: 0.001%~0.1%; and the rest is Fe and inevitable impurities.

[0019] Further, the mass ratio of molten iron to scrap steel is specifically 8:2 or 9:1.

[0020] Further, the chemical composition includes the following weight percentages: C: 0.07%; Mn: 1.65%; Si: 0.14%; P: 0.010%; S: 0.002%; Ni: 0.40%; Mo: 0.35%; B: 0.005%; Ti: 0.09%; rare earth Ce: 0.0025%; and the rest is Fe and inevitable impurities.

[0021] Further, the chemical composition includes the following weight percentages: C: 0.09%; Mn: 1.67%; Si: 0.12%; P: 0.009%; S: 0.001%; Ni: 0.42%; Mo: 0.36%; B: 0.006%; Ti: 0.11%; rare earth Ce: 0.0015%; and the rest is Fe and inevitable impurities.

[0022] Further, the chemical composition includes the following weight percentages: C: 0.10%; Mn: 1.68%; Si: 0.15%; P: 0.007%; S: 0.003%; Ni: 0.39%; Mo: 0.38%; B: 0.004%; Ti: 0.06%; rare earth Ce: 0.0030%; and the rest is Fe and inevitable impurities.

[0023] Further, the wire rod specification is Φ6.5mm.

[0024] Compared with the prior art, the present application has the beneficial technical effects that:

[0025] The present application promotes the precipitation of acicular ferrite (AF) and fine carbides (Mo2C, Cr7C3) through "low C + compound alloying (Ni / Mo synergistic strengthening)" combined with "double refining control of impurities (LF refining + VD vacuum degassing) + controlled rolling and controlled cooling + precise "online tempering" (control of roller speed)", so as to realize the matching of high strength and high toughness; and the grains produced by the conventional process are coarse (the average grain size is 25 μm, and the average grain size of the present application is below 15 μm), the size of the inclusions is also large, and the performance is significantly deteriorated. BRIEF DESCRIPTION OF DRAWINGS

[0026] The present application will be further described below in combination with the description of the accompanying drawings.

[0027] Figure 1 The microstructure of the new rare earth submerged arc welding wire rod for pipeline steel prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0028] A production method of a new rare earth submerged arc welding wire rod for pipeline steel, and the specific process flow is as follows: blast furnace molten iron - molten iron pretreatment - top and bottom combined blowing converter smelting - LF refining - VD vacuum treatment - small billet continuous casting - billet heating - high-pressure water descaling - rough rolling - flying shear - medium rolling - pinch shear - finish rolling - controlled cooling water tank - wire drawing - Stelmor cooling - coil collecting - trimming - sampling inspection - collecting and bundling - weighing - finished wire rod.

[0029] 1. Smelting

[0030] The converter production method of the rare earth submerged arc welding wire rod includes the steps of molten iron pretreatment, converter smelting, LF refining and continuous casting. The process parameters and operation specifications of each step need to be strictly controlled to ensure that the quality and performance of the final product meet the requirements. The molten iron is subjected to desulfurization pretreatment to reduce the sulfur content in the molten iron and ensure the smooth progress of the subsequent smelting process. The materials are loaded into the converter according to a certain proportion, such as 8:2 or 9:1, etc. The final control target is C≥0.03% and T≥1620℃.

[0031] Slagging and blowing: Add lime, magnesium balls, etc. to make slag, and the slagging material can be added in batches. During the blowing process, the gun position and the bottom blowing stirring intensity need to be controlled to ensure the stability and efficiency of the smelting process. At the same time, regular sampling analysis of the molten steel composition is required to adjust the smelting parameters. Tapping operation: After the smelting reaches the end point, the tapping operation is carried out. Before tapping, alloying is required for deoxidation and alloying, such as aluminum manganese iron, low-carbon manganese iron, etc. The slag cone needs to be used to block the slag during tapping to reduce the impact of impurities in the slag on the molten steel. At the same time, the tapping temperature needs to be controlled to ensure the smooth progress of the subsequent refining process. Slagging and deoxidation: During the LF refining process, lime, fluorite, etc. are added to make slag, and silicon iron, etc. is added for deoxidation. Regular sampling analysis of the composition and temperature of the molten steel is required during the refining process to adjust the refining parameters. Alloy fine tuning: According to the results of the composition analysis of the molten steel, silicon iron, medium-carbon manganese iron, nickel plate, molybdenum iron, titanium iron, etc. are added for fine tuning to ensure that the composition of the molten steel meets the target requirements. Soft blowing and temperature measurement: After the refining is completed, soft blowing operation is required to further remove inclusions and gases in the molten steel. At the same time, temperature measurement operation is required to ensure that the temperature of the molten steel meets the requirements of the subsequent continuous casting process. The molten steel needs to be treated by VD vacuum degassing, vacuum degree ≤0.10KPa; deep vacuum time ≥10min; after breaking the vacuum, feed 200mSiCa wire; ensure that the soft blowing time is greater than 13min, and the molten steel should not be exposed during soft blowing. The timing and method of adding rare earth elements have an important influence on the performance of the welding wire steel. Rare earth elements are added in the later stage of VD vacuum degassing, and appropriate methods (such as wire feeding, spraying, etc.) are used to ensure uniform distribution of rare earth elements.

[0032] The molten steel after VD vacuum treatment is subjected to continuous casting operation to obtain the required buried arc welding wire steel billet. The parameters such as casting speed and cooling intensity need to be controlled during continuous casting to ensure that the quality and size of the billet meet the requirements. Continuous casting ensures constant speed operation, and the target control speed is 2.1m / min. The billet should not have serious decarburization, bulging, center shrinkage, and the billet hot acid macroscopic sample taken from each furnace should be tested, the skin crack, skin bubble, corner crack, and intermediate crack defect level should not be greater than 1.5 level, and the remaining defects should not be greater than 2.0 level, and the over-standard billet is judged as a whole. After 36 hours of slow cooling in the slow cooling pit, the billet is sent to the next plant for rolling.

[0033] 2. Rolling

[0034] After the continuous casting billet is heated to the appropriate temperature, it is subjected to rolling operation. Through multi-pass rolling, the continuous casting billet is rolled into the required size of the rod. During the rolling process, the rolling temperature and deformation amount need to be strictly controlled to ensure the organization and performance of the rod. The surface quality of the billet is inspected before rolling in the long material plant, and the billet with surface defects is selected out. The billet heating system and rolling process parameters are shown in Tables 1 and 2.

[0035] Table 1 Casting blank heating schedule

[0036]

[0037] Table 2 Rolling process parameters

[0038]

[0039] A new type of rare earth submerged arc welding wire steel rod for pipeline steel is produced according to the above steps:

[0040] The molten iron is subjected to desulfurization treatment to reduce the sulfur content in the steel and improve the quality of the steel. The desulfurized molten iron is sent to a converter for smelting, and at the same time, phosphorus and other impurities are removed, the steel temperature and chemical composition are controlled to meet the requirements of the subsequent process. In the LF furnace, the chemical composition and inclusion morphology in the steel are further controlled by adjusting the slag composition and adding alloying elements to improve the purity and performance of the steel. After vacuum degassing, a reasonable continuous casting process parameter is adopted, 2.1 m / min constant speed full protection casting, and the secondary cooling water table adopts gas mist strong cooling (K value of 1-4 area is 1.5, 1.3, 1.3, 1.3 respectively), to control the center segregation and shrinkage of the continuous casting blank, and to ensure the surface and internal quality of the continuous casting blank. The continuous casting blank is heated, and the heating section temperature range is controlled within a certain range, and exceeding the maximum temperature limit is strictly prohibited. Then high-pressure water descaling is carried out to ensure that there is no residual iron oxide scale on the surface of the blank. Then rolling is carried out to produce steel rods that meet the specifications, and the rolling Φ6.5mm specification rod is implemented. The finished product composition control is shown in Table 3, and the microstructure is observed after rolling, which is acicular ferrite + bainite.

[0041] Table 3 Example chemical composition control (%)

[0042]

[0043]

[0044] After rolling, the sample is subjected to tensile test according to national standard GB / T 228.1, and the mechanical properties are as follows.

[0045] Table 4 Example rod mechanical property results

[0046]

[0047] The conventional smelting and rolling process does not add rare earth, and single refining is adopted, and the online tempering time of rolling is short, while the present application fully plays the role of rare earth element modified inclusions, controls the inclusions in the steel through double refining, and controls the online tempering time to be more than 5 min.

[0048] Table 5 Performance of new submerged arc welding wire steel after welding

[0049] Indicators Process of the application (key process) Comparative example (conventional process) Impact energy at -60°C (V-notch) 85-95J 45-55J Tensile strength (σb) 690-710 MPa 640-660 MPa Weld deposition rate 12-14 kg / h 8-10 kg / h Deslagging rate 97-99％ 82-85％ Wire surface finish (Ra) ≤ 1.6 μm 3.2-6.4 μm Inclusion size (max) ≤ 10 μm 20-30 μm

[0050] The new rare earth submerged arc welding wire steel obtained by the above production method has a tensile strength of 620 MPa, an elongation of more than 80%, and a low-temperature impact energy of more than 90 J at -60 DEG C after drawing, and has more excellent performance, which can meet the extreme requirements of new pipeline steel on the performance of welded joints. The performance after welding is shown in Table 5, and it can be seen that the performance of the new submerged arc welding wire steel after welding is more excellent.

[0051] The application promotes the precipitation of acicular ferrite (AF) and fine carbides (Mo2C, Cr7C3) through "low C + composite alloying (Ni / Mo synergistic strengthening)" combined with "double refining control of impurities + control of rolling and controlled cooling (large deformation in the unrecrystallization zone) + precise online tempering", realizes the matching of high strength and high toughness, and the performance of the conventional process production is significantly deteriorated due to the coarse grains (the average grain size is 25 μm, while the average grain size of the patent is less than 15 μm) and the large size of the inclusions, which proves the non-obviousness of the production method and parameters of the patent.

[0052] The above-described embodiments are only descriptions of the preferred modes of the present application, and do not limit the scope of the present application, and various modifications and improvements to the technical solutions of the present application made by those skilled in the art without departing from the design spirit of the present application shall fall within the protection scope determined by the claims of the present application.

Claims

1. A novel method for producing rare earth submerged arc welding wire rod for pipeline steel, comprising the following process flow: blast furnace molten iron—molten iron pretreatment—converter top and bottom re-blowing smelting—LF refining—VD vacuum treatment—small billet continuous casting—billet heating—high-pressure water descaling—rough rolling—flying shear—intermediate rolling—cutting shear—finish rolling—controlled cooling water tank—wire feeding—Stelmore cooling—coiling—trimming—sampling inspection—collection and bundling—weighing—finished wire rod, characterized in that, Specifically: Smelting: The pretreated molten iron and scrap steel are loaded into the converter in a certain proportion, and the proportion is adjusted according to the specific production requirements; the end control target is C≥0.03%; T≥1620℃; Slagging and blowing: add slagging materials for slagging, and the slagging materials are added in batches; during the blowing process, the gun position and the bottom blowing stirring intensity are controlled, the low-high-low gun position control is adopted, the gun position is 1.1-1.5m, and the bottom blowing stirring intensity is 100-400NL / min, so as to ensure the stability and efficiency of the smelting process; tapping operation: after the smelting reaches the end point, the tapping operation is carried out; before tapping, alloy is added for deoxidization and alloying; when tapping, the slag cone is used to block the slag, so as to reduce the influence of impurities in the slag on the molten steel; at the same time, the tapping temperature is controlled to be≥1610℃, so as to ensure the smooth progress of the subsequent refining process; slagging and deoxidization: in the LF refining process, lime and fluorite slagging materials are added for slagging, and silicon iron deoxidizer is added for deoxidization; Alloy Fine adjustment: according to the analysis results of the composition of the molten steel, silicon iron, medium-carbon manganese iron, nickel plate, molybdenum iron and titanium iron alloy are added for fine adjustment, so as to ensure that the composition of the molten steel meets the target requirements; soft blowing and temperature measurement: after the refining is completed, soft blowing operation is needed to further remove the inclusions and gas in the molten steel; at the same time, temperature measurement operation is needed to ensure that the temperature of the molten steel meets the requirements of the subsequent continuous casting process; the molten steel needs to be treated by VD vacuum degassing, the vacuum degree is≤0.10KPa, the deep vacuum time is≥10min; after breaking the vacuum, 200mSiCa wire is fed; the soft blowing time is guaranteed to be greater than 13min, and the molten steel shall not be exposed during soft blowing; rare earth is added in the later stage of VD vacuum degassing, and appropriate methods are adopted to ensure the uniform distribution of rare earth elements; The molten steel after VD vacuum treatment is subjected to continuous casting operation to obtain the required buried arc welding wire steel billet; during the continuous casting process, the pulling speed and cooling intensity parameters need to be controlled to ensure that the quality and size of the billet meet the requirements; The continuous casting is guaranteed to be constant speed operation, the pulling speed control target is 2.1m / min, and the air mist strong cooling is used for the secondary cooling water table: the K values of 1-4 zones are 1.5, 1.3, 1.3 and 1.3 respectively; the cast blank shall not have serious squareness, bulging and center shrinkage, the cast blank hot acid low multiple sample is taken for inspection every furnace, the skin crack, skin bubble, corner crack and intermediate crack defect level shall not be greater than 1.5 level, and the remaining defects shall not be greater than 2.0 level, and the over-standard cast blank is changed to another one; the continuous casting blank is put into the slow cooling pit for slow cooling after being taken out of the line, and is sent to the next plant for rolling after slow cooling for 36 hours; Rolling: After the continuous casting blank is heated to an appropriate temperature, rolling operation is carried out; through multi-pass rolling, the continuous casting blank is rolled into the required specification of wire rod; during the rolling process, the rolling temperature and deformation amount need to be strictly controlled to ensure the organization and performance of the wire rod; the surface quality of the blank is inspected by the long material plant before rolling, and the blank with surface defects is picked out; the blank heating system and rolling process parameters are shown in the following table: Blank heating system: Rolling process parameters:

2. The process for the production of new type of RE-Bearing Flux Cored Wire Rod for pipeline steel as claimed in claim 1, wherein, The chemical composition includes the following weight percentages: C: 0.05%-0.10%; Mn: 1.55%-1.80%; Si: 0.08%-0.20%; P:≤0.012%; S: ≤0.003%; Ni: 0.30%~0.50%; Mo: 0.30%~0.45%; B: 0.004%~0.008%; Ti: 0.06%~0.12%; rare earth elements: 0.001%~0.1%; the rest is Fe and inevitable impurities.

3. A novel process for the production of master alloy of rare earth submerged arc welding wire for pipeline steel as claimed in claim 1, wherein The mass ratio of molten iron to scrap steel is specifically 8:2 or 9:

1.

4. A novel process for the production of RE-arc welding wire rod for pipeline steel as claimed in claim 2, wherein Chemical components including the following weight percentages: C: 0.07%; Mn: 1.65%; Si: 0.14%; P: 0.010%; S: 0.002%; Ni: 0.40%; Mo: 0.35%; B: 0.005%; Ti: 0.09%; rare earth Ce: 0.0025%; the rest is Fe and inevitable impurities.

5. The process for the production of new type of RE-Bearing Flux Cored Wire Rod for pipeline steel as claimed in claim 2, wherein, Chemical components including the following weight percentages: C: 0.09%; Mn: 1.67%; Si: 0.12%; P：0.009％； S: 0.001%; Ni: 0.42%; Mo: 0.36%; B: 0.006%; Ti: 0.11%; rare earth Ce: 0.0015%; the rest is Fe and inevitable impurities.

6. A novel process for the production of RE-arc welding wire rod for pipeline steel as claimed in claim 2, wherein, Chemical components including the following weight percentages: C: 0.10%; Mn: 1.68%; Si: 0.15%; P：0.007％； S: 0.003%; Ni: 0.39%; Mo: 0.38%; B: 0.004%; Ti: 0.06%; rare earth Ce: 0.0030%; the rest is Fe and inevitable impurities.

7. A novel process for the production of master alloy of rare earth submerged arc welding wire for pipeline steel as claimed in claim 1, wherein, The wire rod specification is Φ6.5mm.

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