A method of manual arc welding of high-strength corrosion-resistant steel

Abstract

This invention discloses a manual arc welding method for high-strength corrosion-resistant steel. It belongs to the field of high-strength corrosion-resistant steel welding. The chemical composition of the high-strength corrosion-resistant steel is: C: 0.7–1.1 wt%, Si: 0.5–0.7 wt%, Mn: 0.7–0.8 wt%, Cr: 14–18 wt%, Ni: 0.9–1.3 wt%. The specific operating steps are as follows: (1) selection of welding materials; (2) selection of preheating temperature; (3) control of interpass temperature; (4) control of the welding process. This manual arc welding method fills the welding gap for this type of steel, which is beneficial to the application and promotion of this steel. Furthermore, the welding method provided by this invention has a wide range of applications, and the mechanical properties of the welded joint meet the requirements for use, and it also has good corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of welding high-strength corrosion-resistant steel, and specifically to a manual electric arc welding method for high-strength corrosion-resistant steel. Background Technology

[0002] Lateritic nickel ore is an important resource of interest to many countries due to its high nickel content, ease of mining, and high practical value. Domestic steel mills utilize lateritic nickel ore to produce high-strength, corrosion-resistant steel with a Cr-Ni alloy composition. Its tensile strength exceeds 700 MPa, and it exhibits strong resistance to atmospheric corrosion in coastal environments. Furthermore, thanks to the nickel content in the ore, this steel also possesses good low-temperature toughness. In addition, its lower alloy content compared to ordinary stainless steel gives it a cost advantage and promising application prospects.

[0003] Currently, there is no use of this type of high-strength corrosion-resistant steel on the market, especially no welding method, which is not conducive to the promotion and use of this type of steel. The high strength and high Cr content of this type of steel, as well as the significant difference in welding methods compared to ordinary carbon steel, are all challenges in welding.

[0004] Therefore, the present invention aims to provide a manual arc welding method suitable for high-strength (tensile strength ≥700Mpa) corrosion-resistant steel. The manual arc welding is an all-position welding method, which is suitable for various welding environments. It ensures that the various properties after welding meet the usage requirements, laying a good foundation for the application and promotion of this type of steel. Summary of the Invention

[0005] Purpose of the Invention: The purpose of this invention is to propose a manual electric arc welding method for high-strength corrosion-resistant steel. This type of steel is produced from laterite nickel ore and possesses high strength, corrosion resistance, and low-temperature toughness (Cr-Ni system). It is suitable for coastal atmospheric environmental engineering applications, and its cost is significantly lower than that of traditional stainless steel, showing very promising application prospects.

[0006] Technical solution: The present invention provides a manual arc welding method for high-strength corrosion-resistant steel; the welding test plate used for the high-strength corrosion-resistant steel is 20mm thick high-strength corrosion-resistant steel.

[0007] Furthermore, the chemical composition of the high-strength corrosion-resistant steel is as follows: C 0.7-1.1 wt%, Si 0.5-0.7 wt%, Mn 0.7-0.8 wt%, Cr 14-18 wt%, and Ni 0.9-1.3 wt%.

[0008] Furthermore, the mechanical properties of the high-strength corrosion-resistant steel are: tensile strength of 730-780 MPa, and impact energy Akv = 60 J at -40℃.

[0009] Furthermore, a manual arc welding method for high-strength corrosion-resistant steel is provided; the specific operation steps are as follows:

[0010] (1) Selection of welding materials;

[0011] (2) Selection of preheating temperature;

[0012] (3) Control of inter-track temperature;

[0013] (4) Control of the welding process.

[0014] Furthermore, in step (1), the specific conditions of the welding material are as follows: the selected welding electrode is E2209-16 manual welding electrode; wherein, the Cr content is 21-24 wt%.

[0015] Furthermore, in step (2), the preheating temperature is selected as 250-300℃.

[0016] Furthermore, in step (3), the interpass temperature is controlled as follows: the interpass temperature is controlled to be ≤150℃.

[0017] Furthermore, in step (4), the specific conditions for controlling the welding process are: the welding groove is selected as type X according to the engineering application.

[0018] Furthermore, the specific welding method for the high-strength corrosion-resistant steel is as follows:

[0019] Preheating temperature: 250-300℃; use Φ3.2mm welding rod for root pass; welding current for front pass: 90-110A; welding voltage: 20V-25V; welding speed: 12cm / min-15cm / min; welding current for back pass: 120-130A; welding voltage: 25V-30V; welding speed: 22cm / min-26cm / min.

[0020] For filler and cover welding, use Φ4.0mm welding rods, control the interpass temperature to ≤150℃, the welding current to 150A~170A, the welding voltage to 20V~30V, and the welding speed to 18cm / min~22cm / min.

[0021] Furthermore, the final test results of the welded joint were as follows: tensile strength ≥750MPa, bending d=4a, no cracks at 180°; at -20℃, the average impact value of the weld metal was 60J; the average impact value of the fusion line was 50J; the average impact value 1mm outside the fusion line was 48J; and the average impact value 2mm outside the fusion line was 48J.

[0022] The average corrosion rate of the welded joint under 50 g / L NaCl solution spray conditions for 96 hours was 4–5 g / m³. 2The average corrosion rate of ordinary carbon steel Q235 under the same corrosive environment is 143-145 g / m. 2 .

[0023] Beneficial effects: Compared with the prior art, the features of this invention are: 1. This invention is a manual arc welding method for welding high-strength corrosion-resistant steel. It fills the welding gap for this type of steel and is conducive to the promotion and application of this steel; 2. The welding method provided by this invention has a wide range of applications, and the mechanical properties of the welded joint meet the requirements of use, and it has good corrosion resistance. Detailed Implementation

[0024] The present invention will be further described below with reference to embodiments.

[0025] This invention proposes a manual arc welding method for high-strength corrosion-resistant steel; this method has a wide range of applications (manual arc welding is all-position welding), and the welded joint fully meets the usage requirements in terms of various properties.

[0026] The present invention discloses a manual arc welding method for high-strength corrosion-resistant steel, comprising the following process parameters and steps:

[0027] 1) Selection of welding materials: Since the tensile strength of high-strength corrosion-resistant steel is ≥700MPa, and the Cr content in the base material is about 14-18wt%, combined with the corrosion resistance requirements of the welded joint, E2209-16 manual welding rod (Cr content 21-24wt%) is selected.

[0028] 2) Selection of preheating temperature: Because high-strength corrosion-resistant steel has high strength, and the Cr content of the base material is 14-18wt% and the Cr content of the welding material is 21-24wt%, if the preheating temperature is too low, the Cr element will easily deviate near the welding fusion line, resulting in the generation of microcracks, which will eventually cause the weld to crack.

[0029] Therefore, the preheating temperature is higher than that of ordinary carbon steel. In this invention, the preheating temperature is selected as 250-300℃. At this temperature, welding of high-strength corrosion-resistant steel for the bottom layer can ensure that no welding cracks occur.

[0030] 3) Interpass temperature control: Interpass temperature control is particularly important. Generally speaking, the interpass temperature during welding should not be lower than the preheating temperature. However, the preheating temperature of this invention exceeds 250℃. When welding the filler layer, an interpass temperature above 250℃ will cause the grains of the weld metal and the heat-affected zone of the base metal to grow rapidly. The coarse weld structure and heat-affected zone structure seriously affect the mechanical properties and corrosion resistance of the welded joint. Therefore, it is necessary to control the interpass temperature to prevent the joint structure from growing excessively and to ensure the joint performance. Therefore, this invention controls the interpass temperature to ≤150℃.

[0031] 4) Control of welding process: The welding groove is generally selected as X type according to the engineering application; according to the requirements of preheating temperature selection and interpass temperature control, when welding high-strength corrosion-resistant steel, the root pass should be welded continuously and quickly. If possible, the test plate can be heat-insulated to prevent the temperature of the test plate from dropping during the welding process and failing to meet the preheating conditions.

[0032] When performing the root pass welding, reduce oscillation to quickly fill the weld bead. (Although oscillation welding can fill the weld width, the weld length is too short.) When performing the fill pass welding, use a low current and weld quickly to ensure that the interpass temperature is ≤150℃.

[0033] This invention addresses the welding of high-strength corrosion-resistant steel and presents a manual electric arc welding method. It fills a gap in the welding of this type of steel and is beneficial for the application and promotion of this steel.

[0034] The welding method provided by this invention has a wide range of applications, and the mechanical properties of the welded joint meet the requirements of use, and it also has good corrosion resistance.

[0035] Welding of this type of high-strength corrosion-resistant steel using the welding method provided by this invention:

[0036] Preheating temperature: 250-300℃; use Φ3.2mm welding rod for root pass; welding current for front pass: 90-110A; welding voltage: 20V-25V; welding speed: 12cm / min-15cm / min; welding current for reverse pass: 120-130A; welding voltage: 25V-30V; welding speed: 22cm / min-26cm / min.

[0037] For filler and cover welding, use Φ4.0mm welding rods, control the interpass temperature to ≤150℃, the welding current to 150A~170A, the welding voltage to 20V~30V, and the welding speed to 18cm / min~22cm / min;

[0038] Throughout the welding process, oscillations were minimized, welding was performed rapidly, and the preheating temperature and interpass temperature were ensured to meet the requirements of this invention. The final welded joint test results showed a tensile strength ≥750MPa, a bending d=4a, and no cracks at 180°. At -20℃, the average impact value of the weld metal was 60J; the average impact value at the fusion line was 50J; the average impact value 1mm outside the fusion line was 48J; and the average impact value 2mm outside the fusion line was also 48J.

[0039] The average corrosion rate of the welded joint under 50 g / L NaCl solution spray conditions for 96 hours was 4–5 g / m³. 2 .

[0040] Therefore, after welding high-strength corrosion-resistant steel using the manual arc welding method provided by this invention, the welded joint is free of cracks, and all properties meet the application requirements.

[0041] Example 1

[0042] A manual arc welding method for high-strength corrosion-resistant steel is proposed. The test plate bevel is selected as X-type, and the bevel is cleaned with a grinding wheel to remove water rust and oil stains.

[0043] The welding test plate was made of 20mm thick high-strength corrosion-resistant steel.

[0044] The chemical composition of the high-strength corrosion-resistant steel is: C 0.7-1.1 wt%, Si 0.5-0.7 wt%, Mn 0.7-0.8 wt%, Cr 14-18 wt%, and Ni 0.9-1.3 wt%.

[0045] The mechanical properties of the high-strength corrosion-resistant steel are: tensile strength of 730-780 MPa, and impact energy Akv = 60 J at -40℃.

[0046] Manual arc welding process parameters: preheating temperature 250℃, use φ3.2mm welding rod for root pass, welding current for front pass is 90A, welding voltage is 20V, welding speed is 12cm / min; welding current for reverse pass is 120A, welding voltage is 25V, welding speed is 22cm / min.

[0047] For filler and cover welding, use φ4.0mm welding rods, control the interpass temperature to ≤150℃, the welding current to 150A, the welding voltage to 20V, and the welding speed to 18cm / min.

[0048] The mechanical properties of the weld after welding in this embodiment were tested and analyzed, and the results are as follows: the tensile strength of the welded joint is 7069 MPa; no cracks were found when bending d=4a at 180°; the average impact value of the weld metal at -20℃ is 60 J; the average impact value at the fusion line is 50 J; the average impact value 1 mm outside the fusion line is 48 J; the average impact value 2 mm outside the fusion line is 48 J; the average corrosion rate of the welded joint under 50 g / L NaCl solution spray for 96 h at all times is 4 g / m². 2 The average corrosion rate of ordinary carbon steel Q235 under the same corrosive environment is 143 g / m. 2 .

[0049] Test results show that the high-strength corrosion-resistant steel welded using the manual arc welding process of this patent has all mechanical properties that meet the requirements for use after welding, and also has good corrosion resistance.

[0050] Example 2

[0051] A manual arc welding method for high-strength corrosion-resistant steel is proposed. The test plate bevel is selected as X-type, and the bevel is cleaned with a grinding wheel to remove water rust and oil stains.

[0052] The welding test plate was made of 20mm thick high-strength corrosion-resistant steel.

[0053] The chemical composition of the high-strength corrosion-resistant steel is: C 0.7-1.1 wt%, Si 0.5-0.7 wt%, Mn 0.7-0.8 wt%, Cr 14-18 wt%, and Ni 0.9-1.3 wt%.

[0054] The mechanical properties of the high-strength corrosion-resistant steel are: tensile strength of 730-780 MPa, and impact energy Akv = 60 J at -40℃.

[0055] Manual arc welding process parameters: preheating temperature 300℃, φ3.2mm welding rod for root pass, welding current for front pass 110A, welding voltage 25V, welding speed 15cm / min; welding current for reverse pass 130A, welding voltage 230V, welding speed 26cm / min;

[0056] For filler and cover welding, use φ4.0mm welding rods, control the interpass temperature to ≤150℃, the welding current to 170A, the welding voltage to 30V, and the welding speed to 2cm / min.

[0057] The mechanical properties of the weld after welding in this embodiment were tested and analyzed, and the results are as follows: the tensile strength of the welded joint is 7069 MPa; no cracks were found when bending d=4a at 180°; the average impact value of the weld metal at -20℃ is 60J; the average impact value at the fusion line is 50J; the average impact value at 1mm outside the fusion line is 48J; and the average impact value at 2mm outside the fusion line is 48J.

[0058] The salt spray corrosion performance of the welded joint was as follows: 5 g / m² of 50 g / L NaCl solution sprayed for 96 hours, with an average corrosion rate of 5 g / m² over all time periods. 2 The average corrosion rate of ordinary carbon steel Q235 under the same corrosive environment is 145 g / m. 2 .

[0059] Test results show that the high-strength corrosion-resistant steel welded using the manual arc welding process of this patent has all mechanical properties that meet the requirements for use after welding, and also has good corrosion resistance.

[0060] When conventional high-strength steel is preheated to 120°C instead of 250-300°C, the weld will bend and break.

[0061] When preheating is used at 250-300℃ but the interpass temperature is controlled to be higher than the preheating temperature, the weld will bend and break.

[0062] When preheating is performed at 250-300℃ and the interpass temperature is controlled at ≤150℃, the weld bending is intact.

[0063] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A manual electric arc welding method for high-strength corrosion-resistant steel, characterized in that, The high-strength corrosion-resistant steel used in the welding test plate is a 20mm thick high-strength corrosion-resistant steel with the following chemical composition: C: 0.7~1.1wt%, Si: 0.5~0.7wt%, Mn: 0.7~0.8wt%, Cr: 14~18wt%, Ni: 0.9~1.3wt%; and the following mechanical properties: tensile strength of 730~780MPa, and impact energy Akv=60J at -40℃. The welding method operation steps are as follows: (1) Selection of welding materials; the specific conditions of the welding materials are as follows: the selected welding rod is E2209-16 manual welding rod; wherein, the Cr content is 21~24wt%; (2) Selection of preheating temperature; The preheating temperature is selected as 250~300℃; (3) Control of interpass temperature; The interpass temperature is controlled to be ≤150℃. (4) Control of the welding process; The specific conditions for controlling the welding process are: the welding groove is selected as type X according to the engineering application; The specific welding method for the high-strength corrosion-resistant steel is as follows: Preheating temperature: 250~300℃; use Φ3.2mm welding rod for root pass; welding current for front pass: 90~110A; welding voltage: 20V~25V; welding speed: 12cm / min~15cm / min; welding current for reverse pass: 120~130A; welding voltage: 25V~30V; welding speed: 22cm / min~26cm / min. For filler and cover welding, use Φ4.0mm welding rods, control the interpass temperature to ≤150℃, the welding current to 150A~170A, the welding voltage to 20V~30V, and the welding speed to 18cm / min~22cm / min; The final test results of the welded joint were as follows: tensile strength ≥750MPa, bending d=4a, no cracks at 180°; at -20℃, the average impact value of the weld metal was 60J; the average impact value of the fusion line was 50J; the average impact value 1mm outside the fusion line was 48J; and the average impact value 2mm outside the fusion line was 48J. The salt spray corrosion performance of the welded joint is 4-5 g / m2 under the condition of spraying 50 g / L NaCl solution for 96 h on average. 2 .