Vacuum electron beam welding process for low-alloy ultrahigh-strength steel

Abstract

The invention relates to a vacuum electron beam welding process for low-alloy ultrahigh-strength steel, which is used for performing vacuum electron beam welding on large and thick low-alloy ultrahigh-strength steel, meets the requirement that the welding joint coefficient at a welding seam is greater than or equal to 0.90, adopts 35CrMnSiA as a base material, comprises a head part, a body part and a bottom part, adopts vacuum electron beams for welding to form two welding seams, and adopts the welding parameters that the rising gradient is 3-5ms, the rising gradient is 3-5ms, and the rising gradient is 3-5ms; the descending gradient is 35-50 ms, scanning X 200-300 and Y 200-300, circular scanning is carried out, the frequency is 200-300 HZ, the welding linear speed is 240-280 mm / min, the lap joint angle is 7-10 degrees, first positioned welding is carried out with beam 10-20 MA and surface focusing, second preheating welding is carried out with beam 30-50 MA and lower focusing 10-15, third depth welding is carried out with beam 100-130 MA and lower focusing 10-15, fourth modification welding is carried out with beam 50-60 MA and upper focusing 50-60, and the requirements that the joint coefficient at a welding seam of a large and thick piece product is larger than or equal to 0.90 and KU2 is larger than or equal to 40 J are met. The weld joint meets the NB / T47013.2-2015 I-level requirement, the one-time welding qualification rate of products is larger than or equal to 95%, and the mechanical property of the weld joint is consistent with the height of a body.

Description

Technical Field

[0001] The present invention belongs to the technical field of Cr-Mn-Si low alloy ultra-high strength steel manufacturing, and in particular relates to a low alloy ultra-high strength steel vacuum electron beam welding process for performing vacuum electron beam welding on thick low alloy ultra-high strength steel pieces, ultimately satisfying that the welding joint coefficient at the weld is ≥0.90. Background Art

[0002] At present, the standard of low alloy CrMnSiA series materials is GB / T3077-2015, and the grade is 35CrMnSiA. This material is cheap. When used in the quenching and low temperature tempering state, the hardness and strength of the steel are high. It is mainly used to manufacture heavy load, medium peripheral speed, high strength parts, such as high pressure blower impellers, high strength parts used in aircraft, etc. Under the conditions of quenching and low temperature tempering, the mechanical properties that this material can achieve are: Rm ≥ 1620MPa, KU2 ≥ 45J. Due to the large specifications and complex shapes of the products, three-stage welding is required for connection, with deep welds and high processing accuracy, and the joint coefficient at the weld is ≥ 0.90, KU2 ≥ 40J. The traditional argon arc welding method cannot meet the requirements due to the lack of suitable high-strength welding wire. Because the vacuum electron beam has strong penetration ability, large weld depth-to-width ratio, strong welding adaptability, the electron beam welding process parameters can be adjusted in a wide range, and the control is flexible. It can weld 0.1mm thin plates, 200-300mm thick plates, and complex welded parts. It has high production efficiency and is suitable for mass production. Therefore, vacuum electron beam welding is selected. Due to the complex shape and the welding depth of up to 38mm, the existing welding parameters cannot meet the requirements. Therefore, it is necessary to carry out technical research and development based on this background. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a low-alloy ultra-high strength steel vacuum electron beam welding process that meets the requirements of joint coefficient ≥0.90 and KU2 ≥40J at the weld of large and thick products, and at the same time meets the requirements of NB / T47013.2-2015 Level I, and the products produced according to the welding process parameters have a one-time welding pass rate of ≥95%, and the mechanical properties at the weld are highly consistent with those of the main body.

[0004] To achieve the above object, the present invention adopts the following technical solutions: A vacuum electron beam welding process for low alloy ultra-high strength steel, the selected base material is 35CrMnSiA, including three parts: head, body and bottom, and two welds are formed by vacuum electron beam welding, and the steps are as follows: Step 1) Preparation before welding: Step 1.1) The equipment and tools used must be checked and adjusted to be qualified, and welding operations can only be carried out after they are confirmed to be normal; Step 1.2) Check whether the parts to be welded meet the requirements, whether the ingot number is consistent with the matching table, and whether they can be correctly assembled; Step 1.3) Check and clean the 100MM range of the workpiece welding area and the burrs, rust, bumps and oil stains on the inner liner ring, and check whether the size of the inner liner ring matches. If there is rust or bumps that seriously affect the assembly welding, the lathe must be corrected to meet the requirements; Step 1.4), Grind and clean the weld surface and the weld sides within 100mm of the burrs, rust, oil stains and other impurities visible to the naked eye, and clean the iron filings, polishing materials, oil stains and debris inside the workpiece; Step 1.5) Use a Gauss meter to measure whether the workpiece is magnetic and ensure that the workpiece is completely demagnetized; Step 1.6) Use ethanol or acetone to clean the oil and dust impurities within 100mm around the welding surface to ensure that the welding area is clean; Step 2), pairing: Step 2.1) Use horizontal or vertical assembly method to ensure that each weld is seamless straight butt joint without chamfer. Each weld is self-melting by manual tungsten inert gas arc welding, six points are symmetrically spot welded, and the welding length is 100-150mm to ensure firmness and reliability. Step 2.2) It is forbidden to assemble more than 3 pieces at a time, and the time of placing the workpieces on site after assembly should be reduced as much as possible to ensure the cleanliness of the workpieces; Step 3) Welding: Step 3.1) Before entering the chamber, clean the workbench and vacuum chamber to remove debris. The workpiece is hoisted onto the machine with one top and one clamp. The body is equipped with adjustable bracket rollers to ensure that the workpiece rotates horizontally and smoothly. If the roller is close to the weld, a guard plate should be provided to prevent splashes from falling onto the roller surface and affecting the rotation. Use non-woven fabric and ethanol solution to clean the weld area again to make it clean and free of impurities. Step 3.2), the workpiece enters the vacuum box to evacuate the vacuum, and edit the welding program before formal welding; Step 3.3), Formal welding: Fixed parameters of the equipment: electron gun chamber pressure 6E-2---3E-3, working chamber pressure 6E-2---3E-3; bias voltage 2200V, high voltage 85KV, filament 40A; Welding adjustment parameters: rising gradient 3-5ms, falling gradient 35-50ms, scanning X200-300, Y200-300, circular scanning; frequency 200-300HZ, welding line speed 240-280mm / min; overlap angle 7°-10° (6-10 seconds); The first positioning welding: beam 10-20MA, surface focus; the second preheating welding: beam 30-50MA, lower focus 10-15; the third depth welding: beam 100-130MA, lower focus 10-15; the fourth modification welding: beam 50-60MA, upper focus 50-60; if the third welding is not well formed or there are pits on the weld surface, the modification weld should be carried out, if the formation is good, the modification weld may not be carried out; Step 3.4) Fill in the welding record as required; Step 3.5) After welding is completed, the procedure must be completed - decompression and gas filling - exit the vacuum chamber - lift the heat treatment furnace, clean the vacuum chamber and workbench and remove debris; Step 4), post-weld stress relief heat treatment: Step 4.1) Raise the furnace temperature to 450℃ and keep it warm 2 hours before welding; Step 4.2), the welded products are put into the furnace in time, and the temperature is raised to 650℃ after a batch of welding is completed and all the products are put into the furnace. The heating time is 2 hours; Step 4.3), keep at 650℃ for 8 hours and then cool down, the cooling rate is ≤50℃ / h; Step 4.4), the furnace temperature drops to ≤250℃ and the furnace is taken out of the furnace; Step 5) Post-weld non-destructive testing: The welded joints are subjected to radiographic testing, and after passing the test, mechanical properties testing is performed to calculate the joint coefficient.

[0005] Compared with the prior art, the present invention has the following advantages: The parent material selected by the present invention is 35CrMnSiA, which consists of three parts: head, body and bottom. It is welded by vacuum electron beam and has two welds. According to the purpose of the present invention, the production process route adopted by the present invention is: electric furnace smelting + refining outside the furnace + vacuum degassing + continuous casting → heating → forging, rolling → annealing → semi-processing before welding → welding → X-ray detection → performance heat treatment - physical and chemical testing - fine processing → assembly → acceptance.

[0006] The three-stage welding product of the present invention fully meets the use requirements after testing; compared with the traditional welding process, it has a higher welding rate and lower cost. Especially for the complex and thick welding workpieces in the present invention, the electron beam is easy to control, the welding accessibility is good, and the welding qualification rate is high. Its production process can be widely applied to other similar models with the maximum welding parameters of: size Φ600mm*3000mm, maximum weld depth of 50mm, maximum weight of 1000Kg, and the distance between two circumferential welds is not less than 2000mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a schematic diagram of the head before welding of the present invention.

[0008] Figure 2 It is a schematic diagram of the body before welding of the present invention.

[0009] Figure 3 It is a schematic diagram of the bottom before welding of the present invention.

[0010] Figure 4 It is a schematic diagram of the product after welding of the present invention.

[0011] Figure 5 This is the distribution diagram of the joint coefficient after welding of the present invention. DETAILED DESCRIPTION

[0012] The technical solution of the present invention is described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto, and is also applicable to products of other specifications produced by adopting the present invention.

[0013] Example 1: The material is 35CrMnSiA ф600mm continuous casting billet by electric furnace smelting, refining outside the furnace, vacuum degassing and continuous casting.

[0014] Head production process route: ф600mm continuous casting billet → heating → forging into ф455*ф342*850mm → roughing into ф434*ф368*830mm → welding surface welding (such as Figure 1 (as shown) → X-ray inspection → weld performance inspection.

[0015] Body production process route: ф600mm continuous casting billet → heating → rolling into ф473*ф367*1200mm → roughing ф470*ф410*1180mm → welding surface welding (such as Figure 2 (as shown) → X-ray inspection → weld performance inspection.

[0016] Bottom production process route: ф600mm continuous casting billet → heating → rolling → roughing → welding surface welding → X-ray inspection → weld performance inspection. (such as Figure 3 shown) The welding consists of the head, body and bottom parts mentioned above, and vacuum electron beam welding is used for two welds; the steps are as follows: Step 1) Preparation before welding: Step 1.1) The equipment and tools used must be checked and adjusted to be qualified, and welding operations can only be carried out after they are confirmed to be normal; Step 1.2) Check whether the parts to be welded meet the requirements, whether the ingot number is consistent with the matching table, and whether they can be correctly assembled; Step 1.3) Check and clean the 100MM range of the workpiece welding area and the burrs, rust, bumps and oil stains on the inner liner ring, and check whether the size of the inner liner ring matches. If there is rust or bumps that seriously affect the assembly welding, the lathe must be corrected to meet the requirements; Step 1.4), Grind and clean the weld surface and the weld sides within 100mm of the burrs, rust, oil stains and other impurities visible to the naked eye, and clean the iron filings, polishing materials, oil stains and debris inside the workpiece; Step 1.5) Use a Gauss meter to measure whether the workpiece is magnetic and ensure that the workpiece is completely demagnetized; Step 1.6) Use ethanol or acetone to clean the oil and dust impurities within 100mm around the welding surface to ensure that the welding area is clean; Step 2), pairing: Step 2.1) Use horizontal or vertical assembly method to ensure that each weld is seamless straight butt joint without chamfer. Each weld is self-melting by manual tungsten inert gas arc welding, six points are symmetrically spot welded, and the welding length is 100-150mm to ensure firmness and reliability. Step 2.2) It is forbidden to assemble more than 3 pieces at a time, and the time of placing the workpieces on site after assembly should be reduced as much as possible to ensure the cleanliness of the workpieces; Step 3), welding: (such as Figure 4 shown) Step 3.1) Before entering the chamber, clean the workbench and vacuum chamber to remove debris. The workpiece is hoisted onto the machine with one top and one clamp. The body is equipped with adjustable bracket rollers to ensure that the workpiece rotates horizontally and smoothly. If the roller is close to the weld, a guard plate should be provided to prevent splashes from falling onto the roller surface and affecting the rotation. Use non-woven fabric and ethanol solution to clean the weld area again to make it clean and free of impurities. Step 3.2), the workpiece enters the vacuum box to evacuate the vacuum, and edit the welding program before formal welding; Step 3.3), Formal welding: Fixed parameters of the equipment: electron gun chamber pressure 6E-2---3E-3, working chamber pressure 6E-2---3E-3; bias voltage 2200V, high voltage 85KV, filament 40A; Welding adjustment parameters: rising gradient 3-5ms, falling gradient 35-50ms, scanning X200-300, Y200-300, circular scanning; frequency 200-300HZ, welding line speed 240-280mm / min; overlap angle 7°-10° (6-10 seconds); The first positioning welding: beam 10-20MA, surface focus; the second preheating welding: beam 30-50MA, lower focus 10-15; the third depth welding: beam 100-130MA, lower focus 10-15; the fourth modification welding: beam 50-60MA, upper focus 50-60; if the third welding is not well formed or there are pits on the weld surface, the modification weld should be carried out, if the formation is good, the modification weld may not be carried out; Step 3.4) Fill in the welding record as required; Step 3.5) After welding is completed, the procedure must be completed - decompression and gas filling - exit the vacuum chamber - lift the heat treatment furnace, clean the vacuum chamber and workbench and remove debris; Step 4), post-weld stress relief heat treatment: Step 4.1) Raise the furnace temperature to 450℃ and keep it warm 2 hours before welding; Step 4.2), the welded products are put into the furnace in time, and the temperature is raised to 650℃ after a batch of welding is completed and all the products are put into the furnace. The heating time is 2 hours; Step 4.3), keep at 650℃ for 8 hours and then cool down, the cooling rate is ≤50℃ / h; Step 4.4), the furnace temperature drops to ≤250℃ and the furnace is taken out of the furnace; Step 5) Post-weld non-destructive testing: The welded joints are subjected to radiographic testing, and after passing the test, mechanical properties testing is performed to calculate the joint coefficient.

[0017] After welding, the product is subjected to radiographic inspection on the weld according to the requirements of NB / T47013.2-2015, and meets the requirements of Level I.

[0018] Step 6), performance heat treatment: The welded product blank was heat treated as follows: quenching temperature 890±10℃, average temperature 1.5h, heat preservation 2h, water cooling 30~40min, water temperature 40~50℃, average temperature at 230±10℃ for 3h, heat preservation 3h, air cooling after exiting the furnace, and mechanical properties test was performed on samples taken at the two welds after heat treatment. The mechanical properties test results are shown in Table 1: Table 1 Mechanical properties test results

[0019] According to the above method, batch production was carried out, and 73 samples were taken after welding to make the joint coefficient distribution diagram (such as Figure 5 As shown in the figure, it can be seen that the joint coefficients are all greater than 0.90, all indicators meet the requirements, and the one-time welding pass rate is 100%.

Claims

1. A vacuum electron beam welding process for low alloy ultra-high strength steel, characterized in that: The selected base material is 35CrMnSiA, which includes three parts: head, body and bottom. Vacuum electron beam welding is used to form two welds. The steps are as follows: Step 1) Preparation before welding: Step 1.1) The equipment and tools used must be checked and adjusted to be qualified, and welding operations can only be carried out after they are confirmed to be normal; Step 1.2) Check whether the parts to be welded meet the requirements, whether the ingot number is consistent with the matching table, and whether they can be correctly assembled; Step 1.3) Check and clean the 100MM range of the workpiece welding area and the burrs, rust, bumps and oil stains on the inner liner ring, and check whether the size of the inner liner ring matches. If there is rust or bumps that seriously affect the assembly welding, the lathe must be corrected to meet the requirements; Step 1.4), Grind and clean the weld surface and the weld sides within 100mm of the burrs, rust, oil stains and other visible impurities, and clean the iron filings, polishing materials, oil stains and other debris inside the workpiece; Step 1.5) Use a Gauss meter to measure whether the workpiece is magnetic and ensure that the workpiece is completely demagnetized; Step 1.6) Use ethanol or acetone to clean the oil and dust impurities within 100mm around the welding surface to ensure that the welding area is clean; Step 2), pairing: Step 2.1) Use horizontal or vertical assembly method to ensure that each weld is seamless straight butt joint without chamfer. Each weld is self-melting by manual tungsten inert gas arc welding, six points are symmetrically spot welded, and the welding length is 100-150mm to ensure firmness and reliability. Step 2.2) It is forbidden to assemble more than 3 pieces at a time, and the time of placing the workpieces on site after assembling should be reduced as much as possible to ensure the cleanliness of the workpieces; Step 3) Welding: Step 3.1) Before entering the chamber, clean the workbench and vacuum chamber to remove debris. The workpiece is hoisted onto the machine with one top and one clamp. The body is equipped with adjustable bracket rollers to ensure that the workpiece rotates horizontally and smoothly. If the roller is close to the weld, a guard plate should be provided to prevent splashes from falling onto the roller surface and affecting the rotation. Use non-woven fabric and ethanol solution to clean the weld area again to make it clean and free of impurities. Step 3.2), the workpiece enters the vacuum box to evacuate the vacuum, and edit the welding program before formal welding; Step 3.3), Formal welding: Fixed parameters of the equipment: electron gun chamber pressure 6E-2---3E-3, working chamber pressure 6E-2---3E-3; bias voltage 2200V, high voltage 85KV, filament 40A; Welding adjustment parameters: rising gradient 3-5ms, falling gradient 35-50ms, scanning X200-300, Y200-300, circular scanning; frequency 200-300HZ, welding line speed 240-280mm / min; overlap angle 7°-10° (6-10 seconds); The first positioning welding: beam 10-20MA, surface focus; the second preheating welding: beam 30-50MA, lower focus 10-15; the third depth welding: beam 100-130MA, lower focus 10-15; the fourth modification welding: beam 50-60MA, upper focus 50-60; if the third welding is not well formed or there are pits on the weld surface, the modification weld should be carried out, if the formation is good, the modification weld may not be carried out; Step 3.4) Fill in the welding record as required; Step 3.5) After welding is completed, the procedure must be completed - decompression and gas filling - exit the vacuum chamber - lift the heat treatment furnace, clean the vacuum chamber and workbench and remove debris; Step 4), post-weld stress relief heat treatment: Step 4.1) Raise the furnace temperature to 450℃ and keep it warm 2 hours before welding; Step 4.2), the welded products are put into the furnace in time, and the temperature is raised to 650℃ after a batch of welding is completed and all the products are put into the furnace. The heating time is 2 hours; Step 4.3), keep at 650℃ for 8 hours and then cool down, the cooling rate is ≤50℃ / h; Step 4.4), the furnace temperature drops to ≤250℃ and the furnace is taken out of the furnace; Step 5) Post-weld non-destructive testing: The welded joints are subjected to radiographic testing, and after passing the test, mechanical properties testing is performed to calculate the joint coefficient.

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