A method of forming a low-alloy cast steel sling

Abstract

The application discloses a low-alloy cast steel cable clamp forming method, which comprises the following steps: step 1, adopting ZG20Mn low-alloy cast steel to cast a cable clamp blank; step 2, stress relieving annealing, normal tempering and rough machining treatment are carried out on the cable clamp blank; step 3, flaw detection is carried out and casting defects are marked; step 4, corresponding casting defects are removed according to the marks, and a to-be-repaired cavity is formed; step 5, ER69-G welding wire is used to repair and weld the to-be-repaired cavity; step 6, flaw detection is carried out; step 7, quenching heat treatment is carried out through a quenching and tempering furnace; step 8, tempering treatment is carried out through the quenching and tempering furnace; and step 9, the quenched and tempered cable clamp blank is subjected to flaw detection treatment, and is transferred to finish machining treatment if qualified. The application effectively eliminates casting stress, refines and homogenizes internal organization grains, greatly improves material strength, plasticity and toughness, meets the technical requirements of the cable clamp mechanical properties in a suspension bridge structure and is resistant to low temperature of-20 DEG C.

Description

Technical Field

[0001] This invention relates to cable clamp forming technology for suspension bridges, specifically a forming method for low-alloy cast steel cable clamps. Background Technology

[0002] Cable clamps are important load-bearing components in suspension bridge structures. They connect the main cable and the suspenders and are used to transfer the static and dynamic loads of the bridge deck to the main cable. Their reliability is directly related to the safety of the entire bridge.

[0003] Common cable clamps, especially those for long-span suspension bridges, are made of low-alloy cast steel. Their heat treatment process is normalizing and tempering to eliminate internal stress in the cast cable clamp blanks, reduce material hardness, and meet the corresponding mechanical performance requirements. For example, the technology published in Chinese patent literature entitled "A method for manufacturing heat-treated cable clamps for suspension bridges" (Publication No. CN 103103920 A, Publication Date March 25, 2015).

[0004] However, due to inherent casting defects in castings, especially large castings, the cast cable clamp blanks often exhibit uneven microstructure and porosity. These defects inevitably lead to safety hazards such as deformation and cracking during service. Conventional solutions include improving the material of low-alloy cast steel or refining the casting process, but these measures are technically challenging, costly, and have low returns.

[0005] In the prior art, there are disclosed technical measures for repairing casting defects by welding, in order to eliminate casting defects and improve the quality of castings. Examples include Chinese patent documents titled "A Welding Repair Method for Heat-Resistant Steel Castings" (Publication No. CN 108856945 A, Publication Date November 23, 2018) and "A Repair Method for Defects in High Heat-Resistant Alloy Steel Castings" (Publication No. CN 105414878A, Publication Date March 23, 2016). These technical measures for eliminating casting defects by welding are all aimed at heat-resistant alloy steel castings of specific materials and are difficult to apply to eliminating casting defects in low-alloy steel cable clamps. Summary of the Invention

[0006] The technical objective of this invention is to provide a method for forming low-alloy cast steel cable clamps that can effectively eliminate casting defects and improve the quality of cable clamps, taking into account the special characteristics of the aforementioned low-alloy cast steel cable clamps and the shortcomings of existing technologies.

[0007] The technical objective of this invention is achieved through the following technical solution: a method for forming low-alloy cast steel cable clips, comprising the following process steps:

[0008] Step 1. Pour low-alloy steel of material grade ZG20Mn into the cable clamp casting mold to form the cable clamp blank;

[0009] Step 2. Perform stress-relieving annealing, normal tempering, and rough machining on the cable clamp blank in sequence;

[0010] Step 3. Perform overall flaw detection on the rough-machined cable clamp blank and mark any existing casting defects;

[0011] Step 4. According to the casting defect markings, remove the corresponding casting defects on the cable clamp blank and form the cavity to be repaired;

[0012] Step 5. Use welding wire of material grade ER69-G to repair and weld the cavity to be repaired on the cable clamp blank;

[0013] Step 6. Perform flaw detection on the repaired welded parts of the cable clamp blank;

[0014] The cable clamp blanks that pass the flaw detection are then subjected to quenching and tempering treatment.

[0015] Step 7. When the temperature inside the tempering furnace is below 200℃, place the repaired and welded cable clamp blank into the tempering furnace, raise the temperature of the tempering furnace to 900-920℃, hold it at that temperature for at least 2 hours, then take out the cable clamp blank and place it in cooling water for water cooling to complete the quenching heat treatment.

[0016] Step 8. When the temperature inside the tempering furnace is below 200℃, place the quenched heat-treated cable clamp blank into the tempering furnace, raise the temperature of the tempering furnace to 650-670℃, hold it at that temperature for at least 4 hours, then take out the cable clamp blank, air cool it, and complete the tempering treatment.

[0017] Step 9. Perform flaw detection on the quenched and tempered cable clamp blanks;

[0018] The cable clamp blanks that pass the flaw detection are then subjected to precision machining.

[0019] The above-mentioned technical measures involve casting the cable clamps of the suspension bridge using low-alloy cast steel with material grade ZG20Mn, followed by stress-relieving heat treatment to eliminate casting stress, refine grains, and homogenize the microstructure. The resulting cable clamp blanks, after testing, achieve the following mechanical properties R eH ≥285MPa, R m ≥495MPa, A≥18%, Z≥30%, A KU ≥39J. After repairing and welding with ER69-G welding wire to remove casting defects, and undergoing quenching and tempering treatment, the material strength, plasticity, and toughness of the cable clamp blank are significantly improved, resulting in good comprehensive mechanical properties. The formed cable clamp blank, after testing, achieves the following mechanical properties: R eH≥300MPa, R m ≥500MPa, A≥24%, A at -20℃ KV ≥27J, which is superior to the minimum technical requirements for large low alloy steel castings in technical standard JB / T6402, meets the technical requirements for the mechanical properties of cable clamps in suspension bridge structures, and is resistant to low temperatures of -20℃.

[0020] In other words, by using the above-mentioned technical measures for low-alloy cast steel, welding wire, and quenching and tempering processes, it is possible to obtain cable clips with an impact energy of ≥27J in a low-temperature environment of -20℃, exhibiting excellent material strength and low-temperature resistance.

[0021] As one of the preferred options, in step 4, the cavity to be repaired formed by removing casting defects on the cable clamp blank is a concave structure with a small bottom and a large opening.

[0022] The inner wall of the cavity to be repaired is a curved surface structure without right angles.

[0023] The above-mentioned technical measures are conducive to the complete and thorough completion of repair welding, eliminating possible defects in the repair welding process, and improving the quality of the formed cable clamp.

[0024] As one of the preferred options, in step 5, the repair welding adopts the GMAW welding method, the shielding gas is CO2, the gas flow rate is 20-25L / min, the welding polarity is DCEP, and the distance between the conductive tube and the cable clamp blank is 15-20mm.

[0025] The repair welding is performed in the following order: bottom layer welding, intermediate layer welding, and top layer welding.

[0026] The bottom layer welding is a flat welding process performed at the bottom of the cavity to be repaired.

[0027] The intermediate layer welding is performed by sequentially welding flat layers on top of the base layer;

[0028] The welding of the cover layer is performed by flat welding at the top of the intermediate layer and at the opening of the cavity to be repaired.

[0029] Furthermore, the minimum preheating temperature for the root pass welding is 100°C, and the welding wire diameter is [missing information]. The minimum welding current is 260A and the maximum is less than the welding current of the intermediate layer welding; the minimum welding voltage is 28V and the maximum is less than the welding voltage of the intermediate layer welding; the minimum welding speed is 240mm / min and the maximum is less than the welding speed of the intermediate layer welding; the weld layer thickness is 3-5mm; the weld bead oscillation width is less than the weld bead oscillation width of the cover layer; and the interpass temperature is a maximum of 200℃ and greater than the preheating temperature.

[0030] Furthermore, the diameter of the welding wire used for welding the intermediate layer is... The maximum welding current is 320A, which is greater than the welding current for the root pass welding; the maximum welding voltage is 34V, which is greater than the welding voltage for the root pass welding; the maximum welding speed is 500mm / min, which is greater than the welding speed for the root pass welding; the maximum weld bead oscillation is equal to the weld bead oscillation width of the cover layer; and the maximum interpass temperature is 200℃, which is greater than the preheating temperature.

[0031] Furthermore, the oscillation width of the weld bead in the intermediate layer is differentiated according to the welding sequence, with the oscillation width of the later weld bead being greater than that of the earlier and middle weld beads.

[0032] The maximum thickness of the subsequent weld layer in the intermediate layer welding is 3mm, which is less than the thickness of the preceding and intermediate weld layers.

[0033] The thickness of the first and second weld layers of the intermediate layer is 3-5 mm.

[0034] Furthermore, the diameter of the welding wire used for welding the cover layer is... The maximum welding current is 320A, which is greater than the welding current for the root pass; the maximum welding voltage is 34V, which is greater than the welding voltage for the root pass; the maximum welding speed is 500mm / min, which is greater than the welding speed for the root pass but equal to the maximum welding speed for the intermediate pass; the maximum weld thickness is 3mm; the maximum weld bead oscillation width is 15mm; and the maximum interpass temperature is 200℃, which is greater than the preheating temperature.

[0035] The aforementioned welding measures aim to ensure reliable fusion between the root pass weld and the clamp blank. The intermediate and capping passes are the main welding processes. The capping pass weld has a slightly wider filler width than the intermediate pass weld, thus reducing the number of weld passes and improving the surface quality and welding speed. A smooth transition between the intermediate pass weld and the capping pass ensures a stable fusion transition between different filler widths, further enhancing the overall welding quality.

[0036] As a preferred embodiment, in steps 7 and 8, the heating rate of the tempering furnace is ≤70℃ / h. This technical measure helps to refine the grain size and make the internal structure of the cable clamp blank more uniform, effectively eliminating internal stress and obtaining a cable clamp with good comprehensive mechanical properties.

[0037] As one of the preferred solutions, in step 7, the cable clamp blank is water-cooled through in a swinging manner in the cooling water. This technical measure enables the cable clamp blank to have full contact with the quenching medium water, improving the technical effect of quenching through.

[0038] As one of the preferred options, the flaw detection is ultrasonic flaw detection.

[0039] The beneficial technical effects of this invention are: the cable clamp blank formed by the above-mentioned technical measures effectively eliminates casting stress, refines and homogenizes the internal grain structure, and significantly improves the material strength, plasticity, and toughness, thereby obtaining good comprehensive mechanical properties. Testing has shown that it achieves the following mechanical properties: R eH ≥300MPa, R m ≥500MPa, A≥24%, A at -20℃ KV ≥27J, which is superior to the minimum technical requirements for large low alloy steel castings in technical standard JB / T6402, meets the technical requirements for the mechanical properties of cable clamps in suspension bridge structures, and is resistant to low temperatures of -20℃. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the cavity to be repaired on the cable clamp blank.

[0041] Figure 2 This is a schematic diagram of the structure after the repair welding of the cavity to be repaired on the cable clamp blank.

[0042] Figure 3 A schematic diagram of the process for heat treatment of the cable clamp blank after repair welding. Detailed Implementation

[0043] This invention relates to cable clamp forming technology for suspension bridges, specifically a forming method for low-alloy cast steel cable clamps. The main technical solution of this invention will be described in detail below with reference to several embodiments. Embodiment 1 is illustrated in conjunction with the accompanying drawings—that is… Figure 1 , Figure 2 and Figure 3 The technical solution of the present invention will be clearly and thoroughly explained; although other embodiments are not shown in separate drawings, their main structure can still be referred to the drawings of Embodiment 1.

[0044] It should be noted that the accompanying drawings of this invention are schematic, and unnecessary details have been simplified in order to clarify the technical objectives of this invention, so as to avoid obscuring the technical solutions contributed by this invention to the prior art.

[0045] Example 1

[0046] This invention relates to a method for forming low-alloy cast steel cable clamps for suspension bridges, specifically including the following process steps:

[0047] Step 1. Fabricate casting molds based on the design structure of the suspension bridge cable clamps;

[0048] The molten low-alloy cast steel of material grade ZG20Mn is poured into the cable clamp casting mold, and the cable clamp blank is obtained through processes such as opening the mold and removing sand.

[0049] The chemical composition of the low-alloy cast steel molten steel with material grade ZG20Mn meets the requirements of Table 1 below.

[0050] Brand C(％) Si (%) Mn(%) P(％) S(％) Ni (%) ZG20Mn 0.16-0.22 0.60-0.80 1.00-1.30 ≤0.025 ≤0.025 0.13-0.17

[0051] Step 2. Perform stress-relieving annealing, blank cleaning, normal tempering and rough machining on the cable clamp blank in sequence (all are conventional processes);

[0052] Step 3. For the cable clamp blanks that have completed rough machining, use ultrasonic testing to perform overall flaw detection and mark any existing casting defects;

[0053] Step 4. According to the casting defect markings, remove the corresponding casting defects from the cable clamp blanks one by one. During the removal of casting defects, a concave cavity with a small bottom and a large opening is formed on the cable clamp blank to be repaired. The inner wall of the cavity to be repaired is a curved surface structure without right angles (see...). Figure 1 (as shown);

[0054] Step 5. Using welding wire of material grade ER69-G and a YD-500FR1 digital inverter welding machine, repair and weld the cavity to be repaired on the cable clamp blank according to the following process.

[0055] The repair welding employs the GMAW welding method, using CO2 as the shielding gas at a flow rate of approximately 25 L / min. The welding polarity is DCEP, and the distance between the conductive tube and the clamping blank is approximately 18 mm. The repair welding is performed sequentially: first, the root pass welding; then, the intermediate pass welding; and finally, the cover pass welding. The root pass welding is performed as a flat weld at the bottom of the cavity to be repaired. The intermediate pass welding is performed as flat welds layer by layer on top of the root pass welding. The cover pass welding is performed as a flat weld on top of the intermediate pass welding, at the opening of the cavity to be repaired (see...). Figure 2 (as shown);

[0056] The preheating temperature for the root pass welding is approximately 105°C, and the welding wire diameter is [missing information]. The welding current is 280A (usually selected within the range of 260 to 280A), the welding arc voltage is 30V (usually selected within the range of 28 to 30V), the welding speed is about 320mm / min (usually selected within the range of 240 to 320mm), the weld thickness is about 3mm, the weld bead oscillation width is about 10mm, and the interpass temperature is about 140℃.

[0057] The diameter of the welding wire used for welding the intermediate layer is [missing information]. The welding current is 300A (usually selected within the range of 280-320A), the welding arc voltage is 32V (usually selected within the range of 30-34V), and the welding speed is approximately 420mm / min (usually selected within the range of 320-500mm). The oscillation width of the weld beads in the intermediate layer welding varies according to the welding sequence. The oscillation width of the later weld beads (approximately the last 1-3 layers) is slightly larger than that of the earlier and middle weld beads. The oscillation width of the earlier and middle weld beads is approximately 10mm, and the thickness of the earlier and middle weld layers is approximately 3mm. The oscillation width of the later weld beads (approximately the last 1-3 layers) is approximately 13mm, and the thickness of the later weld layer is approximately 2mm. The interpass temperature is approximately 140℃.

[0058] The diameter of the welding wire used for welding the cover layer is [missing information]. The welding current is 300A (usually selected in the range of 280 to 320A), the welding arc voltage is 32V (usually selected in the range of 30 to 34V), the welding speed is about 420mm / min (usually selected in the range of 320 to 500mm), the weld thickness is about 2mm, the weld bead oscillation width is about 13mm, and the interpass temperature is about 140℃.

[0059] Step 6. Perform flaw detection on the repaired welded parts of the cable clamp blank;

[0060] The cable clamp blanks that pass the flaw detection are then subjected to quenching and tempering treatment.

[0061] Step 7. Start the quenching and tempering furnace;

[0062] When the temperature inside the tempering furnace is approximately 160℃, the repaired and welded cable clamp blank is placed inside the furnace. The furnace is heated to approximately 910℃ at a rate of approximately 50℃ / h. After holding at this temperature for about 2.5 hours, the cable clamp blank is removed and placed in cooling water for thorough water cooling using an oscillating motion, completing the quenching heat treatment (see...). Figure 3 (as shown);

[0063] Step 8. When the temperature inside the tempering furnace is approximately 160°C, place the quenched steel clamp blank into the tempering furnace. Heat the furnace to approximately 660°C at a rate of approximately 50°C / h, hold for approximately 5 hours, then remove the steel clamp blank and air-cool it to complete the tempering treatment (see...). Figure 3 (as shown);

[0064] Step 9. Perform overall flaw detection on the completed heat treatment billet using ultrasonic testing.

[0065] The cable clamp blanks that pass the flaw detection are then subjected to precision machining.

[0066] Example 2

[0067] This invention relates to a method for forming low-alloy cast steel cable clamps for suspension bridges, specifically including the following process steps:

[0068] Step 1. Fabricate casting molds based on the design structure of the suspension bridge cable clamps;

[0069] The molten low-alloy cast steel of material grade ZG20Mn is poured into the cable clamp casting mold, and the cable clamp blank is obtained through processes such as opening the mold and removing sand.

[0070] Step 2. Perform stress-relieving annealing, blank cleaning, normal tempering, and rough machining on the cable clamp blank in sequence;

[0071] Step 3. For the cable clamp blanks that have completed rough machining, use ultrasonic testing to perform overall flaw detection and mark any existing casting defects;

[0072] Step 4. According to the casting defect markings, remove the corresponding casting defects on the cable clamp blank one by one. When removing the casting defects, a concave structure with a small bottom and a large opening is formed on the cable clamp blank to be repaired. The inner wall of the cavity to be repaired is a curved surface structure without right angles.

[0073] Step 5. Using welding wire of material grade ER69-G and a YD-500FR1 digital inverter welding machine, repair and weld the cavity to be repaired on the cable clamp blank according to the following process.

[0074] The repair welding adopts the GMAW welding method, the shielding gas is CO2, the gas flow rate is about 23L / min, the welding polarity is DCEP, and the distance between the conductive tube and the cable clamp blank is about 15mm. The repair welding is carried out in the order of first performing the bottom layer welding, then the intermediate layer welding, and finally the top layer welding. The bottom layer welding is performed by flat welding at the bottom of the cavity to be repaired. The intermediate layer welding is performed by flat welding layer by layer on top of the bottom layer. The top layer welding is performed by flat welding at the top of the intermediate layer and at the opening of the cavity to be repaired.

[0075] The preheating temperature for the root pass welding is approximately 120°C, and the welding wire diameter is [missing information]. The welding current is 260A (usually selected within the range of 260 to 280A), the welding arc voltage is 28V (usually selected within the range of 28 to 30V), the welding speed is about 250mm / min (usually selected within the range of 240 to 320mm), the weld thickness is about 4mm, the weld bead oscillation width is about 12mm, and the interpass temperature is about 165℃.

[0076] The diameter of the welding wire used for welding the intermediate layer is [missing information]. The welding current is 320A (usually selected within the range of 280-320A), the welding arc voltage is 34V (usually selected within the range of 30-34V), and the welding speed is approximately 480mm / min (usually selected within the range of 320-500mm). The oscillation width of the weld beads in the intermediate layer welding varies according to the welding sequence. The oscillation width of the later weld beads (approximately the last 1-3 layers) is slightly larger than that of the earlier and middle weld beads. The oscillation width of the earlier and middle weld beads is approximately 12mm, and the thickness of the earlier and middle weld layers is approximately 4mm. The oscillation width of the later weld beads (approximately the last 1-3 layers) is approximately 15mm, and the thickness of the later weld layer is approximately 2.5mm. The interpass temperature is approximately 165℃.

[0077] The diameter of the welding wire used for welding the cover layer is [missing information]. The welding current is 320A (usually selected within the range of 280 to 320A), the welding arc voltage is 34V (usually selected within the range of 30 to 34V), the welding speed is approximately 480mm / min (usually selected within the range of 320 to 500mm), the weld thickness is approximately 2.5mm, the weld bead oscillation width is approximately 15mm, and the interpass temperature is approximately 165℃.

[0078] Step 6. Perform flaw detection on the repaired welded parts of the cable clamp blank;

[0079] The cable clamp blanks that pass the flaw detection are then subjected to quenching and tempering treatment.

[0080] Step 7. Start the quenching and tempering furnace;

[0081] When the temperature inside the tempering furnace is approximately 180℃, the repaired and welded cable clamp blank is placed inside the furnace. The furnace is heated to approximately 918℃ at a rate of approximately 60℃ / h. After holding at this temperature for about 2 hours, the cable clamp blank is removed and placed in cooling water for thorough water cooling using an oscillating motion, completing the quenching heat treatment (see...). Figure 3 (as shown);

[0082] Step 8. When the temperature inside the tempering furnace is about 180°C, place the quenched heat-treated cable clamp blank into the tempering furnace. Heat the tempering furnace to about 670°C at a heating rate of about 60°C / h. Hold the temperature for about 4.5 hours, then take out the cable clamp blank and air cool it to complete the tempering treatment.

[0083] Step 9. Perform overall flaw detection on the completed heat treatment billet using ultrasonic testing.

[0084] The cable clamp blanks that pass the flaw detection are then subjected to precision machining.

[0085] Example 3

[0086] This invention relates to a method for forming low-alloy cast steel cable clamps for suspension bridges, specifically including the following process steps:

[0087] Step 1. Fabricate casting molds based on the design structure of the suspension bridge cable clamps;

[0088] The molten low-alloy cast steel of material grade ZG20Mn is poured into the cable clamp casting mold, and the cable clamp blank is obtained through processes such as opening the mold and removing sand.

[0089] Step 2. Perform stress-relieving annealing, blank cleaning, normal tempering, and rough machining on the cable clamp blank in sequence;

[0090] Step 3. For the cable clamp blanks that have completed rough machining, use ultrasonic testing to perform overall flaw detection and mark any existing casting defects;

[0091] Step 4. According to the casting defect markings, remove the corresponding casting defects on the cable clamp blank one by one. When removing the casting defects, a concave structure with a small bottom and a large opening is formed on the cable clamp blank to be repaired. The inner wall of the cavity to be repaired is a curved surface structure without right angles.

[0092] Step 5. Using welding wire of material grade ER69-G and a YD-500FR1 digital inverter welding machine, repair and weld the cavity to be repaired on the cable clamp blank according to the following process.

[0093] The repair welding adopts the GMAW welding method, the shielding gas is CO2, the gas flow rate is about 20L / min, the welding polarity is DCEP, the distance between the conductive tube and the cable clamp blank is about 20mm, and the repair welding is carried out in the order of first the bottom layer welding, then the intermediate layer welding, and finally the top layer welding. The bottom layer welding is a flat welding at the bottom of the cavity to be repaired, the intermediate layer welding is a flat welding layer by layer on top of the bottom layer, and the top layer welding is a flat welding at the top of the intermediate layer and at the cavity opening of the cavity to be repaired.

[0094] The preheating temperature for the root pass welding is approximately 135°C, and the welding wire diameter is [missing information]. The welding current is 275A (usually selected in the range of 260 to 280A), the welding arc voltage is 29V (usually selected in the range of 28 to 30V), the welding speed is about 280mm / min (usually selected in the range of 240 to 320mm), the weld thickness is about 5mm, the weld bead oscillation width is about 11mm, and the interpass temperature is about 180℃.

[0095] The diameter of the welding wire used for welding the intermediate layer is [missing information]. The welding current is 310A (usually selected within the range of 280-320A), the welding arc voltage is 30V (usually selected within the range of 30-34V), and the welding speed is approximately 400mm / min (usually selected within the range of 320-500mm). The oscillation width of the weld beads in the intermediate layer welding varies according to the welding sequence. The oscillation width of the later weld beads (approximately the last 1-3 layers) is slightly larger than that of the earlier and middle weld beads. The oscillation width of the earlier and middle weld beads is approximately 12mm, and the thickness of the earlier and middle weld layers is approximately 5mm. The oscillation width of the later weld beads (approximately the last 1-3 layers) is approximately 14mm, and the thickness of the later weld layer is approximately 3mm. The interpass temperature is approximately 180℃.

[0096] The diameter of the welding wire used for welding the cover layer is [missing information]. The welding current is 310A (usually selected in the range of 280 to 320A), the welding arc voltage is 30V (usually selected in the range of 30 to 34V), the welding speed is about 400mm / min (usually selected in the range of 320 to 500mm), the weld thickness is about 3mm, the weld bead oscillation width is about 14mm, and the interpass temperature is about 180℃.

[0097] Step 6. Perform flaw detection on the repaired welded parts of the cable clamp blank;

[0098] The cable clamp blanks that pass the flaw detection are then subjected to quenching and tempering treatment.

[0099] Step 7. Start the quenching and tempering furnace;

[0100] When the temperature inside the tempering furnace is about 195℃, the cable clamp blank that has been repaired and welded is placed into the tempering furnace. The tempering furnace is heated to about 920℃ at a heating rate of about 70℃ / h. After holding at this temperature for about 2 hours, the cable clamp blank is taken out and placed in cooling water to be water-cooled through by oscillation, thus completing the quenching heat treatment.

[0101] Step 8. When the temperature inside the tempering furnace is about 195°C, place the quenched heat treatment billet into the tempering furnace and heat the furnace to about 670°C at a heating rate of about 70°C / h. After holding at this temperature for about 4 hours, take out the billet and air cool it to complete the tempering treatment.

[0102] Step 9. Perform overall flaw detection on the completed heat treatment billet using ultrasonic testing.

[0103] The cable clamp blanks that pass the flaw detection are then subjected to precision machining.

[0104] Example 4

[0105] This invention relates to a method for forming low-alloy cast steel cable clamps for suspension bridges, specifically including the following process steps:

[0106] Step 1. Fabricate casting molds based on the design structure of the suspension bridge cable clamps;

[0107] The molten low-alloy cast steel of material grade ZG20Mn is poured into the cable clamp casting mold, and the cable clamp blank is obtained through processes such as opening the mold and removing sand.

[0108] Step 2. Perform stress-relieving annealing, blank cleaning, normal tempering, and rough machining on the cable clamp blank in sequence;

[0109] Step 3. For the cable clamp blanks that have completed rough machining, use ultrasonic testing to perform overall flaw detection and mark any existing casting defects;

[0110] Step 4. According to the casting defect markings, remove the corresponding casting defects on the cable clamp blank one by one. When removing the casting defects, a concave structure with a small bottom and a large opening is formed on the cable clamp blank to be repaired. The inner wall of the cavity to be repaired is a curved surface structure without right angles.

[0111] Step 5. Using welding wire of material grade ER69-G and a YD-500FR1 digital inverter welding machine, repair and weld the cavity to be repaired on the cable clamp blank according to the following process.

[0112] The repair welding adopts the GMAW welding method, the shielding gas is CO2, the gas flow rate is about 24L / min, the welding polarity is DCEP, and the distance between the conductive tube and the cable clamp blank is about 19mm. The repair welding is carried out in the order of first the bottom layer welding, then the intermediate layer welding, and finally the top layer welding. The bottom layer welding is a flat welding at the bottom of the cavity to be repaired. The intermediate layer welding is a flat welding layer by layer on top of the bottom layer welding. The top layer welding is a flat welding at the top of the intermediate layer and at the cavity opening of the cavity to be repaired.

[0113] The preheating temperature for the root pass welding is approximately 150°C, and the welding wire diameter is [missing information]. The welding current is 270A (usually selected in the range of 260 to 280A), the welding arc voltage is 30V (usually selected in the range of 28 to 30V), the welding speed is about 300mm / min (usually selected in the range of 240 to 320mm), the weld thickness is about 4mm, the weld bead oscillation width is about 8mm, and the interpass temperature is about 195℃.

[0114] The diameter of the welding wire used for welding the intermediate layer is [missing information]. The welding current is 280A (usually selected within the range of 280-320A), the welding arc voltage is 33V (usually selected within the range of 30-34V), and the welding speed is approximately 500mm / min (usually selected within the range of 320-500mm). The oscillation width of the weld beads in the intermediate layer welding varies according to the welding sequence. The oscillation width of the later weld beads (approximately the last 1-3 layers) is slightly larger than that of the earlier and middle weld beads. The oscillation width of the earlier and middle weld beads is approximately 8mm, and the thickness of the earlier and middle weld layers is approximately 4mm. The oscillation width of the later weld beads (approximately the last 1-3 layers) is approximately 12mm, and the thickness of the later weld layer is approximately 2.8mm. The interpass temperature is approximately 195℃.

[0115] The diameter of the welding wire used for welding the cover layer is [missing information]. The welding current is 280A (usually selected within the range of 280 to 320A), the welding arc voltage is 33V (usually selected within the range of 30 to 34V), the welding speed is about 500mm / min (usually selected within the range of 320 to 500mm), the weld thickness is about 2.8mm, the weld bead oscillation width is about 12mm, and the interpass temperature is about 195℃.

[0116] Step 6. Perform flaw detection on the repaired welded parts of the cable clamp blank;

[0117] The cable clamp blanks that pass the flaw detection are then subjected to quenching and tempering treatment.

[0118] Step 7. Start the quenching and tempering furnace;

[0119] When the temperature inside the tempering furnace is about 180℃, the cable clamp blank that has been repaired and welded is placed into the tempering furnace. The tempering furnace is heated to about 905℃ at a heating rate of about 65℃ / h. After holding at this temperature for about 3 hours, the cable clamp blank is taken out and placed in cooling water to be water-cooled through by oscillation, thus completing the quenching heat treatment.

[0120] Step 8. When the temperature inside the tempering furnace is about 180°C, place the quenched heat-treated cable clamp blank into the tempering furnace. Heat the tempering furnace to about 650°C at a heating rate of about 65°C / h. After holding at this temperature for about 5.5h, take out the cable clamp blank and air cool it to complete the tempering treatment.

[0121] Step 9. Perform overall flaw detection on the completed heat treatment billet using ultrasonic testing.

[0122] The cable clamp blanks that pass the flaw detection are then subjected to precision machining.

[0123] Example 5

[0124] This invention relates to a method for forming low-alloy cast steel cable clamps for suspension bridges, specifically including the following process steps:

[0125] Step 1. Fabricate casting molds based on the design structure of the suspension bridge cable clamps;

[0126] The molten low-alloy cast steel of material grade ZG20Mn is poured into the cable clamp casting mold, and the cable clamp blank is obtained through processes such as opening the mold and removing sand.

[0127] Step 2. Perform stress-relieving annealing, blank cleaning, normal tempering, and rough machining on the cable clamp blank in sequence;

[0128] Step 3. For the cable clamp blanks that have completed rough machining, use ultrasonic testing to perform overall flaw detection and mark any existing casting defects;

[0129] Step 4. According to the casting defect markings, remove the corresponding casting defects on the cable clamp blank one by one. When removing the casting defects, a concave structure with a small bottom and a large opening is formed on the cable clamp blank to be repaired. The inner wall of the cavity to be repaired is a curved surface structure without right angles.

[0130] Step 5. Using welding wire of material grade ER69-G and a YD-500FR1 digital inverter welding machine, repair and weld the cavity to be repaired on the cable clamp blank according to the following process.

[0131] The repair welding adopts the GMAW welding method, the shielding gas is CO2, the gas flow rate is about 22L / min, the welding polarity is DCEP, and the distance between the conductive tube and the cable clamp blank is about 16mm. The repair welding is carried out in the order of first performing the bottom layer welding, then the intermediate layer welding, and finally the top layer welding. The bottom layer welding is performed by flat welding at the bottom of the cavity to be repaired. The intermediate layer welding is performed by flat welding layer by layer on top of the bottom layer welding. The top layer welding is performed by flat welding at the top of the intermediate layer and at the cavity opening of the cavity to be repaired.

[0132] The preheating temperature for the root pass welding is approximately 140°C, and the welding wire diameter is [missing information]. The welding current is 265A (usually selected within the range of 260 to 280A), the welding arc voltage is 28V (usually selected within the range of 28 to 30V), the welding speed is approximately 260mm / min (usually selected within the range of 240 to 320mm), the weld thickness is approximately 3.5mm, the weld bead oscillation width is approximately 9mm, and the interpass temperature is approximately 170℃.

[0133] The diameter of the welding wire used for welding the intermediate layer is [missing information]. The welding current is 290A (usually selected within the range of 280-320A), the welding arc voltage is 31V (usually selected within the range of 30-34V), and the welding speed is approximately 350mm / min (usually selected within the range of 320-500mm). The oscillation width of the weld beads in the intermediate layer welding varies according to the welding sequence. The oscillation width of the later weld beads (approximately the last 1-3 layers) is slightly larger than that of the earlier and middle weld beads. The oscillation width of the earlier and middle weld beads is approximately 9mm, and the thickness of the earlier and middle weld layers is approximately 3.5mm. The oscillation width of the later weld beads (approximately the last 1-3 layers) is approximately 13mm, and the thickness of the later weld layer is approximately 2mm. The interpass temperature is approximately 170℃.

[0134] The diameter of the welding wire used for welding the cover layer is [missing information]. The welding current is 290A (usually selected in the range of 280 to 320A), the welding arc voltage is 31V (usually selected in the range of 30 to 34V), the welding speed is about 350mm / min (usually selected in the range of 320 to 500mm), the weld thickness is about 2mm, the weld bead oscillation width is about 13mm, and the interpass temperature is about 170℃.

[0135] Step 6. Perform flaw detection on the repaired welded parts of the cable clamp blank;

[0136] The cable clamp blanks that pass the flaw detection are then subjected to quenching and tempering treatment.

[0137] Step 7. Start the quenching and tempering furnace;

[0138] When the temperature inside the tempering furnace is about 190℃, the cable clamp blank that has been repaired and welded is placed into the tempering furnace. The tempering furnace is heated to about 900℃ at a heating rate of about 68℃ / h. After holding at this temperature for about 3.5h, the cable clamp blank is taken out and placed in cooling water to be water-cooled through by oscillation, thus completing the quenching heat treatment.

[0139] Step 8. When the temperature inside the tempering furnace is about 190°C, place the quenched heat treatment billet into the tempering furnace and heat the furnace to about 665°C at a heating rate of about 68°C / h. After holding at this temperature for about 5 hours, take out the billet and air cool it to complete the tempering treatment.

[0140] Step 9. Perform overall flaw detection on the completed heat treatment billet using ultrasonic testing.

[0141] The cable clamp blanks that pass the flaw detection are then subjected to precision machining.

[0142] The mechanical properties of the cable clamp blanks obtained by the above methods all meet the requirements of Table 2 below.

[0143] <![CDATA[Yield strength R eH (MPa)]]> Tensile strength (MPa) Elongation (%) <![CDATA[Impact energy A kv (J) - 20 °C]]> ≥300 500-650 ≥24 ≥27

[0144] The above embodiments are only used to illustrate the present invention and are not intended to limit it.

[0145] Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications can still be made to the above embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the present invention.

Claims

1. A method of forming a low alloy cast steel fishplate, characterised in that, The method comprises the following steps: Step 1. Casting a low alloy cast steel with a material grade of ZG20Mn in a sling clamp casting mold to perform sling clamp blank casting; Step 2. sequentially performing stress relief annealing, normal tempering and rough machining on the sling clamp blank; Step 3. performing overall flaw detection on the sling clamp blank after the rough machining to mark the existing casting defects; Step 4. removing the corresponding casting defects on the sling clamp blank according to the casting defect marks and forming a to-be-repaired cavity; Step 5. performing repair welding on the to-be-repaired cavity of the sling clamp blank by using a welding wire with a material grade of ER69-G; The repair welding adopts a GMAW welding method, the protective gas is CO2, the gas flow is 20-25 L / min, the welding polarity is DCEP, and the distance between the conducting tube and the sling clamp blank is 15-20 mm; The repair welding is sequentially performed in the order of a base layer welding, an intermediate layer welding and a cover layer welding; The base layer welding is performed by flat welding at the bottom of the to-be-repaired cavity; The intermediate layer welding is performed by layer-by-layer flat welding on the top of the base layer; The cover layer welding is performed by flat welding on the top of the intermediate layer and at the opening of the to-be-repaired cavity; The preheating temperature of the base layer welding is at least 100℃, the welding wire diameter is φ1.2 mm, the welding current is at least 260 A and at most less than that of the intermediate layer welding, the welding voltage is at least 28 V and at most less than that of the intermediate layer welding, the welding speed is at least 240 mm / min and at most less than that of the intermediate layer welding, the welding layer thickness is 3-5 mm, the welding bead oscillation width is less than that of the cover layer, and the interpass temperature is at most 200℃ and greater than the preheating temperature; The welding wire diameter of the intermediate layer welding is φ1.2 mm, the welding current is at most 320 A and greater than that of the base layer welding, the welding voltage is at most 34 V and greater than that of the base layer welding, the welding speed is at most 500 mm / min and greater than that of the base layer welding, the welding bead oscillation is at most equal to the welding bead oscillation width of the cover layer, and the interpass temperature is at most 200℃ and greater than the preheating temperature; The welding wire diameter of the cover layer welding is φ1.2 mm, the welding current is at most 320 A and greater than that of the base layer welding, the welding voltage is at most 34 V and greater than that of the base layer welding, the welding speed is at most 500 mm / min and greater than that of the base layer welding but equal to the maximum welding speed of the intermediate layer welding, the maximum welding layer thickness is 3 mm, the maximum welding bead oscillation width is 15 mm, and the interpass temperature is at most 200℃ and greater than the preheating temperature; Step 6. performing flaw detection on the repair welding part of the sling clamp blank; The sling clamp blank that passes the flaw detection is transferred to perform a quenching and tempering treatment. Step 7. When the temperature in the tempering furnace is lower than 200℃, the cable clamp blank after the repair welding process is put into the tempering furnace, the tempering furnace is heated to 900-920℃, and the cable clamp blank is taken out after being kept for at least 2h and is put into the cooling water for water quenching, so as to complete the quenching heat treatment; Step 8. When the temperature in the tempering furnace is lower than 200℃, the cable clamp blank after the quenching heat treatment is put into the tempering furnace, the tempering furnace is heated to 650-670℃, and the cable clamp blank is taken out after being kept for at least 4h and is air cooled, so as to complete the tempering treatment; Step 9. The cable clamp blank after the tempering treatment is subjected to the whole body flaw detection treatment; The cable clamp blank after the flaw detection is transferred to the finishing process.

2. The low-alloy cast steel cable clamp forming method according to claim 1, characterized in that: In step 4, the formed repair cavity on the cable clamp blank is an inner recess structure with a small bottom and a large opening; The inner wall of the repair cavity is a curved surface structure without a right angle.

3. The low-alloy cast steel cable clamp forming method according to claim 1, characterized in that: The welding pass swing width of the intermediate layer welding is differentiated according to the welding sequence, and the swing width of the back pass is greater than that of the front and middle passes; The maximum thickness of the back pass of the intermediate layer welding is 3mm, which is less than the thickness of the front and middle passes; The thickness of the front and middle passes of the intermediate layer welding is 3-5mm.

4. The low-alloy cast steel cable clamp forming method according to claim 1, characterized in that: In step 7 and step 8, the heating rate of the tempering furnace is ≤70℃ / h.

5. The low-alloy cast steel cable clamp forming method according to claim 1, characterized in that: In step 7, the cable clamp blank is water quenched in the cooling water in a swing manner.

6. The low-alloy cast steel cable clamp forming method according to claim 1, characterized in that: The flaw detection is ultrasonic flaw detection.

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