A cast pipe mold submerged arc welding heat cycle feedback heat input adaptive control method

Abstract

The application discloses a kind of cast pipe mould submerged-arc surfacing heat cycle feedback heat input self-adaptive control method.Spatial control section is divided along cast pipe mould multilayer multi-pass surfacing track, before arc reaches, the real-time temperature T p Before welding of target control section is acquired, and the equivalent effective heating frequency Neq and the cooling time T c Of the position recorded are read.T p ,Neq,T c With the reference value of corresponding layer, way, determine that heat accumulation is low, normal or high, and under the condition that welding current, arc voltage is stable, by increasing or reducing the walking speed of arc action point relative to workpiece surface to adjust local heat input;Spiral surfacing simultaneously adjusts the rotation speed and axial feed speed to maintain the pitch or overlap ratio.Heat cycle record of this control section is updated after welding and overlap reheating.This method only needs temperature measurement, coding positioning, table lookup and speed execution to implement, and can be segmented to compensate for the difference of heat accumulation at different positions.

Description

Technical Field

[0001] This invention relates to the field of submerged arc welding of pipe molds, and particularly to an adaptive control method for thermal cycle feedback heat input in submerged arc welding of pipe molds. Background Technology

[0002] Pipe molds are key forming tools in the production of centrifugal ductile iron pipes. Their working surfaces are subjected to long-term erosion by high-temperature molten metal, thermal fatigue, and mechanical wear, making them prone to hot cracking, fissures, spalling, and dimensional losses. Submerged arc welding, due to its high deposition efficiency, stable continuous operation, and controllable weld quality, has become the primary method for large-area repair of the working surfaces of pipe molds.

[0003] Surface cladding on cast pipe molds typically employs multi-pass lap and multi-layer deposition methods. Due to the large size and heat capacity of cast pipe molds, residual heat from previous passes or layers, reheating during subsequent weld overlaps, and differences in waiting time between passes can cause significant spatial unevenness in the temperature distribution of subsequent welded areas. If the welding speed remains constant, areas with excessively high heat accumulation are prone to excessive penetration, grain coarsening, or even burn-through, while areas with insufficient heat accumulation may exhibit forming defects such as inadequate fusion or excessive weld reinforcement. Therefore, relying solely on fixed process parameters is insufficient to guarantee the consistency of the entire repaired surface.

[0004] Existing technologies include methods for adjusting welding parameters based on real-time temperature. However, these methods often only focus on the instantaneous temperature before welding, neglecting whether that location has undergone multiple lap reheats or thermal effects from adjacent weld passes in previous weld passes. In other words, the same pre-weld temperature may correspond to different thermal histories: a higher temperature in one location might be due to recent lap reheat and insufficient cooling time; a similar temperature in another location might be due to excessive preheating but sufficient cooling. The subsequent heat input required for these two locations is not the same. Therefore, using the current temperature as the sole criterion for speed adjustment is prone to misjudgment.

[0005] Furthermore, submerged arc welding equipment for pipe casting molds is typically equipped with welding power sources, rotary drives, axial movement, and programmable controllers. If, based on existing equipment, only pre-emergence infrared temperature measurement and position encoding functions can be added, and control can be achieved through a lookup method that does not rely on complex online thermal models, the modification cost will be significantly reduced, making it easier to promote and apply in the field. Summary of the Invention

[0006] To address the spatial thermal state differences caused by varying residual heat, lap reheat, and cooling intervals in multi-layer, multi-pass submerged arc welding of pipe molds, this invention aims to provide a segmented adaptive heat input control method that comprehensively determines the current temperature and previous heating records at that location. Furthermore, while maintaining stable welding current, arc voltage, and lap relationship, the method adjusts the relative travel speed to achieve localized heat input compensation, thereby improving the uniformity of weld formation.

[0007] To achieve the above objectives, the present invention provides the following technical solution: an adaptive control method for thermal input feedback during submerged arc welding of pipe molds, comprising the following steps: S1. Divide the surface of the pipe mold to be repaired into multiple spatial control segments along the predetermined multi-layer and multi-pass welding trajectory, and establish a position marker for each spatial control segment that includes spatial coordinates and information on the welding layer and weld pass to which it belongs. S2. Before the welding heat source reaches the target space control segment, obtain the real-time temperature T of the target space control segment before welding. p The system reads the historical thermal cycle status associated with the target space control segment based on the location identifier. The historical thermal cycle status includes at least the equivalent effective heating number Neq and the cooling time T since the most recent effective heating. c ; S3. Calculate the pre-welding real-time temperature Tp, equivalent effective heating cycles Neq, and cooling time T. c The reference temperature, reference equivalent effective heating times, and reference cooling time corresponding to the target space control segment are compared respectively, and the thermal state deviation ΔH or thermal state level of the control segment is determined according to the pre-established classification judgment rules; wherein, the equivalent effective heating times Neq is determined by the thermal effects that meet the effective heating criteria in the direct welding action, the thermal effects of the lap area in the thermal effect and the thermal effects of adjacent welds, and is accumulated according to their respective equivalent coefficients; S4. Under the condition that the welding current and arc voltage are within the preset stable process range, determine the target relative travel speed v according to the thermal state deviation ΔH or the thermal state level. * When the thermal state deviation ΔH or the thermal state level, which indicates high heat accumulation, is increased, v is increased. * When the heat accumulation is low, v decreases. * and for v * Set at least one of the following: control dead zone, speed upper and lower limits, and speed change rate constraints; the relative travel speed is the linear velocity of the arc point along the actual welding trajectory relative to the workpiece surface. S5. Complete the welding of the target space control segment according to the target relative walking speed, and update the equivalent effective heating number Neq and the most recent effective heating time of the space control segment based on the direct welding action and the thermal effect of the subsequent overlapping area in the thermal effect or the thermal effect of the adjacent weld bead, so as to evaluate the thermal state when the subsequent weld bead or subsequent deposition layer passes through the corresponding space position again.

[0008] Preferably, the position identifier includes at least the axial coordinate x of the casting mold, the circumferential angular coordinate θ, the layer number i, and the track number j; wherein the circumferential angular coordinate θ is obtained by a rotary encoder mounted on the rotating shaft of the casting mold, and the axial coordinate x is obtained by an encoder, displacement sensor, or servo feedback of the axial travel mechanism.

[0009] Preferably, the real-time temperature T before welding p Temperature data is acquired using a non-contact temperature detection device positioned in front of the direction of motion of the welding heat source, with the detection area of ​​the device located before the flux coverage area. Continuously collected temperature data, after outlier removal and average or median filtering, is used as the pre-welding real-time temperature T. p .

[0010] Preferably, the equivalent effective heating cycles Neq are determined by the following formula: , In the formula, This represents the number of times the k-th type of effective heating effect occurs. is the equivalent coefficient corresponding to the kth type of effective heating effect, and m is the total number of effective heating effect types; the effective heating criterion is determined based on at least one of the following conditions: the control segment reaches a preset characteristic temperature, enters a preset overlap area, or enters a heat-affected neighborhood.

[0011] Preferably, the historical thermal cycling status also includes the historical peak temperature T. max At least one of the following: and the cumulative high-temperature time t0 exceeding the preset characteristic temperature T*; when continuous temperature history acquisition is available, T... max And / or t0 is used as an additional correction term for the thermal state deviation ΔH in the classification determination.

[0012] Preferably, the thermal state deviation ΔH or thermal state level is determined by the control unit using at least one of the following methods: hierarchical table lookup, rule-based judgment, or weighted scoring, based on T. p , Neq and T c The comparison result with the corresponding reference value is determined, and different classification judgment tables can be called according to the layer number, channel number and overlap relationship.

[0013] Preferably, the relative walking speed v to the target * Set control dead zone, hysteresis zone, and speed limit V. max Speed ​​lower limit V min And speed change rate limit; when the thermal state deviation ΔH falls within the control dead zone, the reference relative walking speed v0 remains unchanged.

[0014] Preferably, for the spiral welding trajectory formed by the rotation of the casting mold and the axial feed of the welding head, when changing the relative travel speed, the circumferential linear speed and axial feed speed of the casting mold are adjusted synchronously according to the predetermined pitch or overlap rate, so that the pitch or overlap rate is kept within the preset allowable range.

[0015] Preferably, when the temperature detection, position feedback, historical thermal cycle data, or speed execution signal is abnormal, the speed compensation is stopped and the relative travel speed is reduced to the preset reference speed v0 or welding is paused.

[0016] This invention also provides an adaptive control system for heat input in submerged arc welding of pipe molds, including a pipe mold rotation mechanism, a submerged arc welding head, an axial travel mechanism, a pre-welding temperature detection device, a position detection unit, a control unit, and a speed execution mechanism; the control unit is configured to: establish spatial control segments and their position markers along the actual welding trajectory, store the equivalent effective heating times Neq and the most recent effective heating time of each spatial control segment, and set the pre-welding real-time temperature T... p Neq and cooldown time T c The target relative travel speed is determined by comparing it with a pre-stored reference value and looking up a table, and the historical thermal cycle state of the corresponding space control segment is updated after the welding action; the speed actuator includes a pipe mold rotary drive and an axial travel drive, and the control unit outputs coordinated speed commands to the two drives according to the target relative travel speed and the predetermined pitch or overlap ratio.

[0017] The technical effects and advantages of this invention are as follows: 1. Compared to existing methods that adjust speed at a fixed speed or only based on instantaneous temperature, this invention incorporates both the current temperature of the welding location and the effective heat transfer record already incurred at that location into the control, enabling segmented compensation for localized heat accumulation differences in multi-layer, multi-pass welding. This is achieved by using the equivalent effective heat transfer times (Neq) and cooling time (T). c The introduction of this control criterion enables the distinction between two different scenarios: "current temperature is high but thermal history is low" and "current temperature is similar but thermal accumulation is high," thereby reducing misjudgments.

[0018] 2. This invention uses relative travel speed as the main execution variable. While maintaining stable welding current and arc voltage, it adjusts the heat input per unit length without altering the original arc stability and droplet transition state, thus contributing to process stability. During spiral surfacing welding, coordinated speed regulation of the two axes can maintain a constant pitch or overlap rate while adjusting local heat input, avoiding damage to weld overlap due to speed compensation. The control process mainly relies on mature components such as infrared temperature measurement, coded positioning, PLC table lookup, frequency converters, or servo drives, without requiring online solutions to complex heat conduction models. This facilitates the modification and implementation on existing submerged arc welding equipment for cast pipe molds and helps reduce local overheating, insufficient heat input, and weld formation fluctuations, improving remanufacturing quality consistency. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the overall process of the method of the present invention. Figure 2 This is the closed-loop control logic diagram for thermal cycle state feedback. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1: This invention provides, for example Figures 1 to 2 The above describes an adaptive control method for thermal input feedback during submerged arc welding of pipe molds. The overall control process can be summarized as "spatial segmentation—pre-temperature measurement—reading historical records—grading judgment—speed compensation—historical update".

[0022] The method includes the following steps: S1. Divide the surface of the pipe mold to be repaired into multiple spatial control segments along a predetermined multi-layer, multi-pass welding trajectory, and establish a position identifier for each spatial control segment, including spatial coordinates and information on the corresponding welding layer and weld pass. Specifically, the spatial control segment can be divided along the actual welding path according to a fixed path length or a fixed turning angle. Its length is determined comprehensively based on the temperature measurement response speed, encoder resolution, and the speed adjustment distance achievable by the driver. The position identifier for each spatial control segment includes at least the axial coordinate x of the pipe mold, the circumferential angular coordinate θ, the layer number i, and the pass number j; wherein, the circumferential angular coordinate θ is obtained by a rotary encoder installed on the rotating axis of the pipe mold, and the axial coordinate x is obtained by an encoder, displacement sensor, or servo feedback from the axial travel mechanism. This position identifier is used to uniquely bind the subsequently acquired pre-welding temperature and historical thermal cycle status to the actual spatial position.

[0023] In practice, the casting mold is supported by support rollers, and a rotary drive mechanism drives the casting mold to rotate around its axis. The submerged arc welding head is mounted on an axial travel mechanism and can move along the axial direction of the casting mold. The spatial control section is divided according to a fixed rotation angle of 5° to 15° or a corresponding arc length of 30mm to 100mm. During on-site commissioning, the principle is to avoid frequent speed jumps. Each control section should at least store information such as location identifier, layer number, track number, Neq, and the most recent effective heating time.

[0024] S2. Before the welding heat source reaches the target space control segment, obtain the real-time temperature T of the target space control segment before welding. p The system reads the historical thermal cycle status associated with the target space control segment based on the location identifier. The historical thermal cycle status includes at least the equivalent effective heating number Neq and the cooling time Tc since the most recent effective heating.

[0025] Real-time temperature T before welding pTemperature is obtained through a non-contact temperature detection device positioned in front of the welding heat source's direction of movement. This device, preferably an infrared thermometer, is installed upstream of the flux supply mechanism, ensuring the detection point always falls on the metal surface not yet covered by flux. Before formal operation, the emissivity is calibrated according to the actual surface condition, and the measurement distance and angle are fixed. A lead distance L is set between the temperature detection device and the arc's position. p L p The speed is determined by the sum of "temperature acquisition time + PLC processing and communication time + driver speed transition time" to ensure that the speed command is adjusted before the arc enters the target control segment. In a specific example, if the temperature sampling period is 50ms, PLC processing and communication is approximately 100ms, the driver speed transition is approximately 200ms, and the pre-welding motion speed is 250mm / min, then L... p Approximately 15mm can be used, with a certain margin. The continuously acquired temperature data, after outlier removal and averaging or median filtering, is used as the pre-welding real-time temperature T for this spatial control section. p .

[0026] S3, Set the real-time temperature T before welding p Equivalent effective heating cycles (Neq) and cooling time (T) c The thermal state deviation ΔH or thermal state level of the control segment is determined by comparing it with the reference temperature, reference equivalent effective heating times and reference cooling time corresponding to the target space control segment, and in accordance with the pre-established classification judgment rules.

[0027] The equivalent effective heating frequency (Neq) is used to quantitatively record the cumulative degree of effective heat effect received by a certain spatial control segment. Neq is determined by summing the effective heating effects satisfying the effective heating criterion from direct welding, the thermal effects of the lap joint area, and the thermal effects of adjacent weld passes, according to their respective equivalent coefficients. Its expression is: , In the formula, This represents the number of times the k-th type of effective heating effect occurs. is the equivalent coefficient corresponding to the k-th type of effective heating effect, and m is the total number of effective heating effect types.

[0028] In engineering applications, m is typically taken as 3, corresponding to three types of events: direct welding, lap reheating, and adjacent heat-affected zone. The effective heating criterion can be determined based on at least one of the following conditions: the control section reaches a preset characteristic temperature, enters a preset lap area, or enters the heat-affected zone. The specific threshold is calibrated by benchmark tests and written into the control unit.

[0029] Cooldown time T c This is the time interval between the most recent effective heating time of the space control segment and the current pre-welding temperature measurement time. The controller directly calculates T based on the saved timestamp.c No additional sensors are required.

[0030] The thermal state deviation ΔH or thermal state level is determined by the control unit using at least one of the following methods: hierarchical table lookup, rule-based judgment, or weighted scoring, based on T. p , Neq and T c The comparison result with the corresponding reference value is used to determine the classification. Different grading tables can be called for different layer numbers, track numbers, and overlap positions. For example, when T... p High, Neq is high or T is high c When the temperature is too short and the set condition is met, it is judged as high heat accumulation; when T p Low, Neq is low and T c A prolonged period of low heat accumulation is considered indicative of low thermal accumulation; other cases are considered normal or slightly off. When continuous historical temperature data collection is available, the historical peak temperature T can also be used. max and / or exceeding the preset characteristic temperature T * The cumulative high-temperature time t0 is used as an additional correction term in the judgment to improve the accuracy of the judgment.

[0031] S4. Under the condition that the welding current and arc voltage are within the preset stable process range, determine the target relative travel speed v according to the thermal state deviation ΔH. * When ΔH, representing heat accumulation, is too high, increase v. * When ΔH, which represents low heat accumulation, decrease v * and for v * Set at least one of the following: control dead zone, speed upper and lower limits, and speed change rate constraints.

[0032] Here, the relative travel speed *v* refers to the linear velocity of the arc point along the actual welding trajectory relative to the workpiece surface. When the current *I* and arc voltage *U* remain stable, the nominal heat input per unit length varies with the travel speed, and the two satisfy the following process conversion relationship: , In the formula, q is the nominal heat input per unit length, and η is the thermal efficiency coefficient. This formula is used to explain the relationship between speed and energy input per unit length; however, the controller does not force real-time calculation of q during actual execution, but directly calls the experimentally verified speed setting based on the thermal state level.

[0033] To ensure smooth control, a control dead zone, hysteresis zone, and speed limit V are set for the target's relative walking speed v*. max Speed ​​lower limit V min And speed change rate limit. When the thermal state deviation ΔH falls within the control dead zone, the baseline relative walking speed v0 remains unchanged to avoid frequent speed fluctuations caused by temperature measurement fluctuations.

[0034] In the quantitative control example, taking 21CrMo10 steel as the base material, 4mm diameter 347 stainless steel welding wire, and HJ260 flux as an example, the preliminary test used three speed levels: 200mm / min, 250mm / min, and 300mm / min, with 250mm / min as the reference speed v0. Assume the reference pre-welding temperature T of a certain control section in the second layer, third pass. r The actual temperature was 180℃. p The temperature was 205℃, and the Neq value in this segment was higher than the reference value N. r And T c The cooling time was 90 seconds, shorter than the reference cooling time of 150 seconds. After consulting the table, it was determined that the heat accumulation was too high. The target speed was increased from 250 mm / min to the equipment-verified 280 mm / min, and the acceleration was completed according to the set ramp. In another control section, if T... p The temperature is 160℃, Neq is lower than the reference value, and T c If the value is 240s, then the heat accumulation is considered too low, and the target velocity is reduced to 230mm / min; if T p It was close to 180℃, but Neq was high and T c If the temperature is too short, it is judged as slightly too high, and only the speed level is increased by one gear. The above case demonstrates that the controller not only looks at the current temperature, but also uses the number of times it has been heated and the cooling time at that location to make a judgment.

[0035] S5. Complete the welding of the target space control segment according to the target relative walking speed, and update the equivalent effective heating number Neq and the most recent effective heating time of the space control segment based on the direct welding action and the thermal effect of the subsequent overlapping area in the thermal effect or the thermal effect of the adjacent weld bead, so as to evaluate the thermal state when the subsequent weld bead or subsequent deposition layer passes through the corresponding space position again.

[0036] For the spiral welding trajectory formed by the rotation of the pipe casting mold and the axial feed of the welding head, when changing the relative travel speed, the circumferential linear velocity and axial feed speed of the pipe casting mold are adjusted synchronously according to the predetermined pitch or overlap rate to keep the pitch or overlap rate within the preset allowable range. In specific implementation, let the circumferential linear velocity of the pipe casting mold surface be V. c The axial feed speed of the machine head is V a After establishing the reference pitch, the speed scaling factor obtained from the thermal state determination is applied to both the rotary drive and the axial feed drive. For example, when the target relative speed increases by 10%, the commands for both axes are increased by the same factor so that the axial feed per revolution remains basically unchanged. The same method is used when the speed is reduced. For equipment that cannot be scaled at the same ratio, the commands are converted according to the actual relationship between the rotational speed and the axial feed, but the overlap rate is always constrained to not exceed the allowable range.

[0037] Furthermore, when temperature detection, position feedback, historical thermal cycle data, or speed execution signal is abnormal, the controller stops further expanding speed compensation and reverts the relative travel speed to the preset reference speed v0; if there is a risk to welding safety or forming quality, welding is suspended and an alarm is triggered. In specific implementation, median filtering or rate of change limiting is used when the temperature signal shows a short-term spike; when the temperature continuously exceeds the range, the position encoder has no feedback, the spatial control segment number is inconsistent, historical records are missing, or the driver fails to reach the target speed, the controller stops further expanding compensation and reverts to the reference speed v0; welding is suspended when there is a risk to welding safety or quality; each operation saves the layer number, track number, spatial position, and T. p Neq, T c The system includes thermal condition level, target speed, actual speed, and abnormal conditions, facilitating post-weld traceability and process optimization.

[0038] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for adaptive control of thermal input feedback during submerged arc welding of pipe casting molds, characterized in that, Includes the following steps: S1. Divide the surface of the pipe mold to be repaired into multiple spatial control segments along the predetermined multi-layer and multi-pass welding trajectory, and establish a position marker for each spatial control segment that includes spatial coordinates and information on the welding layer and weld pass to which it belongs. S2. Before the welding heat source reaches the target space control segment, obtain the real-time temperature T of the target space control segment before welding. p The system reads the historical thermal cycle status associated with the target space control segment based on the location identifier. The historical thermal cycle status includes at least the equivalent effective heating number Neq and the cooling time T since the most recent effective heating. c ; S3, Set the real-time temperature T before welding p Equivalent effective heating cycles (Neq) and cooling time (T) c The reference temperature, reference equivalent effective heating times, and reference cooling time corresponding to the target space control segment are compared respectively, and the thermal state deviation ΔH or thermal state level of the control segment is determined according to the pre-established classification judgment rules; wherein, the equivalent effective heating times Neq is determined by the thermal effects that meet the effective heating criteria in direct welding action, lap area thermal effects and adjacent weld thermal effects, and are accumulated according to their respective equivalent coefficients; S4. Under the condition that the welding current and arc voltage are within the preset stable process range, determine the target relative travel speed v according to the thermal state deviation ΔH or the thermal state level. * When the thermal state deviation ΔH or the thermal state level, which indicates high heat accumulation, is increased, v is increased. * When the heat accumulation is low, v decreases. * and for v * Set at least one of the following: control dead zone, speed upper and lower limits, and speed change rate constraints; the relative travel speed is the linear velocity of the arc point along the actual welding trajectory relative to the workpiece surface. S5. Complete the welding of the target space control segment according to the target relative walking speed, and update the equivalent effective heating number Neq and the most recent effective heating time of the space control segment based on the direct welding action and the thermal effect of the subsequent overlapping area in the thermal effect or the thermal effect of the adjacent weld bead, so as to evaluate the thermal state when the subsequent weld bead or subsequent deposition layer passes through the corresponding space position again.

2. The adaptive control method for thermal input feedback of submerged arc welding in pipe casting molds according to claim 1, characterized in that, The position identifier includes at least the axial coordinate x, the circumferential angular coordinate θ, the layer number i, and the track number j of the casting mold; wherein, the circumferential angular coordinate θ is obtained by a rotary encoder installed on the rotating shaft of the casting mold, and the axial coordinate x is obtained by an encoder, displacement sensor, or servo feedback of the axial travel mechanism.

3. The adaptive control method for thermal input feedback of submerged arc welding in pipe casting molds according to claim 1, characterized in that, Real-time temperature T before welding p The temperature is obtained by a non-contact temperature detection device positioned in front of the direction of motion of the welding heat source, wherein the detection area of ​​the temperature detection device is located before the flux-covered area. The continuously collected temperature data, after outlier removal and averaging or median filtering, is used as the pre-welding real-time temperature T. p .

4. The adaptive control method for thermal input feedback of submerged arc welding in pipe casting molds according to claim 1, characterized in that, The equivalent effective heating cycles Neq are determined by the following formula: ， In the formula, This represents the number of times the k-th type of effective heating effect occurs. is the equivalent coefficient corresponding to the kth type of effective heating effect, and m is the total number of effective heating effect types; the effective heating criterion is determined based on at least one of the following conditions: the control segment reaches a preset characteristic temperature, enters a preset overlap area, or enters a heat-affected neighborhood.

5. The adaptive control method for thermal input feedback of submerged arc welding in pipe casting molds according to claim 1, characterized in that, The historical thermal cycling state also includes the historical peak temperature T. max and exceeding the preset characteristic temperature T * At least one of the cumulative high-temperature times t0; when conditions allow for continuous temperature history data collection, T max And / or t0 is used as an additional correction term for the thermal state deviation ΔH in the classification determination.

6. The adaptive control method for thermal input feedback of submerged arc welding in pipe casting molds according to claim 1, characterized in that, The thermal state deviation ΔH or thermal state level is determined by the control unit using at least one of the following methods: hierarchical lookup table, rule-based judgment, or weighted scoring, based on T. p , Neq and T c The comparison result with the corresponding reference value is determined, and different classification judgment tables can be called according to the layer number, channel number and overlap relationship.

7. The adaptive control method for thermal input feedback of submerged arc welding in pipe casting molds according to claim 1, characterized in that, relative walking speed v to the target * Set control dead zone, hysteresis zone, and speed limit V. max Speed ​​lower limit V min And speed change rate limit; when the thermal state deviation ΔH falls within the control dead zone, the reference relative walking speed v0 remains unchanged.

8. The adaptive control method for thermal input feedback of submerged arc welding in pipe casting molds according to claim 1, characterized in that, For the spiral welding trajectory formed by the rotation of the pipe casting mold and the axial feed of the welding head, when the relative travel speed is changed, the circumferential linear speed and axial feed speed of the pipe casting mold are adjusted synchronously according to the predetermined pitch or overlap rate, so that the pitch or overlap rate is kept within the preset allowable range.

9. The adaptive control method for thermal input feedback of submerged arc welding in pipe casting molds according to claim 1, characterized in that, When the temperature detection, position feedback, historical thermal cycle data, or speed execution signal is abnormal, stop further speed compensation and reduce the relative travel speed back to the preset reference speed v0 or suspend welding.

10. An adaptive control system for heat input in submerged arc welding of pipe molds for implementing the method according to any one of claims 1 to 9, characterized in that, The system includes a pipe casting mold rotation mechanism, a submerged arc welding head, an axial travel mechanism, a pre-welding temperature detection device, a position detection unit, a control unit, and a speed actuator. The control unit is configured to: establish spatial control segments and their position markers along the actual welding trajectory; store the equivalent effective heating times (Neq) and the most recent effective heating time for each spatial control segment; and display the pre-welding real-time temperature (T). p Neq and cooldown time T c The target relative travel speed is determined by comparing it with a pre-stored reference value and looking up a table, and the historical thermal cycle state of the corresponding space control segment is updated after the welding action; the speed actuator includes a pipe mold rotary drive and an axial travel drive, and the control unit outputs coordinated speed commands to the two drives according to the target relative travel speed and the predetermined pitch or overlap ratio.

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