A welding method for a tooth base and head body special-shaped angle structure

Abstract

This invention discloses a welding method for an irregularly shaped angled tooth base and head body structure, belonging to the field of welding technology. The method includes selecting welding material as filler material; the yield strength value of the welding material is between the yield strength value of the tooth base and the yield strength value of the head body material, preferably an intermediate value; using the selected filler material, welding the tooth base and head body with a welding torch, the welding torch extending to the root of the weld to fully melt the root of the weld leg; controlling the weld shape to ensure a smooth transition across the entire outer surface of the weld. This invention solves the problem of fatigue cracking in the welds of tooth bases and head bodies in the prior art. The welds produced using this welding method have full penetration at the root, are defect-free, and exhibit a high dilution rate at the interface between the weld and the tooth base and head body, resulting in more complete fusion, high bonding strength, and avoiding incomplete fusion defects. The strength transition between the tooth base, weld, and head body is smooth, reducing stress concentration in the weld area and improving the fatigue resistance of the weld.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding, in particular to a welding method for a special-shaped angle structure of a tooth holder and a head body. BACKGROUND

[0002] With the rapid development of the engineering machinery industry in China, the demand for improving the service life of high-end equipment is increasing, but the most common failure problem of equipment during service is the fatigue cracking of the weld.

[0003] Under the hard rock working condition of a harsh environment, fatigue load and impact load are applied, resulting in the phenomenon that the weld between the tooth holder and the head body of the roadheader cutting head often appears fatigue cracking. The main reasons for the fatigue cracking of the weld include the weld structure, the selection of welding wire, welding defects, stress concentration and the number of alternating load cycles. First, the weld structure between the tooth holder and the head body is one of the main reasons for the defects of welding. The tooth holder and the head body overlap to form an angle of 40°, which is not conducive to the implementation of welding. In the root of the weld, the conditions of incomplete penetration, low dilution rate of the upper and lower base materials, and insufficient fusion of the weld and the base material are prone to occur, which leads to the initiation and propagation of the weld fatigue crack, and significantly reduces the fatigue performance of the weld. In addition, the strength difference between the tooth holder (23MnNi) and the head body (ZG16Mn) is large, and the existing welding wire selection generally follows the low-strength matching principle, that is, the welding wire with the same strength as the head body is selected, which leads to a large strength difference between the weld and the tooth holder. During the service process, stress concentration in the weld area is prone to occur, and the phenomenon of fatigue cracking appears. In addition, the existing process uses stainless steel welding wire to weld the tooth holder and the head body. Although the stainless steel welding wire has good toughness and good weld forming property, the stainless steel welding wire has a large viscosity, which is prone to form defects such as incomplete fusion of the weld sidewall. In addition, the interface bonding area is narrow, which is prone to cause fatigue crack initiation during the later service, resulting in failure and cracking of the tooth holder and the head body. SUMMARY

[0004] The purpose of the present application is to overcome the deficiencies in the prior art, and to provide a welding method for a special-shaped angle structure of a tooth holder and a head body, which solves the problem that the weld of the tooth holder and the head body in the prior art is prone to fatigue cracking.

[0005] To achieve the above-mentioned purpose, the present application is implemented by using the following technical solutions:

[0006] In a first aspect, the present application provides a welding method for a special-shaped angle structure of a tooth holder and a head body, comprising:

[0007] Selecting a welding material as a filler material; the yield strength value of the welding material is between the yield strength value of the tooth holder and the yield strength value of the head body material;

[0008] Using the selected filler material, using a welding gun to weld the tooth holder and the head body, and extending the welding gun to the root of the weld to melt the root of the welding leg;

[0009] The shape of the weld is controlled so that the entire outer surface of the weld is smoothly transitioned.

[0010] In combination with the first aspect, further, the filler material is a high-strength steel welding wire, and the yield strength of the high-strength steel welding wire is 680-720 MPa.

[0011] In combination with the first aspect, further, the welding torch is a manual welding torch, and the nozzle diameter of the manual welding torch is less than 12 mm.

[0012] In combination with the first aspect, further, the yield strength value of the welding material is preferably the intermediate value of the yield strength value of the tooth holder and the yield strength value of the head body material.

[0013] In combination with the first aspect, further, the welding of the tooth holder and the head body using the welding torch includes using an active gas shielded welding method and using a pulse current mode for welding.

[0014] In combination with the first aspect, further, the welding of the tooth holder and the head body using the welding torch further includes increasing the up-and-down swing of the welding torch during welding.

[0015] In combination with the first aspect, further, the control of the shape of the weld includes controlling the length of the joint surface of the weld and the tooth holder to be greater than the welding surface length of the tooth holder and controlling the welding surface length of the weld and the head body to be greater than the welding surface length of the tooth holder.

[0016] The second aspect provides a tooth holder and head body special-shaped corner structure welded by the welding method of any one of the first aspect, and the tooth holder and head body special-shaped corner structure includes a tooth holder and a head body; the tooth holder and the head body are overlapped and welded to form a special-shaped corner weld, the angle of the special-shaped corner weld is 40°, the fusion length of the weld and the head body is greater than 2 times the fusion length of the tooth holder, and the weld root is penetrated, and the outer surface of the weld is smoothly transitioned.

[0017] In combination with the second aspect, further, the special-shaped corner weld is divided into four parts, front, back, left and right, the included angle of the left and right two sides of the weld and the tooth holder and the head body is greater than 150°, the fusion length of the weld and the head body is greater than 0.85 times the transverse contact length of the tooth holder and the head body; the front side of the weld and the tooth holder and the head body are smoothly connected, the included angle of the weld and the head body is less than 30°, the included angle of the weld and the tooth holder is greater than 150°, the fusion surface length of the weld and the head body is greater than 0.75 times the longitudinal contact length of the tooth holder and the head body, the cross-sectional length of the weld is greater than 0.5 times the longitudinal contact length of the tooth holder and the head body, and the fusion surface length of the weld and the head body is greater than 1.5 times the length of the cross section of the weld; the back side of the weld and the tooth holder and the head body are smoothly connected, the included angle of the weld and the tooth holder and the head body is less than 30°, the fusion surface length of the weld and the head body is greater than 1.2 times the longitudinal contact length of the tooth holder and the head body, and the fusion surface length of the weld and the tooth holder is greater than 0.6 times the longitudinal contact length of the tooth holder and the head body.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] The present application discloses a welding method for a tooth seat and a head body special-shaped angle structure, which comprises selecting a welding material as a filler material; the yield strength value of the welding material is between the yield strength value of the tooth seat and the yield strength value of the head body material; the selected filler material is used to weld the tooth seat and the head body by using a welding gun, the welding gun is extended to the root of the weld, and the root of the welding leg is penetrated; the shape of the weld is controlled to make the entire outer surface of the weld smoothly transition. The weld root welded by using the welding method is fully penetrated and has no defects, meanwhile, the dilution rate of the weld and the combination interface of the tooth seat and the head body is high, the fusion is more sufficient, the combination strength is high, and the un-fusion defects are avoided. The strength of the tooth seat, the weld and the head body smoothly transitions, the stress concentration in the weld area is reduced, and the fatigue resistance of the weld is improved. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a welding method flow chart for a tooth seat and a head body special-shaped angle structure provided by the embodiment one of the present application;

[0021] Figure 2 It is a welding joint hardness data chart in the welding method embodiment for a tooth seat and a head body special-shaped angle structure provided by the embodiment two of the present application;

[0022] Figure 3 It is a welding joint hardness data chart in the welding method comparative example 1 for a tooth seat and a head body special-shaped angle structure provided by the embodiment two of the present application;

[0023] Figure 4 It is a welding joint hardness data chart in the welding method comparative example 2 for a tooth seat and a head body special-shaped angle structure provided by the embodiment two of the present application.

[0024] Figure 5 It is a tunneling machine head tooth seat and head body welding structure perspective view in a tooth seat and a head body special-shaped angle structure provided by the embodiment three of the present application;

[0025] Figure 6 It is a tunneling machine head tooth seat and head body welding structure side view in a tooth seat and a head body special-shaped angle structure provided by the embodiment three of the present application. DETAILED DESCRIPTION

[0026] The technical scheme of the present application will be described in detail below by means of the drawings and specific embodiments, and it should be understood that the specific features in the embodiments and the specific embodiments of the present application are detailed descriptions of the technical scheme of the present application, and are not limitations of the technical scheme of the present application, and the technical features in the embodiments and the specific embodiments of the present application can be combined with each other without conflict.

[0027] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0028] Example 1:

[0029] like Figure 1 As shown, this embodiment provides a welding method for a tooth base and a head body with an irregular angle structure, including the following steps:

[0030] Step 1: Select welding material with a strength between the yield strength of the tooth base and the head body material as filler material;

[0031] The filler material of the welding consumable has a low alloy element content, good fluidity, and physical properties similar to those of the gear base and head body, enabling it to achieve good interfacial fusion with both materials. The yield strength of the welding consumable is preferably an intermediate value between the yield strength of the gear base and the yield strength of the head body material. Specifically, high-strength steel welding wire with a yield strength of 680-720 MPa is used as the filler material.

[0032] Step 2: Using the selected filler material, weld the toothed seat and head body with a welding torch, extending the welding torch to the root of the weld and melting through the root of the weld foot;

[0033] The welding torch extends to the root of the weld, ensuring complete penetration of the weld root and a longer fusion dimension on both sides, resulting in greater interface load-bearing capacity. Specifically, an active gas shielded welding method is employed, using pulsed current to ensure adequate melting of both sides. A manual welding torch with a nozzle diameter of less than 12mm is used to ensure the torch reaches the weld root and achieves full penetration. During manual welding, the torch can be oscillated up and down to ensure better fusion of the upper and lower sidewalls of the weld.

[0034] Step 3: When forming the weld, control the joint surface of the weld to be longer on the tooth seat and head body sides, and make the entire outer surface of the weld smooth.

[0035] Among them, the length of the joint surface between the weld and the tooth holder is greater than the length of the welding surface of the tooth holder, while the length of the welding surface between the weld and the head body is greater than the length of the welding surface of the tooth holder, and the entire outer surface of the weld has a smooth transition.

[0036] Example 2:

[0037] like Figures 2-4 As shown, this embodiment provides a specific example and comparative example of a welding method for an irregularly shaped corner structure of a tooth base and a head body. The specific embodiment uses a 23MnNi cylindrical tooth base and a ZG16Mn head body, which are overlapped to form a 40° irregularly shaped corner weld. The specific steps include:

[0038] (1) Fix the tooth seat to the head body and preheat it to 100°C before welding;

[0039] (2) High-strength steel welding wire with a yield strength of 700MPa is used as filler material. A manual welding torch with a nozzle diameter of less than 12mm is used. Active gas shielded welding method is adopted, and pulsed current is used for welding. The welding torch can reach the root of the weld and melt through the root. During welding, the up and down swing of the welding torch is increased to promote the fusion of the weld sidewall.

[0040] (3) During the welding process, ensure that the length of the joint surface between the weld and the tooth seat is greater than the length of the welding surface of the tooth seat, and the length of the welding surface between the weld and the head body is greater than the length of the welding surface of the tooth seat. The entire outer surface of the weld is concave inward.

[0041] Comparative Example 1: Using existing processes, a standard welding machine (25mm welding torch) is selected, and stainless steel welding wire is used. The specific steps include:

[0042] (1) Fix the tooth seat to the head body and preheat it to 100°C before welding;

[0043] (2) Stainless steel welding wire was used as filler material, a 25mm welding torch was used, active gas shielded welding was employed, and pulsed current was used for welding. During welding, the welding torch was too large, the welding position space was too small, and it was not convenient to swing the welding torch.

[0044] Comparative Example 2: Using existing processes, a standard welding machine (25mm welding torch) was selected, and 500MPa grade welding wire was used. The specific steps included:

[0045] (1) Fix the tooth seat to the head body and preheat it to 100°C before welding;

[0046] (2) Welding wire with a yield strength of 500 MPa was used as filler material, a 25 mm welding torch was used, and active gas shielded welding was performed using pulsed current. During welding, the welding torch was too large, and the welding position space was too small, making it inconvenient to swing the welding torch.

[0047] Table 1 shows the interfacial tensile properties of the joints welded with different welding wires in this embodiment and the comparative example. As can be seen from the table, compared with the comparative example, this embodiment uses high-strength steel welding wire with a yield strength of 700MPa as filler material, a manual welding gun with a nozzle diameter of less than 12mm, an active gas shielded welding method, and pulsed current welding. The yield strength and tensile strength of the welded joint interface are both higher.

[0048] Table 1 Tensile properties of welded joints with different welding wires

[0049]

[0050]

[0051] Table 2 shows the fatigue test results of the welded joints using different welding wires in this embodiment and the comparative example. As can be seen from the table, compared with the comparative example, this embodiment uses high-strength steel welding wire with a yield strength of 700MPa as filler material, a manual welding torch with a nozzle diameter of less than 12mm, an active gas shielded welding method, and pulsed current welding. The welded joint has better fatigue resistance, a fatigue life of more than 10 million cycles, and no cracking after the test.

[0052] Table 2 Fatigue test results of welded joints with different welding wires

[0053]

[0054] In this embodiment, high-strength steel welding wire with a yield strength of 700MPa was used as filler material, a manual welding torch with a nozzle diameter of less than 12mm was used, active gas shielded welding method was used, and pulsed current was used for welding. The fusion effect of the welded joint was good. In contrast, the welded joint in the comparative example, which used stainless steel welding wire as filler material, had obvious unfused parts and poor fusion effect.

[0055] Figures 2-4 The figure shows the hardness data of the welded joint in the specific embodiment and the comparative example in this embodiment. It can be clearly seen from the figure that the high-strength steel welding wire with a yield strength of 700MPa is used as the filler material, a manual welding gun with a nozzle diameter of less than 12mm is used, an active gas shielded welding method is used, and a pulsed current method is used for welding. The hardness of the weld is significantly improved compared with the hardness of the weld in the comparative example. The hardness of the head body, weld and tooth seat transitions smoothly, reducing stress concentration during service and significantly improving fatigue resistance.

[0056] Example 3:

[0057] like Figures 5-6 As shown, this embodiment provides a tooth base and head body irregular angle structure, obtained by any of the welding methods for tooth base and head body irregular angle structures described in Embodiment 1. The tooth base and head body irregular angle structure includes a tooth base and a head body; the tooth base and head body overlap and are welded to form an irregular angle weld, the angle of the irregular angle weld is 40°, the fusion length of the weld with the side wall of the head body is greater than twice the fusion length of the side wall of the tooth base, and the root of the weld is fully fused, and the outer surface of the weld has a smooth transition.

[0058] The irregular fillet welds are divided into four sections: front, back, left, and right. The angles between the left and right side welds and the tooth base and head body are greater than 150°, and the fusion length between the weld and the head body is greater than 0.85 times the lateral contact length between the tooth base and the head body. The front side welds are smoothly connected to the tooth base and head body, with an angle less than 30° between the weld and the head body, an angle greater than 150° between the weld and the tooth base, a fusion surface length greater than 0.75 times the longitudinal contact length between the tooth base and the head body, a cross-sectional length greater than 0.5 times the longitudinal contact length between the tooth base and the head body, and a fusion surface length greater than 1.5 times the cross-sectional length of the weld. The rear side welds are smoothly connected to the tooth base and head body, with angles less than 30° between the weld and both the tooth base and the head body, a fusion surface length greater than 1.2 times the longitudinal contact length between the tooth base and the head body, and a fusion surface length greater than 0.6 times the longitudinal contact length between the tooth base and the head body.

[0059] In summary, this invention discloses a welding method for a tooth base and a head body with irregular angles, and the tooth base and head body with irregular angles welded using this method. The weld root is fully penetrated and defect-free. Simultaneously, the interface between the weld and the tooth base and head body has a high dilution rate, resulting in more complete fusion and high bonding strength, avoiding incomplete fusion defects. The strength transition between the tooth base, weld, and head body is smooth, reducing stress concentration in the weld area and improving the fatigue resistance of the weld. The welded specimens of this invention, after testing, showed a fatigue life greater than 10 million cycles without cracking, indicating that the weld joint of the tooth base and head body with irregular angles welded using this method has excellent fatigue resistance.

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A welding method for a tooth base and a head body with an irregular angle structure, characterized in that, The tooth base and head body irregular angle structure includes a tooth base and a head body; the tooth base and head body overlap and are welded to form an irregular fillet weld, the angle of the irregular fillet weld is 40°, the fusion length of the weld with the side wall of the head body is more than twice the fusion length of the side wall of the tooth base, and the root of the weld is fully melted, and the outer surface of the weld has a smooth transition. The irregular fillet welds are divided into four sections: front, back, left, and right. The angles between the welds on the left and right sides and the tooth base and head body are greater than 150°, and the fusion length between the weld and the head body is greater than 0.85 times the transverse contact length between the tooth base and the head body. The front weld has a smooth transition with the tooth base and head body, with an angle less than 30° between the weld and the head body, an angle greater than 150° between the weld and the tooth base, a fusion surface length greater than 0.75 times the longitudinal contact length between the tooth base and the head body, a cross-sectional length greater than 0.5 times the longitudinal contact length between the tooth base and the head body, and a fusion surface length greater than 1.5 times the cross-sectional length of the weld. The rear weld has a smooth transition with the tooth base and head body, with angles less than 30° between the weld and both the tooth base and the head body, a fusion surface length greater than 1.2 times the longitudinal contact length between the tooth base and the head body, and a fusion surface length greater than 0.6 times the longitudinal contact length between the tooth base and the head body. The welding method includes: Welding material is selected as the filler material; the yield strength value of the welding material is between the yield strength value of the tooth base and the yield strength value of the head material; Using the selected filler material, weld the toothed seat and head body with a welding torch, extending the welding torch to the root of the weld and melting through the root of the weld foot; Control the shape of the weld to ensure a smooth transition across the entire outer surface of the weld. The filler material is high-strength steel welding wire, and the yield strength of the high-strength steel welding wire is 680-720MPa; The welding torch is a manual welding torch, and the nozzle diameter of the manual welding torch is less than 12mm; The yield strength value of the welding material is the midpoint between the yield strength value of the tooth seat and the yield strength value of the head material; The method of welding the tooth holder and head body with a welding torch includes using an active gas shielded welding method and using a pulsed current method for welding; it also includes increasing the up-and-down oscillation of the welding torch during welding.

Images