CN112222669B - Welding seam structure and manufacturing method thereof - Google Patents

Abstract

The invention discloses a welding seam structure and a manufacturing method thereof, which are suitable for connecting a valve seat and a valve body, wherein the welding seam structure comprises a tail butt welding seam and a head butt welding seam, under the arrangement of a welding seam medium separation step, a tail heat-preserving barrel and a head heat-preserving barrel, the occurrence of the welding seam stress fatigue failure phenomenon is reduced to the maximum extent, meanwhile, the welding seam avoids the direct heat radiation of an ultra-high temperature medium, the arrangement of the welding seam in a head heat affected zone ensures that the whole area of the welding seam is safer and more reliable under the severe working condition, the arrangement of a welding seam strain tank and a welding seam strain zone effectively prolongs the occurrence of the welding seam fatigue failure phenomenon, the valve seat is made of high-temperature deformation nickel-based alloy 3103, the dissimilar materials are welded to reach the same mechanical strength, the valve seat is connected with the valve body by adopting the tail butt welding seam and the, the defect of root crack of the fillet weld is eliminated.

Description

Welding seam structure and manufacturing method thereof

Technical Field

The invention relates to the technical field of welding, in particular to a welding seam structure and a manufacturing method thereof.

Background

At present, in hypersonic wind tunnel equipment, a high-pressure blowing-vacuum suction temporary-flushing wind tunnel has the characteristics of large model scale, wide simulation range and the like, and is widely applied to the fields of test and experimental calculation of test objects such as aerodynamic force/heat, aerodynamic layout, jet flow control and the like.

Because the special requirement of system to the quick release of ultra-high temperature high pressure test medium in the heater, consequently be equipped with the quick-opening valve at the air feed entry end, the specific operating mode of quick-opening valve does: in the closed state, an inlet bears ultrahigh-temperature and high-pressure test media (the maximum design temperature of the inlet can reach 1000 ℃, and the design pressure is more than 12 MPa), an outlet side has the characteristic of vacuum, and in order to ensure the absolute isolation of the media on two sides of the valve, the high requirement on the thermal deformation of a sealing pair of the valve is provided.

Due to the working characteristics of ultra-high temperature and high pressure medium outside the welding seam and water cooling inside the welding seam, a very harsh working environment exists in the welding seam area, and according to the prior use effect, the welding seam at the position often has crack failure, so that the water leakage phenomenon occurs.

Disclosure of Invention

The present invention is directed to a weld structure and a method for manufacturing the same, which solves the above problems.

In order to achieve the purpose, the invention provides the following technical scheme:

the welding seam structure comprises a butt welding seam at the tail part and a butt welding seam at the head part, wherein the butt welding seam at the tail part is positioned at the outer side of the heat preservation barrel at the head part.

The head of the valve seat is also provided with a head heat affected zone welding seam.

The head of the valve seat is also provided with a welding seam medium blocking step which is positioned between the head butt welding seam and the head heat-insulating barrel.

The valve seat head still is provided with welding seam strain tank, and welding seam strain tank is located between head butt weld and the head heat-preserving container and matches the setting with head butt weld.

The tail part of the valve seat is also provided with a welding line strain area, and the welding line strain area is positioned on the outer side of the tail part heat-insulating barrel and matched with the butt welding line of the tail part.

The valve seat is an NS3103 alloy valve seat, and the valve body is an F304 stainless steel valve body.

The manufacturing method of the welding seam structure comprises the following steps:

s1, calculating the position and the size of a heat affected zone of the head butt weld on the valve body to obtain a region H, and removing the region H in a machining mode;

s2, welding materials with the same material as the valve seat in the valve body removing area H to form a head heat affected zone welding seam;

s3, carrying out ultrasonic flaw detection nondestructive testing and penetration flaw detection nondestructive testing on the weld joint of the heat affected zone of the head;

s4, after the ultrasonic flaw detection nondestructive test and the penetration flaw detection nondestructive test are qualified, welding the valve seat and the valve body through a head butt weld and a tail butt weld, wherein the head butt weld and the tail butt weld are both subjected to backing and cover surface welding by hot wire TIG welding, and single-side welding and double-side forming are performed;

and S5, stress relief treatment is carried out on the welded valve seat and the valve body integrally.

In step S4, the head butt weld and the tail butt weld 7 are both welded by a single-side welding and double-side forming technique.

The invention has the beneficial effects that:

1. under the arrangement of the welding seam medium blocking step, the tail heat-preserving barrel and the head heat-preserving barrel, the temperature of the ultrahigh-temperature high-pressure working medium reaching the head and tail welding seams of the valve seat can be reduced as much as possible according to the structural principle, so that the occurrence of the welding seam stress fatigue failure phenomenon caused by cold and hot stress expansion and contraction caused by external ultrahigh temperature and internal water cooling of the welding seams is reduced to the maximum extent; meanwhile, the direct heat radiation of the ultra-high temperature medium is avoided in the welding line, and the problem of hot corrosion of the welding line ultra-high temperature medium is solved.

2. The welding seam of the heat affected zone of the head part is arranged, and the design of pre-priming transition enables the chemical compositions, mechanical properties and heat intensity of base materials on two sides of the welding seam to be consistent with those of a metal material of a welding seam body when the valve body is welded and connected with the valve seat, so that the whole area of the welding seam can be safely and reliably operated and used under severe working conditions of external ultrahigh-temperature media and internal circulating water cooling.

3. The welding line strain groove and the welding line strain area can compensate composite alternating stress of the valve seat body caused by thermal expansion of an external ultrahigh-temperature medium and stretching and extrusion of a welding line caused by cooling and contraction of circulating water, so that the fatigue failure phenomenon of the welding line is effectively prolonged.

4. The valve seat material adopts high-temperature deformation nickel-based alloy NS3103 with mechanical property similar to that of valve body material F304/F304H, so that dissimilar materials can be welded to achieve the same mechanical strength.

5. The valve seat and the valve body are connected by adopting a butt welding seam at the tail part and a butt welding seam at the head part, and a full-automatic non-consumable electrode argon tungsten-arc welding TIG hot wire bottoming and capping process is adopted, so that the single-side welding and the double-side forming are realized, the equal-strength welding seam is formed, the integral strength of the welding seam is improved, and the defect of root cracks of the angle type welding seam is eliminated.

Drawings

FIG. 1 is a schematic structural view of a prior art valve seat;

FIG. 2 is a schematic view of a weld of a prior art valve seat;

FIG. 3 is a schematic view of a weld in the head region of a prior art valve seat;

FIG. 4 is a schematic view of a weld in the tail region of a prior art valve seat;

FIG. 5 is a schematic view of the weld of the present invention applied to a valve seat;

FIG. 6 is a schematic view of the weld structure of the present invention;

FIG. 7 is a schematic view of the weld structure of the present invention in the head region of the valve seat;

FIG. 8 is a schematic view of the weld structure of the present invention in the aft region of the valve seat.

In the figure: 1-valve seat, 2-valve body, 3-tail heat preservation barrel, 4-head heat preservation barrel, 5-tail fillet weld, 6-head fillet weld, 7-tail butt weld, 8-head butt weld, 9-head heat affected zone weld, 10-weld medium blocking step, 11-weld strain tank, 12-weld strain zone, A-weld external ultra-high temperature high pressure zone, B-weld internal water cooling zone and C-weld heat affected zone.

Detailed Description

The technical solutions of the present invention are further described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the following.

Referring to fig. 1, a cooling system of a valve seat 1 is composed of: the valve body 2, the valve seat 1, the tail heat-preserving container 3 and the head heat-preserving container 4.

Wherein, the cooling water flows in from the cooling hole at the head of the valve seat 1, is guided into the central part of the interior of the valve seat 1 through the flow guide holes at the periphery of the valve seat 1, and then is transferred to the tail part of the valve seat 1, thereby realizing the cooling of the valve seat.

The tail heat-preserving container 3 and the head heat-preserving container 4 play a role in slowing down the speed of the ultra-high temperature medium reaching the weld joint and reducing the temperature, and the flow direction of the ultra-high temperature medium is shown by white arrows in figure 1.

Referring to fig. 2, the structure that can appear from the figure has two welds, respectively: a tail fillet 5 and a head fillet 6.

Referring to fig. 3, the function of the valve seat head region weld (head fillet weld 6) is:

i, connecting a valve body 2 with a valve seat 1;

and II, isolating the ultrahigh-temperature high-pressure area A outside the welding seam and the water cooling area B inside the welding seam, and preventing the two areas from communicating with each other.

Referring to FIG. 4, the valve seat tail region weld (tail fillet weld 5) functions in accordance with the head fillet weld 6.

The main failure modes of the structure are as follows:

i, due to overlarge difference between the internal and external cold and hot temperatures of a welding seam and the huge difference of the linear expansion coefficients of the welding of dissimilar materials, the composite stress of stretching, extruding and the like of the welding seam part is suddenly increased, and further the fatigue failure of a welding seam body and a heat affected zone is caused;

II, high-temperature and high-pressure medium circulation at 1000 ℃ is arranged outside the welding line, and the inside of the welding line is cooled by circulating drinking water, so that the phenomenon of continuous drying (coexistence of water vapor state) exists in the inner area of the welding line, and bubbles are instantaneously broken after steam is dried to cause cavitation;

III, because drinking water is not purified water, a large amount of calcifications and halides are gathered around the welding seam in the process of continuously burning and cooling the inside of the welding seam, and long-term alternating working condition operation has stress corrosion influence on the welding seam and heat affected zones of base metals at two sides;

IV, the existing mature material selection valve body 2 adopts austenitic stainless steel F304/F304H, the valve seat 1 adopts high-temperature deformation nickel-based alloy, and the mechanical properties of the two are shown in the table 1:

TABLE 1 mechanical performance matching table for valve seat GH3128 and valve body F304/F304H

Material of	Tensile strength is more than or equal to MPa	Yield strength is more than or equal to MPa	The elongation of 2in (DN 50) or 4D gauge length is more than or equal to%	The reduction of area is more than or equal to
					F304/F304H	515	205	30	40
GH3128	735	320	40	/

The comparison shows that although GH3128 has better high-temperature oxidation resistance and high-temperature strength, the mechanical property difference with the valve body material is too large, which causes too large stress near the weld seam body and the heat affected zone with the valve body, and accelerates the occurrence of the failure phenomenon of the valve body and the weld seam part material.

The valve seat 1 is welded with the valve body 2in a circular shape in a matched mode through fillet welding (a tail fillet welding 5 and a head fillet welding 6), and belongs to a semi-penetration design, so that crack defects exist at the root of the welding seam from the initial application stage, and the failure phenomena of I-IV are accelerated.

The invention collects and analyzes the failure mode of the welding line under the working condition, invents a novel welding line design and manufacturing method, particularly the welding line bears the working condition that one side bears ultrahigh-temperature high-pressure medium, the other side bears water cooling, and the temperature difference between the two sides is large, and the invention is suitable for the welding line working occasions with large temperature difference stress, composite stress and cold and hot stress.

Referring to fig. 5 to 8, an embodiment of the present invention provides a weld structure, referring to fig. 5, suitable for connection between a valve seat 1 and a valve body 2, where a head heat-insulating barrel 4 is disposed at a head portion of the valve seat 1, a tail heat-insulating barrel 3 is disposed at a tail portion of the valve seat 1, the weld structure includes a tail butt weld 7 and a head butt weld 8, the tail butt weld 7 is located outside the tail heat-insulating barrel 3, and the head butt weld 8 is located outside the head heat-insulating barrel 4.

Wherein, the cooling water flows in from the head diversion hole, flows into the inner hole of the valve seat 1 through the fabrication hole, then flows to the tail part of the valve seat 1 through the branch, and flows out from the diversion hole.

Referring to fig. 6, it can be seen that the improved weld structure has three welds, which are: a tail butt weld 7, a head butt weld 8, and a head heat affected zone weld 9.

Referring to fig. 7, a head heat affected zone welding line 9, a welding line medium blocking step 10 and a welding line strain groove 11 are further arranged at a welding line (head butt welding line 8) of the head region of the valve seat 1, the welding line medium blocking step 10 is located between the head butt welding line 8 and the head heat-preserving container 4 and is attached to the head heat-preserving container 4, the welding line strain groove 11 is located between the head butt welding line 8 and the head heat-preserving container 4 and is close to one side of the head butt welding line 8, and the head heat-preserving container 4 serves as a welding line medium baffle.

Referring to fig. 8, a weld strain region 12 is further arranged at a weld (tail butt weld 7) in the tail region of the valve seat 1, the weld strain region 12 is located on the outer side of the tail heat-preserving container 3 and close to one side of the tail butt weld 7, and the tail heat-preserving container 3 serves as a weld medium baffle.

The valve seat 1 and the valve seat 2 are matched with a welding seam to play the following roles:

1. the whole temperature of the valve seat 1 is cooled by forming the closed cooling water flow channel, so that the high-temperature strength of the valve seat is improved, and the influence of high-temperature deformation on the sealing performance of the valve seat 1 is reduced;

2. the temperature between the valve body 2 and the valve seat 1 is isolated, and the valve body 2 is prevented from causing material failure due to high-temperature working conditions, so that the selection requirement of the material of the valve body 2 is reduced, and the equipment cost is reduced.

In consideration of the above factors, in the welding structure of the invention, the butt weld seam 7 at the tail part and the butt weld seam 8 at the head part are both far away from the medium temperature field, and the welding seam medium blocking step 10 is arranged at the head part heat-insulating barrel 4, so as to reduce the composite alternating stress of the welding seam of the valve seat 1 caused by the temperature difference as much as possible, as shown in fig. 5 and 7;

aiming at the design defects of the fillet weld of the valve seat 1 and the valve body 2, the invention adopts the design of the equal-strength butt weld (namely the butt weld at the tail part 7 and the butt weld at the head part 8), the root part of the weld is designed by the full penetration process, the integral strength is high, the defect rate of the root part is low, and the failure phenomenon of the root part of the weld is reduced to the maximum extent;

the problem of uneven weld stress caused by the difference of the coefficients of thermal expansion of dissimilar materials is solved by adopting a pre-bottoming mode for the weld heat affected zone C of the valve body 2 and the valve seat 1, namely the material of the weld heat affected zone C of the valve body 2 is consistent with that of the weld and the valve seat 1, and the same chemical components, mechanical properties and linear expansion coefficients are adopted, so that the stress of the weld body, the base metal and the heat affected zone is consistent, as shown in fig. 7, a pre-bottoming transition design is arranged at the weld joint of the valve body 2 and the valve seat 1 by a head heat affected zone weld 9;

learn through above-mentioned failure mode analysis that the welding of disk seat 1 material and valve body 2 material has the great factor of mechanical properties difference to exist, consequently this scheme chooses for use with ripe selected material GH3128 sibling material: the high temperature nickel base wrought corrosion resistant alloy NS3103, namely the valve seat 1 of the present invention, is an NS3103 alloy valve seat.

The NS3103 valve seat has mechanical performance similar to that of the F304/F304H valve body, and the material has excellent high temperature performance, can resist the temperature of 1200 ℃ at most and has the mechanical strength of 85MPa under the working condition of 1000 ℃ for a long time; the valve body 2 adopts austenitic stainless steel F304/F304H, the valve seat 1 adopts NS3103, and the mechanical properties of the two are shown in Table 2:

TABLE 2 mechanical matching of valve seat NS3103 to valve body F304/F304H

Material of	Tensile strength is more than or equal to MPa	Yield strength is more than or equal to MPa	The elongation of 2in (DN 50) or 4D gauge length is more than or equal to%	The reduction of area is more than or equal to
					F304/F304H	515	205	30	40
NS3103	550	205	40	/

The specific manufacturing method of the invention comprises the following steps:

s1, obtaining the position and the size of a heat affected zone of the head butt weld 8 on the valve body 2 through calculation (the calculation method is common knowledge of technicians in the field, and therefore the calculation method is not described herein), obtaining a region H, and removing the region H through a machining mode;

s2, welding materials with the same material as the valve seat 1 are welded in the area H removed in the step 1 on the valve body 2 to form a head heat affected zone welding seam 9;

s3, performing UT (ultrasonic flaw detection nondestructive testing) and PT (penetration flaw detection nondestructive testing) on the weld joint 9 of the heat affected zone of the head, wherein the PT (penetration flaw detection nondestructive testing) needs to be subjected to PT 100% nondestructive testing according to design requirements;

and S4, UT and PT are qualified, the welding of the valve seat 1 and the valve body 2 is completed through the head butt weld 8 and the tail butt weld 7, the head butt weld 8 and the tail butt weld 7 are both subjected to bottom covering and cover covering by adopting a fully-automatic non-consumable electrode argon tungsten-arc welding TIG hot wire, and single-side welding and double-side forming are carried out, namely the root part of the weld is fully penetrated.

And S5, performing stress relief treatment on the welded valve seat 1 and the welded valve body 2 integrally.

The foregoing is illustrative of the preferred embodiments of this invention, and it is to be understood that the invention is not limited to the precise form disclosed herein and that various other combinations, modifications, and environments may be resorted to, falling within the scope of the concept as disclosed herein, either as described above or as apparent to those skilled in the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (7)

1. The utility model provides a welding seam structure, is applicable to the connection of disk seat (1) and valve body (2), disk seat (1) head is provided with head heat-preserving container (4), and disk seat (1) afterbody is provided with afterbody heat-preserving container (3), its characterized in that: the welding seam structure comprises a tail butt welding seam (7) and a head butt welding seam (8), wherein the tail butt welding seam (7) is located on the outer side of the tail heat-preserving barrel (3), the head butt welding seam (8) is located on the outer side of the head heat-preserving barrel (4), a welding seam medium blocking step (10) is further arranged at the head of the valve seat (1), and the welding seam medium blocking step (10) is located between the head butt welding seam (8) and the head heat-preserving barrel (4).

2. A weld structure according to claim 1, wherein: the head of the valve seat (1) is also provided with a head heat affected zone welding seam (9).

3. A weld structure according to claim 1, wherein: the valve seat (1) is characterized in that a welding line strain groove (11) is further formed in the head portion of the valve seat (1), and the welding line strain groove (11) is located between the head portion butt welding line (8) and the head portion heat-preserving container (4) and is matched with the head portion butt welding line (8).

4. A weld structure according to claim 1, wherein: the valve seat (1) tail part is further provided with a welding line strain area (12), and the welding line strain area (12) is located on the outer side of the tail part heat-preserving barrel (3) and is matched with the tail part butt welding line (7).

5. A weld structure according to claim 1, wherein: the valve seat (1) is an NS3103 alloy valve seat, and the valve body (2) is an F304 stainless steel valve body.

6. The method for manufacturing a welded joint structure according to any one of claims 1 to 5, wherein: the method comprises the following steps:

s1, calculating the position and the size of a heat affected zone of the head butt weld (8) on the valve body (2) to obtain a region H, and removing the region H in a machining mode;

s2, welding materials with the same material as the valve seat (1) in the area H where the valve body (2) is removed to form a head heat affected zone welding seam (9);

s3, carrying out ultrasonic flaw detection nondestructive testing and penetration flaw detection nondestructive testing on the weld joint (9) of the heat affected zone of the head;

s4, after the ultrasonic flaw detection nondestructive test and the penetrant flaw detection nondestructive test are qualified, welding the valve seat (1) and the valve body (2) through the head butt weld (8) and the tail butt weld (7), backing and capping the head butt weld (8) and the tail butt weld (7) by adopting hot wire TIG welding, and performing single-side welding and double-side molding;

and S5, performing stress relief treatment on the welded valve seat (1) and the welded valve body (2) as a whole.

7. The method of manufacturing a welded joint structure according to claim 6, wherein: in the step S4, the head butt weld (8) and the tail butt weld (7) are both welded by a single-side welding and double-side forming technique.

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