Welding method of austenitic stainless steel connector base for hydraulic support

Abstract

The invention provides a welding method of an austenitic stainless steel joint seat for a hydraulic support, which comprises the following steps of: providing the austenitic stainless steel joint seat which comprises the following components in percentage content: not less than 0.05% and not more than 0.08% of C, not less than 0.50% and not more than 0.80% of Si, not less than 1.0% and not more than 1.50% of Mn, not less than 18.0% and not more than 20.0% of Cr, not less than 10.0% and not more than 11.0% of Ni, not more than 3.0% of Mo, not more than 0.030% of P, not more than 0.005% of S and the balance of Fe; the austenitic stainless steel joint base is hardened through cold extrusion, and the hardness ranges from 240 HBW to 280 HBW; surfacing a stainless steel isolation layer in a to-be-welded joint seat area on the cylinder barrel; and an MAG welding method is adopted, and the austenitic stainless steel connector base is welded to the area, to be welded, of the connector base on the cylinder barrel. The method can solve the problems that cracks are generated when the austenitic stainless steel and the low-alloy high-strength steel are welded, the plasticity and toughness of a connector are reduced, the austenitic stainless steel is softened, and the strength of the connector is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of stainless steel joint seat, in particular to a welding method of austenitic stainless steel joint seat for hydraulic support. BACKGROUND

[0002] The joint seat of the column and the jack in the hydraulic support is usually made of low alloy steel, which has poor corrosion resistance. During the service of the oil cylinder, the column and the jack often leak due to the corrosion of the joint seat. Although the use of austenitic stainless steel instead of low alloy steel to produce the joint seat can significantly improve the corrosion resistance, the hardness of the austenitic stainless steel is generally less than or equal to 190HBW, and the strength and wear resistance are poor. To solve this problem, the joint seat must have high corrosion resistance and hardness, so the austenitic stainless steel needs to be hardened first, then machined into a joint seat, and then welded. However, the material of the oil cylinder of the hydraulic support is low alloy high strength steel, and the welding of austenitic stainless steel and the oil cylinder is dissimilar steel welding. Due to the large difference in chemical composition between austenitic stainless steel and low alloy high strength steel, the element distribution of the welded joint is uneven and the joint structure is uneven, cracks are easily produced during welding, and the plasticity and toughness of the joint are reduced. At the same time, improper welding process may cause softening of austenitic stainless steel, decrease of joint strength, and thus decrease of durability.

[0003] The invention patent with the authorized announcement number CN114147429B discloses a welding method of an upper cavity joint seat of a hydraulic oil cylinder. The cylinder port end of the cylinder barrel of the hydraulic oil cylinder is provided with a stop and a thread, and a liquid passage hole is formed at the intersection of the stop and the thread. The liquid passage hole communicates the upper cavity joint seat with the upper cavity, and the upper cavity joint seat completely covers the outside of the liquid passage hole. The method comprises the following steps: first, a liquid passage blind hole is pre-drilled outside the cylinder port end of the cylinder barrel, so that the closed end of the liquid passage blind hole is entirely left within the machining allowance range of the inner hole of the cylinder port end, and the closed end of the liquid passage blind hole does not extend into the scraping roller machining range; second, the upper cavity joint seat is welded outside the liquid passage blind hole; third, the inner hole of the cylinder port end is scraped; and fourth, the stop and the thread are turned in the inner hole of the cylinder port end to punch the pre-drilled liquid passage blind hole, so that the liquid passage blind hole becomes a liquid passage hole. In the second step, the liquid passage blind hole and the upper cavity joint seat are positioned by a positioning ring. The positioning ring, the liquid passage blind hole and the butt joint hole of the upper cavity joint seat are coaxially arranged. The lower half of the positioning ring is clamped into the liquid passage blind hole, and the upper half of the positioning ring is clamped into the butt joint hole of the upper cavity joint seat. The method has the advantages of no need to increase process holes, low risk of liquid leakage, elimination of upper cavity deformation, and high product yield. However, the method cannot solve the problems of cracks, decrease of joint plasticity and toughness, softening of austenitic stainless steel, and decrease of joint strength when austenitic stainless steel is welded with low alloy high strength steel. SUMMARY

[0004] In order to solve the problems of cracks, joint plasticity and toughness, austenitic stainless steel softening, joint strength reduction and the like when the austenitic stainless steel is welded with the low alloy high strength steel, the technical scheme adopted by the present application is as follows: Step one, provide an austenitic stainless steel joint seat, the austenitic stainless steel joint seat contains the following percentage of components: 0.05%≤C≤0.08%, 0.50%≤Si≤0.80%, 1.0%≤Mn≤1.50%, 18.0%≤Cr≤20.0%, 10.0%≤Ni≤11.0%, Mo≤3.0%, P≤0.030%, S≤0.005%, the balance is Fe; Step two, build up a stainless steel isolation layer on the joint seat area to be welded on the cylinder; Step three, the austenitic stainless steel joint seat is welded on the joint seat area to be welded on the cylinder by using the MAG welding method, wherein the welding protective gas is 80% Ar+20% CO2, the welding wire is ER309LSi, the welding current is 230A-260A, the welding voltage is 26V-28V, and the welding speed is 25cm / min-30cm / min.

[0005] Based on the above, in step three, the welding starting point is located at the center position of one end face of the austenitic stainless steel joint seat, after one round of continuous welding of the welding seam, the welding ending point should be more than 10mm above the starting point, and when the welding seam is at the four end point positions of the austenitic stainless steel joint seat, it should respectively extend outward to form an outer circular arc contour welding seam.

[0006] Based on the above, in step three, the stainless steel isolation layer is also polished, and after polishing, the roughness is ensured to be less than or equal to Ra12.5, and the thickness of the stainless steel isolation layer after polishing is ensured to be 3mm-5mm.

[0007] Based on the above, in step three, the temperature of the stainless steel isolation layer is controlled to be 50℃-100℃ when the austenitic stainless steel joint seat is welded.

[0008] Based on the above, the welding angle size of the outer circular arc contour welding seam is 5mm to 7mm.

[0009] Based on the above, the Brinell hardness of the austenitic stainless steel joint seat is 240HBW-280HBW.

[0010] Based on the above, the austenitic stainless steel joint seat is obtained by adopting LF furnace refining, RH furnace vacuum degassing, then continuous casting, hot rolling, solid solution treatment, and extrusion deformation hardening, wherein the cross section after hot rolling is circular, the extrusion ratio during extrusion is 15%-20%, the extrusion is cold extrusion, and the cross section after extrusion is square.

[0011] Based on the above, in the second step, the surfacing method used is MAG welding, the welding shielding gas is 80% Ar+20% CO2, the welding wire is ER309LSi, the welding current is 180A-220A, the welding voltage is 20V-25V, the welding speed is 25-30cm / min, and the surfacing range is the area of the to-be-welded joint seat and the surrounding 20mm.

[0012] Based on the above, the second step further comprises, before surfacing the stainless steel isolation layer, preheating the area within 30mm of the to-be-welded joint seat by induction, and the preheating temperature is 150℃-300℃.

[0013] The present application has outstanding substantial features and significant progress compared with the prior art. Specifically, the welding method of the austenitic stainless steel joint seat for hydraulic support provided by the present application first controls the composition and content of the stainless steel joint seat to be 0.05%≤C≤0.08%, 0.50%≤Si≤0.80%, 1.0%≤Mn≤1.50%, 18.0%≤Cr≤20.0%, 10.0%≤Ni≤11.0%, Mo≤3.0%, P≤0.030%, S≤0.005%, and the rest is Fe. In the smelting process, LF furnace is used for refining, and RH furnace is used for vacuum degassing, the vacuum degassing time is greater than 25min, and H≤5ppm, N≤10ppm, and O≤10ppm are ensured. This chemical composition can have corrosion resistance, deformation hardening ability, and can also reduce the tendency of welding defects.

[0014] Specifically, since C atoms are interstitial atoms in austenite, they can cause lattice distortion and increase the resistance of dislocation movement, so that a higher C element content can increase the initial hardness of the austenitic stainless steel, and a higher hardness can be obtained after solid solution treatment. At the same time, C element can reduce the stacking fault energy of austenite and induce martensitic transformation, so that the hardness after extrusion hardening can be improved. However, too high C content will reduce the corrosion resistance of the austenitic stainless steel, so the C content needs to be controlled in the range of 0.05%-0.08%. Ni element content ≥10% can make dislocation more prone to cross-slip, make the extrusion hardening effect more sustainable and gentle, can expand the process window, the hardness is more controllable, and the process stability is improved. In addition, since P element is easy to form low-melting-point eutectic with Fe and Cr during welding, S element is easy to form MnS enrichment at grain boundaries to reduce the local melting point, so the content of P and S elements needs to be controlled to reduce the risk of welding hot cracking. Since N element can inhibit the formation of ferrite, the content of N element needs to be controlled to prevent hot cracking during welding.

[0015] Meanwhile, in the manufacturing process, continuous casting, hot rolling, solid solution treatment, extrusion deformation hardening treatment are adopted, wherein the cross section is circular after hot rolling, the extrusion ratio is 15% to 20% during extrusion, cold extrusion is adopted during extrusion, and the cross section is square after extrusion. After hardening treatment, the Brinell hardness of the stainless steel joint seat is ensured to be 240HBW to 280HBW. Through the above-mentioned means, the stainless steel joint seat can have corrosion resistance, strength and wear resistance, so that the service life of the stand jack is higher.

[0016] Further, when the overlaying isolation layer and when the stainless steel joint seat is welded with the cylinder, firstly, according to the material of the welded cylinder, the preheating temperature is determined, the induction preheating is carried out on the to-be-welded area of the stand jack cylinder and the surrounding area within 30mm, and then the ER309LSi welding wire and specific parameters are adopted for welding. Since the stainless steel joint seat is overlaid with the isolation layer between the stainless steel joint seat and the low alloy cylinder, corrosion between the stainless steel joint seat and the low alloy cylinder is avoided.

[0017] Further, by using small current to overlay the stainless steel isolation layer on the low alloy steel cylinder side, the dilution rate, the restraint degree and the stress are reduced, so that the risk of heat cracking during overlaying is reduced.

[0018] Further, by overlaying the austenitic stainless steel isolation layer on the low alloy steel cylinder side and then carrying out the fillet welding between the isolation layer and the stainless steel joint seat, the fillet welding of the same material is realized, high temperature preheating is avoided, and the composition segregation caused by the dilution of the low alloy steel is avoided, so that the risk of welding heat cracking is greatly reduced. At the same time, even if micro cracks are generated on the surface of the overlaying layer, the micro crack defects can be remelted during the fillet welding process, so that the welding defect rate is greatly reduced.

[0019] Further, by designing the stainless steel joint seat of special material and overlaying the isolation layer, the MAG welding method using 80% Ar+20% CO2 protective gas can be used for welding, the welding current is large, and single pass welding can be formed, so that the production efficiency is improved and batch production can be carried out. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a joint seat and cylinder welding schematic diagram in a welding method of an austenitic stainless steel joint seat for a hydraulic support provided by the application.

[0021] Figure 2 is a welding path schematic diagram in a welding method of an austenitic stainless steel joint seat for a hydraulic support provided by the application.

[0022] Figure 3 is an external appearance schematic diagram of the joint seat and the cylinder after welding in a welding method of an austenitic stainless steel joint seat for a hydraulic support provided by the application.

[0023] Figure 4 is a schematic diagram of the internal morphology of the joint seat after welding the joint seat and the cylinder in the welding method provided by the present application.

[0024] Figure 5 is a schematic diagram of the corrosion failure of the joint seat and the cylinder after welding in the welding method provided by the comparative experiment one.

[0025] Figure 6 is a schematic diagram of the internal morphology of the joint seat and the cylinder after welding in the welding method provided by the comparative experiment one.

[0026] Figure 7 is a schematic diagram of the external morphology of the joint seat and the cylinder after welding in the welding method provided by the comparative experiment three.

[0027] Figure 8 is a schematic diagram of the internal morphology of the joint seat and the cylinder after welding in the welding method provided by the comparative experiment three.

[0028] In the figure: 1, cylinder; 2, austenitic stainless steel joint seat; 3, weld; 4, stainless steel isolation layer; 5, arc starting point; 6, arc ending point. DETAILED DESCRIPTION

[0029] The technical solutions of the present application will be further described in detail through specific embodiments.

[0030] Example 1 The present embodiment provides a welding method for an austenitic stainless steel joint seat for a hydraulic support, as shown in Figure 1 , Figure 2 , comprising the following steps: Step one, providing an austenitic stainless steel joint seat 2 containing the following percentage of components: 0.05%≤C≤0.08%, 0.50%≤Si≤0.80%, 1.0%≤Mn≤1.50%, 18.0%≤Cr≤20.0%, 10.0%≤Ni≤11.0%, Mo≤3.0%, P≤0.030%, S≤0.005%, and the balance being Fe; Step two, building up a stainless steel isolation layer 4 on the joint seat area to be welded on the cylinder 1; Step three, using the MAG welding method to weld the austenitic stainless steel joint seat on the joint seat area to be welded on the cylinder, wherein the welding protective gas is 80% Ar+20% CO2, the welding wire is ER309LSi, the welding current is 230A-260A, the welding voltage is 26V-28V, and the welding speed is 25cm / min-30cm / min.

[0031] In the step three, the welding starting point 5 is located at the center of one end surface of the austenitic stainless steel joint seat, and after one round of continuous welding, the welding ending point 6 should be more than 10 mm away from the starting point, and the welding seam should respectively extend outward at the four end points of the austenitic stainless steel joint seat to form an outer circular arc contour welding seam 4.

[0032] In the step two, the surfacing method used is MAG welding, the welding shielding gas is 80% Ar+20% CO2, the welding wire is ER309LSi, the welding current is 180A-220A, the welding voltage is 20V-25V, the welding speed is 25cm / min-30cm / min, and the surfacing range is the to-be-welded joint seat area and the surrounding 20mm. The Brinell hardness of the austenitic stainless steel joint seat is 240HBW-280HBW.

[0033] Example 2 The embodiment provides a welding method of an austenitic stainless steel joint seat for a hydraulic support, and the main difference from the embodiment 1 is that in the embodiment, the step three further includes polishing the stainless steel isolation layer, and ensuring that the roughness of the polished stainless steel isolation layer is less than or equal to Ra12.5 and the thickness of the polished stainless steel isolation layer is 3mm-5mm. The welding of the austenitic stainless steel joint seat is performed when the temperature of the stainless steel isolation layer is controlled to be 50℃-100℃.

[0034] Example 3 The embodiment provides a welding method of an austenitic stainless steel joint seat for a hydraulic support, and the main difference from the embodiment 1 is that in the embodiment, the austenitic stainless steel joint seat is obtained by refining through an LF furnace, vacuum degassing through an RH furnace, and then continuous casting, hot rolling, solid solution treatment and extrusion deformation hardening.

[0035] Example 4 The embodiment provides a welding method of an austenitic stainless steel joint seat for a hydraulic support, and the main difference from the embodiment 1 is that in the embodiment, the step two further includes, before surfacing the stainless steel isolation layer, preheating the to-be-welded joint seat area and the surrounding 30mm range through induction, and the preheating temperature is 150℃-300℃.

[0036] Specifically, the cylinder material can be selected from 27SiMn, 30CrMnSi, 30CrMo and S890. When the cylinder is selected from 27SiMn and S890, the preheating temperature is 150℃-200℃. When the cylinder is selected from 30CrMo, the preheating temperature is 200℃-250℃. When the cylinder is selected from 30CrMnSi, the preheating temperature is 250℃-300℃.

[0037] Detection results and comparative experiments: The product made by the welding method of the austenitic stainless steel joint seat for hydraulic support provided by the application is detected, and the structure is as shown in Figure 3 and Figure 4 The yield strength of the austenitic stainless steel joint seat is ≥450 MPa, the tensile strength is ≥650 MPa, and the Brinell hardness is 240 HBW-280 HBW. After detecting the weld, no welding defects such as cracks and bubbles are found, and the welding performance is good.

[0038] Comparative experiment Comparative experiment one: The main difference between the method provided by the application and the comparative experiment one is that the comparative experiment one does not deposit a stainless steel isolation layer on the joint seat area to be welded on the cylinder.

[0039] The schematic diagram is as shown in Figure 5 The detection result is as shown in Figure 6 After being used for a period of time, rusting phenomenon is found at the gap between the austenitic stainless steel joint seat and the cylinder, and at the side of the cylinder. It is analyzed that, since there is no stainless steel isolation layer, and there is a gap when the joint seat is butt-welded with the cylinder, the hydraulic medium enters the gap during use, thereby corroding the low-alloy steel on the side of the cylinder.

[0040] Comparative experiment two: The main difference between the method provided by the application and the comparative experiment two is that, in the comparative experiment two, the material of the cylinder is 27SiMn, and before depositing the stainless steel isolation layer, the joint seat area to be welded and the surrounding 30mm range are inductively preheated, and the preheating temperature is 70℃.

[0041] The welded structure is detected, and the result shows that there is a defect of excessively high hardness in the heat-affected zone on the side of the cylinder. When the preheating temperature is too low, the cooling speed of the heat-affected zone after welding is relatively fast, thereby producing martensite structure with relatively high hardness. Such structure is hard and brittle, and has poor toughness, which is not conducive to the service life of the welded joint. In the relevant standards of the international and domestic welding systems, it is generally provided that the hardness of the welded heat-affected zone of low-alloy steel is not higher than 450HV.

[0042] Comparative experiment three: The main difference between the method provided by the application and the comparative experiment three is that, in the comparative experiment three, the material of the cylinder is 27SiMn, and no stainless steel isolation layer is deposited on the joint seat area to be welded on the cylinder. When the austenitic stainless steel joint seat is welded on the joint seat area to be welded on the cylinder, the welding current is 280A-300A.

[0043] The welded structure is detected, and the result is as shown in Figure 7 and Figure 8 It is found that there are defects such as surface cracks and internal cracks in the weld.

[0044] Analysis shows that the restraint degree of fillet weld is higher than that of surfacing, and when low alloy steel and austenitic stainless steel are directly welded by fillet welding, due to high preheating temperature, high restraint degree, large welding heat input, and the use of austenitic stainless steel welding wire for filling welding, it is extremely easy to produce welding hot crack defects. When the welding current is too high (280A-300A), the welding heat input increases, which easily leads to the increase of dilution rate, aggravates the composition segregation, reduces the solidification speed of the molten pool, and increases the risk of hot crack.

[0045] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: the specific embodiments of the present application can still be modified or some technical features can be replaced by equivalents; without departing from the spirit of the technical solutions of the present application, they should be covered in the technical solution range of the present application claimed.

Claims

1. A method for welding an austenitic stainless steel adapter for hydraulic support, comprising the following steps: Step 1: providing an austenitic stainless steel adapter containing the following percentage of components: 0.05%≤C≤0.08%, 0.50%≤Si≤0.80%, 1.0%≤Mn≤1.50%, 18.0%≤Cr≤20.0%, 10.0%≤Ni≤11.0%, Mo≤3.0%, P≤0.030%, S≤0.005%, and the balance being Fe; Step 2: depositing a stainless steel isolation layer on the region of the cylinder barrel where the adapter is to be welded; Step 3: using MAG welding method to weld the austenitic stainless steel adapter to the region of the cylinder barrel where the adapter is to be welded, wherein the welding shielding gas is 80% Ar+20% CO2, the welding wire is ER309LSi, the welding current is 230A-260A, the welding voltage is 26V-28V, and the welding speed is 25cm / min-30cm / min. 2.The method for welding an austenitic stainless steel adapter for hydraulic support according to claim 1, characterized in that: in Step 3, the welding starting point is located at the center of one end face of the austenitic stainless steel adapter, and after one round of continuous welding of the weld, the welding ending point should be more than 10mm above the welding starting point, and when the weld is at the four end point positions of the austenitic stainless steel adapter, it should respectively extend outward to form an outer circular arc contour weld.

3. The method of claim 1, wherein the austenitic stainless steel joint seat for hydraulic support is characterized by: in Step 3, the stainless steel isolation layer is also polished, and after polishing, the roughness is ensured to be less than or equal to Ra12.5, and the thickness of the polished stainless steel isolation layer is ensured to be 3mm-5mm.

4. The welding method of the austenitic stainless steel joint seat for hydraulic supports according to claim 1 or 2 or 3, characterized in that: in Step 3, the austenitic stainless steel adapter is welded when the temperature of the stainless steel isolation layer is controlled to be 50℃-100℃.

5. The welding method of the austenitic stainless steel joint seat for hydraulic supports according to claim 2 or 3, characterized in that: the welding angle size of the outer circular arc contour weld is 5mm-7mm.

6. The welding method of the austenitic stainless steel joint seat for hydraulic supports according to claim 5, characterized in that: the Brinell hardness of the austenitic stainless steel adapter is 240HBW-280HBW.

7. The method according to claim 6, wherein the method is characterized by: the austenitic stainless steel adapter is obtained by using LF furnace for refining, RH furnace for vacuum degassing, continuous casting, hot rolling, solid solution treatment, and extrusion deformation hardening, wherein the cross section after hot rolling is circular, the extrusion ratio during extrusion is 15%-20%, the extrusion is cold extrusion, and the cross section after extrusion is square.

8. The welding method of the austenitic stainless steel joint seat for hydraulic support according to claim 1 or 2 or 3, characterized in that: in Step 2, the depositing method is MAG welding, the welding shielding gas is 80% Ar+20% CO2, the welding wire is ER309LSi, the welding current is 180A-220A, the welding voltage is 20V-25V, the welding speed is 25-30cm / min, and the depositing range is the region of the adapter to be welded and the surrounding 20mm.

9. The method according to claim 8, wherein the method is characterized by: in Step 2, before depositing the stainless steel isolation layer, the region of the adapter to be welded and the surrounding 30mm are inductively preheated, and the preheating temperature is 150℃-300℃.

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