A welding core transition type welding rod and its preparation method

Abstract

The invention discloses a welding core transition type electric welding rod. The deposited metal of the electric welding rod comprises the following components in weight percentage: C: 0.07-0.10%, Si: 0.1-0.3%, Mn: 0.3-0.7%, Cr: 8.5-9.5%, V: 0.1-0.3%, W: 2.3-3.1%, Co: 2.7-3.5%, Nb: 0.02-0.08%, B: 0.002-0.015%, N: 0.005-0.018%, Ni: 0.2-0.6%, Cu: 0.15-0.48%, S≤0.01%, P≤0.01%, Al≤0.02%, Ti≤0.02%, Ta≤0.02%, 0.2≤B / N≤1, and Mn+Ni≤1.2%. The welding rod of the present invention can be applied to the welding of heat-resistant steel, meets the requirements of strength, plasticity and toughness, and improves the impact toughness of the weld.

Description

Technical Field

[0001] The invention relates to the technical field of special welding materials, in particular to a welding core transition type welding rod and a preparation method thereof. Background Art

[0002] Increasing the steam temperature and pressure of coal-fired power plants can improve unit efficiency, reduce coal consumption, and lower carbon emissions. Currently, my country has a 630°C coal-fired demonstration power plant, and several companies are planning to build 650°C coal-fired power plants. The main martensitic heat-resistant steels for 630-650°C temperatures include G115, SAVE12AD, MARBN, and CW3. These are all 9Cr-3W-3Co steels. Co inhibits the formation of delta-ferrite, and the boron and nitrogen content, as well as the boron to nitrogen ratio, must be controlled to prevent the formation of boron nitride. CW3 and MARBN are essentially the same chemical elements, but differ in their mass percentages. SAVE12AD partially replaces niobium with ta and adds a trace amount of niobium, while G115 incorporates 1% copper. Furthermore, each steel has specific variations in the boron to nitrogen ratio.

[0003] At present, the field of welding materials, especially welding electrodes, is mainly developed for chemical composition matching of G115 steel, including:

[0004] CN106346167B discloses a welding rod for welding martensitic heat-resistant steel, wherein the welding core composition thereof has a Cu content of 0.8-1.0%, a Mn content of 0.3-0.7%, a P content of ≤0.004%, a S content of ≤0.002%, a N content of 0.007-0.011%, and a B content of 0.011-0.02%;

[0005] CN112404788A discloses a new type of martensitic heat-resistant steel G115 welding rod for power stations, wherein the welding core composition thereof has a Cu content of 0.6-0.8%, a Ni content of ≤0.15%, a Mn content of 0.4-0.65%, a P content of ≤0.006%, and a S content of ≤0.005%.

[0006] CN111590239A discloses a martensitic heat-resistant steel welding rod for ultra-supercritical thermal power units and its preparation method. The welding core has a Ni content of 0.30-0.62%, the deposited metal has a Ni content of 0.28-0.52%, and both the welding core and the coating are Cu-free.

[0007] CN108202189A discloses a core wire transition type heat-resistant steel welding rod for a 650°C ultra-supercritical thermal power unit. The deposited metal has a Cu content of 0.50-1.10%, a Mn content of 0.3-0.9%, P ≤ 0.008%, S ≤ 0.008%, a B content of 0.010-0.024%, and a N content of 0.005-0.025%.

[0008] The Cu content of the welding core is 0.92-0.93%, the Mn content is 0.5-0.52%, the P content is 0.005-0.006%, the S content is 0.004-0.005%, the B content is 0.015-0.016%, and the N content is 0.006-0.007%;

[0009] CN106425158A discloses a steel welding rod for a steam temperature ultra-supercritical thermal power unit, wherein the deposited metal has a Cu content of 0.7-1.1%, a Ni content of ≤0.30%, a Mn content of 0.3-1.0%, a P content of ≤0.01%, a S content of ≤0.01%; a B content of 0.002-0.01%, and a N content of 0.005-0.015%.

[0010] The Cu content of the welding core is 0.7-1.00%, Ni≤0.10%, Mn content is 0.3-0.5%, P≤0.008%, S≤0.008%; B content is 0.002-0.01%, and N content is 0.001-0.05%;

[0011] The above-disclosed welding core or weld metal compositions all contain 0.5% or more Cu or no Cu, and are essentially Ni-free. Cu is an austenite-forming element that can prevent the formation of delta-ferrite. A certain amount of Cu can improve the steel's resistance to high-temperature steam oxidation, but excessive Cu content can affect welding performance. Ni is an austenite-forming element. Adding an appropriate amount of Ni can help improve the impact toughness of the weld metal, primarily because Ni can lower the critical point A of the material. C1 Temperature, thereby improving the tempering reaction of the material. Mn is an austenite-forming element that can prevent the formation of delta-ferrite, stabilize P and S, prevent the formation of low-melting-point sulfides, and promote weld metal deoxidation. However, the total Mn + Ni content should not exceed 1.2% to prevent the reformation of austenite at the highest post-weld heat treatment temperature.

[0012] The inventors of the present application matched the above-mentioned 9Cr-3W-3Co steels, optimized the elements such as Mn, Ni, Cu, B, and N, and provided a manufacturing process method for a welding rod. Summary of the Invention

[0013] The purpose of the present invention is to solve the problems raised in the background technology and to design a welding core transition type welding rod.

[0014] The technical solution of the present invention to achieve the above-mentioned object is a core transition type welding rod, comprising a welding core and a coating covering the welding core, wherein the deposited metal of the core transition type welding rod comprises the following components in percentage by weight:

[0015] C: 0.07-0.10%, Si: 0.1-0.3%, Mn: 0.3-0.7%, Cr: 8.5-9.5%, V: 0.1-0.3%, W: 2.3-3.1%, Co: 2.7-3.5%, Nb: 0.02-0.08%, B: 0.002-0.015%, N: 0.005-0.018%, Ni: 0.2-0.6%, Cu: 0.15-0.48%, S≤0.01%, P≤0.01%, Al≤0.02%: Ti≤0.02%, , Ta≤0.02%, the balance is Fe;

[0016] The weight percentage ratio of B to N is: 0.2≤B / N≤1, and the total weight percentage of Mn and Ni is: Mn+Ni≤1.2%. In some embodiments of the present invention, the welding core comprises the following components in weight percentage:

[0017] C: 0.06-0.09%, Si: 0.1-0.5%, Mn: 0.2-0.7%, Cr: 8.5-9.5%, V: 0.1-0.3%, W: 2.2-3.0%, Co: 2.6-3.3%, Nb: 0.02-0.08%, B: 0.002-0.008%, N: 0.005-0.02%, Al≤0.02%, Ta≤0.02%, S≤0.005%, P≤0.005%, balance Fe;

[0018] The weight percentage ratio of B to N is: 0.2≤B / N≤1, and may also be 0.2≤B / N≤0.5, 0.5≤B / N≤0.8, and 0.8≤B / N≤1.

[0019] In some embodiments of the present invention, the coating is a CaO / CaF2-SiO2 slag system.

[0020] In some embodiments of the present invention, the coating comprises the following components in percentage by weight:

[0021] Rutile: 4-6%, titanium dioxide: 1.5-3%, marble: 30-40%, fluorite: 15-28%, cobalt powder: 3-5%, electrolytic manganese: 1.5-2.5%, metallic chromium: 4-5%, ferrotungsten: 2-3%, ferroniobium: 1-2%, ferroboron: 1.5-2.5%, ferrovanadium: 0.5-1.5%, ferrotitanium: 4-7%, copper powder: 1.5-2.5%, nickel powder: 4-5%, quartz: 3.5-4.5%, alkali 0.5-1.5%.

[0022] In some embodiments of the present invention, the mass ratio of the coating to the welding core is 2-3:7, preferably 3:7.

[0023] In some embodiments of the present invention, the post-weld stress relief heat treatment temperature of the deposited metal is 750-770°C. After the heat treatment at 750-770°C for 10-16 hours, the deposited metal has a room temperature tensile strength Rm ≥ 680 MPa, a yield strength ReL ≥ 540 MPa, an elongation A ≥ 17%, a reduction of area Z ≥ 54%, and an impact energy AKV ≥ 25 J at room temperature at 20°C.

[0024] The present invention further provides a method for preparing the transition type welding electrode in the above embodiment, comprising the following steps:

[0025] S1, preparing welding core;

[0026] S2, mixing the components of the coating uniformly into powder according to the proportion;

[0027] S3. Add 20-40% by mass of water glass to every 100 kg of the medicine powder and stir evenly to form a medicine embryo;

[0028] S4. Using a hydraulic press, the prepared medicine embryo is wrapped and pressed onto the outside of the welding core to form a welding rod;

[0029] S5. Dry the welding rod at room temperature for 10-24 hours, then place it in a drying oven at 70-90°C for 0.5-2 hours;

[0030] S6. Raise the temperature of the drying oven to 300-450°C and dry for 0.5-2 hours;

[0031] S7. Cool the drying furnace to 110-120℃ and take out the welding rods.

[0032] The present invention also provides the application of the transition type welding rod in the above embodiment, which is used for welding 630-650°C martensitic heat-resistant steel, preferably for welding 9Cr-3W-3Co steel, and more preferably for welding G115 steel, SAVE12AD steel, MARBN steel or CW3 steel.

[0033] The present invention provides a transition type welding rod, which has the following beneficial effects:

[0034] 1) Provide a 630-650℃ heat-resistant steel welding rod, particularly suitable for welding 630-650℃ castings and pipelines;

[0035] 2) Select the appropriate formula of each part of the welding rod to match a variety of 9Cr-3W-3Co steel materials to meet the strength, plasticity and toughness requirements;

[0036] 3) The cladding metal of the welding rod of the present invention not only meets the requirements for compatibility with a variety of 9Cr-3W-3Co steel materials, but also meets the requirements for high-temperature creep rupture strength while meeting the room-temperature mechanical properties of the cladding metal;

[0037] 4) Select appropriate formulas for each part of the welding rod so that the deposited metal of the weld has excellent mechanical properties, including tensile strength Rm ≥ 680MPa, yield strength ReL ≥ 540MPa, elongation A ≥ 17%, cross-sectional shrinkage Z ≥ 54%, and room temperature impact energy AkV (20°C) ≥ 25J; the impact toughness of the weld is improved by optimizing the composition of important elements such as Cu, Ni, B, and N.

[0038] 5) Select the appropriate formula of each part of the welding rod to provide high-strength welds;

[0039] 6) The welding rod provided by the present invention can be used for all-position welding, and has the advantages of stable arc combustion, less spatter, good slag removal, no red tail phenomenon, beautiful weld formation, easy slag removal, and less spatter. DETAILED DESCRIPTION

[0040] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0041] The present invention provides a core transition type welding rod, comprising a welding core and a coating covering the welding core. The deposited metal of the core transition type welding rod comprises the following components in percentage by weight:

[0042] C: 0.07-0.10%, Si: 0.1-0.3%, Mn: 0.3-0.7%, Cr: 8.5-9.5%, V: 0.1-0.3%, W: 2.3-3.1%, Co: 2.7-3.5%, Nb: 0.02-0.08%, B: 0.002-0.015%, N: 0.005-0.018%, Ni: 0.2-0.6%, Cu: 0.15-0.48%, S≤0.01%, P≤0.01%, Al≤0.02%: Ti≤0.02%, Ta≤0.02%, the balance is Fe;

[0043] The weight percentage ratio of B to N is: 0.2≤B / N≤1, and the total weight percentage of Mn and Ni is: Mn+Ni≤1.2%.

[0044] The principle of selecting the amount of each component of the deposited metal of the present invention is as follows:

[0045] 1) C element forms carbides with alloy elements such as V, Nb, Cr, and W in the deposited metal to form M 23 Carbides such as C6 improve the thermal strength of the material. Too low a C content results in less carbide precipitation, failing to achieve the desired strengthening effect. However, excessive C content can deteriorate crack resistance and impact resistance, hindering welding. Experimental results indicate that the C content should be between 0.07% and 0.10%. In the present invention, a C content of 0.08% to 0.092% is preferred; alternative values include 0.08% to 0.085%, 0.085% to 0.090%, and 0.090% to 0.092%.

[0046] 2) Mn is an austenite forming element that can prevent the formation of delta-ferrite, stabilize P and S elements, avoid the formation of low melting point sulfides, and promote the deoxidation of weld metal. Mn can effectively improve the strength of weld deposited metal, but excessive Mn content is not conducive to impact toughness and will reduce the critical point A. C1 Temperature will affect the stability of high-temperature performance. Experimental verification shows that the Mn content in the deposited metal is between 0.3-0.7%. In the present invention, the preferred Mn content is 0.5-0.7%; 0.3-0.5%, 0.5-0.6%, and 0.6-0.7% are also possible.

[0047] 3) Ni is an austenite forming element. Adding a proper amount of it is beneficial to improve the impact toughness of the weld metal, mainly because Ni can reduce the critical point A of the material. C1 Temperature, thereby increasing the tempering reaction degree of the material, while Ni can also reduce the sensitivity of δ-ferrite formation. However, too high Ni content will cause the critical point A C1 Too low a temperature will result in the production of new untempered martensite after cooling. Experimental verification shows that the Ni content in the deposited metal is between 0.2-0.6%. In the present invention, the preferred Ni content is 0.4-0.6%; other options include 0.2-0.3%, 0.3-0.4%, 0.4-0.5%, and 0.5-0.6%.

[0048] 4) By increasing the austenite forming elements Mn and Ni, the residual δ-ferrite that deteriorates the impact toughness can be suppressed, thereby improving the impact toughness of the weld. However, the total content of Mn + Ni exceeds 1.2%, which prevents the reformation of austenite at the highest post-weld heat treatment temperature. At the same time, the critical point A is too low. C1Temperature will reduce the post-weld heat treatment temperature, thereby weakening the stress relief effect of the post-weld heat treatment and adversely affecting the impact toughness of the deposited metal. Experimental verification shows that in the present invention, 1.0% ≤ Mn + Ni ≤ 1.2% is preferred; 1.1% ≤ Mn + Ni ≤ 1.2% is more preferred; 1.0% ≤ Mn + Ni ≤ 1.1%, 1.1% ≤ Mn + Ni ≤ 1.15%, 1.15% ≤ Mn + Ni ≤ 1.2% can also be selected; Mn + Ni = 1.16, Mn + Ni = 1.17 can also be selected.

[0049] 5) Cu is an austenite-forming element that inhibits the formation of delta-ferrite. A certain amount of Cu can improve steel's resistance to high-temperature steam oxidation. However, excessive Cu content can impair weldability. Experimental verification indicates that the Cu content in the weld deposited metal should be between 0.15% and 0.5%. In the present invention, a Cu content of 0.2% to 0.3% is preferred; alternatives include 0.15% to 2%, 0.2% to 0.25%, 0.25% to 0.3%, and 0.3% to 0.5%.

[0050] 6) Cr can play a role in solid solution strengthening, Cr and C form M 23 Carbides such as C6 enhance the high-temperature creep rupture strength of the weld. Cr also forms a Cr2O3 or (CrFe)3O4 oxide film, ensuring the weld's resistance to high-temperature steam oxidation. Experimental verification indicates that the Cr content is between 8.5% and 9.5%. In the present invention, a Cr content of 8.5% to 9.3% is preferred; alternatives include 8.5% to 9.0%, 9.0% to 9.3%, and 9.3% to 9.5%.

[0051] 7) W can provide both solid solution and dispersion strengthening, but excessive W can easily produce σ ferrite, which can reduce impact properties. Experimental verification indicates that the W content in the weld deposited metal should be between 2.3% and 3.1%. In the present invention, a W content of 2.6% to 3.0% is preferred; alternatives include 2.3% to 2.6%, 2.6% to 2.9%, and 2.9% to 3.1%.

[0052] 8) V is an MX phase-forming element. It refines grains and significantly improves strength. However, excessive V content is detrimental to impact resistance and can easily lead to intergranular cracking. Experimental verification indicates that the V content in the weld deposited metal should be between 0.1% and 0.3%. In the present invention, a V content of 0.1% to 0.2% is preferred; alternatives include 0.1% to 0.15%, 0.15% to 0.2%, and 0.2% to 0.3%.

[0053] 9) Nb is an MX phase-forming element, exerting a precipitation strengthening effect, imparting excellent high-temperature creep rupture strength to the weld deposit. However, excessive Nb content can reduce impact resistance. Experimental verification indicates that the Nb content in the weld deposit should be between 0.02% and 0.08%. In the present invention, a Nb content of 0.04% to 0.06% is preferred; alternative values include 0.02% to 0.04%, 0.04% to 0.05%, 0.05% to 0.06%, and 0.06% to 0.08%.

[0054] 10) Co enhances the solid solution strengthening effect of Cr in steel, inhibits the formation of σ-ferrite, and improves creep rupture strength. Experimental verification indicates that the Co content in the weld deposited metal is between 2.7% and 3.5%. In the present invention, the preferred Co content is 3.0% to 3.2%, with other possible options being 2.7% to 3.0%, 3.0% to 3.1%, 3.1% to 3.2%, and 3.2% to 3.5%.

[0055] 11) Boron can strengthen grain boundaries and increase creep rupture strength, but excessive boron content can reduce impact resistance and negatively impact welding process performance. Experimental verification indicates that the boron content in the weld deposited metal should be between 0.002% and 0.012%. In the present invention, a boron content of 0.005% to 0.010% is preferred; alternatives include 0.002% to 0.005%, 0.005% to 0.008%, 0.008% to 0.010%, and 0.010% to 0.012%.

[0056] 12) Nitrogen can form fine, dispersed nitrides with elements such as Nb and V to improve strength. However, excessive nitrogen is detrimental to welding performance. Experimental verification indicates that the nitrogen content in the weld deposited metal should be between 0.010% and 0.018%. In the present invention, the preferred nitrogen content is 0.010% to 0.017%, with other possible options being 0.010% to 0.015%, 0.010% to 0.017%, 0.015% to 0.017%, and 0.017% to 0.018%.

[0057] 13) The ratio of B to N should be strictly controlled to prevent excessive N from consuming B and weakening the strengthening effect. The B / N ratio should be controlled between 0.2 and 1. Experimental results indicate that, in the present invention, 0.2 ≤ B / N ≤ 0.5 is preferred; 0.27 ≤ B / N ≤ 0.43 is more preferred; 0.2 ≤ B / N ≤ 0.27, 0.27 ≤ B / N ≤ 0.30, 0.30 ≤ B / N ≤ 0.43, 0.43 ≤ B / N ≤ 0.45, and 0.45 ≤ B / N ≤ 0.5 are also possible.

[0058] In some embodiments of the present invention, the coating comprises the following components in percentage by weight:

[0059] Rutile: 4-6%, titanium dioxide: 1.5-3%, marble: 30-40%, fluorite: 15-28%, cobalt powder: 3-5%, electrolytic manganese: 1.5-2.5%, metallic chromium: 4-5%, ferrotungsten: 2-3%, ferroniobium: 1-2%, ferroboron: 1.5-2.5%, ferrovanadium: 0.5-1.5%, ferrotitanium: 4-7%, copper powder: 1.5-2.5%, nickel powder: 4-5%, quartz: 3.5-4.5%, alkali 0.5-1.5%.

[0060] Among them, rutile is preferably 4.5-5.9%, and can also be 4-4.5%, 4.5-5%, 5-5.5%, 5.5-5.9%, 5.9-6%;

[0061] Titanium dioxide is preferably 2-2.8%, and can also be 1.5-2%, 2-2.5%, 2.5-2.8%, 2.8-3%;

[0062] Marble is preferably 33-36%, and can also be 30-33%, 33-35%, 35-36%, 36-40%;

[0063] Fluorite is preferably 20-25%, and can also be 15-20%, 20-22%, 22-25%, 25-28%;

[0064] Cobalt powder is preferably 4-4.6%, and can also be selected from 3-4%, 4-4.3%, 4.6-4.6%, and 4.6-5%;

[0065] Electrolytic manganese is preferably 1.8-2.3%, and can also be 1.5-1.8%, 1.8-2.1%, 2.1-2.3%, 2.3-2.5%;

[0066] The metallic chromium content is preferably 4.1-4.6%, and may also be 4-4.1%, 4.1-4.3%, 4.3-4.6%, or 4.6-5%;

[0067] Tungsten iron is preferably 2.3-2.8%, and can also be selected from 2-2.3%, 2.3-2.5%, 2.5-2.8%, 2.8-3%;

[0068] The preferred content of ferroniobium is 1.3-1.5%, and other options include 1-1.3%, 1.3-1.4%, 1.4-1.5%, and 1.5-2%.

[0069] The preferred content of ferroboron is 1.8-2.3%, and other options include 1.5-1.8%, 1.8-2.1%, 2.1-2.3%, and 2.3-2.5%;

[0070] The preferred content of ferrovanadium is 0.8-1.2%, and other contents include 0.5-0.8%, 0.8-1.0%, 1.0-1.2%, and 1.2-1.5%.

[0071] The preferred content of ferrotitanium is 4.8-6.5%, and other options include 4-4.8%, 4.8-6.0%, 6.0-6.2%, 6.2-6.5%, and 6.5-7%.

[0072] The copper powder is preferably 1.8-2%, and can also be 1.5-1.8%, 1.8-1.9%, 1.9-2%, 2-2.5%;

[0073] Nickel powder preferably contains 4.6-4.9%, and can also contain 4-4.6%, 4.6-4.8%, 4.8-4.9%, and 4.9-5%;

[0074] Quartz preferably 3.7-4%, 3.5-3.7%, 3.7-3.9%, 3.9-4%, 4-4.5%;

[0075] The alkali content is preferably 0.8-1.2%, 0.5-0.8%, 0.8-1.0%, 1.0-1.2%, or 1.2-1.5%.

[0076] Specific exemplary embodiments are as follows:

[0077] Example 1

[0078] 1-1) The core components of the core transition type welding rod of this embodiment are shown in Table 1:

[0079] Table 1 Weight fraction of each component in the welding core (%)

[0080] C Si Mr Cr V W Co No B N S P 0.089 0.21 0.54 8.85 0.18 2.64 2.98 0.057 0.007 0.01 0.003 0.005

[0081] 1-2) The weight fractions of the components of the coating of the welding core transition type welding rod of this embodiment are: rutile: 4.5%, titanium dioxide: 2.8%, marble: 36%, fluorite: 20%, cobalt powder: 4.6%, electrolytic manganese: 2.3%, metallic chromium: 4.6%, ferrotungsten: 2.8%, ferroniobium: 1.5%, ferroboron: 2.3%, ferrovanadium: 1%, ferrotitanium: 6.5%, copper powder: 1.8%, nickel powder: 4.6%, quartz: 3.7%, and alkali 1%.

[0082] 1-3) Preparation of core transition type welding rod:

[0083] S1. Prepare welding core A according to the composition of welding core shown in Table 1.

[0084] S2. Mix the Chinese medicinal skin according to the composition formula of 2) to form medicinal powder;

[0085] S3. Add 30% by mass of water glass to every 100 kg of the medicine powder and stir evenly to form a medicine embryo;

[0086] S4. Using a hydraulic press, the prepared medicine embryo is wrapped and pressed onto the outside of the welding core to form a welding rod;

[0087] S5. Dry the welding rod at room temperature for 12 hours, and then place it in a drying oven at 80°C for 1 hour;

[0088] S6. Raise the temperature of the drying oven to 400°C and dry for 1 hour;

[0089] S7. Cool the drying furnace to 120°C and take out the welding rods.

[0090] Among them, the welding core and the coating are melted and mixed to form a weld. The weight fraction of each component of the deposited metal at the weld is:

[0091] C: 0.092%, Si: 0.23%, Mn: 0.62%, Cr: 9.24%, V: 0.19%, W: 2.68%, Co: 3.13%, Nb: 0.055%, B: 0.0056%, N: 0.013%, Ni: 0.55%, Cu: 0.26%, S: 0.005%, P: 0.008%, Al≤0.02%: Ti≤0.02%, Ta≤0.02%, balance Fe;

[0092] The weight fraction ratio of B to N is: B / N=0.43, and the total weight fraction of Mn and Ni is: Mn+Ni=1.17%.

[0093] Example 2

[0094] 2-1) The core component composition of the core transition type welding rod of this embodiment is as shown in Table 1 in Example 1.

[0095] 2-2) The weight fractions of the components of the coating of the welding core transition type welding rod of this embodiment are: rutile: 5.8%, titanium dioxide: 2%, marble: 35%, fluorite: 23%, cobalt powder: 4.4%, electrolytic manganese: 2%, metallic chromium: 4.4%, ferrotungsten: 2.5%, ferroniobium: 1.4%, ferroboron: 2.1%, ferrovanadium: 1%, ferrotitanium: 4.8%, copper powder: 1.9%, nickel powder: 4.8%, quartz: 3.9%, and alkali 1%.

[0096] 2-3) The preparation of the core transition type welding rod is the same as that in Example 1. The weight fractions of the components of the deposited metal of the obtained weld are:

[0097] C: 0.089%, Si: 0.21%, Mn: 0.56%, Cr: 9.06%, V: 0.19%, W: 2.65%, Co: 3.10%, Nb: 0.052%, B: 0.0052%, N: 0.014%, Ni: 0.54%, Cu: 0.25%, S: 0.005%, P: 0.006%, Al≤0.02%: Ti≤0.02%, Ta≤0.02%, balance Fe;

[0098] The weight fraction ratio of B to N is: B / N=0.37, and the total weight fraction of Mn and Ni is: Mn+Ni=1.10%.

[0099] Example 3

[0100] 3-1) The core component composition of the core transition type welding rod of this embodiment is as shown in Table 1 in Example 1.

[0101] 3-2) The weight fractions of the components of the coating of the welding core transition type welding rod of this embodiment are: rutile: 5.9%, titanium dioxide: 2%, marble: 33%, fluorite: 25%, cobalt powder: 4%, electrolytic manganese: 1.8%, metallic chromium: 4.1%, ferrotungsten: 2.3%, ferroniobium: 1.3%, ferroboron: 1.8%, ferrovanadium: 1%, ferrotitanium: 5.9%, copper powder: 2%, nickel powder: 4.9%, quartz: 4%, and alkali 1%.

[0102] 3-3) The preparation of the core transition type welding rod is the same as that in Example 1. The weight fractions of the components of the deposited metal of the obtained weld are:

[0103] C: 0.083%, Si: 0.22%, Mn: 0.54%, Cr: 8.98%, V: 0.19%, W: 2.63%, Co: 3.05%, Nb: 0.049%, B: 0.006%, N: 0.014%, Ni: 0.56%, Cu: 0.26%, S: 0.005%, P: 0.008%, Al≤0.02%: Ti≤0.02%, Ta≤0.02%, balance Fe;

[0104] The weight fraction ratio of B to N is: B / N=0.43, and the total weight fraction of Mn and Ni is: Mn+Ni=1.10%.

[0105] Experimental Example 1

[0106] The length of the deposited metal formed by surfacing welding on the test plate is ≥380mm, the width is ≥80mm, and the height is ≥35mm. Samples are taken for tensile and impact tests.

[0107] The deposited metal of the welding rod prepared in Example 1 was subjected to a post-weld heat treatment at 765°C for 12 h. The measured tensile strength Rm was 698 MPa, the yield strength ReL was 559 MPa, the elongation A was 21%, and the reduction of area Z was 64%.

[0108] The deposited metal of the welding rod prepared in Example 1 was subjected to a post-weld heat treatment at 765° C. for 12 h. Five samples were prepared for impact testing: the impact energies (AkV, 20° C.) were 25 J, 38 J, 58 J, 97 J, and 52 J, respectively.

[0109] The deposited metal of the welding rod prepared in Example 2 was subjected to a post-weld heat treatment at 770°C for 10 h. The measured tensile strength Rm was 716 MPa, the yield strength ReL was 568 MPa, the elongation A was 20%, and the reduction of area Z was 62%.

[0110] The deposited metal of the welding rod prepared in Example 2 was subjected to a post-weld heat treatment at 770° C. for 10 h. Five samples were prepared for impact testing: the impact energies (AkV, 20° C.) were 82 J, 74 J, 26 J, 73 J, and 31 J, respectively.

[0111] The deposited metal of the welding rod prepared in Example 3 was subjected to a post-weld heat treatment at 765°C for 10 h. The measured tensile strength Rm was 713 MPa, the yield strength ReL was 560 MPa, the elongation A was 21%, and the reduction of area Z was 64%.

[0112] The deposited metal of the welding rod prepared in Example 3 was subjected to a post-weld heat treatment at 765°C for 10 h. Five samples were prepared for impact testing: the impact energies (AkV, 20°C) were 35 J, 56 J, 61 J, 70 J, and 89 J, respectively.

[0113] In summary, the deposited metal of the above welds can achieve room temperature mechanical properties as shown in Table 2 below after post-weld heat treatment at 750-770°C.

[0114] Table 2 Mechanical properties of deposited metal

[0115]

[0116] Experimental Example 2

[0117] Plate butt joint welding test

[0118] CW3 was used as the base material. Two pieces of CW3 base material were taken and the welding rod prepared in Example 2 was selected for welding.

[0119] The welding process specifications are: preheating temperature 200℃, interpass temperature 300℃, electrode diameter 4.0, welding current I=130~170A, cooling to 150-260℃ after welding, keeping warm for 2h, and then heat treatment at 760℃×16h.

[0120] The obtained welded test plate was subjected to mechanical property test:

[0121] The tensile strength Rm is 677 MPa, the yield strength ReL is 510 MPa, the elongation A is 17%, the cross-sectional reduction Z is 63%, and the fracture position of the tensile specimen is the base material CW3, indicating that the weld strength is high.

[0122] Experimental Example 3

[0123] Plate butt joint welding test

[0124] G115 was used as the base material. Two pieces of G115 base material were taken and the welding rod prepared in Example 3 was selected for welding.

[0125] The welding process specifications are: preheating temperature 200℃, interpass temperature 300℃, electrode diameter 4.0, welding current I=130~170A, cooling to 150-260℃ after welding, keeping warm for 2h, and then heat treatment at 760℃×16h.

[0126] The obtained welded test plate was subjected to mechanical property test:

[0127] The tensile strength Rm is 695 MPa, the yield strength ReL is 550 MPa, the elongation A is 21%, the cross-sectional reduction rate Z is 71%, and the fracture position of the tensile specimen is the base material G115, indicating that the weld strength is high.

[0128] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A welding core transition type welding rod, comprising a welding core and a coating covering the welding core, characterized in that: The deposited metal of the core transition type welding electrode includes the following components in percentage by weight: C: 0.07-0.10%, Si: 0.1-0.3%, Mn: 0.3-0.7%, Cr: 8.5-9.5%, V: 0.1-0.3%, W: 2.3-3.1%, Co: 2.7-3.5%, Nb: 0.02-0.08%, B: 0.002-0.015%, N: 0.005-0.018%, Ni: 0.2-0.6%, Cu: 0.15-0.48%, S≤0.01%, P≤0.01%, Al≤0.02%, Ti≤0.02%, Ta≤0.02%, balance is Fe; The weight percentage ratio of B to N is: 0.2≤B / N≤1, and the total weight percentage of Mn and Ni is: Mn+Ni≤1.2%; The welding core comprises the following components in weight percentage: C: 0.06-0.09%, Si: 0.1-0.5%, Mn: 0.2-0.7%, Cr: 8.5-9.5%, V: 0.1-0.3%, W: 2.2-3.0%, Co: 2.6-3.3%, Nb: 0.02-0.08%, B: 0.002-0.008%, N: 0.005-0.02%, Al≤0.02%, Ta≤0.02%, S≤0.005%, P≤0.005%, balance Fe; And the ratio of the weight percentage of B to N is: 0.2≤B / N≤1.

2. The welding core transition type welding electrode according to claim 1, characterized in that: The weight percentage ratio of B to N in the deposited metal is: 0.2≤B / N≤0.5, and the total weight percentage of Mn and Ni is: 1.0%≤Mn+Ni≤1.2%.

3. The welding core transition type welding electrode according to claim 1, characterized in that: The deposited metal of the welding rod comprises the following components in percentage by weight: C: 0.08-0.10%, Si: 0.20-0.3%, Mn: 0.5-0.7%, Cr: 8.5-9.3%, V: 0.1-0.2%, W: 2.6-3.0%, Co: 3.0-3.2%, Nb: 0.04-0.06%, B: 0.004-0.008%, N: 0.010-0.016%, Ni: 0.4-0.6%, Cu: 0.2-0.4%, S: 0.005-0.01%, P: 0.005-0.01%, Al≤0.02%, Ti≤0.02%, Ta≤0.02%, balance Fe; The weight percentage ratio of B to N is: 0.2≤B / N≤0.5, and the total weight percentage of Mn and Ni is: 1.1%≤Mn+Ni≤1.2%.

4. The welding core transition type welding electrode according to claim 1, characterized in that: The coating is a CaO / CaF2-SiO2 slag system.

5. The welding core transition type welding electrode according to claim 1, characterized in that: The coating comprises the following components in percentage by weight: Rutile: 4-6%, titanium dioxide: 1.5-3%, marble: 30-40%, fluorite: 15-28%, cobalt powder: 3-5%, electrolytic manganese: 1.5-2.5%, metallic chromium: 4-5%, ferrotungsten: 2-3%, ferroniobium: 1-2%, ferroboron: 1.5-2.5%, ferrovanadium: 0.5-1.5%, ferrotitanium: 4-7%, copper powder: 1.5-2.5%, nickel powder: 4-5%, quartz: 3.5-4.5%, alkali 0.5-1.5%.

6. The welding core transition type welding electrode according to claim 5, characterized in that: The coating comprises the following components in percentage by weight: Rutile: 4.5-5.9%, titanium dioxide: 2-2.8%, marble: 33-36%, fluorite: 20-25%, cobalt powder: 4-4.6%, electrolytic manganese: 1.8-2.3%, metallic chromium: 4.1-4.6%, ferrotungsten: 2.3-2.8%, ferroniobium: 1.3-1.5%, ferroboron: 1.8-2.3%, ferrovanadium: 0.8-1.2%, ferrotitanium: 4.8-6.5%, copper powder: 1.8-2%, nickel powder: 4.6-4.9%, quartz: 3.7-4%, alkali 0.8-1.2%.

7. The welding core transition type welding electrode according to claim 1, characterized in that: The mass ratio of the coating to the welding core is 3:

7.

8. The welding core transition type welding electrode according to any one of claims 1 to 7, characterized in that: The post-weld stress relief heat treatment temperature of the deposited metal is 750-770°C.

9. The method for preparing the core transition type welding electrode according to any one of claims 1 to 8, characterized in that: The steps include: S1, preparing welding core; S2, mixing the components of the coating uniformly into powder according to the proportion; S3. Add 20-40% by mass of water glass to every 100 kg of the medicine powder and stir evenly to form a medicine embryo; S4. Using a hydraulic press, the prepared medicine embryo is wrapped and pressed onto the outside of the welding core to form a welding rod; S5. Dry the welding rod at room temperature for 10-24 hours, then place it in a drying oven at 70-90°C for 0.5-2 hours; S6. Raise the temperature of the drying oven to 300-450°C and dry for 0.5-2 hours; S7. Cool the drying furnace to 110-120℃ and take out the welding rods.

10. Use of the core transition type welding electrode according to any one of claims 1 to 8, characterized in that: The transition type welding rod is used for welding 630-650°C martensitic heat-resistant steel.

11. The use of the core transition type welding electrode according to claim 10, characterized in that: Applied to welding of 9Cr-3W-3Co steel.

12. The use of the core transition type welding electrode according to claim 11, characterized in that: Applicable to welding of G115 steel, SAVE12AD steel, MARBN steel or CW3 steel.

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