Identification of welding rod types and grades
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Identification of electrode types and gradesI. Functions and types of electrode coatings
1. Basic functions of electrode coatings:
(1) Protecting the arc and molten pool
The coating melts more slowly than the core wire, forming a sleeve that helps ensure the smooth transition of molten metal droplets into the molten pool； At the same time, the flux releases gases and forms slag, protecting the arc and the molten pool from the harmful effects of air. The slag covering the surface of the deposited metal also reduces the cooling rate of the weld metal, which helps to improve the properties of the joint. (2) Metallurgical treatment: Through metallurgical reactions, impurities such as oxygen, sulfur, and phosphorus are removed, and at the same time the weld metal is alloyed. (3) Endowing the electrode with good welding process properties, enabling easy arc initiation and stable combustion, reducing spatter, increasing penetration, and ensuring proper weld formation. (4) Meeting the special functions of certain specialized welding electrodes. For example, the coating of iron powder welding electrodes contains a relatively large amount of iron powder, which increases the deposition rate of the electrodes and enhances welding productivity. 2. Types of welding rod coatings: Serial number, Coating type, Corresponding grade, Corresponding model, Welding power supply. 1. Special type: ×××0, E××, 00; 2. Titanium type: ×××1, E××, 13 – DC or AC; 3. Titanium-calcium type: ×××2, E××, 03 – DC or AC; 4. Ilmenite type: ×××3, E××, 01 – DC or AC; 5. Iron oxide type: ×××4, E××, 20 – DC or AC; 6. Cellulose type: ×××5, E××, 10, 11 – DC or AC; 7. Low-hydrogen potassium type: ×××6, E××, 16 – DC or AC; 8. Low-hydrogen sodium type: ×××7, E××, 15 – DC; 9. Graphite type: ×××8, E××, 13 – DC or AC; 10. Alkaline type: ×××9, E××, 13 – DC. 3. Acidic welding rods and alkaline welding rods: (1) Welding rods whose coatings melt during welding to form slag, with acidic slag after welding, are called acidic welding rods; those with alkaline slag are called alkaline welding rods. (2) Disadvantages of acidic electrodes: The slag composition of acidic electrodes consists mainly of acidic oxides, which have a strong oxidizing effect on the weld metal; as a result, a significant amount of alloying elements in the weld metal is lost. At the same time, the hydrogen and oxygen contents in the weld metal are high, resulting in lower mechanical properties of the weld metal, particularly its plasticity and toughness. (3) Advantages of acidic electrodes: Low sensitivity to pores caused by rust, oil, and moisture. Acidic electrodes can be welded using either AC or DC power sources. (4) Advantages of basic electrodes: The slag composition of basic electrodes consists mainly of basic oxides, resulting in little oxidizing effect on the weld metal and excellent metallurgical processing properties. During welding with basic electrodes, the flux decomposes to produce CO2 as a shielding gas. The hydrogen content in this shielding gas is very low; therefore, the weld metal produced using basic electrodes has a low hydrogen content and good overall mechanical properties, especially high plasticity and toughness. (5) Disadvantages of basic electrodes: They are quite sensitive to porosity. II. The significance of unified numbering for welding electrodes 1. Welding electrodes are usually identified by their models and grades to reflect their main performance characteristics and categories. 2. The electrode type is a designation method based on the electrode **standard, reflecting the main characteristics of the electrode. 3. The electrode grade is a specific designation for electrode products, based on their main uses and performance characteristics. Defined by the electrode manufacturer. China’s electrode industry uses unified grades: products that belong to the same type of coating, fit the same electrode model, and have similar properties are all given the same grade name. Such as J422, J507. Note: (1) Whether it is a grade designated by the welding rod manufacturer or a unified grade in the national welding materials industry, it is necessary to indicate on the product catalog or label, as well as on the quality certificate, whether the product meets national standards, is equivalent to national standards, or does not meet them at all; this allows users to choose the appropriate product based on its performance requirements and in comparison with the relevant standards. (2) There is only one grade for each electrode product; however, multiple grades of electrodes can correspond to the same model. For example, the grades J507RH and J507R both have the model E5015-G. Comparison of welding rod classifications: by grade, by model. Structural steel welding rods; carbon steel welding rods; low-alloy steel welding rods; low-temperature steel welding rods; molybdenum and chromium-molybdenum heat-resistant steel welding rods; stainless steel welding rods; chromium stainless steel welding rods; chromium-nickel austenitic stainless steel. 3. Method of indicating welding rod grades: 1. It is usually represented by a Pinyin letter (or Chinese character) along with three digits. Examples include A302 (Au 302), W607 (Wen 607). 2. For some electrode types, suffix letters and/or numbers are added after the three-digit code. Such as J507RH, A022Mo, J422Fe16 – the first letter indicates the type of welding rod ； First two digits: indicate the strength of the deposited metal or the alloy type ； Third digit: indicates the type of coating and the type of current ； Letters and numbers after the digit: additional alloying elements or characteristics of the electrode (with special properties and uses). For example: G – high-toughness welding electrode ； R — Welding electrodes for pressure vessels ； Fe — High-efficiency iron powder welding rod: X — Welding rod for vertical down welding ； H——Ultra-low hydrogen welding electrode ； RH — High-toughness ultra-low hydrogen welding electrode ； IV. Methods of Designating Welding Rod Models 1. Carbon steel welding rods: (1) In accordance with the GB/T5117 standard \"Carbon Steel Welding Rods\", the models of carbon steel welding rods are classified based on the mechanical properties of the deposited metal, the type of flux coating, the welding position, and the type of welding current. (2) Method for coding carbon steel electrode models: The initial letter “E” denotes the electrode ； The first two digits indicate the minimum tensile strength of the deposited metal, in kgf/mm2 ； The third digit indicates the welding position of the electrode: “0” and “1” mean that the electrode is suitable for welding in all positions ； ““2” indicates that the electrode is suitable for flat welding and horizontal fillet welding ； “4” indicates that the electrode is suitable for vertical down welding. The combination of the third and fourth digits indicates the type of welding current and the type of flux coating. Attach a letter or digit after the fourth digit: “R” denotes electrodes resistant to moisture absorption, “M” denotes electrodes with special requirements regarding moisture absorption and mechanical properties, and “-1” denotes electrodes with special requirements regarding impact strength. Example: E4303: 43kgf/mm2 ； All positions ； calcium-titanium type ； It works on both AC and DC. E5015: 50kgf/mm2 ； All positions ； Low-hydrogen sodium type ； DC reverse connection. E5018-1: 50 kgf/mm2 ； All positions ； Low-hydrogen type iron powder ； AC or DC reverse polarity ； -Guaranteed value for low-temperature shock at 46℃. 2. Low-alloy steel electrodes: (1) In accordance with the GB/T5118 standard for Low-alloy steel electrodes, the types of low-alloy steel electrodes are classified based on the mechanical properties of the deposited metal, its chemical composition, the type of flux coating, the welding position, and the type of welding current. (2) Method for coding low-alloy steel electrode models: The initial letter “E” denotes an electrode ； The first two digits represent the minimum tensile strength of the deposited metal (kgf/mm2) ； The third digit indicates the welding position of the electrode: “0” and “1” mean that the electrode is suitable for welding in all positions ； “\"2\" indicates that the electrode is suitable for flat welding and fillet welding. The combination of the third and fourth digits indicates the type of welding current and the type of flux coating ； The suffix letter is the classification code for the chemical composition of the deposited metal, and it is separated from the preceding part by a hyphen “-”. When there are additional chemical components, these components are represented directly by their element symbols, which are separated from the preceding suffix letters by a dash “-”. For example: E5515-B2-V (R317). For the weld metal chemical composition classification of low-hydrogen electrodes of types E50XX-X, E55XX-X, and E60XX-X, when the letter “R” is added after the suffix letter or additional chemical components, it indicates an electrode resistant to moisture absorption. Example: (1) E5015-G (J507RH, J507R, etc.): 50 kgf/mm2 (490 MPa) ； Low-hydrogen sodium type ； High toughness (guaranteed value for low-temperature impact) ； DC reverse connection ； All-position welding. (2) E6015-G (J607RH): 60 kgf/mm2 (610 MPa) ； Low-hydrogen sodium type ； Ultra-low hydrogen, high toughness ； (-40°C low-temperature impact guarantee value) ； DC reverse connection ； All-position welding. (3) E5515-C1 (W707Ni): Low-hydrogen sodium type ； Contains 2.5Ni ； 55 kgf/mm2 (540 MPa) ； High toughness (guaranteed impact value at -70°C) ； DC reverse connection ； All-position welding. (4) E5515-C2 (W907Ni): Low-hydrogen sodium type ； Contains 3.5Ni ； 55 kgf/mm2 (540 MPa) ； High toughness (guaranteed impact value at -90°C) ； DC reverse connection ； All-position welding. (5) E5515-B1 (R207): low-hydrogen sodium type ； 0.5Cr-0.5Mo ； 540 MPa, guaranteed value for impact at room temperature ； DC reverse connection ； All-position welding. (6) E5515-B2 (R307): Low-hydrogen sodium type ； 1Cr-0.5Mo ； 540 MPa, guaranteed value for impact at room temperature ； DC reverse connection ； All-position welding. (7) E5515-B2-V (R317): Low-hydrogen sodium type ； 1Cr-0.5Mo-V ； 540 MPa, guaranteed value for impact at room temperature ； DC reverse connection ； All-position welding. (8) E6015-B3 (R407): Low-hydrogen sodium type ； 2.5Cr-1Mo ； 590 MPa, guaranteed value for impact at room temperature ； DC reverse connection ； All-position welding. 3. Stainless steel electrodes: (1) In accordance with the GB/T983 standard for Stainless Steel Electrodes, the types of stainless steel electrodes are classified based on the chemical composition of the deposited metal, the type of flux coating, the welding position, and the type of welding current. (2) Method for coding stainless steel electrode models: The initial letter “E” denotes the electrode ； “The number following “E” denotes the classification code for the chemical composition of the deposited metal; for any chemical components with specific requirements, these are indicated using element symbols and placed after the number ； The two digits following the dash for short circuits indicate the type of flux coating, the welding position, and the type of welding current. “15” indicates an alkaline, titanium-type or titancalcium-type flux, for all-position welding, with AC or DC reverse polarity ； “16” indicates alkaline flux, all-position welding, DC reverse polarity ； “17” is a variant of “16”. (3) The models of stainless steel welding electrodes are the same as those in industrially developed countries such as the United States and Japan. Example: (1) E308L-16 (A002): titanium-calcium type ； Ultra-low carbon (C≤0.04%) ； Nominal composition 00-19Cr-10Ni ； Reverse connection of AC or DC (DC power supply should be used whenever possible) ； All-position welding. (2) E308-15 (A107): Alkaline ； Low carbon (C≤0.08%) ； Nominal composition 0-19Cr-10Ni ； DC reverse connection ； All-position welding. (3) E316L-16 (A022): titanocalcium type ； Ultra-low carbon (C≤0.04%) ； Nominal composition 00-18Cr-12Ni-2Mo ； Reverse connection of AC or DC (DC power supply should be used whenever possible) ； All-position welding. (4) E316-15 (A207): Alkaline ； Low carbon (C≤0.08%) ； Nominal composition of the deposited metal: 0-18Cr-12Ni-2Mo ； DC reverse connection ； All-position welding. (5) E347-15 (A137): Alkaline ； Low carbon (C≤0.08%) ； Nb-containing stabilizer ； Nominal composition: 0-19Cr-10Ni-Nb ； DC reverse connection ； All-position welding. (6) E309-15 (A307): Alkaline ； Contains C ≤ 0.15% ； Nominal composition 1-23Cr-13Ni ； DC reverse connection ； All-position welding. (7) E310-16 (A402): Titania-calcium type ； Containing C= 0.08-0.20% ； Pure austenitic structure, nominal composition 2-26Cr-21Ni ； AC or DC reverse polarity (DC power supply is preferred) ； All-position welding. Note: L indicates a low carbon content (C≤0.04%) ； H indicates a higher carbon content (C > 0.15%). Special case: E5MoV-15 (R507): low-hydrogen sodium type ； 5Cr-0.5Mo-V ； 520 MPa E9Mo-15 (R707): low-hydrogen sodium type ； 9Cr-1Mo, 590 MPa. By grade: It is a welding electrode for pearlitic heat-resistant steel (low-alloy steel). By model: It belongs to stainless steel welding electrodes. GB/T983-1995 proposes: to include it in the next revision of the GB/T5118 standard. V. Comparison of domestic and international grades and models (examples)
Electrode category | Domestic grade | National standard model | AWS model
Carbon steel electrodes | J422 | E4303 | J506 | E5016 | E7016
Low-alloy structural steel electrodes | J506R | E5016-G | E7016-G | J506RH | E5016-G | E7016-G | J607 | E6015-D1 | E9015-D1
Low-temperature steel electrodes | W707Ni | E5515-C1 | E8015-C1
Pearlite heat-resistant steel electrodes | R407 | E6015-B3 | E9015-B3
Chromium stainless steel electrodes | G207 | E410-15 | E410-15
Chromium-nickel austenitic stainless steel electrodes | A042 | E319Mo | E309MoL-16 | A022Mo | E317L-16 | E317L-16
Nickel-based alloy electrodes | Ni307B | ENiCrFe-3