MMAW （Manual Metal Arc Welding）

Summary:

Manual arc welding is a type of metal arc welding that does not utilize shielding gas. In this manual welding process, an electrode with a coated flux layer is used. The electrode serves as both the carrier of the arc and the filler material, preventing atmospheric contamination. Both the protection against the atmosphere and the flux layer's generation of slag or shielding gases come from the electrode itself. The outer flux layer creates slag and/or generates shielding gases, which safeguard the transitioning molten droplets and weld pool from the intrusion of oxygen, nitrogen, and hydrogen present in the atmosphere.

Current type:

Manual arc welding can be performed using both direct current (DC) and alternating current (AC). Most types of welding electrodes are used with DC current, where the electrode is connected to the negative polarity and the workpiece is connected to the positive polarity. However, when using alkaline electrodes, better welding results can be achieved with the workpiece connected to the positive polarity. Some brands of cellulose-type electrodes are also designed for positive polarity welding.

Please note that the listed AWS classifications are commonly used internationally. However, specific regional or country-specific standards and classifications may exist. It is important to refer to the relevant international standards and specifications when selecting and using welding electrodes.

Welding Electrode	AWS Classification	Application
E6010	AWS E6010	General purpose for carbon and low-alloy steels
E7018	AWS E7018	Low hydrogen electrode for high load and critical structures
E7016	AWS E7016	Medium slag electrode for carbon and low-alloy steels
E308	AWS E308	Basic stainless steel electrode for joining stainless steel and carbon steel
E309	AWS E309	Basic stainless steel electrode for joining stainless steel and low-alloy or carbon steel

Welding Electrode	AWS Classification	Application
E6013	AWS E6013	General purpose for carbon and low-alloy steels
E7014	AWS E7014	Medium slag electrode for carbon and low-alloy steels
E6011	AWS E6011	General purpose with good penetration for carbon and low-alloy steels
E7018-A1	AWS E7018-A1	Low hydrogen electrode for high-strength and high-load structures

Types of Welding Electrodes:

The flux coating on welding electrodes can be classified into different categories, and their compositions can vary significantly. The composition of the flux coating determines the melting characteristics, welding performance, and strength of the weld joint. For welding electrodes used with non-alloy steels, there are different types of flux coatings, including basic types and mixed types. The abbreviations used in the classification are derived from the corresponding English terms. Specifically, C stands for cellulose, A for acid, R for rutile, and B for basic. When it comes to welding electrodes for stainless steel, there are only two types available: rutile and basic.

The relationship between welding current (A) and electrode diameter can be estimated using the following empirical formulas:

Welding Electrode Diameter (mm)	Recommended Welding Current (A)
2	40-80
2.5	50-100
3.2	90-150
4	120-200
5	180-270
6	220-360