IS 812 : 1957Method for Coding of Covered Electrodes for Manual Metal Arc Welding

IS 812:1957 is the method for coding of covered electrodes for manual metal-arc welding — the standardised letter/digit code that classifies a welding electrode by its characteristics (covering type, welding positions, current/polarity, and the strength/properties of the deposited weld metal). It lets an engineer specify and a welder select the correct consumable for the joint.

It sits in the welding stack:

• IS 814 Part 1 — specification for covered electrodes (the product the code classifies) · IS 816 — use of metal-arc welding (where the right electrode is selected)
• IS 813 — welding symbols · IS 800 — steel design · IS 1148 — wire rod for electrode core

A welded joint's strength and soundness depend heavily on the right electrode for the parent steel, position and conditions — the code is how that is communicated unambiguously:

• The classification encodes covering/flux type, suitable welding positions, current & polarity, and the deposited weld-metal strength/toughness class (matching consumable to the parent metal strength)
• A mismatched electrode — wrong strength class, wrong covering for the position, or non-low-hydrogen where low-hydrogen is required — produces weak, porous, or hydrogen-cracked welds
• The code lets the IS 816 procedure and the IS 813 drawing call up a specific, reproducible consumable rather than 'any electrode'

The engineering point: a structural weld is only as good as the matched consumable, and the electrode code is the language that makes 'matched' specifiable and verifiable. Treating electrodes as a generic commodity — ignoring the code — is a direct path to under-strength or cracked welds that the design assumed would develop the parent-metal strength.

Scenario: welding a structural connection in IS 2062 steel per an IS 800 design.

Step 1 — match strength: choose an electrode whose deposited weld-metal strength class (per its IS 812 code) matches/exceeds the parent steel and the IS 816 procedure.

Step 2 — match position & current: the code's position and current/polarity characteristics must suit the joint (e.g. overhead/vertical) and the available supply.

Step 3 — hydrogen control: for crack-sensitive/thick/restrained joints, select a low-hydrogen classification and keep electrodes dry (re-bake as required).

Step 4 — specify by code: the IS 813 drawing/IS 816 procedure calls the electrode code, not 'a 3.15 mm rod'.

Step 5 — verify on site: correct coded electrode, in date, dry.

The coded selection makes the consumable reproducible and matched; ignoring the code risks an under-matched or hydrogen-cracked weld.

1. Treating electrodes as a generic commodity. The code classifies strength/position/covering — 'any electrode' risks an under-matched, defective weld.

2. Strength-class mismatch. A weld-metal class below the parent steel makes the weld the weak link.

3. Wrong covering/position for the joint. Position and current/polarity characteristics in the code must suit the actual joint.

4. Ignoring low-hydrogen need / damp electrodes. Crack-sensitive joints need a low-hydrogen class kept dry — a classic cause of hydrogen cracking.

5. Not specifying by code. Drawings/procedures must call the electrode classification so selection is reproducible and verifiable.

• IS 814 Part 1 — covered electrodes specification (the product) · IS 816 — use of metal-arc welding (selection in practice)
• IS 813 — welding symbols (calls the consumable) · IS 1148 — wire rod for electrode core wire
• IS 2062 — structural steel (parent metal) · IS 800 — steel design · IS 3600 Part 1 — welded-joint testing

IS 812 is old (1957) but encodes a permanent welding truth: the consumable must be matched to the joint, and the electrode code is the language that makes 'matched' specifiable, reproducible and verifiable. Structural welds fail when electrodes are treated as a generic commodity — an under-strength weld-metal class makes the weld the weak link, the wrong covering/position gives defective runs, and non-low-hydrogen or damp electrodes cause hydrogen cracking in restrained joints. The discipline: the IS 800 design and IS 816 procedure should call the electrode by its classification (read with the current IS 814 specification), and site QC verifies the correct, in-date, dry coded electrode is actually used. For modern work the classification is read with the current electrode standards, but the principle — specify and verify the matched consumable by code — is unchanged and non-negotiable for sound structural welds.