When to use low hy­dro­gen elec­trodes

DEMM Engineering & Manufacturing - - WELDING - By Joseph Ko­lasa

The steady de­vel­op­ment of new al­loys over the years has shaped the de­sign and spec­i­fi­ca­tion of arc weld­ing stick elec­trodes.

As in­creas­ingly de­mand­ing weld­ing ap­pli­ca­tions be­came stan­dard in fab shops and in the field, the need for durable, low hy­dro­gen stick elec­trodes be­came more preva­lent across a va­ri­ety of in­dus­tries in­volved in weld­ing. As a re­sult, low hy­dro­gen stick elec­trodes emerged.

These ver­sa­tile con­sum­ables have be­come a pri­mary elec­trode for a va­ri­ety of weld­ing ap­pli­ca­tions and have gained wide ac­cep­tance in the in­dus­try. They are ideal for use in other ap­pli­ca­tions where base metals have a ten­dency to crack, where thick sec­tions are to be welded or where the base metal has an al­loy con­tent higher than that of mild steel, such as high car­bon and low al­loy steels.

To­day, there are many types of low hy­dro­gen elec­trodes avail­able for use in shielded metal arc weld­ing (SMAW) ap­pli­ca­tions. These elec­trodes, which in­clude EXX15, EXX16, EXX18, EXX18-X, EXX28 and EXX48, are of­ten spec­i­fied to re­duce the like­li­hood of hy­dro­gen­re­lated cracking dur­ing the stick weld­ing process. Low hy­dro­gen elec­trodes are rec­om­mended for three broad ar­eas of ap­pli­ca­tion: On steels with poor weld­abil­ity: low al­loy, high car­bon, high sul­phur, or other steels where cracking can be a prob­lem. When spec­i­fied by gov­ern­ing codes. For high-de­po­si­tion, outof-po­si­tion welds on heavy plate. Low hy­dro­gen elec­trodes of­fer fast-fill (high-de­po­si­tion) or fill-freeze (out-of-po­si­tion) char­ac­ter­is­tics and are de­signed to pro­duce sound welds of X-ray qual­ity with ex­cel­lent notch/im­pact prop­er­ties and high duc­til­ity.

Some low hy­dro­gen stick elec­trodes have a -1 suf­fix in the AWS clas­si­fi­ca­tion. This in­di­cates the stick elec­trode meets the re­quire­ments for im­proved tough­ness.

Weld­ing con­sum­ables can be clas­si­fied with an op­tional dif­fusible hy­dro­gen des­ig­na­tor.

These des­ig­na­tors in­clude an H4, H8 and H16 des­ig­na­tion. The “H” and cor­re­spond­ing num­ber in­di­cates millil­itres of dif­fusible hy­dro­gen per 100 grams of weld metal.

The “R” des­ig­na­tion for an elec­trode in­di­cates that it has a mois­ture-re­sis­tant coat­ing. While low hy­dro­gen elec­trodes ideally should run on DCEP po­lar­ity (es­pe­cially if the size is 5/32-inch or less), they also can be used on AC po­lar­ity.

Low hy­dro­gen elec­trodes, in­ci­den­tally, are the most widely used class of weld­ing con­sum­ables for such ap­pli­ca­tions as power gen­er­a­tion, gen­eral

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