1950-10-05 — Page 10

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ENGINEERING PAGE

QUALITY-CONTROL TECHNIQUE

FOR WELDING ELECTRODES

Quality-control techniques of appropriate typos ars widely employed in a number of Britain's manufacturing, and, ongincoring Industries to as sure that a uniform, high standard of quality is maintained in the ul- timato products. Some of the techniques are extremely complex in or- dor to guarantee the desired control in intricato manufacturing pro-

cossos.

In the production of welding electrodes, Murex Welding Processes, Ltd.,

of Waltham Cross, Hertfordshire, employ a system of quality control designed to control the following factors:

to

Welding exhibition

At the recent Research and Production Exhibition of the

1. The quality of all row In view of the large volume of The coating of an electrode may British Welding Research As- materials used in manufacture. test work always going forward consist of a dozen or more ali-sociation, the emphasis was

2. The quality of all batches of it is necessary to keep well, terent powders in addition blended powders preparatory to abreast of developments in analy-binding materials, and the pro- placed on the use of wolding processing into electrodo coatings. tical technique; any new rapid portion of any one of them may where economies in manu facture and greater output 3. The processing under rigid methods published in 'the solentibo as small as 0.25 per cent.

The blended powders which can be achieved. conditions of the blended powder fic Press or developed by the batches into electrode, continga, Murex staff are tried out, and have been passed for production

While there are few industries and of the steel and other metals where they show time-saving are processed into paste for «eloc- and alloys into electrode core wire, } without loss of accuracy are trode coatings in accordance with which are not using welding to 4. Concentricity of the core adopted as routine methods. the manufacturing speelftentions. some extent at the present ilmo wire and coating, and electrode

These stipulate the weights of many are not taking full advant diameters.

powder and binder, type of wet age of the potentialitles of weld- mixing machine and period of ing. mixing.

One welding process is often When the powder and binder far more satisfactory than an- have been mixed a sample of other for a spocide application, the paste is tested for extrusion and the exhibition brought out

do not the necessity for using the cor As distinct from mild steels, properties, and if these these special. wires are purchased conform exactly to requirements reet process if optimum economy in the drawn condition, either in small

of powder pr and speed of production are to

5. Drying of electrodes from the extrusion to the packing stage, and

The Spekker method of ab- alysis has been particularly useful in this direction, and the same principle has been applied for the rapid determination of the sur- face area of line powder.

Sogregation of wires

.additions

The quality of electrodes os determined by their running pro- perties and the quality and com- position of the weld metal.

As generally understood, the arc welding electrode consists of a coils or in cut lengths, and check-binder may be necessary with a be achieved. metal or alloy core wire evenly ed for surface condition relative further period of mixing to en- coated with such a mixture of to its effect on conting adhesion.

sure paste uniformity. organic and inorgaale-materials as will ensure satisfactory running properties and characteristic weld deposits of specified composition and quality.

For different types of joints different slag characteristics are required, and thest, or well as the composition of the weld nietal, are controlled, provided that the quality of the wire remains con- stant, by the homogeneity and composition of the coating.

Raw materials

In view of the great importanci of avoiding any possible change

ferent types, each type of wire own specific length. purchased in eut lengths hes Its

Adhesion test

After final checking for con-

are

Rosearch association

The exhibition showed gener

of

$fur="

of admixture of core wires or difsistency, the paste is dischargedly the manner in which the

from the mixer and made into Research Association is pugs for loading into the ex- thering the use of welding, and truders. After pugging precou- the extent to which welding -is assisting industrial production Thus, if at any stage. prior te tions

taken 10 prevent at the present time. extrusion wires of different types, evaporation of the binder, which The main items of the exhi should get mixed, the error woul would result in hardening of the bition included resistance-weld- he discovered at the extrusior poste:

ing equipment and applications, stage, as the extruders are set tr The importanvic of good ad- the non-destructive testing of deal only with wires of uniform hesion is too well known by welds, the welding of corrosion- length,

to users of electrodes require and heat-resisting steals. In the Again, if after extrusion and stressing here, and is dependent chemical and dairy industries

differen

upon certain properties of the und in the drying electrodes of

Hus facts

and types should become mixed, this surface of the wite at the time of turbinos, would be detected at the pack-extrusion. These properties

are photographs of welded struc ing stave by the difference in conferred

upon the

including the new stock lengths.

the processing operations. vire

A laboratory test has been de-storey bulidings, bridges, portal vised by which it is possible to frumes, and a walking dragline. also given ta Attention was into varojus classify adhesion grades, and periodical tests are

repairs and reinforcement by

of carried out to ensure that the logs and the indust light eating alloys, pickling, drawing, and

cations of welding topipe operations are continuing to pro- lines, and to high-tensile steals duce wire giving the required. high standard of conting adhesion.

It will be seen, therefore, that the primary requirement in vlee trode maquiacture is uniformly of quality of the raw materials.

All core wire is purchased to

Further, in view of the fact. rigid specifications. In the ease of mild steel these have been that the same type of core wire compiled after long experience is used for more than one type electrode-for example, of the qualities required, and of usually after close collaboration or at hand "Nico" MC with the research sections of the other steps have to be taken to prevent the possibility of mixing steelmaking industry.

Colour code

In view of the varying quality of strap used in steel manufacture These consist of colour-tipping and of different steelmaking the ends of the core wires after techniques it is now generally re- drying and in some cases of using cognised that the analysis of mild coating ingredients to give dis- steel casis for carbon, manganese,| tinctive colours. sulphur,, phosphorus, and silicon,

The number of different coating

wire during in Bouth Wales, mult

During extrusion rapid cheeks might completely spoil the run on concentricity are made con- ning properties of another.

To cover - this oven tempera. tinuously. For each type and gauge of electrode specificatior tures are checked periodically taken at fixed limite are set for the maximum and electrodes occentricity permissible.

frequent intervals for running is not sufficient as a basis for noterials used in the Murex range Any batches of electrodes show tests. The result of these tests forcecasting electrode perfor- of electrodes is in the region of ing eccentricity higher than the shows whether the electroder

ja hundred. As in the case of

have been dried to the specißed moisture-content.acanağa sa

mance,

Hot-cracking

wire, they are purchased to speel-permissible maximum is rejected

Electrode dryingTM In this connection particular cations, the requirements of

"Those test electrodes are also outside diameters of attention has been paid to the which are based on the results of The

experience.

electrodes, each type and gaug checked by shadowgraph for hot-cracking tendency of mild past

In addition to chemical analysis, of: which has a specific raave contricity as a final check on steel weld deposits and

not which is defined within narrow are also checked at the extru concentricity of finished electrodes has been devised, by means of

Weld metal tests limits

In every specification, on stage, which it is now possible to de-

extrusion. electrode

Standard -mild stool electrodes. tect quite small differences incalies may be included to cover After

travel through continuous belt havinst been checifed -for quality. hot.cracking tendency between pH value, particle size range,

surface area, and particle shape thermostatically controlled drying ut every stage of manufacture var different casts of wire.

It is therefore now routine prac-and density, where these are of ovens. Temperature changes and passed into stock. Intinellately tice to make test batches of plecable to variations

importance and known to bo drying times are speclied for each after pacing. As a check or type and gange, depending upon general quality, packets of these trodes on every east of wire and

the coating moisture content re-electrodes in all- types and gauges submit them to hot-cracking testa. Checks on powders

The various grades of

drawn from stock für routin quired. core Frequent checks. ensure that]

:| avido This may vary over a

checks on wett motül quality. wire required for the large range all materials maintain the quality range for different types of ele. All weld metal test specimens of special electrodes

with con required by the specification rodes and has a marked effect on are prepared and their mechanical rosion, heat, and creep resistance upon delivery, powders are stored their munning properties. Thus properties tested : ngüinst the properties are all subject to rigid in a bulk store from which they the cpating moisture content specification requirements of the chemical analysis to cover every camet be drawn until authority which is satisfactory for one type various classiäcatión sociciisa. cast,

based on test results is given.

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