Soldering Brazing and Wearfacing 6 (1).pdf

8/9/2019 Soldering Brazing and Wearfacing 6 (1).pdf

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CHAPTER 6

SOLDERING, BRAZING, BRAZE WELDING

AND WEARFACING

The information presented in chapter 5 covered the

joining of metal parts by the process of fusion welding.

In this chapter, procedures that do not require fusion are

addressed. These procedures are as follows: soldering,

brazing, braze welding, and wearfacing. These proce-

dures allow the joining of dissimilar metals and producehigh-strength joints. Additionally, they have the impor-

t ant advantages of not a f fect ing the hea t t rea tment or

warping the original metal as much as conventional

welding.

SOLDERING

Soldering is a method of using a fi l ler metal (com-

monly known as solder) for joining tw o metals w i thout

heat ing them t o their mel t ing points . Soldering is valu-

able to the Steelworker because i t is a s imple and fast

means for joining sheet metal, making electrical connec-

t ions, and seal ing seams against leakage. Addi t ional ly ,

it is used to join iron, nickel, lead, tin, copper, zinc,

aluminum, and many other al loys.

Soldering is not classi f ied as a welding or brazing

process, because the melting temperature of solder is

below 800°F. Welding and brazing usual ly take place

above 800°F. The one exception is lead welding that

occurs at 621°F. Do not confuse the process of SILVER

SOLDERING wi th so lder ing , for this process is

actually a form of brazing, because th

is a bove 800° F.

This chapter describes the foll

and materials required for soldering,

used to make soldered joints, and the

required to solder aluminum alloys.

EQUIPMENT

Soldering requires very li ttle eq

soldering jobs, you only need a heat

copper or iron, solder, and flux.

Sources of Heat

The sources of heat used for sol

ing to the method used and the equ

Welding torches, blow-torches, forge

some of th e sources of heat used. No

ing devices are used to heat the sold

supply the heat to the metal surfaces

solder. Sometimes, the heating devic

the metal directly. When this is dcareful to prevent hea t da mage to

surrounding material .

SOLDERING COPPERS.— A

(usually called a soldering iron) co

copper head and an iron rod with a ha


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Figure 6-2.—Soldering copper heads.

Figure 6-3.—Filing a soldering copper.

The handle, which may be wood or fiber, is either forced

or screwed onto the rod.

Soldering heads a re ava ilable in var ious sha pes.

Figure 6-2 shows three of the more commonly used

types. The pointed copper is for genera l soldering w ork

The stub copper is used for soldering flat seams that

need a considerable amount of heat. The bottom copper

is used for soldering seams t ha t a re har d to reach, such

as those found in pai ls , pans, trays, and other similar

objects.

Nonelectrical coppers a re supplied in pa irs. This is

done so one copper can be used as the other is being

heated. The size designation of coppers refers to the

weight (in pounds) of TWO copperheads; thus a refer-

ence to a pair of 4-pound coppers means that each

d d

Figure 6-4.—Tinning a copper (solder ammoniac).

Also, coppers must be filed and ret

ing or for a ny other rea son t ha t cau

solder coating. The procedure for

copper is as follows:

1. Heat the copper to a cherry

2. Clamp t he copper in a vise,

6-3.

3. File the copper with a sing

Bear down on the forward stroke, a

on the retur n st roke. Do not rock the

the tapered sides of the copper unti

smooth.

CAUTION

Remember tha t t he coppe

touch i t with your bare hands.

4. Smooth off the point of th e

off any sharp edges.

5. Reheat the copper until it is

the solder.6. Rub each filed side of the co

across a cake of sal ammoniac, as s

7. Apply solder to the copper u

may rub the solder directly onto the

on the cake of sal am moniac Do no


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Figure 6-5.—Tinning a copper (solder placed directly on copper).

Figure 6-6.—Forging a soldering copper.

powder form. Dissolve the powder in water according

to the directions and dip the soldering copper into the

solution and then apply the solder.

Forging Soldering Coppers.— Soldering coppers

ma y be reshaped by forging wh en they become blunt or

otherwise deformed. The procedure for forging a copper

is as follows:

1. File the copper to remove all old tinning and to

smooth the surfaces.

2. Heat the copper to a bright red.

3 Hold the copper on an an vil and forge it to the

Figure 6-7.—Presto-lite hea

4. Reheat the copper to a bri

f lat-faced hammer to remove as

possible.

5. File and tin the copper us

described procedure.

ELECTRIC SOLDERING C

tric soldering coppers, or soldering i

times a re called, a re built with int ern

soldering heads a re removable an

Tinning is basically the sa me with th

tip usually does not become cher

reshaping is not necessary, because

replaced.

Electric soldering irons are usua

cal work or other small jobs. They a

for this type of work, because th

auxil iary heating and they can be ma

as a pencil.

GAS TORCHES.— Ga s torc

combinat ion wi th soldering head a


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Soft Solder

There are many different types of solder being used

by industry . Solders ar e ava i lable in various forms th at

include bars, wires, ingots, and powders. Wire solders

are avai lable with or without a f lux core. Because of the

many types of solder available, this chapter only coversthe solders most commonly used by Steelworkers.

TIN-LEAD SOLDER.— The largest portion of all

solders in use is solders of th e tin-lead a lloy gr oup. They

have good corrosion resistance and can be used for

joining most metals. Their compatibili ty with soldering

processes, cleaning, and most types of flux is excellent.

In describing solders, it is the custom of industry to state

th e tin conten t first ; for exam ple, a 40/60 solder mea nsto have 40%tin and 60%lead.

Tin-lead alloy melting characteristics depend upon

the ratio of tin to lead. The higher the tin content, the

lower the melting temperature. Tin also increases the

wett ing abi l i ty and lowers t he cracking potent ial of the

solder.

The behavior of tin-lead solder is shown by thediagram in figure 6-8. This diagram shows that 100%

lead melts at 621°F an d 100%tin melts a t 450° F. Solders

tha t contain 19.5%t o 97.5%t in remain a solid unti l they

exceed 360°F . The eut ectic composit ion for tin-lead

solder is a bout 63% tin a nd 37%lead. (“Eutectic” mean s

the point in an al loy system that a l l the parts melt a t the

sa me t empera tu re.) A 63/37 solder b ecomes completely

liquid at 361°F. Other compositions do not. Instead, they

remain in the pasty st age unti l the tempera ture increases

to the melting point of the other alloy. For instance,

50/50 solder ha s a solid t empera tur e of 361° F a nd a

l iquid temperat ure ra nge of 417° F. The past y t empera -

ture range is 56°F—the difference between the solid and

the liquid.

Solders with lower tin content a re less expensive

and primari ly used for sheet metal products and otherhigh-volume solder requirements. High tin solders are

extensively used in electrical work. Solders with 60%

t in or more are called f ine solders and are used in

instrument soldering where temperatures are cri t ical .

TIN-ANTIMONY-LEAD SOLDER.— Ant imony

Figure 6-8.—Tin-lead alloy constitu

TIN-ZINC SOLDER.— Sever

have come into use for the joining o

The 91/9 a nd 60/40 tin-zinc solder s a

pera tu re ra nges (above 300° F), an d ttin-zinc alloys are normally used as p

LEAD-SILVER SOLDER.— L

are useful where strength at modera

tures is required. The reason lead by it

is that it does not normally wet steel, c

and its alloys. Adding silver to lead re

more readily wet steel and copper. F

for s t raight lead-si lver solders ar e ra t

solders are susceptible to humidity an

storage. The wett ing an d f low char

enhanced as well as an increased resi

by int roducing a tin content of 1%.

Lead-silver solders require high

peratures and special fluxing techniq

zinc-chloride base flux or uncoatedmended, because rosin fluxes decomp

temperatures.

TIN-ANTIMONY SOLDER.—

solders ar e used for refrigerat ion w

copper to ca st iron joints The m ost c


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Table 6-1.—Fluxes Used for Soldering Some Common Metals

These solders and the procedures for their use are The most commonly u sed corr

also listed in the Weld in g Mat er i a ls Hand book,

NAVFAC, P -433.

Fluxes

Scale, rust, and oxides form on most metal surfaceswhen exposed to air , a nd heat ing accelerates this forma-

t ion. Solder wi l l not adhere to or wet the metal unless

these pollutants are removed. Fluxes are chemical com-

pounds used to clean and maintain the metal surfaces

during the soldering process. They also decrease the

surface tension of the solder, making i t a bet ter wett ing

agent. Fluxes are manufactured in cake, paste, liquid, or

powder form and are classified as either noncorrosiveor corrosive. Ta ble 6-1 shows t he fluxes tha t a re nor-

ma lly used for soldering common m etals .

NONCORROSIVE FLUXES.— Noncorrosive

fluxes ar e for soldering electrical connections an d for

other work that must be free of any trace of corrosive

residue. Rosin is the most commonly used noncorrosive

f lux. In the solid sta te, rosin is inactive and noncor-

rosive. When heated, it melts and provides some fluxinga ction. Rosin is ava ilable in powder, pa ste, or liquid

form.

Rosin fluxes frequently leave a brown residue. This

residue is nonconductive and sometimes difficult to

ammoniac (ammonium chloride)

These fluxes are frequently used in

paste form. The solvent , i f presen

work heat s, leaving a layer of soli

When the metal reaches the solderi

layer of f lux m elts , pa rt ia l ly decom

hydrochloric acid. The hydrochlori

oxides from the work surfaces and

them ready for soldering.

Zinc chloride (sometimes cal

KILLED ACID) can be made in

safety precautions are followed. To

ride, pour a small amount of muriati

cial form of hydrochloric acid

a cid-resistan t conta iner an d th en

zinc. As you a dd t he zinc, the a cid b

a resul t of a chemical react ion tha t

ride and hydrogen gas. Keep adding

to the mixtur e unti l the l iquid no lo

bles. At this point, the reaction is co

dilute the l iquid in the container w

of water. Make only enough as req

before use. If any is leftover, store glass conta iner .

WARNING

remove. The removal problem can be reduced by addingWhen diluting the a cid you


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ha zar d a s w ell as an explosive. P repare zinc chloride

under a ventilation hood, out in the open, or near open-

ings to the outside to reduce inhalation of the fumes or

the da nger of explosion. I t i s essentia l tha t precautions

be taken to prevent flames or sparks from coming in

contact with the l iberated hydrogen.

Another t ype of corrosive flux in use is known a s

SOLDERING SALTS.Commercially prepared solder-

ing sal ts are normal ly manufactured in a powder form

tha t is wa ter soluble tha t a l lows you to mix only the

amount needed.

After a corrosive flux has been used for soldering,

you should remove as much of the flux residue as

possible from the work. Most corrosive fluxes are water

soluble; therefore, washing the work with soap and

wa ter and then r ins ing thoroughly w i th clear w at er

usually removes the corrosive residue. To lessen dam-

age, you should ensure the work is cleaned immediately

after the soldering.

SOLDERING TECHNIQUES

The two soldering methods most often used

are soldering with coppers or torch soldering. The

considerations that apply to these methods of soldering

are as fol lows:

1. Clean all surfaces of oxides, dirt, grease, and

other foreign matter.

2. Use the proper flux for the particular job. Somew ork requires t he use of corrosive fluxes, while other

work requires the use of noncorros ive f luxes .

Remember, the melting point of the f lux must be

BELOW the melting point of the solder you are going

to use.

3. Heat the surfaces just enough to melt the solder.

Solder does not stick to unheated surfaces; however, you

should be very careful not to overheat the solder, thesoldering coppers, or the surfaces to be joined. Heating

solder above the work temperature increases the rate of

oxidat ion a nd cha nges the proport ions of t in an d lead.

4. After making a soldered joint, you should

remove as much of the corrosive flux as possible.

Figure 6-9.—Soldering a

heat the joint with a soldering copper

solder melts and joins the pieces to

source of heat and keep the parts f irm

the solder has completely hardened

due from the soldered area complete

Seam Soldering

Seam soldering involves runnin

along the edges of a joint. Solder

inside w henever possible. The bes

this process is soldering coppers, b

better control of heat and cause less

Clean and f lux the areas to be s

is not already tacked, grooved, rivete

together, tack the pieces so the wor

Position the piece so the seam does

the support. This is necessary to pre

the support. After you have firmly

together, solder the seam.

Heat the area by holding the c

work. The meta l must absorb eno

copper to melt the solder, or the sol

Hold the copper so one tapered side

aga ins t the seam, a s shown in fig

solder begins to f low freely into th


7/18

Figure 6-11.—Making solder beads.

moving the joint. When you use a corrosive flux, clean

the joint by r ins ing i t wi th wa ter an d then brushing or

wiping i t wi th a clean, damp cloth.

Riveted seams are often soldered to make them

water t ight . Figure 6-10 shows the procedure for solder-

ing a r iveted seam.

Solder beads, or solder shots, are sometimes used

for soldering square, rectangular, or cylindrical bottoms.

Figure 6-12.—Soldering a bott

Figure 6-10.—Soldering a riveted seam.

6-12. Hold the copper in one positi

starts to f low freely into the seam.

slowly along the seam, turning the w

more beads a s you need them a nd renecessary.

To heat a n electric soldering c

plug it in. Otherwise, the procedure is

that just described. Be very careful n

soldering copper overheat. Overheatin

electrical element a s well as da ma

t inning ,

Soldering Aluminum Alloys

Soldering aluminum al loys is m

soldering ma ny other meta ls . The di

mari ly from the layer of oxide that

minum alloys. The thickness of the la

type of alloy and the exposure condi

Using the proper techniques, man

alloys can be successfully soldered. W

al loys are usual ly easier to solder th

alloys. Heat-treated aluminum alloys

ficult to solder as are aluminum allo


8/18

The first step in soldering aluminum is to clean the

surfaces and remove the layer of oxide. If a thick layer

of oxide is present, you should remove the main part of

it mechanically by filing, scraping, sanding, or wire

brushin g. A thin lay er of oxide ca n often be removed by

using a corrosive flux. Remember, remove any residual

flux from the joint after the soldering is finished.

After cleaning and fluxing the surfaces, you should

tin the surfaces with aluminum solder. Apply flux to the

work surfaces and to the solder. You can tin the surfaces

with a soldering copper or with a torch. If you use a

torch, do not apply heat directly to the work surfaces, to

th e solder, or to th e flux. Inst ead, pla y th e torch on a

nearby part of the work and let t he heat conduct t hrough

the metal to the work area . Do not use more heat t ha n is

necessary to melt the solder and tin the surfaces. Work

the aluminum solder well into the surfaces. After tinning

the surfaces, the parts may be sweated together.

Another procedure you can use for soldering alumi-

num a l loys is to t in t he surfaces w ith a n a luminum solder

and then use a regular tin-lead solder to join the tinned

surfaces. This procedure can be used when the shape of

the part s prevents t he use of the sw eating m ethod or

demands a large amount of solder. When using tin-lead

solder with aluminum solder, you do not have to use

f lux.

After soldering is complete, you should clean th e

joints w ith a wire brush, soap and wa ter, or emery c loth.

Ensure that you remove all the flux from the joint since

any flux left will cause corrosion.

BRAZING

Brazing is the process of joining metal by heating

the base metal to a t emperat ure above 800°F a nd adding

a nonferrous f i ller metal th at melts below the base meta l .

B ra zing should not be confused with braze w elding,

even though these two terms are of ten interchanged. In

brazing, the filler metal is drawn into the joint by capil-

lary action and in braze welding i t is distributed by

tinning. Brazing is sometimes called hard soldering or

silver soldering because the filler metals are either hard

solders or silver-based alloys. Both processes require

EQUIPMENT

Brazing requires three basic i

source of heat, fi l ler metals, and flu

paragraphs these i tems are discussed

Heating Devices

The source of heat depends on t

of brazing required. If you are doin

and the pieces a re smal l enough, the

furnace and bra zed al l a t once. Indiv

mounted in groups for assembly lin

use individual oxyacetylene or Mapp

braze individual items.

Filler Metals

Fil ler metals used in brazing are

or a lloys tha t ha ve a melting temp

adjoining base meta l , but a bove 80

must ha ve the abi li ty to wet a nd b

meta l , ha ve sta bil ity , an d not be ex

The most commonly used filler me

based a lloys. Br azing f i l ler meta l i

wire, preformed, and powder form.

Brazing filler metals include t

groups:

1.

2.

3.

4.

5.

6.

7.

8.

Silver-base alloys

Aluminum-silicon alloys

Copper

Copper-zinc (brass) alloys

Copper-phosphorus alloys

Gold alloys

Nickel alloys

Magnesium al loys

Fluxes

Brazing processes require the us


9/18

adjoining base meta ls and permits t he f i ller to penetrat e

the pores of the metal.

You should carefully select the flux for each brazing

operation. Usually the manufacturer’s label specifies the

type of metal to be brazed with the flux. The following

factors must be considered when you a re using a flux:

Base meta l or meta ls used

Brazing fi l ler metal used

Source of heat used

Flux is ava i lable in powder, l iquid, and paste form.

One method of applying the flux in powdered form is to

dip the heated end of a brazing rod into the container of

the powdered flux, allowing the flux to stick to the

brazing rod. Another method is to heat the base metal

slightly and sprinkle the powdered flux over the joint,

a llowing t he flux to part ly melt and st ick to the base

metal. Sometimes, it is desirable to mix powdered flux

with clean water (disti l led water) to form a paste.

Flux in either t he past e or liquid form can be a pplied

with a br ush to the joint . B etter results occur when the

fi ller meta l is a lso given a coat .

The most common t ype of flux used is borax or a

mixture of borax with other chemicals. Some of the

commercial fluxes contain small amounts of phospho-

rus and halogen salts of either iodine, bromine, fluorine,

chlorine, or astatine. When a prepared flux is not avail-

able, a mixture of 12 parts of borax and 1 part boric acid

may be used.

WARNING

Nearly a ll fluxes give off fumes tha t ma y

be toxic. Use them only in WELL-VENTI-

LATED spaces.

J OINT DESIGN

In bra zing, the f i ller metal is distr ibuted by capil lary

action. This requires the joints to have close tolerances

a nd a good fit to produce a st rong bond. Br azing ha s

th b i j i t d i (fi 6 13) l b tt d f

Figure 6-13.—Three types of common join

in thickness of the final product. For

the overlap should be at least three

of the metal. A 0.001-inch to 0.003

tween the joint members provides t

with silver-based brazing filler meta

precautions to prevent heat expan

joints that have initial close toleranc

Butt J oints

But t joints a re l imited in size to

section so maximum joint strength

joint strength can be maximized by

clea ra nce of 0.001 to 0.003 of an i

braze. The edges of the joint must b

maintain a uniform clearance betw

joint. Butt joints are usually used

th ickness of a la p joint is und esira

metal thickness is objectionable a

strength, the scarf joint is a good ch

Scarf Joints


10/18

Figure 6-14.—J oints designed to produce good brazing results.

Figure 6-15.—Some well-designed joints that have been prepared for brazing, and some poorly designed joints show

Figu re 6-14 shows some variat ions of butt and lap

joints designed to produce good bra zing result s. A com-

parison of good and bad designed joints is shown in

figure 6-15.

BRAZING PROCEDURES

voids in the joint or accidental moveme

and cooling operations.

Surface Preparation


11/18

Figure 6-16.—Brazing a butt joint.

because abrasive particles or oil might become embed-

ded in the meta l .

Work Support

Mount t he w ork in position on firebricks or oth er

suitable means of support , and i f necessary, clamp i t .

This is important because if the joint moves during the

brazing process, the f inished bond will be weak and

subject to failure.

Fluxing

The method of application varies, depending upon

the form of f lux being used and the t ype of meta l you

ar e bra zing. Refer t o the ma terial on fluxes previously

described. I t is extremely important that the f lux is

suitable for your job.

Brazing

The best way to determine the

joint , as you heat i t , is by watching

flux. The flux first dr ies out a s t he m

off a t 212° F. Then the flux turns milk

to bubble at about 600°F. Final ly , i

liquid at about 1100°F. That is just

temperature. The clear appearance o

tha t i t is t ime to star t a dding the f i lle

the joint, not t he f lame, should meWhen the temperature and al ignm

f i l ler metal spreads over the metal s

joint by capillary attraction. For go

the filler metal penetrates the compl

meta l. Figure 6-16 shows a good po

and f i l ler metal when brazing a butt

St op heat ing as soon a s the f il

pletely covered the surface of the jo

cool slow ly. Do not remove th e sup

move the joint in a ny w ay unti l the

the filler metal has completely solid

Finally, clean the joint after i


12/18

Table 6-2.—Silver Brazing Filler Metal Alloys

Silver Brazing compa ra ble to those made by fusio

Often, you w ill be called on to do a silver bra zing

job. Ta ble 6-2 lists different types of si lver brazing

al loys and their characterist ics. A popular way to apply

silver bra zing meta l on a tubing is to use silver a lloyrings, as shown in figure 6-17. This is a practical a nd

economical wa y to a dd silver a lloy w hen using a pro-

duction line system. Another method of brazing by using

prepla ced bra zing shims is shown in fig ur e 6-18. The

requirements of each job varies; however, through ex-

the destruct ion of the base metal ch

welding is also called bronze weldin

Bra ze welding has ma ny a dvan

welding. It al lows you to join dis

minimize heat distort ion, and to red

heating. Another side effect of bra

elimina t ion of stored-up str esses t ha

in fusion w elding. This is extremel

repair of lar ge cast ings. The disadva

of strength when subjected to high tem


13/18

Figure 6-17.—Silver-brazed joints designed to use preplaced silver alloy rings. The

perfect fillets, and no further finishing is necessary.


14/18

Table 6-3.—Copper Alloy Brazing Filler Metals

Filler Metal BRAZE WELDING PROCEDUR

The primary elements of a braze w elding rod a re

copper and zinc. These elements improve ductili ty and

high strength. Smal l amounts of i ron, t in, a luminum,

manganese, chromium, lead, nickel, and silicon are also

added to improve the welding characteristics of the rod.

They aid in deoxidizing the weld metal, increasing flow

action, and decreasing the chances of fuming. Table 6-3

l ists some copper alloy brazing fi l ler metals and their

use. The most commonly used are brass brazing alloy

an d na val bra ss. The selection of the proper brazing filler

metal depends on the types of base metals.

Flux

Proper fluxing is essential in braze welding. If the

surface of the metal is not clean, the filler metal will not

f low smoothly a nd evenly over the w eld a rea. E ven af ter

mechanical cleaning, certain oxides often remain and

interfere with the flow of the filler metal. The use of the

correct flux eliminates these oxides

Edge preparation is essential in

edges of the thick parts can be bev

machining, or filing. It is not necessa

par ts (one-fourth inch or less). The m

and clean on t he underside as wel l a

joint. Cleaning with a fi le, steel wool

removes most foreign matter such a

oxides. The use of the proper flux co

and permits the tinning to occur.

After you prepare the edges, th

aligned and held in position for the b

ess. This can be done with clamps

combination of both. The next step

assembly to reduce expansion and meta ls during w elding. The meth o

upon the size of the casting or assem

Once preheating is completed,

tinning process. Adjust the flame

slightly oxidizing flame and flux th


15/18

Figure 6-19.—Braze welding cast iron, using the backhand method.

an example of tinning being used with the backha nd

method of welding.

Temperature control is very important . I f the base

metal is too hot, the filler metal bubbles or runs around

like beads of water on a hot pan. If the filler metal forms

lit t le balls and runs of f the meta l , then the base metal istoo cold.

After the base metal is t inned, you can star t adding

beads of f i ller meta l to th e joint. Use a slight circular

motion wi th the torch and run the beads as you would

in regular fusion welding. As you progress, keep adding

f lux to the w eld. I f the w eld requires several passes, be

sure that each layer is fused into the previous one.

After you have completed the braze welding opera-

tion, heat the a rea a round the joint on both sides for

several inches. This ensures an even rate of cooling.

When t he joint is cold, remove an y excess flux or a ny

other part icles wi th a s t i f f wire brush or s teel wool .

WEARFACING

WEARFACING is the process you use to apply an

overlay of special ferrous or nonferrous alloy to the

surface of new or old parts. The purpose is to increase

their resistance to abrasion, impact, corrosion, erosion,

or to obtain other properties. Also, wearfacing also can

are put into service for the first time

different methods of wearfacing; ho

cussion we only cover the oxygas pr

Wearfacing provides a means o

cutting edges and can reduce wear b

It is an excellent means for reducing

and downtime. These and other adv

ing add up to increased service life

of equipment.

Wearfacing wi th the oxygas f la

spects, similar to braze welding. Th

generally consist of high-carbon fille

chromium or a Cr-Co-W alloy, but, special surfacing al loys are require

w earfa cing is a process in wh ich a la

composition is bonded to the sur

another composition.

The process of hard-surfacing is

carbon al loy and stainless s teels as

cast iron. It is not intended for alumi

or bronze, as the melt ing point of th

hibits t he use of the ha rd-surfa cing p

to increase th e hardn ess of alumin

zinc-aluminum solder to the surface.

bronze can be improved in their w

WEARFACING MATERIALS f If d b h


16/18

WEARFACING MATERIALS

A surfacing operation using a copper-base alloy

filler metal produces a relatively soft surface. Work-

hardening bronzes are soft when applied and give

excellent resistance against frictional wear. Other types

of al loys are ava ilable that produce a surface that is

corrosion a nd w ear resistant at high temperat ures. Wear-facing mat erials are produced by ma ny di f ferent ma nu-

facturers; therefore, be sure that the filler alloys you

select for a particular surfacing job meet Navy specifi-

cations.

Two types of hard-surfacing materials in general use

in the Navy are iron-base al loys and tungsten carbide.

Iron-Base Alloys

These materials contain nickel, chromium, manga-

nese, carbon, and other hardening elements. They are

used for a number of applications requiring varying

degrees of ha rdness. A St eelw orker frequently w orks

with iron-base alloys when he builds up and resurfaces

parts of construction equipment.

Tungsten Carbide

You use this for building up wear-resistant surfaces

on steel parts. Tungsten carbide is one of the hardest

substances known to ma n. Tungsten carbide can be

applied in the form of inserts or of composite rod. Inserts

are not melted but are welded or brazed to the base

metal , as shown in figure 6-18. The rod is a pplied w ith

the sam e surfacing technique as tha t used for oxygas

welding; a slightly carburizing flame adjustment is nec-

essary.

WEARFACING PROCEDURES

Proper preparat ion of the metal surfaces is an im-

portant part of wearfacing operat ions. Make sure that

scale, rust , a nd foreign ma tt er are removed from themeta l surfaces. You can clean t he meta l surfaces by

grinding, ma chining, or chipping. The edges of grooves,

corners, or recesses should be well rounded to prevent

base metal overheating and to provide a good cushion

for the wearfacing material .

wearfacing. If in doubt as to when t

you should check with your leading

Preheating

Most par ts tha t require wearfa c

with a neutral welding f lame bef

should use a neutral f lame of ab

preheat to a temperature higher th

perature of the metal or to a temper

the formation of scale.

Application

In general , the torch ma nipulat i

ing procedures are similar to braziever, higher temperatures (about 22

for w earfacing, and t ips of one or tw

normal a re used.

To begin, you heat a smal l are

sweeping torch movement until the

metal takes on a sweating or wet ap

surface of the base metal is in this

end of the surfacing al loy into the fmelt. Do not stir or puddle the allo

the surface area has been properly

flows freely over the surface of the

Being able to recognize a sweat

t ia l for surfacing. Sweat ing occurs

steel with a carburizing f lame to a

ture. This carburizes an extremely t

metal, approximately 0.001 inch thlayer has a lower melt ing point than

a result, it becomes a liquid, while t

remains a solid. This liquid fi lm p

for flowing the fi l ler metal over the

metal. The liquid fi lm is similar to

purpose as a tinned surface in solde

ing.

When you heat steel with a carbu

becomes red. As heating continues

lighter and lighter until a bright whit

this point, a thin film of liquid, carbu

on the surface. Surfacing al loy adde

over the sw eated surface and absorb


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Figure 6-20.—Grader blade with hardfacing material applied to cutting edge.

cone. Unless the excess fuel-gas flame is used, the gra der blade is usually wea rfaced

proper ba se meta l surfa ce condition ca nnot be devel- process. If the electric arc process is

oped. Without this condition, the surfacing alloy does may use the oxygas torch.

not spread over the surface of the part. Weldi ng M ater i als H andbook,

Figure 6-20 shows a grader blade wi th a deposi t of an excellent source of information

hardfacing material appl ied along the cut t ing edge. A struction equipment.


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Documents

Soldering Brazing and Wearfacing 6 (1).pdf