A brief description is given of different groups of high chromium steels (rustless iron and stainless steels) according to their composition and more generally accepted names. The welding procedure for a given group will be much the same regardless of the slight variations in chemical composition which may exist within a certain group. Information is given for the tensile properties (yield point and ultimate strength) of metal sheets and welds before and after annealing on coupons one and one-half inches wide. Since welds in rustless iron containing 16 to 18 percent chromium and 7 to 12 percent nickel show the best combination of strength and ductility in the 'as welded' or annealed condition, it is considered the best alloy to use for welded construction

Miller, W B

English

NASA Technical Reports Server

TECHNICAL I?OTES
l:A’i’IO?fALADVISORY CO1,WITTEEFOR A3XOKAUTICS
,
No. 290
WELDING OF’HIGH CHFUMIUM STEELS
By W. B. Miller
-Union Carbide and Carbon Research Laboratories, Inc.
.
,.
Washington
June, 1928
https://ntrs.nasa.gov/search.jsp?R=19930081018 2020-03-17T04:25:07+00:00Z
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XATIOI?A.LADVISORY CO&MITTEE FOR AERONAUTICS.
TECHNICAL ifOTENO. 290.
The high chromium steels designed to resist various forms ,
of corrosion are generally known under a,laxge vaxiety of trade
names. Each name may apply to a group of alloys in which the
percentage content of some ele~lentor elements varies according .==
to the specific properties desired. Tl+eelement chromium is
the most important of the corrosion–resisting group. The other _
constituents such as nickel, silicon, manganese and car-eon@aY ...
an important part in this class of al.lo..ys,especially with re-
gard to the welding problem. No attempt will be made to clas–
sify the different alloys according to their trade names as such
a classification would require needless repetition and would be
confusing. A brief description will be given of the different
groups according to their composition and zaoregenerally accept-
ed naiies. The welding procedure.for a given group will there-
fore be nuch the sae regardless of the slight v~iations in
—
chemical composition which may exist within a certain group.
Rustless iron is considered here as that group of alloys
containing between 121 and 20~ chromium with less than l15$
carbon, the balance being chiefly iron with normal amounts of
manganese and silicon. Within this composition range there are
two classes of alloys which me commercially available, the class
. N.A.C.A. Technical Note No. 290 2
being determined by the chromium content. The alloys containing
12-14% chromium constitute one t-ype,aad those with 14-2@~ chrom-
ium, the other type. Alloys containing 12-14’$chromium are more
susceptible to heat treatment than those containing 18–20% chrom–
.
ium. The resistance to corrosion increases with the chromium
content.
Stainless steel belongs to the group containing 12-14% ““
chromium with upwards of .2’$carbon. The difference between
rustless iron and stainless steel lies in the carbon content.
Stainless steel is very susceptible to heat treatment, its cor-
rosion resistance depending on its heat treatment and surface
finish. On account of the aiz-hardening properties of the alloy,
welds and metal adjacent to the weld in stainless steel will be
hard and brittle, This brittle condition may be remqdied some-
what by annealing followed by slow furnace cooling. After this
treatment the metal will not have its maximum stainless proper-
“9
ties which are developed only by quenching and drawi%g operations
followed by proper surface ftnishing. On aCCOUnt of the had-
ness and brittleness of welds in stainless steel and the diffi-
culty of properly heat tr$ating and surface finishing the mater-
ial after welding, stainless steel is unsuitable for welded
parts subjected to corrosion, stress and vibration unless sup-
—
.—
ported by other metals.
The addition of nickel to rustless iron produces another
class of alloys. Nickel has a marked effect upon the”physical
mX.A.C.A. Technical Kcte Nc. 290 3
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Properties of chromiuiiiron alleys. The amount @f nickel used
varies from 7-12% in alleys suitable for airnraft construction.
An all~y containing 16-18$ chromium and 7–122 niqkel is charac-
terized by a combination of physical and corrosion–resisting
qualities rendering it particularly suitable for aircraft pro-
ducti~n, Since welds and metal adjacent to the weld in this ~a–
teriel will be ductile and require ns subsequent heat treatment.
The chromium and nickel may be varied somewhat without materisll-
ly altering its corrosi~n–resisting properties, which are de–
.
pendent in large measure on the chrcmium content. At.out1* each ._
of manganese and silicon improve the welding quality of the .—
higher chromium alleys with or withcut nickel.
All greups aforementioned are commercially available in
the forx of forged or rolled shapes. Seamless tubing is now
.—
available with all classes except the stainless steel. Welded
tubing made from strip or sheet may also be obtained,‘especi–
ally in sizes under 311in diameter.- Relatively thin material
will be used in aircraft work and for that reason the weldink
.—
methods to be described will pertain more particularly to the
thin gauges. It is practically necessary to use the oxyacety-
lene method of welding for material 16-gauge or lighter. Al-
though the metallic arc method may be used with certain reserva- .
tions, it is not ge~.erallyapplicable to the light gauge.
Approximately the same preoedue may be followed in weld-
ing all classes of al?ys herein described by the oxyacetylene
.X,A,C.A. Technical Note ito.290 4
.
method; the chief difference lies particularly in the after
treatment. The general procedure will therefore be described
and such details as necessary for any particular class will be
btought OUt. In the discussion to follow, it is assumed that
the materisJ-is in sheet form of 16-gauge or lighter.
It is desirable, where possible, to flange the edges which ,_
are to be welded; this is especially true for sheet lighter
than 16-gauge. Butt welding without flanging the edges is per–
?nissiblewith sheet 16-ga~~e or heavier. A flange about 1/161!
wi.(,ie
down,
will furnish the requisite amount of material for melting
—
thus eliminating the use of a filler rod. For filling
small holes or reinforcing; welding rods of the same composi–
.
tion as the sheet being welded should be used. It is advisable
. to clean the scale from the edges to be joined and they should
be painted or coated with a special flux developed for this
.
.
class of work. This flux is now on the ‘marketunder the trade
naae of ‘I(lronaloyFlux.’f To obtain best results, the importance
—
of this flux camnot be stressed too ,strongly. Wherever possible
pickled material should be used, as this insu-es a surfaco free
from objectionable oxide. At the present time the greatest ap-
plication of welding to aircraft is in fuselage construction,7
which involves the welding together of v~ious miter joints.
With this construction the same design of joint can be welded
in the chrome alloy tube as is now welded in ordinary tubes.
Flanged joints are not used in welding together the ends of
tubing.
*.
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l
N.A.C.A. Technical Note No. 290 . 5
A neutral oxyacetylene flame should be maintained during
the welding operation.,i.e~, it should not contain an excess of
either acetylene or oxygen, The neutral point is determined by
the appearance of the inner cone of the flame and is easily
reco~ized by those familiar with the use of am oxyacetylene
blowpipe. An excess of acetylene especially should be avoided
it will cause an appreciable increase in the carbon content
the weld, increasing the hardness and lowering the ductility
the weld metal. An increase in c~bon will also lower the
resistance of the weld metal to corrosion. An excess of oxygen
results in the formation of a refractory slag resulting in poor
quality welds. Welding should be accomplished with a flame
just large enough to secure satisfactory fusion, since a large . ._
excess of heat causes the metal to boil, tesulting in porous
.
welds.
Rustless iron has a tendency to be brittle in the weld
metal and in that portion of the base metal adjacent to the weld
as a result of the high temperature attained during welding.
Rustless irons, particularly the 12-14% chromium grade, are sub-
ject to air hardening and require annealing to restore tough-
ness to=the weld met&1 and base metal adjacent to the weld.
Proper subsequent heat treatment will remedy the brittleness to
a large extent. However, it is not always possible to apply a
heat treatment because of size or other features of construc-
tion. Good results are obtained by heating the welds to 650-
N,A.C.A. Technic~ Note No. 290 6
750°C for one-half hour and cooling slowly. The torbh is often
utilized for applying the heat where it is not possible to emplOY
furnaces. When using the torch for annealing, great care must
be exercised so as not to heat the material above
ing to just below the critical point is necesssXy
soften rustless iron. The material after heating
800°C. Heat-
in order to
to 650–75C10C
may be air-cooled.
ing will depend on
about five minutes
some good.
The benefit to be derived from torch anneal-
tetiperatureand time of lieating. Usua Zy
within the above temperature range will t-o
*
Rustless irons which contain appreciable amunts of nickel
are not subject to this brittleness and are quite ductile ir.t>e\
!ta8 ~~eldedllconditiOn. These alloys are austenitic under all”
conditions of heat treatment, consequently they do not air
harden. Weld metal cooled eithe~ rapidly or slowly is conse-
quently malleable and ductile and requires$no heat tre%.tment.
.
However, the tensile strength and ductility are enhanced by a
water quench from 1050°C. On account of distortion, it.would
not ‘be feasible to apply this treatment to aircraft welds.
In order to show what results may be obtained with weldst
in the various types of alloys discussed, three compositions in —
the form of 18-ga~”e sheet were used as follows, all aateri~
being annealed before welding ti ensure starting with material
in the same condition. The rustless irons containing 12-14$
chromium and 14-2@0 chromium with no nickel were annealed at
4
*.
N.A.C.A. Technical Note No. 290 ?
750°C, a temperature commercially used. The nickel containing -.
rustless iron was annealed at 1050°C to impaxt maximum ductility.
1. Rustless Iron 12-14% Cr.
Caxbon .11*
Mangw.ese l 335
Silicon .39$
Chromium 12.30~
Thickness .0541J
Suface condition - pickled
Annealed 30 minutes at 750°0, air-cooled.
2/ Rustless Iron 14-20~ Cr.
Carbon .Oq%
Manganese .29$
Silicon 1.05f
Chromium 17.21$
Thickness eo531~
Surface condition - pickled
Annealed 30 minutes at 750°C, air-cooled.
3* Rustless Iron 16-18~ Cr. 7-12~ l?i.
Carbon .124
Manganese .32+
Silicon .13$
Chromium 17.42$
Nickel 7.58$
Thickness .04611
Surface condition - pickled
AnneXled 1 hour at
Welds were made by the
flmges. The flanged edges
1050°C, water-quenched.
flange method using 1/1611wide
to be welded were painted with a
water paste
ment”of the
Only enough
of “Cromdoy Flux,‘1clamped in a jig to ensure align–
edges, and welded with a neutrsl oxyacetylene flaae.
heat was used to obtaim satisfactory fusion. The
Melting down of the two 1/1611flanges gave a weld 1/8’!to 3/16!;
wide with 50-?5$ reinforcement. It was not advisable to grind
off the reinforcement on account of the danger of producing thin
f&
N.A.C.,A..Technical Note No. 290 8
‘areasat the edge of the weld.. Coupons from welds in each type
of material were tested in the ‘as weldedl[condition and after
torch and furnace annealing;.the temperatures for furnace eanea,l.
ing were the same as for the sheet before welding.. Bends were
made transverse to the line of welding which gave an indicatiofi
of the ductility of the weld and adjacent metal.
The tensile properties of the sheet and welds before ant
after annealing were determined on coupons 1-$’1wide. A ~r:;j~t~;jfl
test piece is nonhomogeneous, the weld having a higher yield
point than the base metal. When such a test piece is tested in
tension, the “Dasemetal adjacent to the Hold i~ n~t free tc
elongate due to the propping or staying actiml Qf ZLC &:ji:1:::+?
9 weld metal. Consequently, the per cent elongation obtained in
.
—
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-—
.=--
a tensile test of a welded coupon does not necessarily express
.
the true ductility of the weld rnet~ or met~ adjacent to the
weld. When the weld has a higher yield poi~t than the base
metal, no appreciable lateral contraction t~es place at the
weld. As a measure of the ductility of the weld metsL, bend
tests are used, the test being evaluated by measuring directly
the per cent elongation in the outside fibers. On account of
the thinness of the sheet it was impossible to measure the per
cent elongation in the outside fibers in the bend test. The
angle of bend was therefore measured. This method of evaluating
the bend test does not give qu~titative data, but does show
# the relative ductility of the welds in the different types of
alloys.
9N.A.C,A. Technical Note No. 290
1. Rustless Iron - 12.30~ Chromium
Sheet as lb. per sq.in. ~ elonga-
received Yield Ultimate tion in 211 Remarks
coupon point strength over weld
R1-1 53,000 ~8,200
2 54,300 ~9,100
Bend test
Sheet
annealed
RIA- 1 49,100 77,400
2 48,600 7~,ooo
Bend test
As ~yelded
R 1 A W-1 - 23,800
2 32,4oo 43,TOO
3- 16,800
Bend test
Torch
annealed
R I T A-1 55,350 76,400
Bend test
Furnace
annealed
R I F A-1 46,700 70,000
2 43,400 !’6,200
3 43,900 ~7,200
4 46,700 65,300
5 46,~00 ~5,800
6 41,600 60,200
Bend test
36.0
31.0
180°
33.0
34.0
180°
0
4.0
0
330
.
8~~5
6.0
8::
4,0
1100
4.5
140°
Z elongation taken over
fracture
II“
. .
11
II
Broke in sheet adjacent
to weld
II
Broke ~.nsheet and w3.C. .
Broke in weld
Broke in edge of weld
II 1’sheet
tl II
II
‘1e~e of weld
11
‘1sheet snd edge
of weld
Broke in weld. Weld
cracked.
r, N.A.C,A. Technical lToteNo. 290 10
2. Rustless Iron - 17.212 Chromium
Sheet as lb. per sq,in. ~ elonga- .
received Yield Ultimate tion in 21r Remarkscoupon point strength over weld
EN-1 ~ elongation in 211
2
Sheet ‘
annealed
EN A-1
2
As welded
ENAW-1
2
3
Torch
annealed
1
2
3
62,400 76,400
64,TOO 77,800
Bend %~st
46,~00 75,400
46,650 74,700
Bend test
47,400
2y,200
41:500 53,400
Bend test
68,250
46,100 65,300
49,100 73,300
Bend test
Furnace
annealed
ENFA-1
2
3
4
5
6
?4,490
55,000
52,~00
49:100
46,200
Bend test
31.5
31.0
180°
30.0
28.0
180°
0’
0
1,0
250
5*5
4.0
9,0
110°
11.0
1%
14.0
13.0
10.5
150°
over fracture .
II
II
H
Broke in edge of weld
Coarse crystalline
II
[1
Broke in sheet adjacent
to weld
II
Broke in sheet outside
211gauge marks
Broke in sheet adjacent
to weld
Broke in weld
If II sheet
II !1 II
11 !1 ![
II II II
?l N.A.C.A. Technical Note No. 290 11
3* Rustless Iron - 1~.42~ Chromium, 7,58* Nickel
Sheet as lb. per sq.in. ~ elonga-
received Yield Ultiinate tion in 2![ Remarks
coupon point strength over weld
2 52,600 100,300
Bend test
Uu.ti [Q GLULL~tLULUIL -LIL O
over fracture
67.5 If
180°
Sheet
annealed
SAA-1
2
As welded
SAA W-1
z
3
b
Torch
annealed
SAT A-1
2
Furnace
annealed
SAF A-1
2
3
4
:
105,400
58:800 103,300
Bend test
55,500 65,000
5’7,000 68,200
50,250 65,500
Bend test
51,500 63,800
49,300. 52,200
Bend test
55,800 74,100
72,500
56:000 80,400
58,000 70,300
55,600 7’4,100
57,000 ~2,600
Bend test
.
74.0
63 0
1805
14.0
15.5
16.0
150°
10.5
y,o
1400
24.5
23.5
29.0
23.5
$ 23.5
%3.5
1800
B~oke in sheet at
edge of weld
.
!!
II
II
H
H
II
11
II
.N.A.C.A. Technical Note No. 290 12
.
.1
Bend angles up to 35° indicate brittle material; 85-110°
may be considered as indicating good ductility; 140-180° bends
indicate excellent ductility. From a consideration of the ten-
sile and bend tests, it may be seen that welds in rustless irons
of either the 12-14% chromium or l&20$ chromium grades are brit–
tle and void of any appreciable ductility in the IIasweldedll
condition. Considerable toughness may be imparted to the welds
bY torch annealing at a dull,red heat for five to fifteen min-
utes followed by air cooling. Torch annealing of”the 12-14*
grade will give results about on a par with furnace annealing. .=
In the tensile test 10% elongation in 2![over the weld seems to
be about the Maximum ductility obtainable on wealed welds in
12-14% chromiuq rustless irons.
Rustless irons contai,ning,16-18$chromium together with
about 1% silicon do not air-harden so readily as the 12-142
grade after welding. They are, however, liable to excessive grain
growth at high temperatures and for this reason welds and sheet
adjacent to the weld in high chromium rustless irons are consid-
erably reduced in ductility. Torch annealing or furnace anneal-
.
ing at temperatures of 650-~50°C will impart softness and duc-
tility to welds in 14-20~ chromium rustless iron. Alloys con-
taining about 12 silicon are more
taining less than 0.5%. Welds in
will yield approximately the same
easily welded than those con-
both types of rustless iron
vtiues after annealing; name-
ly, yield point 42,000-55,000 lb./sq.in. ultimate strength
.
4 N.A.C.A. Technical Note No. 290 13
65,000-~5,000 lb./sq.in.; ~ elongation-in 21’over weld 4-14$.
Rustless iron containing 16-18* chromium and 7-12* nickel
is austenitic and does not harden or become brittle in cooling
rapidly or slowly from the welding temperature. Welds in this
material are consequently ductile and require HO after treatment.
In the lrasweldedllcondition, welds in this alloy will have a
yield point of 50,000-60,000 lb./sq.in.; ultimate strength of
65,000-70,000 lb./sq.in. with about 15* elongation in 2~fover the
weld, Welds in this material may be bent through an angle of
140-180° indicating very good ductility. Since welds in this
alloy show the best combination of strength and ductility in , “
.
* either the ~iasw?
M
edllor annealed condition, it is considered
the best alloy to use for welded construction. It can be ob-L
tained in the form of either welded or sbamless tubing which
would be the material used for fusel,ageconstruction. Weld
strength and ductility of the same order as obtained on the 18-
gauge sheet should be obtained in welded tubing of this com~osi-
tion.
—
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Union Carbide and Carbon
Research Laboratories, Inc.,
Long Island City, N. Y.,
March 14, 1928.


Welding of high chromium steels

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