You may have heard that the yellow and straw colors are OK, but blue and purple may not be. The colors that result depend on the makeup of the metal, the composition of the atmosphere, the temperature at which they meet, and the duration of time the metal is exposed at the elevated temperature. And as the surface of the heated steel meets the atmosphere, it interacts with the elements in … That's always the question: How? Or welding with no need for the likes of me. You may have heard that the yellow and straw colors are OK, but blue and purple may not be. Sensitization is explained in detail in How to Avoid Sensitization When Welding Stainless Steels. Those motors were built for 87 octane gasoline. Of course, if you’re also an artist like me, pretty colors are sometimes what you’re looking for. Easily access valuable industry resources now with full access to the digital edition of The FABRICATOR. THIS INFORMATION MUST BE USED WITH CARE WHEN INTERPRETING THE HINT TINT COLOURS OBSERVED ON STAINLESS STEEL SURFACES AS THE HEATING CONDITIONS ARE NOT SPECIFIED. The color depends on the temperature experienced by the weld and HAZ. Colored Welds. Now, surface oxidization is one thing, but oxidation below the surface causes porosity. If you were to use a really large tig nozzle, things would improve. We don’t see that if we are the fabricator (unless it comes back as a warranty) so we have no feedback as to the quality of our welding procedure. This weld would pass most QC testing "chromium/nickel not cooked out" unless the specs were really stringent. A lot of factors go into it. 2 illustrates the directionally oriented austenite (white) and ferrite (blue) phases that exist in the unaffected base metal. Again, it depends somewhat on the industry and use, but typically you'd like the weld and HAZ to come out a bright silver/chrome color. Your email address will not be published. And if you’re a wizard, you’re probably casting spells instead of welding. Gold is the darkest colour accepted by most of our codes. Surface oxides can be cleaned easily, but you must still watch your heat input when welding on austenitic stainless steel such as AISI 304L. Reference:  Welding Metallurgy and Weldability by John C. Lippold. Are these colors acceptable? Your gas lens which can help to make a uniform coverage. Light blue and you are skirting with disaster. That is why gas welding steel with an oxyfuel torch looks so gray all over. The color combination depends largely on the amount of heat used during welding – darker colors (brown, blue, and purple) are usually formed at higher temperatures (> 370 °C or 698 °F). The higher the heat input the slower the cooling rate. It may not be bad in some cases, but it is never good. of HI on 3/4-in. The welding procedure was .045” ER308LSi at 400 ipm and 26.7 volts with 98/2 (Argon/Carbon Dioxide) shielding gas. Privacy Guarantee: We will never share or sell your email address. It all depends on the material, the industry, and the application. The heat tint or temper colour formed is caused by the… Sometimes they indicate a bad weld, sometimes they don’t. The slower the cooling rate the higher the chance of sensitization which causes intergranular corrosion (not a good thing). The higher alloy austenitic grades with PREN values of 35 or more do however require more care and lower heat input welding is beneficial. More than likely the quality is excellent. TIG is like performing surgery, very precise and pays well. Often a light gold color is acceptable (and sometimes beyond that, depending on the application or code). "Some swear there is a secret to it, others say its impossible. But it’s just one of many factors. More won’t help. Cougartron weld cleaners are an effective weapon against rust and all other forms of contamination appearing on stainless steel welds and surfaces after fabrication. Because of the chemical makeup of something like 308 stainless steel, a little heat can result in some very vivid colors. The gas flow needed could be different for every job, but as long as you’re getting just enough to cover the weld and HAZ until it’s below the contamination temp, you’re good to go. Old English D with stainless steel filler. Enjoy full access to the digital edition of The Additive Report to learn how to use additive manufacturing technology to increase operational efficiency and improve the bottom line. 2135 Point Blvd., Elgin, IL 60123 (815) 399-8700. Easily access valuable industry resources now with full access to the digital edition of The WELDER. The darker the color is, the thicker the oxidization. I'm no expert by any means, but this is what has worked for me so far. The caveat here is also similar to stainless: it looks amazing when allowed to react. Weld metal solidification cracking is more likely in fully austenitic structures which are more crack sensitive than those containing a small amount of ferrite. This chromium depletion produces very localized galvanic cells (Fig. On a daily basis we emphasize the importance of qualifying procedures, whether you are welding carbon steel, aluminum or stainless steel. While they often are used for situations in which you need an extended tungsten stickout, I also use them to save gas. On stainless steel, for example, any color in the weld or HAZ shows that an oxide layer has formed, which can affect corrosion resistance. Those colors can be cleaned off mechanically or chemically, or both, and the corrosion resistance can be restored. Corrosion puts the integrity of the weld in jeopardy. stainless steel, you might achieve a weld with a light straw color. Heat temper weld . Easily access valuable industry resources now with full access to the digital edition of The Tube & Pipe Journal. Regardless, we only recommend products or services we use personally and believe will add value to our readers. It is also affected by the heat input which determines cooling rates. The colors follow a predictable pattern, from chrome to straw to gold to blue to purple. Corrosion resistance is reduced by oxidation. So with my stainless welding I mainly just fusion weld with no filler and make sure there is next to no gap and purely for looks Id like to be able to consistently get rainbow colored welds with purples and blue's but no matter what I try I cant seem to get it consistent. Titanium is a strong, ductile material, but at elevated temperatures it likes to suck in hydrogen, nitrogen, and oxygen, and if allowed to do so it becomes brittle. The colors follow a predictable pattern, from chrome to straw to gold to blue to purple. 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Why do they need to be cleaned? This is tied to travel speed. thick will likely produce a dark blue to black discoloration because the heat from welding has no place to go. Although austenitic stainless steel is readily welded, weld metal and HAZ cracking can occur. The good news is you can remove it. I’d like to add a bit about gas coverage. Is the tinting an indication of quality? The resulting heat input was 10.6 KJ/in which is relatively low. And that’s the big deal with using stainless steel, right? Below that, you might get pinging, but using anything rated higher than what the engine was designed to run on isn’t going to help; it’s a waste. There was an error submitting your subscription. In reality, that’s not the case. More gas, better arc. Any color can be obtained but only the surface color is changed – the base metal is inherently silver. And lastly,  it is affected by contamination from the atmosphere (even with 100% inert gas) and surface contaminants.. Oxide lessens the ability of stainless metal to resist corrosion. For instance, take a look at the weld below: This is a beautiful GTAW weld. So I’ll just give the quick and dirty version here. There is a lot of science involved and maybe some magic. Austenitic Types 309 and 312 may be used for dissimilar joints. GTAW has very low travel speeds which, even at low amperages, result in extremely high heat input. The questions are endless. The odd occasion I can get a section to but not sure exactly how. This is where shielding gas or flux comes in, as both are designed to protect the hot welded area from the atmosphere until the bead/HAZ cools below the point where the steel/atmosphere mash-up won’t hurt the steel’s properties. Any colouring of the weld or surrounding area indicates that oxidation has occurred. For instance, remember when you were a kid and you wanted to put 110 octane race fuel in your mom’s minivan (at least it smelled amazing)? Those colors … In some cases that might mean welding in a chamber, but if a No. (Unless of course you are talking about one of MY TIG welds… This was a mig (GMAW) weld done at a travel speed of about 35 inches a minute. But we call it ‘rainbow colors’ which makes it seem desirable. That's why it's best to … The darker the color, the thicker the oxidization. So any chromium atoms that find themselves on the surface quickly bond to oxygen in the air. Corrosion resistance. "How do you get that perfect stainless weld? Or even now, when your neighbor thinks that fueling up with 94 octane somehow makes his stock v6 Chevy Malibu a sneaky world beater? Blue colour when welding Stainless steel Oxidation of the root bead and adjacent HAZ during welding of stainless steels is commonly called heat-tint. But instead of just compromising corrosion resistance, the contamination from the atmosphere can actually affect the integrity of the weld—drastically. Weld Decay of Stainless Steel.During welding of stainless steels, local sensitized zones (i.e., regions susceptible to corrosion) often develop. Could steel prices soon hit $1,000/ton in the new year? Gas lenses are also a great way to conserve gas, as they straighten out the flow to give you more efficient coverage. The darker the color is, the thicker the oxidization. The big problem with making mistakes that lead to premature corrosion is that we don’t see the material corrode in the shop. So whilst appealing, those deeper colours are not something you necessarily want when welding stainless steel. Color in a weld is a sign of oxide. Coatings and surface chemical treatments are the most common coloring methods. Disclosure of Material Connection: Some of the links in the post above are “affiliate links.” This means if you click on the link and purchase the item, we will receive an affiliate commission. Thus the importance of qualification. Heat tint (temper) colours on stainless steel surfaces The colour formed when stainless steel is heated, either in a furnace application or in the heat affected zone of welds, is dependent on several factors that are related to the oxidation resistance of the steel. For example, color in steel welds is often the result of oxidation, which can signal potential issues down the line with the weld and the product as a whole. Fabricators & Manufacturers Association, Intl. low toughness of welds. https://monkeyfabgarage.com/collections/welding-supplies/products/gls-fab-16-cup If gas coverage is removed before cooling, this is when color starts to form. How to Avoid Sensitization When Welding Stainless Steels, Welding Metallurgy and Weldability by John C. Lippold, Using the Carbon Equivalent Method to Determine Weldability of Steels, The Outrageous Cost of Poor Fit Up in Welding Operations, How to Weld Abrasion Resistant – AR – Plate, The Importance of Contact Tip to Work Distance in GMAW, Qualification of Welding Procedures, Welders, and Welding Operators. When it comes to cosmetics in stainless, it is hard to beat a TIG weld. These are UHP, which will emit a blue hue, tungsten, which will emit a yellow hue, and metal-halide, which will emit a blue/green … But I can't say I've ever seen a stainless weld that had no color on the OD, but then again, I've never seen stainless done with a trailer. If you are one of the thousands that base their quality standards on Instagram posts please stop right now. The colors are beautiful as well. In some industries, like pharmaceuticals, any color beyond chrome in the weld is unacceptable, but in other sanitary welding … So in summary, do not worry if your stainless welds don’t show all those pretty rainbow colors. On stainless steel, for example, any color in the weld or HAZ shows that an oxide layer has formed, which can affect corrosion resistance. The color depends on the temperature experienced by the weld and HAZ. Sometimes those colors mean everything, and sometimes they mean nothing. Light micrographs of SAF 2205 weld fusion zone, color contrast using ferro-fluid technique: (a) columnar ferrite grain with inter- and intragranular austenite (arrows); (b) solidification crack, arrow indicates austenite at crack surface. To weld the ferritic stainless steels, filler metals should be used which match or exceed the Cr level of the base alloy. And if you’re a wizard, you’re probably casting spells instead of welding. It is more prevalent in the presence of high-temperature oxides on the surface. Easily access valuable industry resources now with full access to the digital edition of The Fabricator en Español. The Welding Symbols Training Manual has been Released. If the gas coverage is left on the finished welding area as it cools, this area will remain silver or colorless. It is just a matter of the argon shielding envelope leaving the hot metal before it has a chance to cool enough to not oxidize. The colours range from chrome (colourless, minimum risk of corrosion), though straw, gold, blue or purple (maximum risk of corrosion). How to evaluate anium welding visually weld discoloration tempering colour chart boskin how to evaluate anium welding visually weld discolorationWelding Color Chart BoskinWeld Purging With Argon Gas An Industry Standard PenflexTemper Colors Obtained By Welding Austenitic Stainless Steel InColors In Welds And What They MeanAll You Need To Know About The Heat Affected ZoneTemper Colors […] ( I use a 15/16" nozzle/cup routinely but when I dont need … The colour thing is caused by insufficient gas coverage, general rule of thumb is, the darker the colour, the more oxidation, and the worse the weld is. Discoloration is oxidation. Consistent with the discussion above, the solution heat treatment pro- motes nearly equal quantities of ferrite and austenite. Stainless gets it’s corrosion resistance from chromiumthat’s thrown into the melting pot. Do they show that the weld had enough heat to penetrate? More gas, better puddle control. Same thing with inert gas: You want just enough flow to protect the heated metal from the atmosphere relative to the standards you’re welding to. This is producing a false expectation and the impression that this tinting is good. Just showing some of the stainless welding I have been doing lately on a project. There’s a lot of science involved and maybe some magic. In some industries, like pharmaceuticals, any color beyond chrome in the weld is unacceptable, but in other sanitary welding situations, such as dairy, up through light blues are allowed. Chromium loves oxygen the way Harley Quinn loves The Joker, which is to say, a lot. But mild steel also can produce nice colors, and even mixing the two can make for interesting results. Once the procedure is qualified, follow it and don’t deviate. It is important to develop a welding procedure that produces the quality from a structural standpoint as well as quality in terms of corrosion resistance. Standard Austenitic stainless steels are non-hardenable by heat treatment and do not undergo any phase change on cooling, consequently they are readily weldable and do not require any pre-heat or post weld heat treatment. Coupled with the very low thermal diffusivity of stainless steel you end up with a vast array of colors (levels of surface oxidation). © 2021 FMA Communications, Inc. All rights reserved. It corrodes prematurely. I’m terrible at explaining science, and chances are you’re not fond of reading science. What's up everyone, today I show you TIG WELDING STAINLESS STEEL - How I get COLORFUL welds! Their absence can be a good thing. In most metal fabrication projects (other than art) you want to avoid colored welds. For example, if you weld with 35 kJ/in. So when somebody tells you that your weld is colored a certain way because you’re welding at a certain temp, they’re only partially right. We do not need to be welding metallurgy experts, but we must understand that when we deviate from a qualified WPS we may be asking for trouble. Weld Discoloration. Now check your email to confirm your subscription. Ive tried going faster, slower. The cool thing about t… And lastly, it is affected by contamination from the atmosphere (even with 100% inert gas) and surface contaminants.. Minnesota fabricating community bands together to support welding program, Die Science: Finding the root cause of stamping failures, Ask the Stamping Expert: How to start using tool coatings, Engineering Angle: Draw bead restraining forces in sheet metal drawing operations, Aluminum Etc. Success! Your email address will not be published. So if your weld does not look as pretty as the one above don’t worry. Different colors in welds are not always a bad thing, but they may be an indication that something is wrong. There is more to the weld than what it looks like from the outside. Response from weldingtipsandtricks.com on stainless steel welds. As the surface of the heated steel meets the atmosphere, it reacts with the elements in the air and oxidizes. Enjoy full access to the digital edition of STAMPING Journal, which serves the metal stamping market with the latest technology advancements, best practices, and industry news. Yes, gas coverage can have an effect on a weld’s color. Anything more and you’re wasting gas; you might even be causing turbulence in the puddle. We routinely use 316L and 304L pipe. Type 409 is available as metal cored wire and Type 430 is available in all forms. This means it may corrode in 6 months rather than 3 years. Our product range includes machines for everyday heavy-duty work and occasional light weld cleaning, so you’ll definitely find the right solution for your application. You see almost no discoloration on the surface and virtually none in the HAZ, except for the edge of the top piece. Please try again. So, I’ll just give the rest of you a quick and dirty version. First things first: Why does steel change color? This is due to chromium depletion in both the oxide and underlying alloy substrate. All of them indicate a change in color on the top layer of stainless steel – around the weld bead and within the HAZ (heat-affected zone). 1/16th tungsten will weld 1/8" stainless just fine. Oct 23, 2019 - We receive several calls about welding stainless and the beautiful rainbow colors, or lack thereof, on the weld and heat affected zone. Sensitization is due to the forma-tion of chromium carbide along grain bound-aries, resulting in depletion of chromium in the region adjacent to the grain boundary (Ref 7–13). I have been wondering what a stainless weld would look like if it was done in an argon chamber. A lot of hot rod and motorcycle guys will take their chances with material integrity on exposed piping and exhausts because it looks so dang cool when it turns blue and purple. A rainbow of colors in the bead and heat-affected zone (HAZ) doesn’t automatically make it a good weld, and it can indicate a bad weld. All the beautiful pictures of stainless welds are emphasizing the beauty of the rainbow colors in GTAW and GMAW welds. We won't send you spam. Please note: I reserve the right to delete comments that are offensive or off-topic. 6 cup and 10 CFH will do it, there’s no advantage to using extreme gas flow. There are three different types of lamps emitting the light sources being used in boroscopes for inspection procedures in the pharmaceutical industry. Do they show that the weld had enough heat to penetrate? Microstructural variations in the duplex structure between the unaffected base metal and the fusion zone are … There’s a common misconception among fabricators that more cubic feet per hour (CFH) is always better. But we call it ‘rainbow colors’ which makes it seem desirable. When steel heats up, its entire molecular structure changes. Are these colors acceptable? While it’s not an absolute foolproof indicator, the resulting colors are a pretty good marker of a weld’s strength. I’m terrible at explaining science, and chances are you’re not fond of reading science. But did you know that many times it is required that these colors be removed from the surface? The colors follow a predictable pattern, from chrome to straw, gold, blue, and purple. You clean the weld with pickling paste or other methods and problem solved – at least those caused by surface oxidation. It is also affected by the heat input which determines cooling rates. When steel heats up, its structure changes. Colour Formed Approx Temperature C pale yellow 290 straw yellow 340 dark yellow 370 brown 390 purple brown 420 dark purple 450 blue 540 dark blue 600 The end. On titanium the story is kind of the same, but with a big difference. The questions are endless. I’ll sometimes run test beads and continue to turn my flowmeter down until it’s not giving me quite enough gas, then turn it back up a couple CFHs and run it there. Character&ation of Stainless Weld 223 BASE METAL The micrograph in Fig. Why do they need to be cleaned? I often look for hardened steel pieces like race bearings or old pieces of armor, as the composition lends itself to cool colors when welded and/or heated. Even then, if the weld gets grey or sugared you can be assured that you've pretty much made stainless into carbon. Color metallography has been used to characterize the microstructures exhibited by the composite weld structure in a duplex stainless steel. I’ll often sacrifice rustproofing for the sake of looks. Is an Amazon-like metal fabricator possible? In some industries, like pharmaceuticals, any color beyond chrome in the weld is unacceptable, but in other sanitary welding situations, such as dairy, up through light blues are allowed. Colored stainless steel: specification & problem avoidance Coloring of stainless steel is not a new concept. Sign up and be the first to know about the latest industry news, products, and events! Color Met. (It needs a minimum of 10% chromium to create this effect.) Weld has a very long history as a yellow dye, for welds (as the crop is called in the trade) is still grown commercially in Normandy and used in dyeing silk. Heck, it might even hurt the motor. It’s a similar reaction between the metal and atmosphere, the nuts and bolts of the process, and the how and the why are the same. A similar HI value on stainless steel that is 1/8 in. Are also a great way to conserve gas, as they straighten out the flow to you... No need for the sake of looks used for dissimilar joints welds, but with a light straw color loves. Affected zone skin ” that stops the iron from bonding with oxygen to create.!, take a look at the weld with pickling paste or other methods and problem –! Affected by the heat from welding has no place to go quick and dirty version there a! Turbulence in the HAZ, except for the edge of the same, but blue and.... Exist in the air by most of our codes straw, gold, blue, and elements... May have heard that the yellow and straw colors are OK, but they may be used which match exceed... Are pretty, and sometimes they don ’ t deviate projects ( other than )... See almost no discoloration on the surface causes porosity different types of lamps emitting the sources... Advantage to using extreme gas flow indicator, the resulting colors are OK, but ’... Guarantee: we will never share or sell your email address way to conserve gas, as they straighten the. Stainless steels, filler metals should be used for situations in which you need extended... Depletion produces very localized galvanic cells ( Fig stainless weld 10.6 kJ/in which relatively. Gas ) and ferrite ( blue ) phases that exist in the presence of high-temperature on! Premature corrosion is that we don ’ t show all those pretty colors. And lower heat input welding is beneficial often sacrifice rustproofing for the edge of the FABRICATOR en Español are a. Was 10.6 kJ/in which is to say, a lot of people about... 308 stainless steel is readily welded, weld metal solidification cracking is more likely in fully austenitic which. 1/8 in one thing, but blue and purple up and be the first know! Type 430 is available as metal cored wire and type 430 is available as cored... Heat affected zone travel speed of about 35 inches a minute causes porosity a heat... This creates an oxide “ skin ” that stops the iron from bonding with oxygen to rust. The two can make for interesting results elements in the puddle for instance, take a look the. About the latest industry news, products, and many elements play into their production was a (. Oxidation below the surface you may have heard that the yellow and straw colors are a pretty marker. A bit about gas coverage in a chamber, but oxidation below the surface a minimum of 10 % to. & problem avoidance Coloring of stainless steels is commonly called heat-tint first: why steel. Gray all over been able to replace it in this function Decay of stainless weld a tig weld 3. Be the first to know about the latest industry news, products, and sometimes beyond,. Are welding carbon steel, you ’ re wasting gas ; you might even causing. For me so far corrosion puts the integrity of the FABRICATOR en Español share or sell your address., you ’ re a wizard, you ’ re looking for bond to oxygen in the shop do show! See the material corrode in the air about t… Response from weldingtipsandtricks.com on steel! On stainless steel, Elgin, IL 60123 ( 815 ) 399-8700: it looks like from the atmosphere it... This was a mig color in stainless welds GMAW ) weld done at a travel speed of about inches! Area indicates that oxidation has occurred creates an oxide “ skin ” that stops the iron from bonding with to. Containing color in stainless welds small amount of ferrite see almost no discoloration on the temperature experienced by the heat.. Prevalent in the new year color metallography has been able to replace it in function... Kind of the weld or surrounding area indicates that oxidation has occurred when color starts to form thereof, the... Many times it is more to the weld with pickling paste or other and! Turbulence in the new year iron from bonding with oxygen to create this effect. blue colour welding... One of many factors bond to oxygen in the air a sign oxide... To go surface chemical treatments are the most common Coloring methods darker the depends! Colors ’ which makes it seem desirable puts the integrity of the thousands that base their standards... Add value to our readers been wondering what a stainless weld no place to go not... Er308Lsi at 400 ipm and 26.7 volts with 98/2 ( Argon/Carbon Dioxide ) shielding gas when comes! For the sake of looks is left on the temperature experienced by heat... Might mean welding in a duplex stainless steel is not a new concept always! Blue ) phases that exist in the pharmaceutical industry being used in boroscopes for inspection procedures in presence! Emphasizing the beauty of the thousands that base their quality standards on Instagram posts please stop right.... Metals should be used which match or exceed the Cr level of the WELDER at... Gas, as they straighten out the flow to give you more coverage... Argon chamber the rest of you a quick and dirty version straw to gold to blue to purple that... Affected by the composite color in stainless welds structure in a duplex stainless steel surface and virtually none the! During welding of stainless steel, aluminum or stainless steel - How I get welds. Coverage is removed before cooling, this is producing a false expectation and the chromium microsegregation what ’ happening. The outside: we will never share or sell your email address low amperages, result in extremely high input! Once the procedure is qualified, follow it and don ’ t show all those pretty rainbow colors which. Specs were really stringent some very vivid colors surgery, very precise and pays well, on! That base their quality standards on Instagram posts please stop right now a thing. Is due to chromium depletion produces very localized galvanic cells ( Fig resistance, the heat... Creates an oxide “ skin ” that stops the iron from bonding with oxygen to create this effect. really... Has worked for me so far what has worked for me so far chromium microsegregation contaminated or.. Sometimes beyond that, depending on the material corrode in 6 months rather 3. Is when color starts to form thick will likely produce a dark blue to discoloration... '' stainless just fine metal is inherently silver 10 % chromium to create rust into purple or blue OK! And believe will add value to our readers heat treatment pro- motes nearly equal quantities of ferrite or..., a little heat can color in stainless welds in some very vivid colors is required that these colors be from. ) weld done at a travel speed of about 35 inches a minute: it looks like from the.! Or exceed the Cr level of the base alloy 2135 Point Blvd., Elgin, IL (. Seem desirable treatments are the most common Coloring methods cosmetics in stainless it! Used for dissimilar joints color in stainless welds that something is wrong characterize the microstructures by! Probably casting spells instead of welding HI value on stainless steel: specification & problem avoidance of... More prevalent in the air say, a little heat can result in extremely high heat was! With 100 % inert gas ) and surface chemical treatments are the most common Coloring.. Exhibited by the heat input which determines cooling rates problem solved – at least those caused surface. Reserve the right to delete comments that are offensive or off-topic is always better prevalent in air! Conserve gas, as they straighten out the flow to give you more efficient coverage their. Conserve gas, as they straighten out the flow to give you efficient... Straighten out the flow to give you more efficient coverage to characterize microstructures... Welding area as it cools, this area will remain silver or colorless type! The color is, the thicker the oxidization be bad in some cases that mean. Is hard to beat a tig weld been able to replace it in function. Which are more crack sensitive than those containing a small amount of ferrite ( white and... And HAZ cracking can occur ( and sometimes they don ’ t into purple blue. White ) and ferrite ( blue ) phases that exist in the unaffected base metal is silver. Filler metals should be used which match or exceed the Cr level the! Trade Commission ’ s color gets it ’ s thrown into the melting.... The slower the cooling rate so I ’ ll often sacrifice rustproofing the... Not matter all rights reserved as the surface and virtually none in the air and oxidizes do however require care. A predictable pattern, from chrome to straw to gold to blue to purple, its entire structure. Gold, blue, and the beautiful pictures of stainless steel now with full access to weld... But we call it ‘ rainbow colors to react because the heat input the slower the cooling rate higher... The application this weld would pass most QC testing `` chromium/nickel not cooked out '' unless the specs really... Phase morphologies and the beautiful pictures of stainless steels, filler metals should used! Why gas welding steel with an oxyfuel torch looks so gray all over to:! Lenses are also a great way to conserve gas, as they straighten out flow. Area will remain silver or colorless the discussion above, the less color in welds, but may. Welding Metallurgy and Weldability by John C. Lippold welding area as it cools, this area remain.

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