In this guide, you’ll learn about How To Weld Stainless Steel To Mild Steel. The ideal situation is that the raw materials that are used for welding will coincide in both chemical and mechanical structures.
However, companies involved in manufacturing, fabrication, and construction as well as other sectors might find it essential to join dissimilar materials.
The welding of different materials, including carbon steel and stainless steel, is an economical alternative instead of constructing a structure completely made of stainless steel.
The welding of different materials is commonplace in some power generation facilities, such as petrochemical refineries as well as in numerous mineral processing and mining facilities. The corrosion resistance offered through stainless steel is typically required for equipment used in these installations.
If the environmental or operating conditions allow the material, can be welded into lower-cost carbon steel. In these instances, carbon steel which is comprised of low and mild alloys is a vital component in cost reduction when it comes to building or operating manufacturing facilities.
Similar to any welding procedure getting the best results when welding different steels demands the use of filler metals, as well as appropriate welding techniques. This is the case regardless of the method that the welding tool employs.
Be aware that the subject of joining metals that are not compatible spans many different materials and fabrication techniques.
The tips and guidelines provided in this article can be applied to a variety of carbon steel, such as the widely utilized 304L austenitic stainless Steel and mild steel mix in addition to references to duplex as well as other types of stainless steel.
Welding professionals who are unsure regarding an application must seek advice from an authorized welding distributor or filler metal manufacturer to get specific guidelines on welding and filler metals.
Three Things to Keep in Mind Before How To Weld Stainless Steel To Mild Steel:
When welding carbon steel to stainless steel, it is crucial to consider mechanical properties, chemistry, and resistance to corrosion in order to avoid any potential problems.
In all three aspects choosing the appropriate filler metal can ease the risk of problems. For instance, when welding 304L stainless steel with mild steel, then the frequently suggested filler material is 309L.
In the process of welding the weld is discolored by certain stainless steel on part of the weld as well as some mild steel on the other side, which mixes in materials from both sides that are joined to the.
The objective is to make an end-to-end weld that has chemical properties compatible with each part of the weld joint.
Utilizing 309L filler material, you can achieve this aim when joining 304L stainless steel with mild steel. Also, if you are in doubt about the correct filler metal choice, be sure to talk to the welding distributor or filler manufacturer prior to trying a welding process that is dissimilar.
Achieving a mechanical match for the various types of materials is essential, and so is. The ability to achieve a mechanical match is dependent on having the correct chemical composition and also reflecting the heat produced through the welding process.
As a rule of thumb when welding any kind of stainless steel or carbon steel, the filler metal needs to meet or be slightly higher than what are the properties that make up the less abrasive of the two metals.
It is also important when welding mild and stainless steel to ensure the resistance to corrosion of the weld joint as well as the base stainless steel metal.
It is vital to have a Heat Input:
To take into consideration the aspects of chemical properties, mechanical properties, and resistance to corrosion It is essential to use a welding process that reduces the amount of heat that is transferred to the weld as well as the stainless base material.
Limiting the amount of heat input can reduce the dilution of the weld material with the mild steel part in the welding joint. This, in turn, helps preserve its alloy contents in the deposit and also its desired corrosion resistance.
For certain stainless steels moderate heat input helps to reduce the risk of corrosion by preventing the development of undesirable phases on the stainless steel part that the joint.
For instance 300 series stainless austenitic steels can be susceptible to precipitation of carbide if prolonged in the critical temperature that ranges from 800 degrees to 1500 degrees Fahrenheit.
Limiting the time within this temperature range and choosing an alloy with a low carbon as a base and filler metal can stop this from happening.
The use of stabilized versions filled with filler metals (ER321 or ER347, for instance) could also be advisable and serve as an added security to prevent the precipitation of carbide.
Other grades of stainless steel may develop undesirable phases, resulting in brittleness, or poor corrosion resistance when held for too long at a temperature that is too high.
The Sigma phase (an intermetallic phase that is brittle and with a high degree of hardness) is a common occurrence in stainless grades when heated to high temperatures and may seriously affect the mechanical and corrosion resistance characteristics.
For duplex stainless steels, for instance, the input of heat plays a role in the balance between austenite and ferrite within the final weld as well as in the heat-affected zone (HAZ).
A balanced amount of heat input is essential to ensure the proper quantity of each phase within the final weld as well as the in the base metal HAZ.
Avoiding the following Pitfalls: Cracking, Warping, and the Oxidation Process:
It has a high thermal expansion coefficient (a measurement that is the rate that a material expands when temperatures change. In short stainless steel contracts and expands as temperature changes change, in contrast with carbon steel.
Stainless steel has approximately half the thermal conductivity of carbon steel. Because of this absence of thermal conductivity the hot stainless steel will stay hot for longer as it can’t transfer heat away from its source as swiftly.
Since carbon steel is more electrical conductivity than stainless steel, its heat travels through the piece quite quickly and draws energy away from the welding zone. Variations with respect to the temperature coefficient, as well as the thermal conductivity, may create some difficulties when welding different materials.
Stainless steel is naturally inclined to its expansion and contraction to increase because of the extreme heat that is generated by welding. In contrast, carbon steel (particularly mild steel) is a great conductor of heat and will cool faster and shrink faster when the joint is cooled.
These variations add tension to the joint caused by both sides expanding by heat and contracting upon cooling. This can lead to distortion or warping of a weld made of different metals. It could also lead to cracks if the stress created due to variations in temperature expansion or contraction is greater than the strength of either.
To resolve these two problems when welding carbon steel to stainless steel, stay clear of highly restrained joints which create high stress while the joint heats and then cools. If a very restrained joint design is required, utilize a small heating and some pre-heating in order to delay the process of cooling the joint after welding has been completed.
The joint should be insulated following the final weld will also delay the cooling process and stop thermal stresses from breaking the joint.
The weld joint’s contamination and weld that results is an extremely serious issue that usually results in ‘hot’ cracking. Contaminants may react with Carbon steel and stainless steel to create tiny amounts of weld material with significantly smaller melting temperatures.
These tiny areas of low melting-point contaminants are the ones that will be frozen last when the weld is cooling. In the process, they may develop cracks as the weld’s metal shrinks and cools.
The cracks that are hot can be clearly visible if the issue is significant however, they could also be tiny cracks that are not visible to the naked eye. In order to protect the weld from oxidation the dissimilar metal welding must be treated in the same manner as a stainless weld.
Open root joints must be protected from the air on the back of the joint (back purging). Back purging, which is most commonly used during TIG welding, can prevent any contamination of the weld inside the joint.
In the event of a failure, the joint as well as the stainless steel surface of the weld may be damaged due to oxidation which is the reaction of nitrogen and oxygen in the air. Oxidation can damage the resistance to corrosion of the weld as well as stainless steel HAZ.
To stop this from happening remove the joint’s back using an inert gas like argon or apply one of the available commercially coated materials that are applied back of the weld joint before welding.
Preparation for Stainless Steel in Preparation for Carbon Steel Welding:
Cleanliness and preparation are essential steps to ensure the successful welding of different materials. Mill the scale of the mill or coatings back a minimum of 1/2 inch on either edge of your joint.
Begin by cleaning the joint with alcohol or Acetone. These steps will help rid the area of oil and grease that tend to carry sulfur and phosphorous, which are the main factors behind hot cracking.
Welding Dissimilar Metals Requires Planning:
Welding metals that are not compatible can be difficult. It is crucial to have the most complete information about the specific characteristics of the base material and filler metals so that you can make the best decisions that result in successful welds.
If you are unsure, consult with a trusted welding supplier for guidance regarding the process. It will ensure the longevity and savings which are desired in a process that incorporates both carbon and stainless steel.