This one is sure to stir the pot but as everyone goes lighter and looks for higher strength materials, welding 4130 comes up, and it drives me crazy how bad information is permeating the offroad racing world which then trickles into the weekend warriors. I have really appreciated one vendor who has not fallen victim to the 4130 craze and offers a wide selection of parts for the builder in good old fashion mild steel versus all the 4130 junk. It saves all of us money, blades bits and lots of frustration from cracked or broken parts.
Here we go:flipoff2:
The two most popular types of steel used by the off-road nation are often referred to as “mild” steel and “chromoly” steel but there are actually 100’s of alloys of steels used throughout the automotive and aerospace industries. The “mild” steel and “chromoly” steel used by most off-road fabricators is typically AISI/ASE 1010, 1020 steel or AISI/SAE 4130 steel in sheet, tube, and bar geometries.
AISI/SAE 1010 and 1020 are low carbon steels that are readily formable and weldable because of their low carbon content. 1020 is one of the best low carbon steels to use in fabrication and is slightly stronger than 1010. 1020 comes in two primary forms, hot rolled and cold drawn. Cold drawn undergoes final processing in a cold condition (room temperature) versus white hot for the hot rolled processing. By cold processing the steel it is work hardened in the same way that dimple dies and bead rollers cold work and change the geometry of sheet metal into stronger stiffer parts. Work hardening is a process that aligns the granular structure in the steel that makes it stronger. It also results in a scale free final product that is dimensionally more accurate than hot rolled steel. 1010 and 1020 steel cannot be heat-treated to increase strength but they can be annealed after cold working them, intentionally, or unintentionally when welding.
AISI/SAE 4130 is a medium carbon steel that is also readily formable and is weldable, when welding is performed properly. Unlike 1010 & 1020, 4130 is heat treatable because of its higher alloy content (Carbon, Chromium, Molybdenum) but this ability comes with a price, proper welding requires careful selection of weld filler material pre-heat, post-heat and Post Weld Heat Treatment (PWHT). Unfortunately there is a lot of incorrect information on the Internet and within the racing and off-roading communities about the use and welding requirements of 4130 and that 4130 is the best stuff for every situation, which it is not. That is why there 100’s of alloys of steel.
With all structural materials there is a yielding point where the material undergoes permanent deformation and when the material finally fails/breaks the ultimate strength has been reached. The amount of deformation in the material at the final failure point is referred to as the elongation and it is measured as a percentage of the original cross section before it is tested. The higher the elongation of a material the more ductile the material is and the better it is at absorbing energy. There is a limit to acceptable ductility because we use these materials to build roll cages to protect us in a crash and if the material is too ductile it will collapse on us and fail to do its job. On the other hand if a material is too brittle, it will fail to bend at all, or crack and break, resulting in all of the energy of a crash being transferred to us in the passenger compartment. A balance must be maintained between ductility and brittleness for the construction of vehicle parts. Table 1 outlines some of the most popular steels used in fabrication, with there condition, yield strength, ultimate strength, elongation, and Rockwell hardness.
From this table we can see that 4130 clearly looks like the superior material to use for all cases in the fabrication of parts for our off-road projects and that has been the position taken by a large portion of the off-road community. It has higher yield and ultimate strength properties as well as reasonable elongation/ductility when compared to 1020 but what this table doesn’t factor in, is that anything useful must be machined, bent, and welded together to make roll cages, tube frames, suspension arms, etc. What can also be seen on this table is that 4130 strength and ductility is heavily influenced by heat. Heating 4130 to different temperatures and cooling it at different rates causes it to become stronger but also much harder, which is illustrated by the reduction in the elongation at failure and the Rockwell hardness value. The harder the steel the more brittle it is and the more susceptible it is to crack. This is the advantage and disadvantage of 4130.
Care must be taken whenever heating (welding) is performed on 4130 and how we treat 4130 before and after it is welded. The way we perform the preheating, post heating, and PWHT will determine if the part will successfully survive the torture we subject it too, or if it will break and leave us stranded or cause us to loss the race. Unfortunately there are a lot of “experts” and a lot of free flowing advice on the Internet about welding 4130 and their success in doing so. In reality, the way most of these people use 4130, they are fabricating parts that are more expensive, weaker and harder to fabricate than if the part had been made from the lowly 1020 mild steel. Unfortunately this has permeated the industry to the point that racing organizations actually encourage the use of 4130 without further elaboration.
Elaboration is very important when dealing with 4130. The typical recommendation for building chassis and suspension components out of normalized 4130 is to use the Gas Tungsten Arc Welding (GTAW) process with a minimum heat input using ER70S-2 filler rod. This recommendation has been quite successful and in some cases is the only solution when the part is too large to PWHT. Normalized, means the steel has been heated to approximately 1650 deg F and then air cooled in still air. The other common form of 4130 is annealed, which means the steel has been heated to approximately 1500 deg F and then furnace cooled to ambient temperature. Pre-heat treated 4130 material is available as raw stock, but should never be used in the fabrication of parts. While this method of welding 4130 has proven to be “successful”, it yields a part that is more expensive, difficult to fabricate, and most importantly a part that is much more susceptible to fatigue cracking than the same part fabricated from 1020. When any metal is welded, no matter what welding process is used, the metal is melted to allow the two parts to be joined. Specifically when welding medium carbon steels, the material next to the weld tends to form brittle crystals, called martensite, because the cooling rate in a welding process exceeds the allowable cooling rate to prevent these crystals from forming. This region is called the Heat Affected Zone (HAZ) because the welding process has heated the area. An illustration of the HAZ is shown in Figure 1 where the dark gray is the weld, the medium gray is the HAZ and the light grey is the virgin steel.
It is also quite visible as the discolored dark purple region around the weld as shown in Figures 2 & 3.
The original method for welding 4130 was with OxyFuel welding (OFW), and more recently with the Gas Metal Arc Welding (GMAW) and GTAW processes. Let’s examine the three methods on thin-walled 4130 tubing (less than 0.125” wall), typically used in the aerospace, racing & off-road industries.
At one extreme we have the GTAW process that is the industry standard at this point. The GTAW process concentrates a very large amount of heat into a very small area, that negates the need for much preheating of the weld area before welding can start, resulting in a much faster welding process and a much cooler area around the weld, which is advertised as a good thing when welding 4130, but by minimizing the heat introduced to the weld area the cold tubing around the weld area combined with the already rapid cooling fillet weld results in brittle martensite formation in the HAZ. This results in a chassis that forms cracks after every race and plate suspension components that open like a sardine can when they hit a large rock instead of bending and so on. I have seen numerous examples of all forms of failed components or “worn out” frames because of brittle HAZ cracks.
The GMAW process is similar to the GTAW process as far as filler materials, strength of weld, etc, but introduces slightly higher heat levels than the GTAW process. GMAW is also faster and more easily produces convex fillet geometries that are much stronger than the small concave fillets that everyone in the racing industry is obsessed with, but are not preferred under American Welding Standards (AWS) because they encourage solidification cracking and put the weld under tension (weld material should not be placed under tension). Figure 4 illustrates the incorrect and correct shape of a fillet weld. GMAW still does not introduce sufficient heat to the weld are to eliminate the need for pre/post heating when welding 4130.
The OFW method is the oldest and viewed by many as archaic, but OFW has many advantages when welding 4130. Let’s review the OFW process, the area to be welded is pre-heated to allow welding to begin and because the heat output of a OFW process is diffuse (large) when compared to GMAW or GTAW the entire area around the weld is pre-heated to allow welding, then the weld is completed, the joint entire area is a cherry red color (1375 deg F) and higher near the weld fillet and the large heated mass allows the 4130 to slowly return to the ambient temperature resulting in a normalized condition if the air around the weld is calm, alleviating the stresses induced from the welding process and minimizing the martensite in the HAZ. Because of these unique attributes, OFW , may still be the correct way to weld 4130 in the normalized condition when PWHT is not practical. OFW is also very portable and the easiest to use in the field or more appropriately the middle of the desert and will burn away impurities that would contaminate a GTAW or GMAW weld.
When PWHT is an option and cost allows the use of 4130, then the GTAW or GMAW methods combined with the appropriate process will result in a very strong product (Correct filler material, bead contour, appropriate pre-heat, post-heat and PWHT). By using a PWHT the HAZ and residual stresses are eliminated, the structure is much more fatigue resistant, and as illustrated by the 4130 quenched and tempered rows of Table 1 can attain a much greater strength than normalized or annealed 4130. 4130 should not be heat treated past a Rockwell C30 hardness for any structural part, as the part will become too brittle for use. PWHT also reduces the hydrogen that can become trapped in the weld pool. Hydrogen is another source of cracks (part failure) in alloy steels. Table 2 provides the list of acceptable filler materials for welding 4130 in the As Welded (AW) and PWHT conditions.
ER70S-2 is clearly the choice for AW configurations but should 4130 really be used in such a configuration, as 1020 will provide similar overall strength with superior ductility, fatigue strength, cost, and machinability. 4130 filler should be the first choice for PWHT configurations because it will heat treat to the same strength as the parent material, it is also the aerospace standard for welding on 4130. RG-65/Oxweld 32-CMS are not the preferred filler material for GTAW or GMAW welding because they do not contain de-oxidizers but clearly they can be used, as many in the automotive and aerospace industry do use them. A note of caution for all filler materials and welding on 4130 is to ensure all oxides, slag, oil, dirt, etc are removed from the base materials and filler rods before welding and clean welding gloves are used if handling rods for OFW or GTAW.
Please do not base the quality of this data on the quality of my welds which are not nearly as good as many of those on Pirate
Here we go:flipoff2:
The two most popular types of steel used by the off-road nation are often referred to as “mild” steel and “chromoly” steel but there are actually 100’s of alloys of steels used throughout the automotive and aerospace industries. The “mild” steel and “chromoly” steel used by most off-road fabricators is typically AISI/ASE 1010, 1020 steel or AISI/SAE 4130 steel in sheet, tube, and bar geometries.
AISI/SAE 1010 and 1020 are low carbon steels that are readily formable and weldable because of their low carbon content. 1020 is one of the best low carbon steels to use in fabrication and is slightly stronger than 1010. 1020 comes in two primary forms, hot rolled and cold drawn. Cold drawn undergoes final processing in a cold condition (room temperature) versus white hot for the hot rolled processing. By cold processing the steel it is work hardened in the same way that dimple dies and bead rollers cold work and change the geometry of sheet metal into stronger stiffer parts. Work hardening is a process that aligns the granular structure in the steel that makes it stronger. It also results in a scale free final product that is dimensionally more accurate than hot rolled steel. 1010 and 1020 steel cannot be heat-treated to increase strength but they can be annealed after cold working them, intentionally, or unintentionally when welding.
AISI/SAE 4130 is a medium carbon steel that is also readily formable and is weldable, when welding is performed properly. Unlike 1010 & 1020, 4130 is heat treatable because of its higher alloy content (Carbon, Chromium, Molybdenum) but this ability comes with a price, proper welding requires careful selection of weld filler material pre-heat, post-heat and Post Weld Heat Treatment (PWHT). Unfortunately there is a lot of incorrect information on the Internet and within the racing and off-roading communities about the use and welding requirements of 4130 and that 4130 is the best stuff for every situation, which it is not. That is why there 100’s of alloys of steel.
With all structural materials there is a yielding point where the material undergoes permanent deformation and when the material finally fails/breaks the ultimate strength has been reached. The amount of deformation in the material at the final failure point is referred to as the elongation and it is measured as a percentage of the original cross section before it is tested. The higher the elongation of a material the more ductile the material is and the better it is at absorbing energy. There is a limit to acceptable ductility because we use these materials to build roll cages to protect us in a crash and if the material is too ductile it will collapse on us and fail to do its job. On the other hand if a material is too brittle, it will fail to bend at all, or crack and break, resulting in all of the energy of a crash being transferred to us in the passenger compartment. A balance must be maintained between ductility and brittleness for the construction of vehicle parts. Table 1 outlines some of the most popular steels used in fabrication, with there condition, yield strength, ultimate strength, elongation, and Rockwell hardness.
From this table we can see that 4130 clearly looks like the superior material to use for all cases in the fabrication of parts for our off-road projects and that has been the position taken by a large portion of the off-road community. It has higher yield and ultimate strength properties as well as reasonable elongation/ductility when compared to 1020 but what this table doesn’t factor in, is that anything useful must be machined, bent, and welded together to make roll cages, tube frames, suspension arms, etc. What can also be seen on this table is that 4130 strength and ductility is heavily influenced by heat. Heating 4130 to different temperatures and cooling it at different rates causes it to become stronger but also much harder, which is illustrated by the reduction in the elongation at failure and the Rockwell hardness value. The harder the steel the more brittle it is and the more susceptible it is to crack. This is the advantage and disadvantage of 4130.
Care must be taken whenever heating (welding) is performed on 4130 and how we treat 4130 before and after it is welded. The way we perform the preheating, post heating, and PWHT will determine if the part will successfully survive the torture we subject it too, or if it will break and leave us stranded or cause us to loss the race. Unfortunately there are a lot of “experts” and a lot of free flowing advice on the Internet about welding 4130 and their success in doing so. In reality, the way most of these people use 4130, they are fabricating parts that are more expensive, weaker and harder to fabricate than if the part had been made from the lowly 1020 mild steel. Unfortunately this has permeated the industry to the point that racing organizations actually encourage the use of 4130 without further elaboration.
Elaboration is very important when dealing with 4130. The typical recommendation for building chassis and suspension components out of normalized 4130 is to use the Gas Tungsten Arc Welding (GTAW) process with a minimum heat input using ER70S-2 filler rod. This recommendation has been quite successful and in some cases is the only solution when the part is too large to PWHT. Normalized, means the steel has been heated to approximately 1650 deg F and then air cooled in still air. The other common form of 4130 is annealed, which means the steel has been heated to approximately 1500 deg F and then furnace cooled to ambient temperature. Pre-heat treated 4130 material is available as raw stock, but should never be used in the fabrication of parts. While this method of welding 4130 has proven to be “successful”, it yields a part that is more expensive, difficult to fabricate, and most importantly a part that is much more susceptible to fatigue cracking than the same part fabricated from 1020. When any metal is welded, no matter what welding process is used, the metal is melted to allow the two parts to be joined. Specifically when welding medium carbon steels, the material next to the weld tends to form brittle crystals, called martensite, because the cooling rate in a welding process exceeds the allowable cooling rate to prevent these crystals from forming. This region is called the Heat Affected Zone (HAZ) because the welding process has heated the area. An illustration of the HAZ is shown in Figure 1 where the dark gray is the weld, the medium gray is the HAZ and the light grey is the virgin steel.
It is also quite visible as the discolored dark purple region around the weld as shown in Figures 2 & 3.
The original method for welding 4130 was with OxyFuel welding (OFW), and more recently with the Gas Metal Arc Welding (GMAW) and GTAW processes. Let’s examine the three methods on thin-walled 4130 tubing (less than 0.125” wall), typically used in the aerospace, racing & off-road industries.
At one extreme we have the GTAW process that is the industry standard at this point. The GTAW process concentrates a very large amount of heat into a very small area, that negates the need for much preheating of the weld area before welding can start, resulting in a much faster welding process and a much cooler area around the weld, which is advertised as a good thing when welding 4130, but by minimizing the heat introduced to the weld area the cold tubing around the weld area combined with the already rapid cooling fillet weld results in brittle martensite formation in the HAZ. This results in a chassis that forms cracks after every race and plate suspension components that open like a sardine can when they hit a large rock instead of bending and so on. I have seen numerous examples of all forms of failed components or “worn out” frames because of brittle HAZ cracks.
The GMAW process is similar to the GTAW process as far as filler materials, strength of weld, etc, but introduces slightly higher heat levels than the GTAW process. GMAW is also faster and more easily produces convex fillet geometries that are much stronger than the small concave fillets that everyone in the racing industry is obsessed with, but are not preferred under American Welding Standards (AWS) because they encourage solidification cracking and put the weld under tension (weld material should not be placed under tension). Figure 4 illustrates the incorrect and correct shape of a fillet weld. GMAW still does not introduce sufficient heat to the weld are to eliminate the need for pre/post heating when welding 4130.
The OFW method is the oldest and viewed by many as archaic, but OFW has many advantages when welding 4130. Let’s review the OFW process, the area to be welded is pre-heated to allow welding to begin and because the heat output of a OFW process is diffuse (large) when compared to GMAW or GTAW the entire area around the weld is pre-heated to allow welding, then the weld is completed, the joint entire area is a cherry red color (1375 deg F) and higher near the weld fillet and the large heated mass allows the 4130 to slowly return to the ambient temperature resulting in a normalized condition if the air around the weld is calm, alleviating the stresses induced from the welding process and minimizing the martensite in the HAZ. Because of these unique attributes, OFW , may still be the correct way to weld 4130 in the normalized condition when PWHT is not practical. OFW is also very portable and the easiest to use in the field or more appropriately the middle of the desert and will burn away impurities that would contaminate a GTAW or GMAW weld.
When PWHT is an option and cost allows the use of 4130, then the GTAW or GMAW methods combined with the appropriate process will result in a very strong product (Correct filler material, bead contour, appropriate pre-heat, post-heat and PWHT). By using a PWHT the HAZ and residual stresses are eliminated, the structure is much more fatigue resistant, and as illustrated by the 4130 quenched and tempered rows of Table 1 can attain a much greater strength than normalized or annealed 4130. 4130 should not be heat treated past a Rockwell C30 hardness for any structural part, as the part will become too brittle for use. PWHT also reduces the hydrogen that can become trapped in the weld pool. Hydrogen is another source of cracks (part failure) in alloy steels. Table 2 provides the list of acceptable filler materials for welding 4130 in the As Welded (AW) and PWHT conditions.
ER70S-2 is clearly the choice for AW configurations but should 4130 really be used in such a configuration, as 1020 will provide similar overall strength with superior ductility, fatigue strength, cost, and machinability. 4130 filler should be the first choice for PWHT configurations because it will heat treat to the same strength as the parent material, it is also the aerospace standard for welding on 4130. RG-65/Oxweld 32-CMS are not the preferred filler material for GTAW or GMAW welding because they do not contain de-oxidizers but clearly they can be used, as many in the automotive and aerospace industry do use them. A note of caution for all filler materials and welding on 4130 is to ensure all oxides, slag, oil, dirt, etc are removed from the base materials and filler rods before welding and clean welding gloves are used if handling rods for OFW or GTAW.
Please do not base the quality of this data on the quality of my welds which are not nearly as good as many of those on Pirate