CSWIP Question 4

The side bend test would be the most suitable for detecting lack of interun fusion on a 25mm thick carbon steel butt weld. This test involves bending a specimen along its side, perpendicular to the weld, to assess the integrity of the fusion between the base metal and the weld metal. By applying a specific amount of force, any lack of fusion or incomplete bonding can be identified through visible cracks or separation. This test is particularly effective for detecting flaws in the side fusion zone of a weld.

The Charpy Vee notch test is a destructive test that measures the impact toughness of a material, including the weld metal, parent metal, and heat-affected zone (HAZ). This test involves striking a notched specimen with a pendulum to measure the energy absorbed during fracture. The higher the energy absorbed, the tougher the material. Therefore, the Charpy Vee notch test is used to determine the toughness value of the weld metal/parent metal and HAZ.

Mild steel is considered to be the easiest material to weld because it has a low carbon content, making it more malleable and less prone to cracking during the welding process. It also has good weldability and can be welded using a variety of welding techniques, such as MIG, TIG, and stick welding. Additionally, mild steel is widely available and relatively inexpensive, making it a popular choice for welding applications.

If the welding travel speed is doubled but the amps and volts remain the same, the heat input value will be reduced by 50%. This is because heat input is directly proportional to the travel speed. When the travel speed is doubled, the time for which the heat is applied to the material is reduced by half, resulting in a 50% reduction in heat input.

Rimming steel is a type of steel that contains a high amount of carbon and low levels of other elements. During the welding process, the high carbon content can lead to the formation of porosity. This is because the carbon reacts with oxygen and forms carbon monoxide gas, which gets trapped in the weld. This results in the formation of voids or porosity in the weld. Therefore, when autogenously welded with an arc welding process, rimming steel is more likely to give rise to the formation of porosity compared to other types of steel.

Welds made with high heat inputs show a reduction in toughness. When excessive heat is applied during the welding process, it can cause the material to become brittle and less resistant to cracking or breaking under stress. This reduction in toughness can lead to weld failures or structural weaknesses in the welded component. Therefore, it is important to carefully control the heat input during welding to maintain the desired level of toughness in the weld.

If arc strikes are found on a component made of a high tensile strength material, it is important to have the area checked for possible cracking. Arc strikes can cause localized heating and stress concentration, which can lead to cracks in the material. Therefore, it is necessary to inspect the affected area for any potential cracks that may have been caused by the arc strikes. This is important for ensuring the integrity and safety of the component.

The Welding Procedure Specification (WPS) provides instructions to the welder on how to perform the welding operation. It includes details such as the welding process, welding parameters, joint design, and any pre- and post-welding treatments. The WPS ensures that the welding is done in a consistent and standardized manner, meeting the required quality and safety standards. The other documents listed (PWPS and WPAR) may be related to welding procedures or records, but they do not specifically provide instructions to the welder.

A reduction in-service temperature to sub zero-conditions can increase the likelihood of a brittle fracture in steels. When the temperature drops below zero, the steel becomes more susceptible to brittle fracture due to reduced ductility. At low temperatures, the steel loses its ability to deform plastically and instead becomes more prone to sudden and catastrophic failure. This is why a reduction in-service temperature to sub zero-conditions can increase the risk of brittle fracture in steels.

Normalizing is a heat treatment process in which steel is heated to a temperature above its critical range and then cooled down in air. This process helps to refine the grain structure of the steel, improve its mechanical properties, and relieve internal stresses. Unlike other heat treatments such as annealing, tempering, and stress relieving, normalizing involves air cooling from the austenite region, rather than using a specific cooling medium like water or oil. This allows for a controlled and gradual cooling process, resulting in a more uniform and predictable microstructure in the steel.

The correct heat input for the given parameters can be calculated by multiplying the current (amps) by the voltage and dividing it by the travel speed. In this case, the calculation would be (350 amps * 32 volts) / 310 mm/minute = 2.16 KJ/mm. This value represents the amount of heat energy input per unit length of the weld.

All of the above need to access the welding procedure (WPS). Welders need to access the WPS in order to understand the specific instructions for carrying out the welding process correctly. Inspectors need to access the WPS to ensure that the welding is being done according to the specified procedures and standards. NDT tech's (Non-Destructive Testing technicians) need to access the WPS to understand the welding process and identify any potential defects or flaws in the welds. Therefore, all three categories of individuals mentioned in the options need to have access to the welding procedure.

Silicon is needed in the coating of an electrode to prevent the formation of porosity when welding rimming steel. Silicon acts as a deoxidizer and helps to remove impurities from the weld pool. It also improves the fluidity of the molten metal and reduces the surface tension, which helps to prevent the formation of porosity. By adding silicon to the coating of the electrode, it ensures a cleaner and stronger weld with minimal porosity.

Hydrogen induced cold cracking occurs when hydrogen is present, there is a grain structure that is susceptible to cracking, there is stress on the material, and the temperature is below 200°C.

The tee joint (fillet welded) would normally require the highest preheat temperature because it involves welding a fillet weld, which is a type of weld that joins two pieces of metal at a right angle. This joint type typically requires a higher preheat temperature to ensure proper fusion and to prevent cracking in the weld.

The test piece taken from the Heat Affected Zone (HAZ) is most likely to have the lowest toughness. The HAZ is the region of the metal that experiences a high level of heat during the welding process, which can lead to changes in the microstructure and mechanical properties of the steel. This heat-affected zone is more prone to brittleness and reduced toughness compared to the parent metal or the weld metal. Therefore, the test piece taken from the HAZ is expected to have the lowest toughness.

Austenitic stainless steels have a high coefficient of thermal expansion, meaning they expand more when heated compared to ferritic steels. This, combined with their low thermal conductivity, makes them more susceptible to distortion. When heated, the austenitic stainless steels expand more but do not dissipate the heat quickly, leading to uneven expansion and distortion.

In the martensitic grain structure, hardness would be expected to increase. This is because martensite is a very hard and brittle phase of steel, formed by rapid cooling or quenching. The rapid cooling prevents the formation of other softer phases, resulting in a structure with high hardness. Ductility and toughness, on the other hand, would generally decrease in martensitic structures due to the lack of plastic deformation and the presence of brittle phases.

An increase in travel speed will most likely require the preheat temperature to be increased because a higher travel speed means that the welding process will be completed more quickly, resulting in less time for the heat to transfer to the base material. Therefore, increasing the preheat temperature compensates for the shorter duration of heat exposure and ensures that the weld joint reaches the desired temperature for proper fusion.

Preheating is done before welding to reduce the chance of a brittle grain structure and to minimize the risk of hydrogen entrapment. Preheating helps in slowing down the cooling process, which prevents the formation of a brittle microstructure in the weld zone. It also helps in reducing the risk of hydrogen being trapped in the weld, which can cause cracking and weakening of the joint. By reducing the chance of a brittle grain structure and hydrogen entrapment, preheating improves the overall quality and integrity of the weld.

A transition joint is often referred to when two different materials are to be welded together. This joint allows for a smooth transition between the two materials, ensuring a strong and secure bond. It is commonly used in industries such as construction and manufacturing, where different materials need to be joined together for various applications.

Hydrogen cracking in the Heat Affected Zone (HAZ) is most likely to occur when welding carbon manganese steels. Carbon manganese steels have a higher susceptibility to hydrogen cracking due to the presence of carbon and manganese, which can react with hydrogen and form brittle compounds. This can lead to the formation of cracks in the HAZ during the welding process. Austenitic stainless steel, micro alloyed steel (HSLA), and low carbon steel have lower susceptibility to hydrogen cracking compared to carbon manganese steels.

A carbon equivalent (EC) of 0.5% indicates a high carbon content in carbon manganese steel. This high carbon content can lead to increased hardness and brittleness, making the steel more prone to cracking during welding. Therefore, a preheat temperature over 100°C may be necessary to reduce the risk of cracking and ensure a successful weld.

All of the above are considerations for the selection of a preheat temperature. The preheat temperature is determined by factors such as the arc energy, which affects the heat input during welding, the material thickness, which determines the amount of heat required for proper fusion, the hydrogen scale, which indicates the level of hydrogen present in the material and can affect the weld quality, and the carbon equivalent, which is a measure of the material's susceptibility to cracking. Considering these factors is important in determining the appropriate preheat temperature for a welding process.

The Charpy test is used to measure the impact toughness of a material, specifically its ability to absorb energy before fracturing. The test involves striking a notched sample with a pendulum and measuring the amount of energy absorbed. The comparison for ductile to brittle transition curve is relevant in the Charpy test because it helps determine the temperature at which a material transitions from a ductile to a brittle behavior. This information is important for assessing the material's performance and safety in low-temperature environments.

The purpose of microscopic examination of a weld is to determine the number and type of defects present, as well as to determine the grain size. This examination allows for a detailed analysis of the weld's quality and helps identify any potential issues or weaknesses.

The main reason for qualifying a welding procedure is to show that the welded joints meet the requirements of the specification. This is important to ensure that the welding process is capable of producing strong and reliable joints that meet the desired quality and performance standards. Qualifying a welding procedure also helps to determine the welder's ability, check if the acceptance criteria specific to the project can be met, and show that the fabricator has good welding control. Therefore, the correct answer is "To show the welded joints meet the requirements of the specification."

The purpose of a transverse tensile test is to measure the ultimate tensile strength, the elongation of the material, and the yield strength of the material. This test is used to determine the maximum amount of stress a material can withstand before it breaks, as well as its ability to stretch or elongate before breaking. By measuring these properties, engineers and scientists can evaluate the strength and ductility of a material, and determine its suitability for specific applications.

A Charpy test is a dynamic test used to determine a material's notch toughness in the weld region. This means that it measures the ability of a material to absorb energy in the presence of a notch or defect, which is important in determining its resistance to brittle fracture. The test involves striking a notched specimen with a swinging pendulum and measuring the energy absorbed by the material before it fractures. Therefore, the given answer is correct.

A carbon steel weld (CE 048) welded without preheat may result in a narrow heat affected zone and hardness value in excess of 400HV. This is because welding without preheat can lead to rapid cooling of the weld area, causing a smaller heat affected zone. Additionally, the rapid cooling can result in higher hardness values in the weld, exceeding 400HV.

A MIG/MAG welding plant is best described as a transformer/rectifier (constant voltage) because it uses a transformer to step down the input voltage and a rectifier to convert the AC voltage to DC voltage. This constant voltage output is necessary for MIG/MAG welding, as it ensures a stable arc and consistent weld quality. The constant voltage output allows for better control of the welding process and is suitable for a variety of materials and thicknesses.

The correct answer is d) Both a and b. This means that the HAZ (Heat Affected Zone) associated with a fusion strength cannot be avoided and usually has the highest tensile strength.

Tensile specimens are usually measured in pounds per square inch (psi). This unit is commonly used to quantify the amount of force or stress that a material can withstand before breaking or deforming. Newton per square inch (N/in^2) is not a commonly used unit for measuring tensile specimens. Joules (J) is a unit of energy and is not applicable for measuring the strength or stress of a material. Therefore, the correct answer is a) Pounds per square inch.

Macro specimens should be inspected both after etching and after cutting and before etching. Inspecting the specimen after etching allows for the examination of the microstructure and the identification of any defects or abnormalities. Inspecting the specimen after cutting and before etching helps to ensure that the correct area of interest has been selected for further analysis and that the specimen has been properly prepared for etching. Therefore, both inspections are necessary to obtain a comprehensive understanding of the specimen's characteristics.

The EN499 standard refers to covered electrodes for MMA (Manual Metal Arc) welding. This standard specifies the requirements for the classification of these electrodes, including their chemical composition, mechanical properties, and usability. It ensures that the electrodes meet the necessary quality and performance standards for MMA welding applications.

A single-U butt with backing would normally be considered for a mechanical welding process because it provides better control and stability during the welding process. The backing ensures that the weld is supported and prevents distortion or warping. This type of butt weld preparation allows for a stronger and more reliable weld joint, which is important in mechanical applications where structural integrity is crucial. The other options listed do not provide the same level of support and control, making them less suitable for mechanical welding processes.

EN 287 is a European standard that specifies the qualification testing of welders for fusion welding of metallic materials. It outlines the requirements for welder approval and certification.

A multi-pass weld refers to a welding technique where multiple layers of weld are deposited to form a joint. In this case, a 5-pass weld was made using a 6mm electrode. The heat input in this weld would be higher due to the larger electrode diameter.

In contrast, a 12-pass weld made using a smaller 4mm electrode would have a lower heat input because the smaller electrode diameter requires less energy to melt and deposit the weld metal.

Additionally, the smaller electrode diameter used in the 12-pass weld would result in a higher degree of grain refinement. This is because the smaller electrode allows for better control of the heat input, resulting in finer grains in the weld metal.

Therefore, the correct answer is a) A lower heat input and higher degree of grain refinement.

The tensile test can be used to give a quantitative measurement of weld zone ductility. This test involves applying a tensile force to a specimen until it fractures. By measuring the elongation and reduction in cross-sectional area of the specimen before fracture, the ductility of the material can be determined. In the case of a weld zone, the tensile test can provide valuable information about the strength and deformation properties of the weld. The bend test and Charpy V notch test may also provide information about the weld zone, but they are not specifically designed to measure ductility.

Carbon has the greatest effect on creep strength when added to steel. Carbon forms carbides with iron, which increases the strength and hardness of the steel. It also improves the heat resistance and stability of the steel, making it less susceptible to deformation under high temperatures and prolonged stress. Therefore, the addition of carbon significantly enhances the creep strength of steel.