Q345 I-Beam
Q345 I-beam is a structural steel grade with comprehensive mechanical properties and good low temperature performance. It is widely used in welding structural parts for ship, rail vehicle and bridge, steel oil tank and general metal construction.
The stress-strain (s-e) curve of Q345 LAS columns was obtained and the applicability of the five-stage constitutive model was verified. In order to calculate the buckling capacity of short Q345 LAS columns, column curve a is preferred.
Mechanical Properties
Q345 steel is a carbon structural steel with good comprehensive mechanical properties and welding property. This steel grade is often used in manufacturing of ship, railway and vehicles, bridges, boiler, pressure vessel container, steel oil tank, etc.
The tensile strength of steel is a measure of how much force can be applied to the material before it fails, for example breaking. It is expressed as the stress divided by its cross-sectional area in Mega Pascals (MPa).
A material’s yield point is the maximum amount of load it can withstand before it begins to deform plastically. This value is typically measured in Mega Pascals, and Q345 I-beam is a key parameter when designing a structure.
In this study, the stress-strain relationship of corroded Q345 and Q420 structural steels was investigated using both bilinear constitutive model and Rasmussen’s models. The results show that the tensile strength of both steels decreases significantly with increasing mass loss rate. However, the ultimate strength obtained from the true stress-strain curves is less sensitive to corrosion than the yield point. The ductility of both types of steel also decreases with increasing mass loss rate. Based on the test data, prediction equations for the residual ductility of both steels were developed. The predicted values agree well with the experimental results. This is an indication that the proposed prediction equations are able to accurately predict the residual ductility of both steels.
Heat Treatment
The low alloy high strength steel Q345 is mainly used for metal construction. It can be welded without problems and is also suitable for cold forming. It is a better choice than low carbon steel, such as Q235, for metal construction that requires greater strength and resistance to corrosion.
The high temperature oxidation resistance of Q345 can be improved by hot-dip aluminizing and diffusion annealing. This is because the aluminized layer contains a large amount of Al2O3, which is a good oxygen barrier. The aluminized layers can protect the low-carbon steel from high-temperature oxidation by blocking the oxygen supply to the underlying metal.
Compared with 16Mn steel, Q345 steel has higher yield strength and tensile strength. The higher strength makes it a safer choice for construction applications that require more extreme stresses or heavy loads. The high-strength steel is often found in parts of a building that are most likely to experience heavy stresses or pressures.
Sulfide stress cracking (SSC) failure is a major concern for Q345 steels because of their use in harsh sour oil and gas environments that contain hydrogen sulfide (H2S). Although methods can be used to improve the strength of the steel, these methods decrease its SSC resistance. In this study, a quenching and tempering (Q&T) process was used to achieve both increased strength and improved SSC resistance in Q345 pressure vessel steel. The resulting fracture surfaces were analyzed to determine the effects of the heat treatment on the mechanical properties of the steel.
Welding Properties
The Q345 steel is characterized by its good welding properties. It can be easily welded using traditional manual arc welding and gas-shielded arc welding. It can also be welded with oxyacetylene or plasma welding processes. The arc voltage used in the welding process can vary from 10 to 55 V. It is important to select a Q195 round steel suitable arc voltage for the application. High arc voltage results in large thermal stresses in the weld. This can lead to spatter and porosity in the weld. A lower arc voltage results in a more controlled weld and less stress.
A quasi-linear thermo-elastic-plastic finite element model is developed in this study to simulate the welding residual stresses and deformation. Based on the commercial FE software Marc, this model takes into account both the moving heat source and material nonlinearity. An H-section butt-welded joint was fabricated and the simulated welding residual stresses were compared with experimental data.
The microstructure of the base metal is characterized by white-banded ferrite and some black pearlite. The chemical compositions of the base metal and filler metal are shown in Table 1. The welding experiments were carried out using an ultrasonic-frequency pulse underwater wet welding system with a diameter of 1.6 mm TiO2-Fe2O3 self-shielded flux-cored wire. The welding parameters are given in Table 2.
The longitudinal residual stresses along L1 were similar for the three cases. However, the transverse residual stresses differed remarkably. In the vicinity of the fusion zone, the transverse residual stresses were tensile and lower than the weld’s room-temperature yield strength (487 MPa).
Applications
Q345 I-beam is used in construction applications that require strength and ductility. The main difference between it and a lower-carbon steel like Q235 is its carbon content. The higher carbon content results in a stronger structure with better welding properties but also makes it more susceptible to corrosion.
This low alloy structural steel is commonly used as a medium, low pressure vessel, oil tank, vehicles, cranes, mining machinery, power stations, bridges and other structures that bear dynamic loads, mechanical parts, building structures, and general metal structural parts. It is delivered in hot rolled or normalized state, and can be used in cold regions.
Since it is stronger than 16Mn steel, it can withstand more extreme stresses and heavier loads. However, it is important to note that the allowable stress of this material will be different depending on its thickness. Thus, it is important to use the correct thickness group when determining the allowable stress for this grade of steel. It is also important to understand that this type of steel requires more careful treatment and inspection than lower-carbon grades of steel.