Welded Armor Steel Research Articles

Characterization of Fillet Welded Armor Steel Performed by Robotic Gas Metal Arc Welding: Effect of Heat Input on Microstructure and Microhardness

Characterization of Fillet Welded Armor Steel Performed by Robotic Gas Metal Arc Welding: Effect of Heat Input on Microstructure and Microhardness

Effect of Rotating Arc (Spin Arc) on Mechanical Properties and Microstructural Characteristics of Gas Metal Arc Welded Armour Steel Joints

Effect of Rotating Arc (Spin Arc) on Mechanical Properties and Microstructural Characteristics of Gas Metal Arc Welded Armour Steel Joints

Microstructural and Impact Considerations of Heat Affected Zone in Gas Tungsten Arc Welding of Armor Steel

Abstract Gas tungsten arc welding is a preferred welding process due to its excellent heat control which provides high quality joinings of various metals. Welded armor steels are widely used in armored vehicles for the ease of production. Thus, characterization of gas tungsten arc welding of armor steels reveals important data on both present applications and potential uses of gas tungsten arc welding in future. In this study, microstructural and mechanical properties of welded armor steel were investigated. Optimal welding parameters depending on a previous research were used to eliminate welding defects. The results have shown that application of pre-heating and/or multi-pass welding on armor steel could provide fine and homogeneously dispersed carbides in heat affected zone.

The effect of weld-groove surface modification on the joint performance of military grade armour steel: A sustainability approach

The welding of armour grade steel plays a vital role in combat vehicle structures. A work is conducted to investigate the effect of Water Jet (WJ) and Flame Cutting (FC) on the metallurgical and mechanical properties of the welded armour steel plates. The sustainable WJ machining shall produce the weld groove by a single pass without heat formation in the cut surface, which is unavoidable in the flame cutting process. The results demonstrate that the WJ weld plate is more desirable, as the martensite structure is obtained in different Heat-Affected Zones (HAZ). It is achieved by one-time heat involvement compared to ferrite – pearlite structure in HAZ of the flame cut weld plate. A higher hardness of 335 HV is observed in the fusion zone of the WJ weld plate compared to 212 HV in the flame cut weld plate. The tensile failure occurs in the fusion zone of both water jet and flame cut weld plates and the fusion zone has a higher impact strength of 108 J (8 times higher than base plate). Thus, implementing sustainable WJ machining in preparing the weld groove enhanced the welding properties in military-grade armour steel.

Microstructure Effect of Heat Input on Ballistic Performance of Welded High Strength Armor Steel

The effect of two different heat inputs, 1.2 and 0.8 kJ/ mg, on the microstructure associated with a welded high hardness armor (HHA) steel was investigated by ballistic tests. A novel way of comparing the ballistic performance between fusion zone (FZ), heat-affected zone (HAZ), and base metal (BM) of the HHA joint plate was applied by using results of the limit velocity V50. These results of V50 were combined with those of ballistic absorbed impact energy, microhardness, and Charpy and tensile strength revealing that the higher ballistic performance was attained for the lower heat input. Indeed, the lower heat input was associated with a superior performance of the HAZ, by reaching a V50 projectile limit velocity of 668 m/s, as compared to V50 of 622 m/s for higher heat input as well as to both FZ and BM, with 556 and 567 m/s, respectively. Another relevant result, which is for the first time disclosed, refers to the comparative lower microhardness of the HAZ (445 HV) vs. BM (503 HV), in spite of the HAZ superior ballistic performance. This apparent contradiction is attributed to the HAZ bainitic microstructure with a relatively greater toughness, which was found more determinant for the ballistic resistance than the harder microstructure of the BM tempered martensite.

Mechanical properties and fatigue behavior of CO2 laser beam welded armor steel joints

Abstract Armor 500T steel used in armored military vehicles and marine vehicles were joined by CO2 laser beam welding method by applying three welding powers and two welding speeds under shielding argon atmosphere. From microstructure and microhardness results, under low laser welding power and high welding traveling speeds, microstructural transformation in the joining region of the performed welds occurred at a narrower distance as compared to other parameters, and it was determined that four regions formed independent of each other for each parameter group. Furthermore, it was determined that there is a gradual decrease in the microharness values of samples in which welding parameters cause heat input to decrease. The fatigue test results of all samples showed high strength properties in the parameters with high heat input. Additionally, tensile test results for all samples with high heat input parameters also exhibited high strength properties. Fracture at the intersection at high heat input parameters of a relatively ductile separation type occurred in HAZ whereas, at other parameters fracture occurred at the weld center and wide gap semi-brittle fracture behavior was observed. As a consequence, it was found that the most effective parameter as compared with laser welding power is laser welding traveling speed.

Mechanical properties and fatigue behavior of CO2laser beam welded armor steel joints

AbstractArmor 500T steel used in armored military vehicles and marine vehicles were joined by CO2laser beam welding method by applying three welding powers and two welding speeds under shielding argon atmosphere. From microstructure and microhardness results, under low laser welding power and high welding traveling speeds, microstructural transformation in the joining region of the performed welds occurred at a narrower distance as compared to other parameters, and it was determined that four regions formed independent of each other for each parameter group. Furthermore, it was determined that there is a gradual decrease in the microharness values of samples in which welding parameters cause heat input to decrease. The fatigue test results of all samples showed high strength properties in the parameters with high heat input. Additionally, tensile test results for all samples with high heat input parameters also exhibited high strength properties. Fracture at the intersection at high heat input parameters of a relatively ductile separation type occurred in HAZ whereas, at other parameters fracture occurred at the weld center and wide gap semi-brittle fracture behavior was observed. As a consequence, it was found that the most effective parameter as compared with laser welding power is laser welding traveling speed.

The protective capability of the laser welded armour steel plates

Despite the intensive development of plastics and composite materials in the case of armours employed to protect vehicles, armour steel remains a material commonly and effectively used. This is especially evident in the base armour of armoured vehicles, where the body is made of welded armour steel plates. However, the area of joining both the weld and the heat affected zone are sensitive areas with the reduced protective capability. In the case of laser welding in comparison with methods such as shielded metal arc welding and gas metal arc welding, it is possible to narrow down the above mentioned areas. The paper presents the results of research on the protective capability of welded zone of armour steel plates with a hardness of 500 HB. In the first part of the work, in order to select the proper parameters for the bonding process, different connection variants were made and their microstructure and selected mechanical properties were analysed. After selecting the best variant of the welding process, samples (200 mm × 200 mm) consisting of two welded plates with dimensions 100 mm × 200 mm were made for testing. The thickness of the plates was selected in such a way that in the areas outside the bonding zone, the lack of complete perforation by the projectiles used in the tests is guaranteed. The samples were shot at the weld location and at different distances from the weld to verify, for the chosen method of joining steel plates, if the welded armour loses its protective capability and, possibly, how wide this area may be.

Improving the weld microstructure and material properties of K-TIG welded armour steel joint using filler material

Motivated by the undesired microstructure and unsatisfactory weld properties during keyhole tungsten inert gas (K-TIG) welding process, the use of filler materials was introduced for the first time in K-TIG to modify the weld microstructure and improve weld properties. Single pass full penetration was achieved on 6.2 mm armour steel plate at a welding speed of 350 mm/min. The metal transfer behaviour, microstructure and mechanical properties of weld joint were analysed in detail. The results showed that the introduction of filler material was very effective in modifying microstructure and improving joint properties. The wire feeding speed can reach up to 300 cm/min without compromising full penetration, providing a great scope for microstructure modification. The applied austenitic filler material can significantly change the weld microstructure with just 6.7% dilution, along with much increased weld metal hardness and joint efficiency, matching the welds produced by using conventional arc welding processes with V-joint preparation and matching filler metal. The introduction of filler material dramatically expands the capability of K-TIG process and also shows great potential to produce high performance armour steel joint with high productivity.

Fracture mechanic and charpy impact properties of a crack in weld metal, HAZ and base metal of welded armor steel

Welding of armored steel is complicated by the high percentage of carbon in the base metal, the presence of faults in the form of cracks and pores that occur in the weld metal and heat affected zone (HAZ) during the welding process. For heavy structural engineering such as military armored vehicles that are frequently under the influence of impact loads, it is important to know the fracture toughness in all zones of the welded joint. The crack formed in base metal or HAZ, due to dynamic or impact loads, can easily continue to propagate to the fusion line, after which its accelerated growth may occur. The fracture mechanics testing was applied to SEN (B) test specimens, which investigated cracks initiation and certain fracture mechanics parameters. Due to the significant interest in quantifying the resistance of material to propagation of cracks, the fracture mechanic was measured in the zone of base metal, weld metal and HAZ, at temperature 20 °C. The fracture toughness in the base metal is 86.1 MPa*m1/2, while in HAZ and weld metal zones is 286 MPa*m1/2 and 355 MPa*m1/2, respectively.

Development and design of microstructure based coated electrode for ballistic performance of shielded metal arc welded armour steel joints

Joining of high strength armour steel plate developed for lighter armour vehicles using both austenitic and ferritic type of electrode/filler wire could show inferior ballistic performance of the welds. Combination of hard facing electrode and softer Austenitic Stainless Steel electrodes, though provided improved ballistic performance, might not satisfy main design criteria such as strength and toughness due to non-homogeneous microstructure of weld metal. In order to satisfy improved ballistic performance as well as other design parameters, it is highly desirable to develop coated electrode which will attribute more homogeneous microstructure in weld metal similar to high strength armour steel plate.The present investigation has attempted to obtain martensite, bainite and some amount of retained austenite in the weld metal by proper design of alloying elements in the coating of SMAW electrode based on metallurgical index. Three different electrodes attributing different combination of microstructural constituents in armour steel weld metals exhibited excellent ballistic performance combined with other design criteria such as strength and toughness at −40°C. However, among the different microstructural constituents lower bainite along with retained austenite showing maximum toughness both at room temperature and at −40°C could be considered as most desirable microstructure in armour steel weld metal.

Influence of Welding Wire Selection on the Strength and Toughness of Welded Armor Steel Joints*

Abstract Since MIL-A-46100D high hardness armor steel plates with excellent resistance to penetration exhibit high strength, selecting the proper electrode used in the gas metal arc welding process is particularly important to obtain a weld joint with high quality satisfying the adequate strength and toughness requirements at the same time. Selecting a consumable electrode with a lower strength than the armor material enhances the ductility and the toughness, reduces the risk of cracking in the weld zone, but it may lead to a considerable loss in strength of welded armor steel joints as well. Thus, an optimization of strength and toughness is required in welding high hardness armor steel plates. Within the scope of this study, two different austenitic stainless solid wires, one of which conforms to AWS 5.9 and the other one to AWS 5.28, and two different cored wires conforming to AWS 5.29 standards were analyzed and compared with respect to weld joint strength and toughness. Although weld joints fabricated with solid wires were superior in weld toughness, weld joints with austenitic cored wires exhibited considerably higher tensile strengths without a significant loss in toughness.

Effect of Hardfaced Interlayer Thickness and Low Hydrogen Ferritic Capping on Ballistic Performance of Shielded Metal Arc Welded Armour Steel Joints

Armour grade quenched and tempered steel closely confirming to AISI 4340 is well known for its superior ballistic performance and hence used in the fabrication of combat vehicles. The traditional fillers like austenitic stainless steel showed poor ballistic performance of these welded joints as compared to the base metal. Attempts have been made to deposit hardfaced interlayer between austenitic stainless steel weld metals. Though this method, marginal improvements in ballistic performance can be yielded, and cracks were observed in between base metal and hardfaced layer. Thickness of the hardfaced interlayer plays a vital role for the effective ballistic performance. Thus, an attempt has been made to investigate the effect of hardfaced interlayer thickness on ballistic performance of armour steel welds. The results of effect of buttering, low hydrogen ferritic (LHF) filler and three different hardfaced layer thicknesses (4, 5.5 and 7 mm) on ballistic performance of shielded metal arc welded armour steel joints were given.

Microstructural Analysis of Ballistic Tests on Welded Armor Steel Joints

The deformation and fracture behavior of welded joints made from quenched and tempered steel closely conforming to AISI 4340 were investigated. Due to weld thermal cycles and under matching fillers, the welded armor steel joints showed poor ballistic performance compared with the base metal (BM). The problems encountered in the past were reduced by depositing a soft austenitic stainless-steel buttering layer in between the BM and the hardfaced layer. This method showed enhancement in ballistic performance and good weld integrity. In this investigation, an attempt is made to investigate the microstructure after ballistic testing on the weld metal zone consisting of the hardfaced interlayer. The results reveal the microstructural characteristics before and after ballistic testing of armor steel welds fabricated using the shielded metal arc welding (SMAW) process.

Analysis of Welding Groove Angle and Geometry on Strength of Armor Steel

The primary reason for the widespread use of armor steel in tanks and other similar military vehicles is its material properties such as high strength, good weldability, sufficient toughness, and its lower manufacturing cost compared to other armor materials. The purpose of this study is to examine the effects of welding groove angle and geometry on mechanical properties such as tension, compression, and bending strength of butt-joint armor steel. Armor steel plates have been prepared using X and V type welding geometries and three different types of groove angles, and these were joined through gas metal arc welding method (GMAW). The effects of welding parameters such as welding groove geometry and welding groove angle on tension, compression, and bending strength have also been studied numerically using finite element analysis (FEA). As a result, a welding angle of 54 degree and V-groove geometry were found to be the best mechanical properties for tension strength. Additionally, welding groove angle of 48 degree and X-groove geometry were found to be the best solution for compression strength of butt-joint welded armor steel.

Effect of PTA Hardfaced Interlayer Thickness on Ballistic Performance of Shielded Metal Arc Welded Armor Steel Welds

Ballistic performance of armor steel welds is very poor due to the usage of low strength and low hardness austenitic stainless steel fillers, which are traditionally used to avoid hydrogen induced cracking. In the present investigation, an attempt has been made to study the effect of plasma transferred arc hardfaced interlayer thickness on ballistic performance of shielded metal arc welded armor steel weldments. The usefulness of austenitic stainless steel buttering layer on the armor grade quenched and tempered steel base metal was also considered in this study. Joints were fabricated using three different thickness (4, 5.5, and 7 mm) hardfaced middle layer by plasma transferred arc hardfacing process between the top and bottom layers of austenitic stainless steel using shielded metal arc welding process. Sandwiched joint, in addition with the buttering layer served the dual purpose of weld integrity and ballistic immunity due to the high hardness of hardfacing alloy and the energy absorbing capacity of soft backing weld deposits. This paper will provide some insight into the usefulness of austenitic stainless steel buttering layer on the weld integrity and plasma transferred arc hardfacing layer on ballistic performance enhancement of armor steel welds.

Effect of hardfaced interlayer thickness on ballistic performance of armour steel welds

Due to weld thermal cycles and under matching fillers, the armour steel welded joints showed poor ballistic performance compared to the base metal. An attempt was made to enhance the ballistic performance of armour steel welded joints by depositing hardfaced (HF) interlayer between austenitic stainless steel weld metal. Though this method yielded marginal improvements in ballistic performance, cracks were observed in between base metal and HF layers. A novel method was proposed by the same authors to eliminate these cracks by depositing a soft buttering layer using austenitic stainless steel (ASS) consumable in between base metal and HF layer shows additional improvements on ballistic performance. Buttering layer enhanced the ballistic immunity by keeping the weld layer intact successfully at the time of impact, but the bullet was pierced through. In this investigation, an attempt has been made to stop the bullet completely by varying HF interlayer thickness. This paper reveals the effect HF layer thickness on ballistic performance of shielded metal arc welded armour steel welds. A HF interlayer thickness of 0.3 times, the plate thickness is found to be optimum from this investigation.

Effect of buttering and hardfacing on ballistic performance of shielded metal arc welded armour steel joints

Quenched and tempered (Q & T) steel closely confirming to AISI 4340 is well known for its superior ballistic performance and hence used in the fabrication of armour vehicles. These steels are traditionally welded by austenitic stainless steel (ASS) fillers to prevent hydrogen induced cracking. Due to weld thermal cycles and under matching fillers, the armour steel joints show poor ballistic performance compared to the base metal. Attempts were made to deposit hardfaced interlayer between ASS weld metals. Though this method yielded marginal improvements in ballistic performance, cracks were observed in between base metal and hardfaced layers. In this investigation an attempt has been made to eliminate these cracks by depositing a soft buttering layer using ASS consumable in between base metal and hardfaced layer. This paper reveals the effect of buttering and hardfacing on ballistic performance of shielded metal arc welded armour steel joints.

Formation of the stress-relieved structure in the welded region of gas tungsten–arc–welded armor steel with the help of heat distribution

The structure and properties of welded joints of armor steel formed by gas tungsten arc welding (GTAW) are studied.

Microstructural and Impact Considerations of Heat Affected Zone in Gas Tungsten Arc Welding of Armor Steel

Abstract Gas tungsten arc welding is a preferred welding process due to its excellent heat control which provides high quality joinings of various metals. Welded armor steels are widely used in armored vehicles for the ease of production. Thus, characterization of gas tungsten arc welding of armor steels reveals important data on both present applications and potential uses of gas tungsten arc welding in future. In this study, microstructural and mechanical properties of welded armor steel were investigated. Optimal welding parameters depending on a previous research were used to eliminate welding defects. The results have shown that application of pre-heating and/or multi-pass welding on armor steel could provide fine and homogeneously dispersed carbides in heat affected zone.