Mechanical Properties and Microstructure of Austenite-Ferrite Duplex Stainless Steel Hybrid (Laser + GMAW) and SAW Welded Joint

The purpose of the research was to develop a technology for producing thick-walled duplex steel welded joints. The material used in the research was X2CrNiMoN22 duplex steel in the form of a 15 mm thick plate. The welded joint was produced by the modern, high-performance Hybrid Laser Arc Welding (HLAW) method. The HLAW method involves welding a joint using a laser, the Gas Metal Arc Welding (GMAW) method and the Submerged Arc Welding (SAW) method. The HLAW method was used to make the root pass of the double butt welded joint, while the filler passes were made by the SAW method. The obtained welded joint was subjected to non-destructive and destructive testing. The non-destructive and macroscopic tests allowed the joint to be classified to the quality level B. Microscopic examinations revealed the presence of ferritic-austenitic microstructure in the base material and the weld, with different ferrite content in specific joint areas. The analysed joint had high strength properties (tensile strength (TS) ~ 790 ± 7 MPa) and high ductility of weld metal (~160 ± 4 J) heat-affected zone (~216 ± 26 J), and plasticity (bending angle of 180° with no macrocracks). At the same time, hardness on the cross-section of the welded joint did not exceed 280 HV10.

Evaluation of the Properties and Microstructure of Thick-Walled Welded Joint of Wear Resistant Materials

The research was conducted on a thick-walled welded joint between the HTK 900H wear-resistant steel plates and the A6 cast profile. The aim of the experiment was to produce a joint with the relevant performance requirements, i.e., a good abrasion resistance joint in the weld face area while ensuring its proper plasticity. The welded joint was made using the MAG PULSE and the high-performance MAG TANDEM methods under automated conditions using the linear welding energy ranging from 1.2 to 2.2 kJ/mm for the different joint regions. The scope of the research included both non-destructive and destructive testing. The non-destructive visual (VT), magnetic-particle (MT), and ultrasonic (UT) tests revealed a good quality of the welded joint with no significant welding imperfections. The microstructure of the welded joint in the weld zone was characterized by a dominant volume fraction of martensite/bainite. The measurement of hardness near the face of the weld confirmed obtaining similar values for this parameter. The HTK 900H steel was characterized by hardness at the level of 383 HV10, whereas the A6 cast-328 HV10, and the weld-276 HV10. At the same time, the analyzed joint showed high ductility in the range of 86 to 159 J. The tests carried out showed that the linear energy control allowed a welded joint with the required performance characteristics to be obtained.

Microstructure and Mechanical Properties of Modern 11%Cr Heat-Resistant Steel Weld Joints

In addition to good high-temperature creep resistance and adequate heat resistance, steels for the power industry must have, among other things, good weldability. Weldability of such steels is one of the criteria determining whether or not the material is suitable for applications in the power industry. Therefore, when materials such as martensitic steel Thor 115 (T115) are introduced into the modern power industry, the quality and properties of welded joints must be assessed. The paper presents the results of metallographic and mechanical investigations of T115 martensitic steel welded joints. The analysis was carried out on joints welded with two filler metals: WCrMo91 (No. 1) and EPRI P87 (No. 2). The scope of the investigations included: microstructural investigations carried out using optical, scanning and transmission electron microscopy and mechanical testing, i.e., Vickers microhardness and hardness measurement, static tensile test and impact test. The macro- and microstructural investigations revealed correct structure of the weld, without welding imperfections. The microstructural investigations of joint No. 1 revealed a typical structure of this type of joint, i.e., the martensitic structure with numerous precipitates, while in joint No. 2, the so-called Nernst’s layers and δ-ferrite patches were observed in the weld fusion zone as well as the heat affected zone (HAZ). The mechanical properties of the test joints met the requirements for the base material. A slight influence of the δ-ferrite patch on the strength properties of joint No. 2 was observed, and its negative effect on the impact energy of HAZ was visible.

Pelvic fractures in children and adolescents in polytrauma and high-energy injuries

BACKGROUND

This paper is a retrospective analysis of the treatment of pelvic fractures in children and adolescents who sustained polytrauma and high-energy injuries. Incidence varies from 0.2% to 7.5% of all pediatric injuries. Most often, these are isolated stable fractures that do not require hospitalization. However, a group of unstable fractures requiring surgical intervention remains.

MATERIAL AND METHODS

37 patients aged 5 to 17 years (mean: 13.6), were hospitalized between 2002 and 2010. This group comprised 21 boys and 16 girls who were followed up for 1 to 8 years (mean: 3.2). In this cohort, only cases of pelvic fractures that required hospitalization for other reasons were taken into account. The causes of injuries were car accidents, falls from bicycles and sports injuries. The Torode and Zieg classification was used for assessment, including surgical guidance by Mears/Gordon.

RESULTS

There were 11 cases of type I, 7 cases of type II and III and 9 cases of type IV fractures. Moreover, 3 cases of S-H II acetabular fractures were identified. The surgical treatment made use of external pelvic fixators, combined internal coaptation with cannulated screws or K-wires, and LCP plates or combined techniques.

CONCLUSIONS

1. Torode and Zieg type I to III pelvic fractures in children do not usually require surgical treatment. 2. To rode and Zieg type IV unstable fractures require operative treatment in order to avoid complications and aid faster recovery.

[Analysis of treatment results of humeral lateral condyle fractures in children]

On the basis of 60 cases authors analyze treatment results of the humeral lateral condyle fractures in children. This type of fracture is a second most common elbow fracture in children after supracondylar fracture of the humerus. Authors consider this fracture to be the most difficult to diagnose among all elbow injuries. Analyzed cohort of patients consists of 54 at age between 1.5 to 10 years and 6 patients between 12 to 17 years of age. In 75% of cases operative treatment was delayed due to late referral from other hospitals. According to appearance of the fracture line on X-rays there were 53 cases of type II and 7 cases of type 1 according to Milch classification system. The amount of displacement was evaluated according to Jakob scale and there were 35 cases of III degree, 17 cases of II degree and 8 cases of I degree of displacement. All patients were evaluated with antero-posterior and lateral distal humerus x-rays. In some cases other diagnostic techniques were used. In older children computerized tomography and in younger children ultrasound examination was performed. The treatment results were evaluated according to Hardacre scale. Follow-up time was 1 to 13 years. There were 27 very good and 27 good results in a 54 cases group of patients who underwent surgery within 15 days since injury. In other group which consists of 6 patients who underwent surgery more than 5 weeks after injury there were 2 cases of very good, 2 cases of good; and 2 cases of bad results. Authors believe that putting a proper diagnosis of humeral lateral condyle fracture in children and performing an operative treatment results in a good and a very good outcomes. Basing on the analysis of treatment results of authors cohort of patients, they claim that precise diagnosis and proper determining of degree of displacement increases the number of patients qualified to operative treatment.

[Application of Ponseti method in case of neglected talipes equinovarus in 4 years and 9 months old boy with DiGeorge syndrome--case report]

Case report of application of Ponseti method in treatment of neglected congenital talipes equinovarus in boy with DiGeorge syndrome who was 4 years and 9 months of age at the beginning of the treatment. Foot was classified as very severe, scored 4.5 points according to Pirani and 15 points according to DiMeglio classification. After 9 casts set according to Ponseti protocol good correction of all components was achieved accept for the equinus deformity. Achilles lengthening procedure was done, but there was necessity to perform posterior release to achieve good dorsiflexion. Finally, goals of treatment were achieved: the foot is flexible, well shaped, pain free, ready for weight-bearing and use of commercial shoes. At current stage of treatment the foot scores 0.5 points according Pirani and 4 points according to DiMeglio classifications.

[Results of treatment of the intercondylar eminence of tibia in children]

Fracture of the tibial eminence in children is a condition in which there is no widely accepted and approved therapeutic scheme. The greatest divergence of treatment options concerns type II according to Mayers and McKeever classification. Described therapeutic options range from cast immobilisation of the lower extremity without attempt of closed reduction to open reduction with internal fixation. Paper shows the results of treatment of tibial emienence fractures in children treated at our institution. Cohort of patients consists of 21 children at age 7 to 16 years of age (mean 12.2 years). There were three cases of type I, five cases of type II and thirteen cases of type III fracture according to Mayers and McKeever classification. Operatively 16 patients were treated with type II and III fracture, and the rest of them were treated nonoperatively. Open reduction and internal fixation was performed according to modified technique described in 1937 by H. Lee. The results were evaluated by X-ray, clinical examination of stability and range of motion of the affected knee and by subjective clinical outcome with use of modified Lysholm knee scale. All patients treated operatively presented very good and good clinical outcome. Nonoperatively treated patients was a small and no homogenous group. Results of treatment ranged from very good to poor. Worse outcomes were associated with additional injuries to the affected knee (poor result in patient with type II fracture) and qualification for the conservative treatment in patient with type III fracture.

[Split posterior tibial tendon transfer as a selected technique of treatment of spastic equino-varus deformity in children]

Equinovarus deformity is one of the most common deformities seen in patients with cerebral palsy. During years between 1993 and 2004 in 36 patients with cerebral palsy 46 operative procedures of split posterior tibial tendon transfer to peroneus brevis muscle were performed to correct varus deformity of the foot. Additionally equinus was corrected by lengthening lengtheninglengthening of the calcaneal tendon in 42 cases and in 4 cases by gastrocnemius recession according to Baker modification of Vulpius procedure. Children's age at the time of operation was between 3.5 and 16 years of age (average 7.5). In our cohort of 36 patients there were 10 cases of quadriplegia (28%), 12 cases of hemiplegia (33%), 12 cases of paraparesis inferior (33%) and 2 cases of monoplegia (6%). 25 patients with 34 operated feet (73.9%) reported for final examination. Follow-up period was from 18 months to 11 years (average 5.5 years). At final examination we evaluated clinical effectiveness of gait, passive and active range of movement, plantograms, and subjective evaluation of patient and patients' parents. Wearing of orthoses and orthopaedic footwear was noted. The results were divided into groups according to Green's classification. There were 67.6% of very good results, 23.6% of good results and 8.8% of poor results. Basing on our experience in treatment of spastic equinovarus deformity of the foot in children with cerebral palsy we stand, that split posterior tibial tendon transfer can bring good results and is a valuable surgical technique in treatment of equinovarus deformity.

[The surgical treatment of proximal humerus fractures in children and adolescent]

The aim of his study was to evaluate outcomes of the surgical treatment of proximal humerus fractures in children. The studied group consisted of 24 patients who were operated on during the period 1997-2006. Operative and postoperative complications were evaluated. For the follow up evaluation Constant-Murley Score and Oxford Shoulder Score in own modification were employed. The scores assessed the following characteristics: pain, activity level in daily living, range of motion and shoulder strength. In all reported cases a correct union was obtained as well as the anatomical axis of the bone (only in one child 20 degrees varus curve of the bone remained but without limitation in the shoulder motion range). The total of 21 patients were evaluated during follow-up visits, 13 patients obtained the result "very good" and 8 "good" in the Consant-Murley Score. According to the Oxford Schoulder Score 18 patients obtained maximum results, and 3 children results above 95% of the maximum score. In the study group the results of the surgical treatment of proximal humerus fractures were very good. We can therefore recommend this type of treatment in patients with proximal humerus fracture with large dislocation and angulation.

[Feet deformation treatment in children with arthrogryposis multiplex congenita (AMC)--evaluation of the results]

In Arthrogryposis Multiplex Congenita (AMC) feet deformations are frequent. They have form of talipes equinovarus, or less frequently of plano-valgus. The study included influence of various surgical techniques on final result of foot treatment in arthrogryposis. The aim of the study was to analyse errors in classification and surgical technique influencing the final result. Between 1986 and 2004 21 AMC children were surgically treated. In all of the patients the disease was accompanied by heavy feet deformations: 38 talipes equinovarus deformations and 1 plano-valgus. Age of the treated children was between 7 months and 4 years. All feet required surgery. Follow-up period was 3 to 20 years, mean 12.5 years. During the follow-up examination the following elements were evaluated: foot appearance, gait mechanics, foot load level, wearing commercial shoes or orthopaedic equipment. Additionally radiography of feet in AP and lateral projection was performed. Posterior liberation was performed in 21 feet, peritarsal reposition in 18 feet. In case of 13 feet the primary correction was satisfactory. In the remaining 26 feet re-surgeries were necessary, including astrogolectomy in 9 feet. 13 good results were obtained--in which feet were properly loaded, adapted to common shoes and painless. 15 satysfying results were obtained--the feet required orthopaedic shoes; and 11 bad results, where temporary foot pain additionally occurred. Excessively conservative primary surgery in case of heavy foot deformations was a cause for multiple re-surgeries.