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.

Download Full-text

Effect of Alloying Composition on Microstructure and Mechanical Properties of Ultranarrow Gap Welded Joints of U71Mn Rail Steel

Advances in Materials Science and Engineering ◽

10.1155/2021/9282463 ◽

2021 ◽

Vol 2021 ◽

pp. 1-11

Author(s):

Lian Gong ◽

Hui Liu ◽

Cheng Lv ◽

Lijun Zhao

Keyword(s):

Mechanical Properties ◽

Base Metal ◽

Welded Joints ◽

Alloy Composition ◽

Rail Steel ◽

Base Material ◽

Average Hardness ◽

Microstructure And Mechanical Properties ◽

Fine Pearlite ◽

The Impact

A new welding method, ultranarrow gap welding with constrained arc by flux band, is proposed to compensate for the low quality of rail thermite welded joints. This article presents the results of research on the microstructure and mechanical properties of ultranarrow gap welded joints of U71Mn rail steel made using three types of alloying composition content flux bands. Results indicated that the base metal metallographic microstructure consisted mainly of pearlitic, the HAZ was mainly composed of fine pearlite, and the microstructure of the welded bead was composed of acicular ferrite, while the weld grain size decreased as the alloy composition increased. The average hardness noticeably changed in weld metal as the alloy composition increased, and when the alloy composition reached 19%, the hardness was equivalent to the base material. The average hardness value of the HAZ (35.8 HRC) was higher than that of the base metal (24.8 HRC). The tensile strength increased, and the percentage elongation after fracture decreased with increasing alloying composition from 9% to 19%. The impact absorbing energies were decreased as the alloying composition increased. Consequently, all the mechanical properties of rail ultranarrow gap welding were higher than those of the standard requirements of the rail flash welding. And the optimal alloying composition of flux band was 19%.

Download Full-text

Microstructure and Mechanical Properties of Laser-Welded DP Steels Used in the Automotive Industry

Materials ◽

10.3390/ma14020456 ◽

2021 ◽

Vol 14 (2) ◽

pp. 456

Author(s):

Hanbing He ◽

Farnoosh Forouzan ◽

Joerg Volpp ◽

Stephanie M. Robertson ◽

Esa Vuorinen

Keyword(s):

Mechanical Properties ◽

Fatigue Limit ◽

Welded Joints ◽

Base Material ◽

High Strength ◽

Strength Properties ◽

Fatigue Tests ◽

Steel Sheets ◽

Lower Elongation ◽

Similar Yield

The aim of this work was to investigate the microstructure and the mechanical properties of laser-welded joints combined of Dual Phase DP800 and DP1000 high strength thin steel sheets. Microstructural and hardness measurements as well as tensile and fatigue tests have been carried out. The welded joints (WJ) comprised of similar/dissimilar steels with similar/dissimilar thickness were consisted of different zones and exhibited similar microstructural characteristics. The trend of microhardness for all WJs was consistent, characterized by the highest value at hardening zone (HZ) and lowest at softening zone (SZ). The degree of softening was 20 and 8% for the DP1000 and DP800 WJ, respectively, and the size of SZ was wider in the WJ combinations of DP1000 than DP800. The tensile test fractures were located at the base material (BM) for all DP800 weldments, while the fractures occurred at the fusion zone (FZ) for the weldments with DP1000 and those with dissimilar sheet thicknesses. The DP800-DP1000 weldment presented similar yield strength (YS, 747 MPa) and ultimate tensile strength (UTS, 858 MPa) values but lower elongation (EI, 5.1%) in comparison with the DP800-DP800 weldment (YS 701 MPa, UTS 868 MPa, EI 7.9%), which showed similar strength properties as the BM of DP800. However, the EI of DP1000-DP1000 weldment was 1.9%, much lower in comparison with the BM of DP1000. The DP800-DP1000 weldment with dissimilar thicknesses showed the highest YS (955 MPa) and UTS (1075 MPa) values compared with the other weldments, but with the lowest EI (1.2%). The fatigue fractures occurred at the WJ for all types of weldments. The DP800-DP800 weldment had the highest fatigue limit (348 MPa) and DP800-DP1000 with dissimilar thicknesses had the lowest fatigue limit (<200 MPa). The fatigue crack initiated from the weld surface.

Download Full-text

Microstructural and Mechanical Characterization of Electron Beam Welded Joints of High Strength S960QL and Weldox 1300 Steel Grades

Archives of Metallurgy and Materials ◽

10.1515/amm-2017-0092 ◽

2017 ◽

Vol 62 (2) ◽

pp. 627-634 ◽

Cited By ~ 7

Author(s):

S. Błacha ◽

M.S. Węglowski ◽

S. Dymek ◽

M. Kopyściański

Keyword(s):

Mechanical Properties ◽

Electron Beam ◽

Welded Joints ◽

Base Material ◽

Steel Grade ◽

Fusion Line ◽

Bending Test ◽

Metallographic Examination ◽

Steel Grades ◽

The Impact

Abstract The paper shows the results of metallographic examination and mechanical properties of electron beam welded joints of quenched and tempered S960QL and Weldox 1300 steel grades. The aim of this study was to examine the feasibility of producing good quality electron beam welded joints without filler material. Metallographic examination revealed that the concentrated electron beam significantly affects the changes of microstructure in the weld and the adjacent heat affected zone (HAZ) in both steel grades. The microstructure of the welded joints is not homogeneous. The four zones, depending on the distance from the weld face, can be distinguished. Basically, the microstructure of the weld consists of a mixture of martensite and bainite. However, the microstructure of HAZ depends on the distance from the fusion line. It is composed of martensite near the fusion line and a mixture of bainite and ferrite in the vicinity of the base material. Significant differences in mechanical properties of the welded joints were observed. For a butt welded joint of the S960QL steel grade the strength is at the level of the strength of the base material (Rm = 1074 MPa). During the bending test the required angle of 180° was achieved. The impact strength at −40°C was 71,7 J/cm2. In the case of the Weldox 1300 steel grade butt welded joints exhibit high mechanical properties (Rm = 1470 MPa), however, the plastic properties are on the lower level than for the base material.

Download Full-text

Microstructure and Mechanical Properties of Heat-Affected Zone of Repeated Welding AISI 304N Austenitic Stainless Steel by Gleeble Simulator

Metals ◽

10.3390/met8100773 ◽

2018 ◽

Vol 8 (10) ◽

pp. 773

Author(s):

Y.H. Guo ◽

Li Lin ◽

Donghui Zhang ◽

Lili Liu ◽

M.K. Lei

Keyword(s):

Mechanical Properties ◽

Stainless Steel ◽

Austenitic Stainless Steel ◽

Impact Energy ◽

Heat Affected Zone ◽

Ferrite Content ◽

Equipment Safety ◽

Microstructure And Mechanical Properties ◽

Δ Ferrite ◽

The Impact

Heat-affected zone (HAZ) of welding joints critical to the equipment safety service are commonly repeatedly welded in industries. Thus, the effects of repeated welding up to six times on the microstructure and mechanical properties of HAZ for AISI 304N austenitic stainless steel specimens were investigated by a Gleeble simulator. The temperature field of HAZ was measured by in situ thermocouples. The as-welded and one to five times repeated welding were assigned as-welded (AW) and repeated welding 1–5 times (RW1–RW5), respectively. The austenitic matrices with the δ-ferrite were observed in all specimens by the metallography. The δ-ferrite content was also determined using magnetic and metallography methods. The δ-ferrite had a lathy structure with a content of 0.69–3.13 vol.%. The austenitic grains were equiaxial with an average size of 41.4–47.3 μm. The ultimate tensile strength (UTS) and yield strength (YS) mainly depended on the δ-ferrite content; otherwise, the impact energy mainly depended on both the austenitic grain size and the δ-ferrite content. The UTS of the RW1–RW3 specimens was above 550 MPa following the American Society of Mechanical Engineers (ASME) standard. The impact energy of all specimens was higher than that in ASME standard at about 56 J. The repeated welding up to three times could still meet the requirements for strength and toughness of welding specifications.

Download Full-text

The Influence of Severe Plastic Deformation Process on Structure and Properties of AZ 31 Alloy after Selected Heat Treatment

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.275.134 ◽

2018 ◽

Vol 275 ◽

pp. 134-146

Author(s):

Stanislav Rusz ◽

Ondřej Hilšer ◽

Stanislav Tylšar ◽

Lubomír Čížek ◽

Tomasz Tański ◽

...

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Plastic Deformation ◽

Severe Plastic Deformation ◽

Structure Refinement ◽

Hardness Measurement ◽

Az31 Alloy ◽

Strength Properties ◽

Aviation Industry ◽

Initial State

The technology of structure refinement in materials with the aim of achieving substantial mechanical properties and maintaining the required plasticity level is becoming increasingly useful in industrial practice. Magnesium alloys are very progressive materials for utilization in practice thanks to their high strength-to-weight ratios (tensile strength/density). The presented paper analyses the effect of the input heat treatment of the AZ31 alloy on the change of structure and strength properties through the process of severe plastic deformation (SPD), which finds an increasing utilization, especially in the automotive and aviation industry. For the study of the influence of the SPD process (ECAP method) on the properties of the AZ31 alloy, two types of thermal treatment of the initial state of the structure were selected. The analysis of the structure of the AZ31 alloy was performed in the initial state without heat treatment and subsequently after heat treatment. In the next part, the influence of the number of passes on the strengthening curves was evaluated. Mechanical properties of the AZ31 alloy after ECAP were evaluated by hardness measurement and completed by structure analysis.

Download Full-text

Improving the mechanical properties of PHS laser welded joints by adding Ni foil to suppress δ-ferrite

Journal of Materials Research and Technology ◽

10.1016/j.jmrt.2020.03.035 ◽

2020 ◽

Vol 9 (3) ◽

pp. 5184-5193 ◽

Cited By ~ 1

Author(s):

Xiaming Chen ◽

Xiaonan Wang ◽

Qian Sun ◽

Zengrong Hu ◽

Pengcheng Huan ◽

...

Keyword(s):

Mechanical Properties ◽

Welded Joints ◽

Δ Ferrite

Download Full-text

Data Mining Methods for Prediction of Multi-Component Al-Si Alloy Properties Based on Cooling Curves

Journal of Materials Engineering and Performance ◽

10.1007/s11665-019-04442-z ◽

2019 ◽

Vol 28 (12) ◽

pp. 7431-7444 ◽

Cited By ~ 2

Author(s):

Krzysztof Regulski ◽

Dorota Wilk-Kołodziejczyk ◽

Tomasz Szymczak ◽

Grzegorz Gumienny ◽

Zenon Pirowski ◽

...

Keyword(s):

Mechanical Properties ◽

Data Mining ◽

Strength Properties ◽

Cooling Curve ◽

Cooling Curves ◽

Alloying Additives ◽

Statistical Relationships ◽

Alloy Properties ◽

Short Time ◽

The Impact

AbstractThe paper concerns the mechanical properties of hypoeutectic Al-Si alloy (silumin) with the addition of Cr, Mo, V and W. Changes in microstructure under the impact of these elements result in a change in the mechanical properties. Crystallization of Al-Si alloys determines grain size reduction, which causes a significant increase in their strength properties. Crystallization subjected to modifications through the influence of alloying additives can be described by the cooling curve run. Statistical relationships between the characteristic values of cooling curves and mechanical properties are investigated with data mining techniques of regression, especially regression trees. Such knowledge could provide an ability of a property prediction on the basis of cooling curves in terms of the benefits of a short time of the curve registration.

Download Full-text

Mechanical Properties of Fibre-Metal Composites Connected by Means of Bolt Joints

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.837.296 ◽

2013 ◽

Vol 837 ◽

pp. 296-301

Author(s):

Sławomir Zolkiewski

Keyword(s):

Mechanical Properties ◽

Composite Materials ◽

Polyester Resin ◽

Steel Plate ◽

Fibrous Composite ◽

Laminate Plate ◽

Strength Properties ◽

Fibre Metal Laminates ◽

Fibre Metal ◽

The Impact

The fibre-metal laminates made of a steel plate and fibreglass laminate plate were tested in the special laboratory stands. Epoxy resin and polyester resin were used as matrix to fabricate the composites. The fibre-metal laminates combine advantages of metals and laminates. These materials have very good force versus displacement characteristics and overall mechanical properties. They are very popular and widely applied in technical systems. They can be put to use in connecting materials made of various fabrics, connecting high number layer laminates and most of all connecting metals and laminates. In this paper there are the results of testing fibrous composite materials connected in bolt joints presented. Composite materials reinforced with fiberglass, carbon and aramid fibers are considered. The impact of number of applied bolts in a joint on strength properties was investigated. The connections by means of eight or sixteen bolts were compared. A major problem of modelling the composites is assuming physical and material parameters of the analyzed elements.

Download Full-text

The structure and properties of laser seam stepper system (LSS) welded the low alloy high strength steel DOCOL 1200M with martensitic structure

Materials Science Advanced Composite Materials ◽

10.18063/msacm.v2i1.660 ◽

2018 ◽

Vol 2 (1) ◽

Cited By ~ 1

Author(s):

Jacek Górka 1 ◽

Andrzej Ozgowicz 2

Keyword(s):

Welded Joints ◽

Base Material ◽

High Strength ◽

Hardness Measurement ◽

Welding Parameters ◽

Martensitic Structure ◽

Structure And Properties ◽

Destructive Testing ◽

Metallographic Examination ◽

Actual Length

This paper will present the influence of joining process parameters on the structure and properties of overlapped welded joints of 1.8 mm DOCOL 1200M steel. The obtained welded joints were subjected to micro- and macroscopic metallographic examination and hardness measurement. The visual inspections and non-destructive testing made it possible to develop the field of welding parameters to allow obtaining full penetration joints (depending on requirements) or partial penetration joints. For present welding parameters, i.e. feed rate and weld length, which are constant, the actual length of weld is determined by welding frequency. In each case, the microscopic examinations revealed martensitic structure in the weld area, and with the increase in linear welding energy the size of martensite needles became larger, especially in relation to the base material. In HAZ, the martensitic structure is tempered. It has been shown that with appropriately selected parameters the Laser SEAM Stepper method is suitable for welding the DOCOL 1200M steel. With the increase in welding power, the penetration depth increases.

Download Full-text

Assessment of Service Life of HCM12 Steel After 100 000 Hrs of Service

Archives of Metallurgy and Materials ◽

10.1515/amm-2016-0173 ◽

2016 ◽

Vol 61 (2) ◽

pp. 1021-1029 ◽

Cited By ~ 1

Author(s):

A. Zieliński ◽

H. Paszkowska ◽

P. Skupień ◽

G. Golański

Keyword(s):

Mechanical Properties ◽

Creep Resistance ◽

Residual Life ◽

Strength Properties ◽

Steam Superheater ◽

Significant Loss ◽

Creep Tests ◽

Supercritical Steam Parameters ◽

Steam Parameters ◽

The Impact

AbstractThe subject of the research was a material in the form of a ϕ38×4 pipe from HCM12 steel used for steam superheater coils in power boilers with supercritical and ultra-supercritical steam parameters. This article presents results of investigations of mechanical properties and microstructure of material of the examined tube in the as-received condition and after 100,000 h service at 585°C under creep conditions. Creep tests were carried out for the material after 100,000 h service to determine the disposable residual life. The impact of changes in mechanical properties and degradation of the microstructure on the loss of creep resistance compared to the as-received condition was assessed. The investigations have revealed that the examined steel after 100,000 h service meets the requirements for this steel in the as-received condition with regard to strength properties at room and elevated temperature. The creep tests have revealed a significant loss of creep resistance, which was estimated at around 60-70% compared to the as-received condition.

Download Full-text