Improving the Thermal Fatigue Strength of Hot-Working Tools by Laser Treatment

A method for increasing the thermal fatigue strength of a tool used in hot forming of bearing rings by applying circular laser tracks to the working surfaces is considered. Laser treatment is carried out with a power of 2.0...2.5 kW by applying on the end face working surface of the tool in the direction from the center to the periphery of the circular tracks with a common center coinciding with the center of the circumference of the end face; the tool is rotated at a constant angular rate, the spot diameter ds for each track is selected according to the dependence ds,i+1/ds,i = 0.85...0.90, and the laser radiation spots of adjacent tracks have a common point of contact. The results of pilot testing are presented, which confirmed the high technical and economic efficiency of the use of laser quenching for ejectors and punches. A tool made by machining, for example, an ejector of an AMP-70 automatic press, is subjected to volume quenching and tempering. The ejector material was steel 3Kh3M3F, quenching temperature in oil – 1030...1050 °С, tempering temperature – 580...610 °С. After volume quenching, additional machining is carried out, usually grinding, in order to remove the decarbonized layer of material formed during heat treatment and to give the working surface the required roughness class. The final stage in the tool manufacturing is the quenching of its working surface by laser treatment. Pilot testing showed that the use of laser treatment made it possible to increase the durability of ejectors of various types by 2 ... 3 times, of deforming punches – by 2.2 times.

Analisis Struktur Mikro dan Kekerasan Paduan Aluminium ADC 12 Hasil Proses Pengecoran Semi Solid dengan Proses Perlakuan Panas

This research aims to analyze the effect of providing additional heat treatment and artificial aging with variations in temperature of quenching and variations in aging time of ADC12 semi-solid casting result which include hardness and microstructure values. The Selected quenching temperature variations are 10°C, 30°C and 50°C. While the aging time variations are 0 h, 1 h, 3 h, 5 h, 7 h, 9 h, 11 h and 13 h. The tests carried out are hardness testing as well as microstructure that will be used to calculate the grain size values and structural density. The highest hardness value was at 180°C, 10°C cooling media variation with 5 h aging time is 83.10 HB. While the smallest grain size value was at the temperature of 10°C cooling media with an aging time of 5 h is 42.797 µm. The optimal value lies at a temperature of 10°C with an aging time of 5 h resulting hardness 83.7911 HB, the average of grain size is 13.5995 µm and the grain density value is 0.8892 with desirability reaching 0.920.

Mn4+ Activated Deep Red Emitting Perovskite Type Phosphors for Horticulture Lighting

Red emitting Mn4+ doped oxides are a promising class of materials to improve the colour rendering and luminous efficacy of phosphor-converted light-emitting diodes (pcLEDs). For pcLEDs, the optical properties are crucial w.r.t commercial acceptance. In this work, luminescence spectra and decay curves of Sr2YNbO6, Sr2YTaO6 and Sr2LaNbO6 have been recorded, other Mn4+ doped phosphors show that quenching occurs through thermally activated crossover between the 4T2 excited state and 4A2 ground state. The quenching temperature can be optimized by designing the host lattice in which Mn4+ has a high 4T2 state energy. The main target is to study the influence of the above-mentioned host materials on the emission spectra, PL quenching, and quantum yield of the deep red Mn4+ ion. The present study provides detailed insights into temperature and concentration quenching of Mn4+ emission and can be used to realize superior narrow-band red Mn4+ phosphors for horticultural lighting.

Analisis Struktur Mikro dan Kekerasan Paduan Aluminium ADC 12 Hasil Proses Pengecoran Semi Solid dengan Proses Perlakuan Panas

This research aims to analyze the effect of providing additional heat treatment and artificial aging with variations in temperature of quenching and variations in aging time of ADC12 semi-solid casting result which include hardness and microstructure values. The Selected quenching temperature variations are 10°C, 30°C and 50°C. While the aging time variations are 0 h, 1 h, 3 h, 5 h, 7 h, 9 h, 11 h and 13 h. The tests carried out are hardness testing as well as microstructure that will be used to calculate the grain size values and structural density. The highest hardness value was at 180°C, 10°C cooling media variation with 5 h aging time is 83.10 HB. While the smallest grain size value was at the temperature of 10°C cooling media with an aging time of 5 h is 42.797 µm. The optimal value lies at a temperature of 10°C with an aging time of 5 h resulting hardness 83.7911 HB, the average of grain size is 13.5995 µm and the grain density value is 0.8892 with desirability reaching 0.920.

Effect of Hot Working Processes on Microstructure and Mechanical Properties of Pipeline Steel

The microstructure and microhardness of X70 pipeline steel were investigated after conducting different processing routes. The microstructure was characterized using optical and electron microscopy. Scanning electron microscopy equipped with electron backscattered diffraction (EBSD) and transmission electron microscopy techniques were applied for investigation of different thermal processing treatment conditions. Mechanical properties were characterized by a microhardness tester. The results show that the microstructure mainly consists of granular bainite, acicular ferrite and a small amount of M/A constituents under hot rolling states. There are many dislocations inside the acicular ferrite. The thermal simulation experiments show that the microstructure becomes homogeneous with the increase in cooling rate. The acicular ferrite morphology becomes fine and uniform, and the content of M/A constituents increases at the same compression amount. The compression gives rise to the accumulated strain and stored energy, which accelerate the transformation of acicular ferrite and refine the microstructure of the pipeline steel. The microhardness rises with the increase in deformation ratio and cooling rate. The microstructure of the pipeline steel subjected to the isothermal quenching process is ultrafine ferrite and M/A islands. When the isothermal quenching temperature reaches 550 °C, a small amount of upper bainite appears in the microstructure. With the increase in isothermal quenching temperature, the microhardness decreases. Acicular ferrite is a better candidate microstructure than ultrafine ferrite for the pipeline steels.

Heat Treatment Design for a QP Steel: Effect of Partitioning Temperature

Designing a new family of advanced high-strength steels (AHSSs) to develop automotive parts that cover early industry needs is the aim of many investigations. One of the candidates in the 3rd family of AHSS are the quenching and partitioning (QP) steels. These steels display an excellent relationship between strength and formability, making them able to fulfill the requirements of safety, while reducing automobile weight to enhance the performance during service. The main attribute of QP steels is the TRIP effect that retained austenite possesses, which allows a significant energy absorption during deformation. The present study is focused on evaluating some process parameters, especially the partitioning temperature, in the microstructures and mechanical properties attained during a QP process. An experimental steel (0.2C-3.5Mn-1.5Si (wt%)) was selected and heated according to the theoretical optimum quenching temperature. For this purpose, heat treatments in a quenching dilatometry and further microstructural and mechanical characterization were carried out by SEM, XRD, EBSD, and hardness and tensile tests, respectively. The samples showed a significant increment in the retained austenite at an increasing partitioning temperature, but with strong penalization on the final ductility due to the large amount of fresh martensite obtained as well.

The effects of morphology of ferrite and non-metallic inclusions on corrosion behaviour of as-cast 304 stainless steel

The effects of morphology of ferrite and non-metallic inclusions on corrosion resistance of as-cast 304 stainless steel (304 SS) were investigated. With the decrease in quenching temperature from 1723 K to 1648 K, the different microstructures of the as-cast 304 SS were obtained as the following series: austenitic-lathy δ ferrite, austenitic-colony δ ferrite and austenitic-blocky δ ferrite, and the average inclusion size increased. The electrochemical results show that the sample with the microstructure of austenitic- lathy δ ferrite and smaller size inclusions had a higher corrosion tendency and the lower pitting resistance. Furthermore, the effect of morphology and content of ferrite on corrosion resistance was greater than that of inclusion size under the current experimental conditions. Therefore, a promising method was developed to improve the corrosion resistance of as-cast 304 SS by changing the solidification process.