Billet Preparation Research Articles

Heat treatment technology for roll billets of steel 150KhNM for improving their quality and operating life

An optimum production scheme is developed and assimilated at the ChMK for preparation of roll billets of steel 150KhNM in order to provide high operating properties. Heat treatment technology is developed for roll billets of in-house production, metal properties (hardness, microstructure) are studied after different versions of heat treatment, and scrapping of billets for cracks during production is excluded.

Prepartion of Semisolid AM60 Alloy by Novel Self-Inoculation Method

A research focus on semi-solid metal processing is the preparation of semi-solid slurry with non-dendritic microstructure. During the past several decades, people tended to obtain the non-dendritic structure by stirring melt of alloy which downs to the semi-solid temperature range, such as mechanical stirring and electromagnetic stirring; In recent years, with the technological innovation of semi-solid slurry preparation turned to be more convenient and efficient, most of these processes are based on the control of nucleation and growth process of primary phase during solidification, such as NRC, SSR, SLC, SEED, and CRP. In this paper, a novel process, named as “Self-Inoculation Method (SIM)”, has been proposed for semi-solid slurry preparation. The process involves self-inoculants addition to the melt, and then pouring the melt to mould through a multi-stream mixed cooling channel. The melt was avoided chemical pollution due to the particles of self-inoculants from the same composition as the melt. The semi-solid billets of AM60 alloy with non-dendritic structure were prepared by SIM. The effects of process parameters on the microstructure and the mechanism on refinement of alloy were investigated. The results indicate that pouring temperature, addition amount of self-inoculants and slope angle of the cooling channel are key factors for SIM process. The optimized parameters for the billet preparation of AM60 alloy are obtained: pouring temperature is at 680°C~700°C；addition of self-inoculants are between 5%~7% (mass fraction)；slope angle of the cooling channel is at 30°~45°. The heterogeneous nucleation was enhanced as the addition of self-inoculants; the formation of chill crystal and the fragmentation of dendrites because of cooling and shearing of the cooling channel, resulting in the increase of grains density and a small grain size.

Towards the first generation micro bulk forming system

The industrial demand for micro mechanical components has surged in the later years with the constant introduction of more integrated products. The micro bulk forming process holds a promising pledge of delivering high quality micro mechanical components at low cost and high production rates. This work describes a number of prototype system units, which collectively form a desktop sized micro forming production system. The system includes a billet preparation module, an integrated transfer system, a temperature controlled forming tool, including process simulation, and a dedicated micro forming press. The system is demonstrated on an advanced micro forming case where a dental component is formed in medical grade Titanium.

The Optimization of the Technologic Parameter in Strong Cooling with Single-Tube on the A356 Alloy

The tube spread around strong cooling technology is new technology of the making semisolid slurry and semisolid billet in Semi-Solid Processing. The technologic parameter of its on the A356 Alloy is researched in the article. It is showed by the result of the experimentation: that the fine and form verge on rotundity crystal grain is made at 180L/h and at 640-650°C. It has met all the conditions in the semi-solid processing on semisolid billet. Semi-solid forming technology has been called the "new metal processing technology in the 21st century", which in foreign countries has certain industrial applications. In 1996 in the United States the sales of semi-solid casting was up to 1 billion dollars. But the industrial application in China is almost empty, one of the most important reasons is: the preparation of slurry or billet is too complicated or cost of production is too high, so that semi-solid forming technology in China has suffered serious setbacks on the road of industrialization. According to this situation, we have done a little attempts on manufacturing slurry and billet of semi-solid forming and have developed a new technology of spread around strong cooling whose intellectual property rights belong to us, equipment production is simple and the process is easy to control and the semi-solid slurry is east to prepare continuously. It will be discussed in this paper that process parameters of the single-tube strong cooling impacts on the microstructure of semi-solid

Theory and application research development of semi-solid forming in China

In order to adapt to the trend of “energy saving and emission reduction” and impel the practical application of semi solid processing (SSP) in China, the progress and application of semi-solid theory in China have been reviewed briefly and systematically. It was emphasized on basic theories, such as formation of globular grains, rheology, high pressure solidification and plastic deformation and applications, such as material design, preparation of semi-solid billets (slurries), thixoforming and application status, which are based on the advantage of semi-solid processing. The results show that the gap of SSP between world level and China exists, especially in application technologies, including market recognition, application fields exploiting, developing of billets (slurries) preparation technologies with low cost and special equipments. The prospect of semi-solid forming development path in China is presented. And we hope that application of SSP has great new breakthrough and development and China will be changed from a large metal processing country to a powerful metal processing country.

Influence of Billet Quality on Hot Extrusion Die Life and its Relationship with Process Parameters

Apart from other factors such as die design and manufacturing, heat treatment, working conditions etc, performance of hot extrusion die can directly be related to the billet quality used in the extrusion press. The purpose of this paper is to investigate the effect of Al-6063 billet source (primary or secondary) on extrusion die life based on microstructural and statistical analyses. In microstructural investigation, secondary (remelt) billet cast in-house at local extrusion plant is compared with primary (smelter) billet by applying different material characterization techniques including optical microscopy, hardness measurement, X-ray diffraction (XRD) analysis, and energy dispersive spectroscopy (EDS). The statistical study is based on the failure history of some 53 hollow-profile dies in which the effect of billet quality on various measurable process parameters including extrusion ratio, billet temperature, exit temperature and repeated nitriding is analysed and related with useful die service life. Comparatively coarse grain structure, non-homogeneous distribution of secondary phases, and high hardness in the case of secondary billet were found responsible for poor die performance as observed in statistical investigation of failed dies. Two types of regression models are also proposed for prediction of die life in terms of secondary billets’ usage and measurable influencing parameters. Using current results, some suggestions during in-house billet preparation of secondary billets have been devised for improved die life.

Performance of Al-6063 Primary and Secondary Billets Used in Hot Aluminum Extrusion

The service life of tooling plays an important part in the economics of the extrusion process. A number of causes are considered responsible for initiating damage to the dies before its designated life is reached. Apart from other factors such as die design and manufacturing, heat treatment, working conditions, etc, the performance of the die can directly be related to the billet quality used in the extrusion press. The purpose of this paper is to investigate the effect of Al-6063 billet source (primary or secondary) on extrusion die failure, based on microstructural investigation. A secondary (remelt) billet cast in-house at a local extrusion plant is compared with a primary (smelter) billet by applying different material characterization techniques, including optical microscopy, Vickers microhardness measurement, X-ray diffraction (XRD) analysis, and energy dispersive spectroscopy (EDS). It is observed that a secondary billet has a comparatively coarse grain structure, nonhomogeneous distribution of secondary phases, inclusions, and high hardness that can be associated with poor casting and homogenization practice. In view of present results, some suggestions during in-house billet preparation of secondary billets have been formulated for improved die service life.

Effect of Al-6063 Billet Quality on the Service Life of Hot Extrusion Die: Metallurgical and Statistical Investigation

The current paper presents results about the effect of Al-6063 billet quality on the service life of AISI-H13 hot extrusion dies based on microstructural and statistical investigation. In the first half of the paper, secondary (remelt) billet cast in-house at local extrusion plant is compared with two sources of primary (smelter) billet by applying different material characterization techniques including optical microscopy, hardness measurement, x-ray diffraction (XRD) analysis, and energy-dispersive spectroscopy (EDS). The second half of the paper evaluates the performance of primary and secondary billet types based on statistical analysis of data collected on 53 hollow-profile dies from a local commercial extrusion setup. It was observed that the secondary billet has a comparatively coarse grain structure, nonhomogeneous distribution of secondary phases, and high hardness that can be associated with poor casting and homogenization practice. Statistical analysis covers overall analysis of collected data followed by detailed study of percentagewise use of billet quality in terms of die profile complexity/extrusion ratio. Analysis has shown that dies extruding a high percentage of secondary billets are more susceptible to early die failure on overall basis. For more complex dies with high extrusion ratio, average die life further reduces with increased percentage of secondary billet usage. Regression models are also proposed for prediction of die life in terms of secondary billet usage and extrusion ratio. Considering results of present microstructural and statistical analysis, some suggestions during in-house billet preparation of secondary billets have been formulated to prevent early die failure.

Preparation of Semi-Solid Billet of ZW61 Alloy by Equal Channel Angular Extrusion

Strain induced and melt activated (SIMA) is used for the preparation of semi-solid billet through equal channel angular extrusion (ECAE) as strain induced step in SIMA and completing melt activated step by semi-solid isothermal treatment, by which semi-solid billet with fine spherical grains can be prepared. As comparison, extruded ZW61 alloy is also remelted to the semi-solid state. Furthermore, both of the semi-solid isothermal treatment microstructures in as-cast and extruded ZW61 alloy are discussed. ECAE process is found more potential for semi-solid thixoforming for as-cast ZW61 alloy.

Numerical Simulation of Semi-Solid Billet Preparation by Equal Channel Angular Extrusion

Equal channel angular extrusion (ECAE) is a technology of refining crystal grain. In this paper, ECAE was introduced into the preparation of semi-solid billet and the extrusion process was simulated using finite element method. The variation of stress (mean stress, max principle stress, effective stress), the distribution of strain, the lattice change were obtained. The results show that not only does the shear stress exist, but also the normal stress in the extrusion process; the stresses in die inner corner of channel and outer corner of channel are not the same. In the inner corner, besides the simple shear, there are compression, and in the outer corner, tension. The strain is non-homogeneous and appears a graded distribution.

Micro-extrusion of ultra-fine grained aluminium

Microforming of normal, coarse grain (CG) metals leads to scale problems which originate from the fact that the grain size becomes comparable to the part size. A possible way of dealing with these problems is replacing CG metals with ultra-fine grained (UFG) metals. UFG metals can be produced in bulk by severe plastic deformation (SPD). This paper describes using UFG aluminium 1070 for preliminary trials of micro extrusion of a cylindrical cup. The process of producing bulk UFG aluminium by SPD is explained and the material obtained characterised. The preparation of micro billets for the extrusion operation is discussed. Backward extrusion is carried out for two types of material, CG and UFG. This enables a comparison of the material behaviour and product characteristics. Using UFG aluminium in microforming results in more uniform products with improved mechanical properties.

Preparation of semi-solid billet of magnesium alloy and its thixoforming

Preparation of semi-solid billet of magnesium alloy and thixoforming was investigated by applying equal channel angular extrusion to magnesium alloy. The results show that mechanical properties of AZ91D alloy at room temperature, such as yield strength(YS), ultimate tensile strength(UTS) and elongation, are enhanced greatly by four-pass equal channel angular extrusion(ECAE) at 573 K and microstructure of AZ91D alloy is refined to the average grain size of 20 βm. Through using ECAE as strain induced step in SIMA and completing melt activated step by semi-solid isothermal treatment, semi-solid billet with fine spheroidal grains of 25 βm can be prepared successfully. Compared with common SIMA, thixoformed satellite angle frame components using semi-solid billet prepared by new SIMA have higher mechanical properties at room temperature and high temperature of 373 K.

Possibilities for compacting specimens of aluminum turnings by screw extrusion

Compaction of aluminum AK7 alloy turnings during preparation of prismatic billets by screw extrusion is studied. It is shown that with an extrusion pressure of 800 MPa and a back-pressure of 100 MPa compacts are prepared with porosity not exceeding 3%. At the same time, with compaction of turnings in a rigid container with an axial pressure of 1200 MPa specimen porosity is 13%. This effect is explained by intense shear in powder material during screw extrusion.

Effect of the Homogenisation Conditions on the Extrudability and High Temperature Fracture Resistance of AA6063 Aluminium Alloy

Homogenisation is an essential step in the preparation of aluminium billets for extrusion. It is designed to produce an homogeneous solid solution and to transform the beta-Al5FeSi particles to the more equiaxed and thus more acceptable cubic alpha-Al-12(Fe-x,Mn1-x)(3)Si variety. The effect of the homogenisation conditions on high temperature surface damage and fracture is investigated through full scale industrial extrusion experiments on AlMgSi alloy. The transformation of AlFeSi intermetallic particles from the beta-Al5FeSi thin plate like shape to the more rounded alpha-Al-12(Fe,Mn)(3)Si form, quantified by EDS measurements, is shown to postpone the formation of surface defects. Transmission Electron Microscopy (TEM) analysis of extruded samples close to the location of extrusion defects, reveals that damage initiates by microcracks within the brittle beta-Al5FeSi particles or due to incipient melting caused by the eutectic transformation Al + beta-Al5FeSi + Si --> Liquid at 578degreesC. These microcracks open by plastic deformation around the cracked brittle phase and, after sufficient growth, coalesce into a large crack.

Extrusion of nickel–titanium alloys Nitinol to hollow shapes

Nickel–titanium alloys, Nitinol, with their special characteristics such as like superelasticity and shape-memory effect have achieved significant importance in recent years. The major part of superelastic Nitinol alloys applies at present in medical technology. For this application particularly, tube products are used. The present production of Nitinol tubes usually takes place via forging, gun-drilling and hot/cold drawing procedures. For the production of solid and hollow semi-finished materials by extrusion, which enable a substantially larger cross-section of reduction in one step, compared to the above mentioned process, so far no fundamental realizations have been presented. This paper describes the results of the hot extrusion of Nitinol alloys. The deformation resistance of these alloys can be determined experimentally, provided that the extrusion forces are known. The deformation resistance of Nitinol and the tool stresses in relation to the extrusion temperature and ram velocity, and billet preparation and process details, will be reported. These results are of great importance in two aspects: the evaluation of the extrusion process and the design of extrusion tools.

Casting of dendritic Cu-Nb alloys for superconducting wire

Consumable electrode-arc-casting techniques have been developed for the preparation of large billets of dendritic Cu-Nb alloys which are suitable for the fabrication of multifilamentary superconducting wire. The dendrite structure is somewhat more coarse than chill cast material but metallographic and chemical analyses show acceptably small radial and longitudinal segregation. The billets can be drawn to wire with no intermediate anneals. Both external diffusion after tin plating and internal diffusion of wire with a tin core can be used to transform the Nb filaments to Nb3Sn. The arc cast wire displays Jc values equivalent to previously reported values on in situ wire at high fields, but somewhat lower values at low fields.

Effect of method of billet preparation on decarbonization of wire rod

Effect of method of billet preparation on decarbonization of wire rod

Modern Trends in the Manipulation of Metals

THE paper began with a brief historical survey of the cold extrusion process since its first practical use over sixty years ago. The extrusion of special materials such as molybdenum, beryllium and zirconium was described. The problems relating to the production of suitable tooling for the extrusion process and the preparation, heat treatment and lubrication of extrusion billets and slugs were discussed. Following discussion on temperature and speed effects, prestrain of work material, presses for extrusion and component design, the paper concluded with an outline of the applications and advantages of the cold extrusion process.