3D printing metal chromium powder mainly detect what properties

In metallurgy, aviation, military industry, automobile and other fields, chromium parts have high hardness, wear resistance, high temperature resistance and other characteristics, so they are widely used.  The 3D-printed chrome parts are highly customizable, featuring curved surfaces, holes and slots that are difficult to achieve compared to traditional manufacturing processes.  For additive manufacturing technology, metal powder is the key raw material, especially requires high sphericity, narrow particle size distribution, low oxygen content, good fluidity.

Plasma spheroidizing preparation of spherical powder technology is the use of the high temperature characteristics, will be sent to any one of the particles by convection, conduction, radiation, chemical four heat transfer mechanism of the effect, the surface tension and rapid quenching rapidly shrink under the function of molding, molding powder particles liquidity improved significantly, with good dispersion, the spherical degree is high. Thus, the spherical chromium powder can be effectively promoted in the additive manufacturing field.

Confirmation of test items of chrome pure

Refer to GB/T 35022-2018 "Additive Manufacturing Main Characteristics and Test Methods Parts and Powder Raw Materials".  Additive manufacturing metal powder raw materials can be detected: powder particle size and distribution, shape or shape, specific surface area, loose or apparent density, vibration density, fluidity, ash, hydrogen, oxygen, nitrogen and sulfur content, melting temperature fire glass transition temperature, etc.  

1. Chemical composition  

The chemical composition requirements of each element of metal chromium can be implemented according to GB/T 3211-2008.  Of course, some manufacturers will also develop their own chemical composition requirements in order to ensure that the comprehensive performance of metal chromium powder for additive manufacturing can meet the design requirements.  The specific section shall be executed according to the requirements of the testing party.  The detection method for chemical composition analysis can be carried out according to GB/T 4702.6-2016 "Determination of ferrous chromium, Aluminum, Silicon and Copper contents by inductively coupled plasma atomic emission Spectrometry".  

2. Particle size analysis  

The metal chromium powder used in additive manufacturing is mainly prepared by plasma spheroidization method and generally classified by standard screening.  The particle size distribution is different from that of additive manufacturing process.  The powder can be divided into three types: Class I is suitable for selective laser melting additive manufacturing process, the particle size range is 15 ~ 53μm;  Class ⅱ is suitable for electron beam melting additive manufacturing process, particle size range of 45 ~ 150μm;  Class ⅲ is suitable for laser energy deposition additive manufacturing process, particle size range of 30 ~ 4250μm.  Particle size detection is carried out in accordance with GB/T1480 "Determination of Particle Size by Dry screening of Metal Powder" and GB/T19077 "Particle size Distribution Laser diffraction Method".

3. Loose packing density detection  

Loose packing density of powder is the bulk density measured after the powder is freely filled with standard container under specified conditions, that is, the mass per unit volume of powder when it is loosely filled, which is a kind of technological performance of powder.  Loose packing density is a comprehensive reflection of powder properties, can reflect the powder density, particle shape, particle surface state, particle size and particle size distribution, etc., on the stability of product production process and product quality control have an important impact.  In general, the more regular the shape of the powder particles, the smoother the surface of the particles, the more dense the particles, the greater the bulk density of the powder.  Higher powder bulk density is beneficial to the setup and optimization of additive manufacturing process, and ensure that the final product density of additive manufacturing meets the target product requirements.  The loose density shall not be less than 4.0g/m, and the detection can be carried out in accordance with the provisions of GB/T1479.1 "Determination of the loose density of metal powder - Part 1: Funnel method".  

4. Vibration density detection  

Vibration density is the powder in the container through mechanical vibration to achieve a better arrangement of the powder collective density, its relative to the loose packing density is mainly a comprehensive reflection of a variety of physical and technological properties of the powder, such as powder size and distribution, particle shape and surface roughness, specific surface area, etc.  Generally speaking, the higher the vibration density, the better the powder flow performance.  The vibration density should not be less than 5.0g/cm3. The detection can be carried out according to GB/T5162 "Determination of vibration density of Metal Powder".  

5. Liquidity testing  

Powder fluidity refers to the time required by a certain amount of powder to flow through a standard funnel with a specified aperture, usually in units of S /50g. The smaller the value, the better the fluidity of the powder. It is a kind of technological performance of the powder.  Powder flow properties are related to many factors, such as particle size, shape and roughness, specific surface, etc.  Generally speaking, increasing the coefficient of friction between particles will make the powder flow difficult.  Generally, the powder with spherical particles has the best fluidity, while the powder with irregular shape, small size and rough surface has poor fluidity.  In addition, the fluidity of powder is affected by the adhesion between particles, and the adsorption of moisture and gas on the surface of particles will reduce the fluidity of powder.  The fluidity of powder has great influence on the properties of powder metallurgy forming and additive manufacturing.  The fluidity of the product should not be greater than 20s/50g. The test can be carried out in accordance with the provisions of GB/T1482 "Standard funnel Method for the Determination of fluidity of metal Powder (Hall Current Meter)".

In additive manufacturing, the performance of raw materials will greatly affect the finished product characteristics of the final parts.  The development and application of metal chromium powder for additive manufacturing plays an important role in its industry development and promotion.  Although China has not issued the relevant standards, but the market demand has formed a certain scale, products like this test has actually reached the stage of large-scale production.  Therefore, the standardization of relevant indicators, sampling, preparation and detection methods requires an authoritative national standard to guide the formulation in addition to entrusting testing institutions to provide professional plans.