Etched Magnesium Plates 

Etched Magnesium Plates

The demand for magnesium alloy sheets in the printing field mainly manifests in hot stamping printing, that is, magnesium alloy etching plates. The plate-making process involves several steps such as plate exposure, plate opening, acid washing, and alkali washing. The processed products are installed directly on the hot stamping machine for use.

Magnesium etching plates, introduced to the market in the early 1970s, gained recognition for their superiority. Subsequently, with the flourishing development of the printing and packaging industries, magnesium etching plates became widely accepted and popular in the high-end hot stamping printing field.

In recent years, due to strict environmental requirements and intensified competition, printing companies have continuously raised their demand for high-quality metal plate materials. The application of magnesium etching plates has been increasing rapidly. Moreover, because the hot stamping speed of magnesium plates is much faster than that of copper and zinc plates, with a 20% higher resistance to printing than copper plates, it can effectively improve processing speed and save labor costs. Therefore, the application fields and quantities of magnesium etching plates are rapidly increasing, showing a trend of surpassing traditional copper and zinc plates.

The low melting point and reactive chemical properties of magnesium present challenges and bottlenecks in magnesium alloying. Its densely packed hexagonal structure with minimal slip systems results in poor deformation performance at room temperature. The preparation of high-performance deformable magnesium plates requires multiple passes of isothermal equal-angle rolling, leading to high processing costs, which also limits the rapid popularization of magnesium etching plates.

Large-format magnesium etching plates, subjected to up to four layers of successive etching, can form deeply embossed patterns with rich layers, delicate textures, varying depths, and clear stripes, suitable for embossing and hot stamping on thick paper such as wine boxes, mooncake boxes, gift boxes, cosmetics, book covers, and back covers.

The refractive embossed patterns on the etched magnesium plates can be directly brushed out in a 5-degree nitric acid solution, with fast corrosion rates and simple operation, saving the process of etching in the machine once again.

Moreover, simultaneous exposure of multiple film sheets results in clear and rich patterns after one etching, saving the processes of degumming, gluing, exposure, and etching of magnesium plates, thus saving labor and time.

After passing through the hot rolling mill and undergoing annealing treatment, magnesium plates have uniform thickness, minimal thickness tolerance, and almost no anisotropy, eliminating internal stresses. Additionally, the yield strength of etched magnesium plates exceeds 200 MPa, making them less prone to edge lifting, bulging in the middle, or warping during hot stamping or embossing processes.

In the production industry of New Year paintings, couplets, blessings, invitations, and other products, the speed and efficiency of hot stamping determine the product's cost, with significant economies of scale generated by large production quantities. Magnesium etching plates are increasingly being used due to their significant advantages of fast heat transfer, deformation resistance, and high resistance to printing.

In products such as dip molding, leather embossing, high-frequency molds, heat transfer printing, clothing labels and logos, adhesive knife molds, shoe sole molds, conference signs, door signs, medals, nameplates, product trademarks, badges, braille signs, and more, magnesium etching plates are also widely used abroad.

Magnesium has a specific gravity of 1.738 and an internal hexagonal crystal lattice structure, which is one-fifth the density of copper and one-quarter the density of zinc. In terms of transportation, installation, and preservation, magnesium etching plates have advantages due to their small size and lightweight.

With a low specific heat capacity, magnesium plates quickly heat up and cool down, efficiently transferring heat during the hot stamping process. After completing one hot stamping process, the heat from magnesium etching plates is rapidly dissipated, causing the temperature to decrease significantly, thus preventing significant expansion and deformation. This is a significant advantage of magnesium plates over copper plates, which have slower heat dissipation and greater volume expansion, causing softening at the edges. The linear thermal expansion coefficient of magnesium etching plates is 26, compared to 17.5 for copper plates and 36 for zinc plates.

The Brinell hardness value of etched magnesium plates (AZ31b material) is 110, higher than 95 for brass plates (H59) and 49 for zinc plates. The surface hardness of magnesium plates is twice that of zinc plates and significantly higher than that of brass plates. If it is AZ80 material etched magnesium plates, the surface Brinell hardness value can reach 140.

Magnesium etching plates are made from thoroughly purified and completely crushed magnesium alloy sheets to a particle size of 5 microns (99% purity), with uniform, stable, and defect-free internal composition. In nitric acid solution, magnesium plates can be uniformly and steadily etched.

Inside the magnesium plate etching machine, the reaction between etched magnesium plates and nitric acid is vigorous and fast, releasing a large amount of heat and accompanied by the production of yellow gas. Yellow gas is a nitrogen oxide, and attention should be paid to ventilation inside the etching machine. The rapid increase in temperature inside the machine is due to the heat generated during the reaction between magnesium plates and nitric acid, which cannot be dissipated in time. The solution is to increase the effective cooling capacity of the refrigeration equipment or, based on experience, adjust the initial temperature as appropriate.

After being etched by nitric acid, magnesium plates form a dense and continuous oxide layer on the surface, preventing further reaction of internal magnesium metal. Due to good material purification, magnesium plates' exposed surfaces are virtually free of slag spots (slag spots can cause primary battery reactions, further corroding magnesium plates), and long-term exposure to air does not lead to corrosion.

The market demand for magnesium alloy etching plates is very large and growing rapidly. Only the European market's demand for magnesium alloy etching plates exceeds 2,000 tons per year, with the total demand from other continents also exceeding 1,000 tons per year. Currently, the Chinese hot stamping printing industry still uses zinc plates and copper plates, with demand exceeding 7,000 tons per year. If these plates were replaced with magnesium alloy etching plates, the demand would exceed 1,500 tons per year. In the field of hot stamping printing alone, the global demand for magnesium alloy rolled plates exceeds 4,500 tons per year