Vanadium toxicity and environmental safety

First, the toxicity of vanadium

The toxicity of vanadium is closely related to its valence and water solubility. High-valence vanadium is easily soluble in water and is highly toxic. Atmospheric vanadium compounds have a stimulating effect on the skin and respiratory tract. Long-term exposure to V 2 O 5 dust and V 2 O 5 thick environment can cause respiratory irritation accompanied by mucus production, bronchitis, chest pain, dermatitis and the like.

Second, the environmental safety indicators of vanadium

For a place where 8 hours of work per day and 40 hours of work per week, the upper limit of vanadium-containing dust is 0.5 mg/m3, and the upper limit of fine dust environment should be 0.05 mg/m3. The upper limit for short-term workers is 1.5 mg/m3. The toxicity of vanadium compounds is listed in Table 1.

Table 1 Toxicity of vanadium compounds

Compound

Oral and lethal dose of kilograms of body weight

LD 50 (14d)/mg

Inhaled lethal dose

LD 50 (14d) / (mg · L - 1 )

Kilogram weight epidermal lethal dose

LD 50 (14d)/mg

male

female

male

female

male

female

Analytical pure V 2 O 5

470

467

11.09

4.3

>2500

>2500

Industrial pure V 2 O 5

8713

5639

>6.65

>6.65

>2500

>2500

Ammonium metavanadate

218

141

2.61

2.43

>2500

>2500

Potassium metavanadate

318

314

1.85

4.16

>2500

>2500

From a biological point of view, vanadium is a very important element. It is known that vanadium contributes to the function of biological nitrogen fixation. Due to the discovery of vanadium halide peroxidase in seaweed, it has ignited a boom in its research. Because it can form an intermediate of enzyme-vanadium hydrochloride, vanadate is The cells are easily reduced to a tetravalent state and exist as VO 2 + . In the extracellular, animal body fluids, it is easily oxidized by air to pentavalent, and exists as VO 3 - . Vanadium in the cell can promote the phosphorylation and de-phosphorylation of cellular process, control the activity of many enzymes, and participate in the regeneration of free radicals.

It is believed that vanadium has an anticancer effect in the body. Studies have shown that glutathione S-transferase (CST) is a detoxification enzyme for cancer. In the screening of trace element feeding experiments, drinking water containing NH 4 VO 3 in the mucosa of the liver and kidney of the test mouse, It was found that the activities of glutathione and CST were significantly improved, and thus vanadium was considered to have an anticancer effect.

"Gravity Die Casting. A permanent mould casting process, where the molten metal is poured from a vessle of ladle into the mould, and cavity fills with no force other than gravity, in a similar manner to the production of sand castings, although filling cn be controlled by tilting the die."

Gravity Die Casting

Sometimes referred to as Permanent Mould, GDC is a repeatable casting process used for non-ferrous alloy parts, typically aluminium, Zinc and Copper Base alloys.

The process differs from HPDC in that Gravity- rather than high pressure- is used to fill the mould with the liquid alloy.

GDC is suited to medium to high volumes products and typically parts are of a heavier sections than HPDC, but thinner sections than sand casting.

There are three key stages in the process.

  1. The heated mould [Die or Tool] is coated with a die release agent. The release agent spray also has a secondary function in that it aids cooling of the mould face after the previous part has been removed from the die.
  2. Molten metal is poured into channels in the tool to allow the material to fill all the extremities of the mould cavity. The metal is either hand poured using steel ladles or dosed using mechanical methods. Typically, there is a mould [down sprue" that allows the alloy to enter the mould cavity from the lower part of the die, reducing the formation of turbulence and subsequent porosity and inclusions in the finished part.
  3. Once the part has cooled sufficiently, the die is opened, either manually or utilising mechanical methods.

Advantages

  • Good dimensional accuracy
  • Smoother cast surface finish than sand casting
  • Improved mechanical properties compared to sand casting
  • Thinner walls can be cast compared to sand casting
  • Reverse draft internal pockets and forms can be cast in using preformed sand core inserts
  • Steel pins and inserts can be cast in to the part
  • Faster production times compared to other processes.
  • Once the tolling is proven, the product quality is very repeatable.
  • Outsourced Tooling setup costs can be lower than sand casting.

Gravity Casting Parts

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