Modern smoky gunpowder is made in the form of grains of irregular shape. Depending on the composition of the components, four types of smoke powder are distinguished: military, hunting, sulfurless with a grain size of 0.75-1.25 mm, and cordless powder, in 1 gram of which contains from 400 to 7000 grains.
Varieties and brands of smoke powder, composition, properties, energy and ballistic characteristics, products from smoke powder.
Depending on the grain size (particles), the following grades of military smoke powder are distinguished:
Prismatic gun, grain size 25.0-40.0 mm.
Cannon, 7.0-21.0 mm.
Coarse smoky gun powder, KZDP 5.1-10.2 mm.
Smoke gunpowder DRP No. 1 1.25-2.0 mm.
Smoke gunpowder DRP No. 2 0.75-1.25 mm.
Smoke gun powder DRP No. 3 0.15-0.75 mm.
The compositions of smoke powder were finally established at the end of the 17th century and have not undergone significant changes to date. Smoke powder includes the following substances in various proportions: oxidizing agent potassium nitrate, combustible charcoal and cement sulfur.
The composition of smoky powder, military, hunting, cord, sulfurless.
Individual components in smoke powder.
Nitrate (potassium nitrate KNO3) in the composition of smoke powder.
Nitrate is an oxidizing agent and, when heated, easily gives off oxygen. The oxygen released oxidizes sulfur and coal. With an increase in the content of nitrate in the powder to a certain limit (~ 80%), the power of the powder increases and its burning rate increases.
In nature, there are many oxygen-rich substances, but potassium nitrate is used almost exclusively for porcine production, since it best satisfies all the requirements for oxidizing agents in the composition of gunpowder. It has low hygroscopicity and low sensitivity.
Coal in the composition of smoke powder.
Coal is a combustible substance. Charcoal (mainly alder or buckthorn) with a content of 72-80% carbon is used for breezing. Coal from resinous tree species is undesirable, since gunpowder prepared using such coal is difficult to ignite. With an increase in the amount of coal in gunpowder, the burning rate of gunpowder decreases, but with an increase in the carbon content in coal, it increases.
Sulfur in the composition of smoke powder.
Sulfur (S) serves as a cementer between nitrate and coal, giving the powder a certain mechanical strength. In addition, sulfur is a combustible component and facilitates the ignition of gunpowder, as it ignites at a lower temperature than coal. Sulfur ignition temperature lower than charcoal.
From the increase in sulfur content in gunpowder, the power of gunpowder and the burning rate decrease. Sulfur is found in crystalline and amorphous forms. Sulfur only uses crystalline form with a melting point of 114.5 degrees.
Some properties of smoke powder.
Smoke powder is a low-hygroscopic substance, which is determined by the properties of the components. Charcoal is poorly wetted (hygrophobic substance), and potassium nitrate and sulfur have low hygroscopicity. Smoke powder has a high chemical resistance, that is, it is characterized by high shelf life under normal operating conditions.
Smoke-powder is from blue-black to gray-black with a metallic sheen. An intensely black color indicates the presence of a large amount of moisture in the powder. Good gunpowder is relatively difficult to squeeze between fingers, doesn’t get your hands dirty and doesn’t leave dust at all even from a height of 1 meter.
The powder poured onto a sheet of paper during ignition should quickly flare up and form a vertical column of smoke, while the paper should not catch fire and there should be no traces of soot (carbonization) on it.
Smoke powder is easily ignited by flame and spark. Its flash point is about 300 degrees. A lightning strike always causes an explosion. Small amounts of gunpowder only flare up when lit, while large ones explode.
An increase in moisture has a significant effect on the flammability of gunpowder. With a moisture content of more than 2%, the powder is difficult to ignite, and with 15% moisture it completely loses its ability to ignite.
The burning rate of smoke powder depends on its composition, external pressure and the density of the powder elements. The burning rate of smoky gunpowder pressed into distance rings, when burning in air 8-10 mm / s. At a certain density, gunpowder tends to burn in parallel layers. This property is widely used in the manufacture of all kinds of moderators..
Smoke powder is susceptible to shock and friction. In terms of sensitivity to shock, it surpasses some high explosives. When shot through by a bullet, it ignites. A bullet hit at a speed of more than 500 m / s almost always causes a powder explosion. During friction between the surfaces of iron or stone, smoky gunpowder flares up or explodes. A large amount of gunpowder when ignited, as a rule, explodes. Powder dust explodes especially easily.
Energy and ballistic characteristics of smoke powder.
Smoke powder has low energy and ballistic characteristics compared to other types of powder. The burning rate of smoke powder is highly dependent on the density of grains (products from gunpowder) and environmental pressure. Density varies from 1600 to 1900 kg / m3. At an ambient pressure of up to 10 MPa and a density equal to or more than 1700 kg / m3, the powder burns in parallel layers.
The values of the heat of combustion (Qw) and combustion temperature (T1) are in the lower limit of values. The small volume of gaseous products formed during the combustion of smoke powder determines the low value of the specific volume of the gas (Wi) and the “power of the powder” (f). During the combustion of smoke powder, only about 43.6% of the total weight by weight of powder turns into gases.
Energy and ballistic characteristics of gunpowder.
The presence of low energy and ballistic characteristics excludes the possibility of using smoke powder for propellant charges of artillery systems. However, smoke powder is widely used in practice:
In ignitors of the main charges in the barrel artillery and missile systems (KZDP, DRP No. 1, DRP No. 2, DRP No. 3, sulfur-free).
In fire retardants and amplifiers in remote projectiles of shells (tubes and fuses) to ensure the burst of shells at any point on the trajectory (DRP No. 1,2,3).
In expelling charges for shrapnel-type shells, incendiary and lighting shells.
In fire-resistant cords (cord gunpowder).
In hunting weapons (hunting).
In mining, when mining decorative stone, for example, marble and granite, which need to be chipped off with blocks, and not crushed into small pieces, that is, without a brisant effect.
In other areas.
All products from black powder can be divided into two groups. The first group includes curly powder of powder of a cubic and prismatic shape, igniters, firecrackers for capsule sleeves and some others (KZDP, DRP No. 1). This powder elements are manufactured separately from the details of the elements of the shot, into which they are then inserted.
The second group includes powder parts for fuses, powder retarders, fuses and amplifiers. These products are most often pressed into the corresponding part of the tube or fuse (DRP No. 2, DRP No. 3).
Separately, a fire-resistant cord stands out, which is a lightly pressed core from cordless powder, tightly wrapped on the outside with cotton yarn. A cotton thread guide is passed inside the powder core to evenly distribute the powder along the entire length of the cord.
Smoke powder can be used (and used for a long time) as missile charges. However, its insufficient energy characteristics, the limited possible structural forms of charges and their dimensions, as well as fragility, the danger of production and use, all this hindered the development of rocket technology based on smoke powder.
Based on the book Explosives and gunpowder.
A.N. Kalyazhenkov, D.P. Malgin.