Screw Production Process And How To Distinguish Between Stainless Steel Bolts, Galvanized And Nickel Plated Bolts
Jun 27, 2023
In the large market of China, standard parts include bolts, screws, studs, nuts, machine screws, self tapping screws, washers, pins, rivets, retaining rings, pin keys, expansion bolts, rigging, industrial and mining construction, irregular screws, various equipment, steel, molds, etc., all of which belong to standard parts in various industries. Mechanical components that are also widely used in various industries, their function is to connect various parts, just like the aircraft we make, which has various standard components connected and fixed. To achieve permanent connections, these connections can also be disassembled before making relevant connections. This can prevent damage to certain components and enable timely repair.
Screw production process flow
Screw heat treatment, also known as screw hardening. There are two types of screws: iron and stainless steel. Iron screws generally require a slightly harder hardness, and both require hardening. But stainless steel screws rarely need to be hardened because their own hardness is sufficient. Please take a look at the heat treatment method for iron screws below.
1、 For heat treatment methods, different heat treatment methods can be selected based on the purpose and purpose. Quenched and tempered steel: high temperature tempered after quenching (500-650 ° C) spring steel: medium temperature tempered after quenching (420-520 ° C) carburized steel: low temperature tempered after carburizing and quenching (150-250 ° C) low-carbon and carbon (alloy) steel quenched into Martensite, with the increase of tempering temperature, the general rule is that the strength decreases, and the reproducibility of, increases. However, due to the different carbon content in carbon steel, the tempering temperature has different effects on it. Therefore, in order to achieve good comprehensive mechanical performance, the following methods can be used separately:
(1) Low carbon (alloy) steel is selected and tempered below 250 ℃ after quenching to obtain low carbon Martensite. In order to improve the surface wear resistance of this type of steel, only by increasing the carbon content of each surface layer can surface carburization be carried out, commonly known as carburized structural steel.
(2) Adopting medium carbon steel with high carbon content, quenching and tempering at high temperature (500-650 ℃) (also known as quenching and tempering treatment) to maintain sufficient strength under high plasticity conditions, this type of steel is generally referred to as quenched and tempered steel. If one wishes to obtain high strength and prefers to reduce plasticity and toughness, low-temperature tempering can be adopted for low carbon content gold containing quenched and tempered steel, thus obtaining the so-called "ultra high strength steel". (3) For steel grades with carbon content between medium and high carbon (such as 60 and 70 steels) and some high carbon steels (such as 80 and 90 steels), if they are used to manufacture springs, in order to ensure high Elastic Limit, yield limit and Fatigue limit, they shall be tempered at medium temperature after quenching.
2、 Operation process
(1) Quenched and tempered steel
1. Preheating treatment: normalizing → annealing (pearlitic steel) → high-temperature tempering (martensitic steel) Normalizing aims to refine the grain, reduce the banded degree in the structure, and adjust the hardness to facilitate machining. After normalizing, the steel will have equiaxed fine grains.
2. Quenching: Heat the cylinder body to around 850 ℃ for quenching, and the quenching medium can be selected based on the size of the steel piece and the hardenability of the steel. Generally, water, oil, or even air quenching can be chosen. Steel in a quenched state has low plasticity and high internal stress
3. Tempering:=1 * GB3
① In order to make the steel have high plasticity, toughness, and appropriate strength, the steel is subjected to high-temperature tempering at around 400-500 ℃. Steel with high sensitivity to temper brittleness must be rapidly cooled after tempering to suppress the occurrence of temper brittleness.
② If the parts are required to have particularly high strength, they shall be tempered at about 200 ℃ to obtain medium carbon tempered Martensite structure.
(2) Spring steel:
1. Quenching: Oil quenching at 830-870 ℃.
2. Tempering: Tempering at around 420-520 ℃ to obtain tempered troostite structure.
(3) Carburized steel:
1. Carburization: A type of chemical heat treatment that refers to the penetration of C element into the surface of steel parts in an active medium containing a certain chemical element at a certain temperature. Pre heating (850 ℃) carburization (890 ℃) diffusion (840 ℃) process
2. Quenching: Carbon and low alloy carburized steel, generally using direct quenching or one-time quenching.
3. Tempering: Low temperature tempering to eliminate internal stress and improve the strength and toughness of the carburized layer.
How can stainless steel screws, galvanized screws, and nickel plated screws be distinguished from each other in terms of appearance?
Firstly, it is distinguished by color: stainless steel is the primary color of iron, galvanized screws are white, colored, or black, and nickel plated screws are silver.
1. Stainless steel screws are made of stainless steel material, and the color of stainless steel is mainly an alloy of iron and carbon, so the color is close to that of iron;
2. The surface of galvanized screws is galvanized with white zinc, colored zinc, black zinc, etc. Therefore, the colors of galvanized screws are generally white, colored, and black;
3. The color of nickel plated screws is related to nickel and generally presents a very bright silver color.
Other methods to distinguish between stainless steel screws, galvanized and nickel plated screws:
1. Distinguished by magnets: Stainless steel generally does not have magnetism, and what cannot be adsorbed by magnets is stainless steel screws. Galvanized and nickel plated screws can be adsorbed by magnets,
2. Distinguished by oxidant: Metal nickel has strong passivation ability, and during electroplating, an extremely thin passivation layer can be quickly generated on the surface. Therefore, the surface of nickel plated screws has a passivation film, while the galvanized surface is a layer of zinc. The stainless steel surface has nothing, and can be distinguished by strong oxidant
3. Distinguished by strong acids and strong alkalis: stainless steel contains chromium and nickel, which have strong corrosion resistance and are not corroded by strong acids and strong alkalis. The surface of nickel plated screws has a passivation film, which is slowly corroded by strong acids and strong alkalis. Galvanized screws are corroded the fastest.
How can stainless steel screws, galvanized screws, and nickel plated screws be distinguished from each other in terms of appearance?
Firstly, it is distinguished by color: stainless steel is the primary color of iron, galvanized screws are white, colored, or black, and nickel plated screws are silver.
1. Stainless steel screws are made of stainless steel material, and the color of stainless steel is mainly an alloy of iron and carbon, so the color is close to that of iron;
2. The surface of galvanized screws is galvanized with white zinc, colored zinc, black zinc, etc. Therefore, the colors of galvanized screws are generally white, colored, and black;
3. The color of nickel plated screws is related to nickel and generally presents a very bright silver color.
Other methods to distinguish between stainless steel screws, galvanized and nickel plated screws:
1. Distinguished by magnets: Stainless steel generally does not have magnetism, and what cannot be adsorbed by magnets is stainless steel screws. Galvanized and nickel plated screws can be adsorbed by magnets,
2. Distinguished by oxidant: Metal nickel has strong passivation ability, and during electroplating, an extremely thin passivation layer can be quickly generated on the surface. Therefore, the surface of nickel plated screws has a passivation film, while the galvanized surface is a layer of zinc. The stainless steel surface has nothing, and can be distinguished by strong oxidant
3. Distinguished by strong acids and strong alkalis: stainless steel contains chromium and nickel, which have strong corrosion resistance and are not corroded by strong acids and strong alkalis. The surface of nickel plated screws has a passivation film, which is slowly corroded by strong acids and strong alkalis. Galvanized screws are corroded the fastest.
Summary: The method to distinguish stainless steel screws, galvanized and nickel plated screws from their appearance is to look at the color of the screws. The color of stainless steel screws is close to the original color of iron, while galvanized screws are white, colored, and black, and nickel plated screws are very bright silver. In addition, magnets, oxidants, and strong acids and alkalis can also be used to distinguish stainless steel screws, galvanized and nickel plated screws.
