St3ps steel – advantages, scope of application, chemical composition, production

Decoding

The interpretation of steel st3ps is given in GOST 380-2005. According to the document:

• st indicates that the steel belongs to alloys of ordinary quality. Depending on the sulfur and phosphorus content, steels are of ordinary quality, high-quality, high-quality and especially high-quality. For steel st3ps and other steels of this class, the sulfur content cannot exceed 0.06%, phosphorus 0.07%.
• 3 serial number of the grade according to GOST 380-2005 means that the steel corresponds to the chemical composition specified in the document for grade 3.
• ps - means that the degree of deoxidation of the steel is semi-quiet. Deoxidation is the process of removing oxygen and nitrogen gases. There are three categories of steel according to the degree of deoxidation: calm (sp), semi-quiet (ps), boiling (kp). The less gases are released during the solidification of the alloy, the fewer pores and bubbles in the metal structure, the higher the strength.

Interpretation of steel grade VSt3ps

Interpretation of steel: The letter B at the beginning denotes a group of steel that determines the tensile strength criteria for the chemical composition. Steel, in the name starting with the letter B, the strength is 20-30 MPa lower than steel of group A. The following letters St. indicate that the steel is of ordinary quality, although most steels are high quality. The numbers from 0 to 6 are the conventional brand number depending on the chemical composition and mechanical properties. Typically, the higher the number, the more carbon and the greater the strength. In our case, 3 indicates the carbon content in the alloy is 0.14–0.22%. The letters after the brand number indicate the degree of deoxidation: ps - semi-calm.

Chemical composition

St2ps steel is 98% iron. The remaining 2% includes carbon, manganese, nickel, chromium, silicon, copper, sulfur, phosphorus, arsenic, scandium, nitrogen, aluminum. The table below shows the exact content of the most significant elements. Minor impurities do not seriously affect the characteristics of the metal and are therefore not taken into account.

The most important alloy elements, besides iron, are:

• carbon high carbon content provides steel with hardness, strength and elasticity;
• manganese in the composition is responsible for deoxidation and removal of sulfur, and also makes steel stronger;
• silicon deoxidizer, which forms a fine-grained structure of steel, improves technological properties, strength, and does not reduce ductility.

Harmful impurities are sulfur and phosphorus; the lower their concentration in the alloy, the higher quality the steel is considered.

Chemical composition, % (GOST 380-94)

Production Features

The properties of the finished material are determined by the substances that make up its composition and largely depend on what technologies were used in the production of a particular alloy.

The basis of the steel alloy is ferrite. It is a component of iron-carbon alloys. It is, in fact, a solid solution of carbon and alloying components. To increase its strength, the melt is saturated with carbon.

Impurities from which nothing but harm can be expected include phosphorus and sulfur, as well as their derivatives. Phosphorus, reacting with ferrite, reduces the ductility of the alloy when exposed to high temperatures and increases brittleness when exposed to cold. During the melting process, iron sulfide may be formed, which can lead to red brittleness. St3 steel contains no more than 0.05% sulfur and 0.04% phosphorus.

For the production of structural steels, two steelmaking technologies are used:

• open hearth;
• converter

The parameters of the St3 grade, obtained by one or another method, differ little from each other, but the converter technology is simpler and cheaper.

Application of St3sp steel, taking into account characteristics and properties

This type of steel is one of the most popular in construction and industry.

The absence of oxygen in the alloy and a homogeneous structure are factors that increase resistance to corrosion in aggressive environments. These qualities, as well as high ductility, make this steel indispensable in the production of structures and elements that have high rigidity requirements.

These are rolled products - sheet and shaped (channels, I-beams and T-beams, angles), blanks for fittings, pipeline elements (in particular, square pipes), etc.

The characteristics of steel make it possible to construct supporting load-bearing structures and frames from it, the operation of which is carried out in difficult conditions.

Elements and parts are made from St3sp steel without heat treatment, which makes it possible to preserve all the characteristics of the alloy - flanges, tees, transitions.

Steel is also used as a base layer in the production of hot-rolled 2-layer sheets that are resistant to corrosion.

Application

St3ps steel is a carbon structural steel of ordinary quality; it is a general purpose steel. It is used at normal temperatures, and is used to make welded and non-welded structures in construction and mechanical engineering. The properties of steel allow it to be used in load-bearing structures and loaded elements, such as load-bearing trusses, beams, channels, rails, etc. Steel is not alloyed and is not protected from corrosion in direct contact with water, and is also vulnerable in alkaline and acidic environments. A thick layer of galvanic coating or paint is required for protection.

Standardized indicators of St3ps steel by rolled category (GOST 535-2005)

NOTE

• The “+” sign means that the indicator is normalized, the “-” sign means that the indicator is not normalized.
• The chemical composition of steel according to heat analysis or in finished rolled products is in accordance with the order.

Parameters for the use of electric-welded straight-seam pipes made of St3ps steel (GOST 32569-2013)

• NOTE. Groups of media, see table 5.1 GOST 32569-2013

Parameters for the use of electric-welded spiral-welded pipes made of St3ps steel (GOST 32569-2013)

Conditions for using St3ps steel for bodies, covers, flanges, membranes and valve assembly made from rolled products, forgings (stampings) (GOST 33260-2015)

Brand analogues

According to the production system, the St3ps steel grade is related to other similar alloys, both domestic and foreign produced. Among them we can note C245 manufactured in accordance with GOST 27772, VSt3ps6 - GOST for which is 23570-79 and foreign E-235-B (better known as Fe 360-B). All of them are united by the characteristic of universal rolled steel intended for the construction of building structures with welded and non-welded type of connection.

Steel 245

Of course, alloys of different markings cannot be called complete analogues of each other. For example, the same domestic C245, although it has characteristics similar to 3ps steel in terms of strength, withstand temperature and pressure, conditions for welding and construction of structures, is endowed with differences in composition. Namely, the amounts of iron and manganese are the same, but other components, such as flint or carbon, have a smaller or larger percentage of the total mass. With other analogues the situation is approximately the same.

Assortment

• Channels are parallel (P), with sloped flanges (U), equal-flange bent;
• round sections circle and reinforcement;
• VGP pipes, electric welded (ES), seamless (BGD), nominal diameter 10, 15, 20, 25, 32, 40, 50, 65, 80, 90, 100 mm;
• I-beams, wide-flange, column, special, with flange slopes;
• steel square;
• steel wire rod;
• corners equal and unequal;
• square and rectangular profile;
• sheet steel: hot-rolled, corrugated, expanded metal, strip.

Type of delivery

Differences between st3ps and st3sp

Alloys st3sp and st3ps, being varieties of the same steel, differ from each other in the degree of deoxidation.

• Steel st3sp is considered calm, the degree of deoxidation is maximum.
• St3ps steel is semi-quiet, with a medium degree of deoxidation.

As a result of deoxidation, the intensity of gas formation during steel hardening decreases. The resulting gas bubbles make the steel porous and, as a result, less strong, affecting technological properties such as weldability. Calm steel (sp) is the highest quality in terms of the degree of deoxidation, boiling steel (kp) is the least quality, and semi-quiet steel (ps) occupies an intermediate position between them.

The differences between calm and semi-quiet steel for widely used metals are insignificant; both varieties cope quite well with average loads. At the same time, mild steel is more expensive, its production process is more complicated, and its use is advisable where the requirements for the quality of the metal are increased.

Application of steel St3

When considering different grades of steel, you need to take into account the fact that they are classified according to the degree of deoxidation. This chemical process involves removing oxygen from the composition. Too high an oxygen concentration determines a decrease in physical and mechanical properties.

The classification is carried out as follows:

1. Calm is characterized by the fact that the composition includes from 0.16 to 0.3% silicon.
2. Semi-calm has an average concentration of the element in question.
3. Boiling differs in chemical composition from calm in that it contains at least 0.05% silicon.

St3 material is marked accordingly. Various substances can be used to carry out a chemical process.

It is worth considering that a quiet one is much more expensive than other options. This can be associated with the following points:

1. The structure is homogeneous, thereby increasing the degree of protection of the material from environmental influences.
2. The composition includes a small amount of oxygen, which determines high performance.

Production

St3ps steel is produced in two ways: converter and open-hearth. A converter furnace is a pear-shaped vessel lined with brickwork on the inside and covered with sheet steel on the outside. Scrap metal (scrap) is placed into the converter, then liquid cast iron heated to 1400C is poured. At the oxygen purge stage, oxygen is supplied to the converter under high pressure, causing the oxidation of cast iron impurities, resulting in the formation of steel. In open hearth furnaces, steel is produced using the same oxidation method, but using a different principle through slag. Deoxidation and alloying (if necessary) is carried out at the final stages of production.

St3ps steel does not change its characteristics depending on the production method, but the converter method is cheaper, and therefore is considered more preferable.

Why does steel deoxidize?

Deoxidation is part of the metal refining process. If you do not deoxidize the steel before it hardens, the structure of the steel will be heterogeneous, porous, with gas pockets. Such steel welds worse, wears out and breaks faster. Deoxidized steel has a homogeneous and solid structure. Undeoxidized steel is also used in various industries, but is not suitable for the manufacture of loaded parts operating under pressure. The production of such steel has its advantages: it is waste-free, cheap and simple.

Advantages and disadvantages

The main distinguishing feature of St3 steel is its combination of positive characteristics or versatility. This means that it does not have any one key advantage, it shows decent characteristics from all sides, which makes it the first on the market. This steel is not intended for highly specialized applications in special conditions, but is ideal for a wide range of everyday applications.

The disadvantages of steel include low performance at low temperatures.

Advantages of steel st3Gsp:

1. homogeneous structure, due to which the steel becomes homogeneous, ductile and protected from adverse environmental influences;
2. resistance to atmospheric corrosion;
3. high elasticity and hardness;
4. insensitivity to flakes;
5. impact strength, allowing to withstand dynamic loads well;
6. not subject to temper brittleness;
7. simple production process, no expensive alloying additives;
8. relatively low cost.

Separately, it should be mentioned that the material is perfectly weldable. It can be carried out using any known technology without preliminary and subsequent treatments.

Technological properties

Characteristics of steel grade VSt3ps

VSt3ps - Structural carbon steel of ordinary quality, welds well, welding is carried out without restrictions, welding methods: RDS, ADS submerged and gas shielded, ESW and KTS. For thicknesses greater than 36 millimeters, heating and subsequent heat treatment are recommended; it is not prone to flake sensitivity and there is no tendency to temper brittleness. Machinability by cutting in the hot-rolled state at НВ 124 and σв=400 MPa, Kυ hard alloy. = 1.8 and Kυ b.st. = 1.6, has found its application in load-bearing and non-load-bearing elements of welded and non-welded structures and parts operating at positive temperatures. Shaped and sheet metal (category 5) up to 10 mm thick for load-bearing elements of welded structures operating under variable loads in the range from -40 to +425 °C. Rolled products from 10 to 25 mm - for load-bearing elements of welded structures operating at temperatures from -40 to +425°C, subject to delivery with guaranteed weldability. Forging at temperatures from 1300 to 750 0C, cooling is carried out in air.

How to weld

St3ps steel is unpretentious in processing; it can be welded without restrictions by any existing method. Pre- and post-temperature treatment is not required. The seams are strong and not prone to cracking. The following types of welding are widely used:

1. contact using high voltage current;
2. automatic submerged arc using a welding machine with a wire electrode;
3. electroslag using molten flux (slag);
4. manual arc welding with coated electrodes;
5. manual argon arc manual welding in an argon gas environment;
6. mechanized welding in a carbon dioxide environment with a consumable electrode in a gas environment.

Welding materials for electric arc welding

Welding materials for gas shielded welding

Welding materials for submerged arc welding

Welding materials for welding St3ps steel with other steels

Temperature of preliminary and accompanying heating and tempering when welding structures made of St3ps steel

Recommended welding modes for correcting weld defects

NOTE. * - along with the electrode brand UONI 13/..., it is possible to use the brand UONII 13/..., depending on the designation of the brand in the specifications of the electrode manufacturer.

Modes of electric arc welding of samples and products

NOTE. * - along with the electrode brand UONI 13/..., it is possible to use the brand UONII 13/..., depending on the designation of the brand in the specifications of the electrode manufacturer.

Modes of argon arc welding of samples for incoming inspection of welding materials

Density ρ p kg/cm 3

Young's modulus (normal elasticity) E, GPa

Mechanical characteristics

Specifications

The characteristics of ST3PS steel include: weldability, hardness HB (HB 10-1), melting range, density, increase in tensile length.

Temperature of critical points, °C

Legend

Mechanical properties

Mechanical properties

Impact strength KCU (GOST 380-94)

Mechanical properties of rolled products under tension, as well as cold bending test conditions (GOST 535-2005)

NOTE

1. By agreement between the manufacturer and the consumer, the following is allowed:
   reduction in yield strength by 10 N/mm2 (1 kgf/mm2) for shaped steel with a thickness of over 20 mm;
2. reduction in relative elongation by 1% (abs.) for shaped rolled products of all thicknesses.
3. It is allowed to exceed the upper limit of tensile strength by 49.0 N/mm2 (5 kgf/mm2), and by agreement with the consumer - without limiting the upper limit of tensile strength, provided that other standards are met. At the request of the consumer, exceeding the upper limit of temporary resistance is not allowed.

Foreign analogues of 3ps steel

Physical properties

Physical properties of the material St3ps