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What is the yield strength of S690ql structural steel?

S690QL high-strength structural steel is a special steel with a yield strength in the range of 690MPa. S960QL Structural Steel is mainly used in the manufacture of automobiles, ships, tractors, machines and other parts subject to high stress, and S690QL Steel also used in the manufacture of other large special steel products. For example, during the heating and cooling process of ordinary carbon hot-rolled round steel billets, cracks may occur or cracks may occur during rolling to break the steel ingot. Therefore, an annealing treatment must be performed before quenching to prevent this from happening; in addition, local hardened structures may appear during quenching. S690ql steel is widely used in shipbuilding, automobile and other industrial fields because of its high strength and toughness, good welding performance, high temperature plasticity and low temperature toughness. Its mechanical properties can be obtained through tensile tests. S690ql steel has a high strength value after machining or heat treatment, and can be processed with various complex stresses; but high strength does not mean that toughness must be good; at the same time, two conditions need to be met: one is that it must be able to pass through stretching Second, it must be possible to further improve the performance of the steel through heat treatment (increase the strength to twice the original).

1. Yield strength

The S690ql carbon structural steel's  yield strength is the ratio of the tensile stress at the yield point of the steel to the length of the specimen during the tensile test. When the tensile stress at the yield point reaches the yield strength of the material, the material no longer undergoes plastic deformation or cracking, and this value is called the yield strength. Because S690ql steel is a kind of carbon structural steel, there are a lot of stress corrosion cracking phenomena in the actual use process. Therefore, it is very important to effectively protect steel and avoid stress corrosion cracking in actual use. According to the relationship between yield strength and ultimate strength of steel, S690ql steel is usually used in the manufacture of stressed parts, important equipment parts, large structural parts and their parts, important pipelines, etc. of automobiles, tractors, cranes and large mechanical equipment. [Example:] The ultimate strength of the automobile front axle and final reducer packing made of S690ql steel is 300 MPa when it is cracked by stress corrosion [4];

2. Tensile strength of S690ql structural steel

Test method: At room temperature, when the strength of the metal decreases to a certain value, the tensile fracture stress is about 50 MPa, and more stretching times are required at this time. - If the yield strength is 300 MPa, the specimen can be broken only by stretching it three times, so the tensile strength can be used as an index of the yield strength. -Usually, the larger the tensile value, the smaller the yield; at the same time, the influence of deformation should also be taken into account. (In actual production, reasonable ingredients should be made according to product requirements to meet the standard requirements.)

3. Elongation

Elongation reflects the steel's ability to yield under tensile loads. Because of the strong correlation between elongation and stress, it is often referred to as the "correlation curve" (Figure 2). According to GB/T 1399-1993 "Standards for Carbon Structural Steel for Steel Structures", steel contains elements such as C and N, and the higher the content, the lower the elongation. For S690ql steel with a yield strength between 400 and 600 MPa, it is appropriate for the elongation to fluctuate between -10% and 3%.

4. Fracture toughness/elongation

Fracture shape: single fracture, smooth surface, generally triangular. Cross-sectional shape: arc-shaped (sharp at both ends, round in the middle, and blunt at both ends); Elongation after fracture: less than 1 times the maximum elongation of the material Fracture toughness: Yield strength/elongation at fracture Rate (maximum stress/yield strength in material) (%) Elongation after fracture: the amount of remaining plastic deformation before fracture.


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EN 10025-6 S690QL High Strength Steels