精品人妻少妇一区二区三区,亚州视频a,五月天开心激情成人婷婷,久久永久精品网站视频

Construction steel

1, steel classification
Hardness: partial volume inside the steel surface to resist foreign objects pressed into the ability to produce plastic deformation, is a measure of the degree of soft and hard steel.
By Carbon Content: Low Carbon (C <0.25), carbon steel (C = 0.25-0.6%), high carbon (C> 0.6%)
According to the quality points: ordinary steel, high quality steel, high-grade steel
By incorporation of alloy content: low-alloy steel (alloy content <5%), the alloy (alloy amount of 5-10%), high-alloy steel (alloy volume> 10%)
BY PURPOSE: structural steel, tool steel, special steel
On civil engineering is commonly used in low carbon steel and low alloy steel
2, the technical nature of the steel
① affect the chemical composition of carbon, silicon, manganese, phosphorus, sulfur, oxygen, nitrogen steel performance
② process performance include: cold bending properties, weldability
③ mechanical properties:
⑴ tensile strength: low carbon steel by pulled from breaking through flexibility, yield enhancement, necking four stages.
⑵ toughness: steel shock load capability.
⑶ fatigue resistance: In the alternating load under the action repeatedly, within the prescribed period in the base can withstand the maximum stress fracture does not occur.
3, cold steel reinforcement, aging treatment and welding
① arc welding, contact welding
② strain aging, natural aging, artificial aging
③ civil engineering carried out at room temperature with steel cold-drawn, cold drawn, cold-rolled, to produce plastic deformation, increase the yield strength, lower ductility

And toughness.
4, steel corrosion and corrosion
① anti-corrosion measures: alloying, metal coating, non-metallic covering
② There are two types of chemical corrosion and electrochemical corrosion.
5, construction steel, steel and selection criteria
① civil engineering structural steel
⑴ same kind of steel, open-hearth steel and steel than BOF converter steel air; special killed steel is superior killed steel, killed steel is better than semi-killed steel, excellent

In boiling steel.
⑵ low carbon steel: steel grades by letter on behalf of the yield strength, yield strength values lower quality rating symbols, symbols and other four deoxy degree

Composition parts.
② Steel steel: hot-rolled steel (angles, L-beam, I-beam, channel, H-beam), cold-formed steel, steel pipes and steel (seamless steel pipe

Welded steel pipe, hot rolled steel, cold rolled steel, tread plate)
③ steel reinforced concrete: hot rolled steel, cold-rolled ribbed [CRB550 (for non-prestressed concrete), CRB650, CRB800,

CRB970, CRB1170], tendons