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E470 is a low-carbon, vanadium micro-alloyed steel. The prefix “E” signifies tubular format. The steel is characterised by considerably higher strength than conventional hollow bars in regular structural steels such as E355. In spite of the higher strength, weldability remains good and the steel is easy to machine. Tibnor’s stock programme of higher strength hollow bar is made up in part by E470 and in part by 280. Hollow bars in the latter have tighter chemical analysis, higher strength and better tolerances than their equivalents in E470.
Hollow bars in grade E470 are standardised in SS-EN 10294 - 1. The closest (discontinued) SS-designation is 2142. 280 is very similar to E470 but has a tighter control of its chemical analysis. Yield and tensile strength for E470 vary from 470 to 430 MPa and 650 to 500 MPa respectively depending on wall thickness. For 280, the levels for these tensile parameters are 5 to 10 % higher and in addition, elongation is better.
Tolerances on outside diameter and wall for E470 hollow bars are defined in SS-EN 10294 - 1. Hollow bars in 280 are characterised by somewhat tighter tolerances. The inside and outside dimensions which can be achieved after machining are important parameters. Levels for these are defined in SS-EN 10294 - 1 for outer as well as inner chucking. The designations given relate to outer chucking and concur with those given SS-EN 10294 - 1. The first 2/3 numbers denote the greatest guaranteed outside diameter while the final 2/3 relate to the lowest guaranteed inside diameter. These guaranteed dimensions apply over a length of 3 times the outside diameter or 200 mm whichever is the smaller. For inner chucking, the guaranteed dimensions after machining are generally somewhat less.
SS-EN 10294 - 1 also stipulates straightness with height of arc at most 0.001 times length.
If a guaranteed level of impact toughness is required, then both E470 and 280 respond well to normalising. However, some loss of both yield and tensile strength is to be expected after such heat treatment.