GB2157199A

GB2157199A - Ribbed cold worked high yield model reinforcement

Info

Publication number: GB2157199A
Application number: GB08409193A
Authority: GB
Inventors: Dr Faiz Alam Noor
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-04-09
Filing date: 1984-04-09
Publication date: 1985-10-23
Also published as: GB8409193D0; GB2157199B

Abstract

Reinforcement wire for concrete is made from steel wire with a carbon content >0.2% by heat treatment before cold raking with grooved rolls, straightening and again heat treating.

Description

SPECIFICATION Ribbed cold worked high yield model reinforcement This invention relates to the production of high yield steel reinforcement, less than 4.2mm in diameter, for microconcrete models. Microconcrete may be defined as concrete in which the maximum aggregate size is less than 5mm.

It is generally understood that for adequate bond with microconcrete, the surface of wire needs to be deformed. Whilst low carbon wire can be deformed easily, it cannot be heat-treated to give the stress-strain characteristics of the prototype, ribbed, hot rolled high yield steel bars. Cold rolling of a wire with a greater carbon content would not be expected to give the similitude of stress-strain characteristics and the ratio of rib height to effective diamter of prototype bars. The effective diameter is that used in strength calculations.

A new process has been developed for producing straight lengths of model reinforcement with the typical stress-strain characteristics given in Figure 1. The curve illustrated shows that for a model reinforcement with a yield strength, fy in the range of 410 to 650 N/mm2 there is a sharp yield point, a yield plateau extending beyond a strain, E,, of0.01, a strain hardening effect and an ultimate strain, Eu, greater than 0.1. These properties are close to those of prototype bars, manufactured in accordance with BS 4449.

It has been found that the above properties can be obtained if a steel wire with a carbon content in excess of 0.2% is heat-treated, at a temperature of about 650"C before and after cold rolling, with appropriate dies, in order to produce deformations on the surface. The two periods of heat-treatment vary with the carbon content of the steel, the diameter of the wire, the degree of surface deformations and the desired yield strength. In order to obtain given properties accuractely, rapid cooling is necessary at the end of the final heat-treatment.

The variable speed mill used is shown in Figure 2. It consists of a pair of rolls with bearings 1 under pressure. The dies 2 are linked to the central bolt 3 with the keys 4. The dies 2 are thicker at the keyways 5 with their sides clamped by the aid of side pieces 6, nuts 7 and washers 8. Another illustration of the dies, which form the ribs is given in Figure 3. Their essential features are the long keyway 1, for transmitting the high torque required, and the shallow groove 2, with slots for forming the ribs on the wire. It has also been found that in order to model the ratio of rib height to effective diameter of the prototype bars, it is necessary to make the width of groove greater than the initial diameter of wire before rolling and depth less than the effective radius after rolling. Figure 4 shows some dimensional details of the model reinforcement.The ribs 1 have a thickness, t, of 0.5mm and a spacing, s, of about 0.7 x effective diameter. The maximum rib height is 2 (D2 - De) and the effective diamter is approximately V(1.05 D,D,).

For minimum variation of properties of model reinforcement, it is necessary to straighten the wire immediately after rolling and before the final heattreatment. The tube furnace required to treat straight lengths should have an inert atmosphere to prevent oxidation whilst limiting the variation of temperature along its working length to t 5"C. It should be noted that before the product is marketed large quantities of the model reinforcement will need to be produced at reasonable cost, and further improvements in the design of the rolling mill are envisaged.

Ribbed cold worked high yield model reinforcement 1. Cold worked high yield model reinforcement produced by a process in which steel wire with a carbon content in excess of 0.2% is heat-treated before cold-rolling with special dies, straightened and heat-treated again in a tube furnace with an inert atmosphere.

2. Cold worked high yield model reinforcement, as in Claim 1, produced with the following properties: a) Effective diameters in the range of 2.0 4.2mm.

b) Ratio of rib height to effective diameter greater than or equal to that of prototype steel bars.

c) A stress-strain relationship which shows a sharp yield point, a yield strength in the range of 410 to 650N/mm2, a yield plateau extending beyond a strain of 0.01, a strain hardening effect and an ultimate strain greater than 0.1, as shown in Figure 1.

3. Cold worked high yield model reinforcement, as claimed in 1 and 2, rolled with dies having a long key-way for good torque transmission.

4. Cold worked high yield model reinforcement, as claimed in 1, 2 and 3, rolled with dies which have a slotted circumferential groove, wider than the initial diameter of the material with a depth less than the effective radius of the model reinforcement.

5. Cold worked high yield model reinforcement, as claimed in 1 and 2, rolled in a mill, incorporating the dies claimed in 3 and 4, which is illustrated in Figure 2.

6. Cold worked high yield model reinforcement as claimed in 1 and 2, which is straightened immediately after rolling and before the final heat-treatment.

7. Cold worked high yield model reinforcement, as claimed in 1 and 2, which is heat treated in a tube with an inert atmosphere and a uniform temperature zone where the temperature variation at 650 is limited to t 5 C.

8. Cold worked high yield model reinforcement, as described above, with reference to Figures 1-4 of the accompanying drawings.

Amendments to the claims have been filed, and have the following effect: (b) New or textually amended claims have been

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Ribbed cold worked high yield model reinforcement This invention relates to the production of high yield steel reinforcement, less than 4.2mm in diameter, for microconcrete models. Microconcrete may be defined as concrete in which the maximum aggregate size is less than 5mm. It is generally understood that for adequate bond with microconcrete, the surface of wire needs to be deformed. Whilst low carbon wire can be deformed easily, it cannot be heat-treated to give the stress-strain characteristics of the prototype, ribbed, hot rolled high yield steel bars. Cold rolling of a wire with a greater carbon content would not be expected to give the similitude of stress-strain characteristics and the ratio of rib height to effective diamter of prototype bars. The effective diameter is that used in strength calculations. A new process has been developed for producing straight lengths of model reinforcement with the typical stress-strain characteristics given in Figure 1. The curve illustrated shows that for a model reinforcement with a yield strength, fy in the range of 410 to 650 N/mm2 there is a sharp yield point, a yield plateau extending beyond a strain, E,, of0.01, a strain hardening effect and an ultimate strain, Eu, greater than 0.1. These properties are close to those of prototype bars, manufactured in accordance with BS 4449. It has been found that the above properties can be obtained if a steel wire with a carbon content in excess of 0.2% is heat-treated, at a temperature of about 650"C before and after cold rolling, with appropriate dies, in order to produce deformations on the surface. The two periods of heat-treatment vary with the carbon content of the steel, the diameter of the wire, the degree of surface deformations and the desired yield strength. In order to obtain given properties accuractely, rapid cooling is necessary at the end of the final heat-treatment. The variable speed mill used is shown in Figure 2. It consists of a pair of rolls with bearings 1 under pressure. The dies 2 are linked to the central bolt 3 with the keys 4. The dies 2 are thicker at the keyways 5 with their sides clamped by the aid of side pieces 6, nuts 7 and washers 8. Another illustration of the dies, which form the ribs is given in Figure 3. Their essential features are the long keyway 1, for transmitting the high torque required, and the shallow groove 2, with slots for forming the ribs on the wire. It has also been found that in order to model the ratio of rib height to effective diameter of the prototype bars, it is necessary to make the width of groove greater than the initial diameter of wire before rolling and depth less than the effective radius after rolling. Figure 4 shows some dimensional details of the model reinforcement.The ribs 1 have a thickness, t, of 0.5mm and a spacing, s, of about 0.7 x effective diameter. The maximum rib height is 2 (D2 - De) and the effective diamter is approximately V(1.05 D,D,). For minimum variation of properties of model reinforcement, it is necessary to straighten the wire immediately after rolling and before the final heattreatment. The tube furnace required to treat straight lengths should have an inert atmosphere to prevent oxidation whilst limiting the variation of temperature along its working length to t 5"C. It should be noted that before the product is marketed large quantities of the model reinforcement will need to be produced at reasonable cost, and further improvements in the design of the rolling mill are envisaged. CLAIMS Ribbed cold worked high yield model reinforcement

1. Cold worked high yield model reinforcement produced by a process in which steel wire with a carbon content in excess of 0.2% is heat-treated before cold-rolling with special dies, straightened and heat-treated again in a tube furnace with an inert atmosphere.

5. Cold worked high yield model reinforcement, as claimed in 1 and 2, rolled in a mill, incorporating the dies claimed in 3 and 4.

Amendments to the claims have been filed, and have the following effect: (b) New or textually amended claims have been filed as follows:

4. Cold worked high yield model reinforcementt, as claimed in 1, 2 and 3, rolled with dies which have a slotted circumferential groove, wider than the initial diameter of the material with a depth less than the effective radius of the model reinforcement.