A method for rolling a 30mm x 90mm rectangular flat steel

Abstract

A 30mm*90mm rectangular flat steel rolling method, parameters as follows: 1) semi-finished product circle diameter is 90-100mm; 2) the mode of flat roller 5-flat roller 4-K4-flat roller 3-flat roller 2-K2-flat roller 1 is adopted, wherein K4, K2 are 30mm*90mm rectangular flat steel special pass; 3) limiting reduction; 4) the corresponding mill guide opening degree of flat roller 5, flat roller 4, flat roller 3, flat roller 2 is 5-8mm larger than the material type; the corresponding mill guide opening degree of K4, K2, flat roller 1 is 1-3mm larger than the material type; 5) limiting guide roller; 6) the slot width of K4 is 70-74mm, the slot bottom width is 62-65mm, the R angle radius of K4 pass slot bottom corner is 17-19mm, the r angle radius of K4 pass slot corner is 9-12mm, the side wall slope is 5-8°, and the slot depth is 40-43mm; the slot width of K2 is 30-31mm, the slot bottom width is 40-44mm, the R angle radius of K2 pass slot bottom corner is 10-12mm, the r angle radius of K2 pass slot corner is 9-12mm, the side wall slope is 3-5°, and the slot depth is 38-40mm.The application prolongs the steel quantity of rolling groove, improves the efficiency and reduces the cost.The obtained finished product size is stable, meets the requirements of customers and national standards, and has no stress cracks at corners.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of spring steel flat steel rolling, in particular to a 30mm*90mm rectangular flat steel rolling method. BACKGROUND

[0002] At present, there are few domestic spring flat steel manufacturers, the price of flat steel has obvious advantages, and the market demand is large. It is estimated that the demand for spring flat steel will be 8 million tons per year in 2024-2025, and the demand for automobile spring flat steel will be about 3 million tons. In order to achieve lightweight, the automobile industry has adopted a new spring steel plate structure, which is a variable cross-section spring steel plate with the thickest middle section of the single-piece spring and gradually thinned to both ends. Therefore, the automobile spring industry has put forward the demand for rectangular spring flat steel. Because the cross section of the finished product is rectangular, the four corners have small round angles, so it is easy to not fill the corners during rolling. At the same time, improper control of the front pass reduction and incoming material can easily lead to accidents such as folding, scratching, and twisting during rolling. If the R angle of the rectangular flat steel is not properly designed, the stress cannot be released, and stress concentration occurs, which can easily cause fatigue cracks.

[0003] Chinese patent application with publication number CN112893454A discloses a 38mm-thick rectangular spring flat steel rolling method, which is implemented according to the following steps: 1. Determine the cross-sectional size of the rectangular spring flat steel, and the round angles of the four corners of the spring flat steel are all R15mm; 2. Redesign the K2 and K4 vertical rolling hole patterns in the spring flat steel rolling production line, wherein the main parameters of the K2 hole pattern are: the distance L between the two rollers is 91mm, the roller round angle R is 15mm, the left roller depth H is 27mm, the width B is 44.62mm, the right roller width b is 38.22mm, and the main parameters of the K4 hole pattern are: the distance L1 between the two rollers is 93mm, the left roller depth H1 is 27mm, the roller round angle r is 8mm, the right roller bottom width B1 is 52.58mm, and the right roller top width B2 is 45mm; 3. The K2 and K4 adopt box hole patterns, and small reduction is adopted for K1-K2 to ensure stable material shape during rolling and meet the quality requirements of the finished product. However, according to section 4.1.3 of GBT 33164.1-2016 Spring Steel for Automotive Suspension Systems Part 1: Hot Rolled Flat Steel, the r angle is 8mm±2mm when the thickness is ≤40mm. However, the r angle of the K2 roller in the Chinese patent application with publication number CN112893454A is 15mm, and K2 is the pre-product hole pattern, which is crucial for controlling the r angle of the finished product. According to the above-mentioned patent, although it is beneficial to solve the stress concentration of the corner of the finished product, it is relatively difficult to control the size of the finished product, and the rolling process is unstable. SUMMARY

[0004] The technical problem solved by the present application is to overcome the problems of easy stress concentration at the corner of the rectangular flat steel during rolling, difficult control of the r angle shape of the finished product, relatively difficult control of the finished product size, and instability during rolling, and to provide a 30mm*90mm rectangular flat steel rolling method.

[0005] The technical solution adopted by the present application to solve its technical problem is:

[0006] A 30mm*90mm rectangular flat steel rolling method, and the specific process parameters are as follows:

[0007] 1) The semi-finished product round diameter is 90-100mm;

[0008] 2) The rectangular rolling system adopts the mode of flat roller 5-flat roller 4-K4-flat roller 3-flat roller 2-K2-flat roller 1, wherein K4 and K2 are 30mm*90mm rectangular flat steel special pass;

[0009] 3) The reduction of flat roller 5 is 25-35mm, the reduction of flat roller 4 is 15-25mm, the reduction of K4 is 18-28mm, the reduction of flat roller 3 is 5-15mm, the reduction of flat roller 2 is 5-15mm, the reduction of K2 is 9-18mm, and the reduction of flat roller 1 is 2-7mm;

[0010] In the rolling program table, the reduction is an important control parameter in the rolling process, and its size directly affects the stability of the rolling process, the product quality after rolling, and the service life of the equipment. If the reduction of each rolling mill is too small, it will cause problems such as increased product surface roughness, wrinkles, and affect the surface quality of the product; at the same time, it will cause the twisting probability between the finishing mill groups to increase, the rolling mill load between the finishing mill groups to increase, and the rolling groove between the finishing mill groups to be not wear-resistant. Too small reduction will also cause insufficient compensation of solid shrinkage, which may cause center segregation and center porosity problems to be not obviously improved. Too large reduction will increase the load of the rack, and may cause the roll to break, and may cause the molten steel which has not solidified and is rich in solute elements to flow to the adjacent bulging area, resulting in white band, negative segregation and reverse V segregation;

[0011] 4) The corresponding rolling mill guide opening of flat roller 5, flat roller 4, flat roller 3 and flat roller 2 is 5-8mm larger than the material type; the corresponding rolling mill guide opening of K4, K2 and flat roller 1 is 1-3mm larger than the material type;

[0012] 5) In order to ensure the stability of the rolled piece in the mill group, the guide roller pass of step 4) is specified, the guide roller R of flat roller 5 and flat roller 4 is 42-46mm, and the guide roller R of flat roller 3 and flat roller 2 is 38-42mm;

[0013] 6) wherein the K4 slot width (B) is designed to be 70-74mm, the slot bottom width (b) is 62-65mm, the K4 hole type slot bottom fillet R angle radius is 17-19mm, the slot opening fillet r angle radius is 9-12mm, the side wall slope is 5-8°, and the slot depth (H) is 40-43mm; the K2 slot width (B) is designed to be 30-31mm, the slot bottom width (b) is 40-44mm, the K2 hole type slot bottom fillet R angle radius is 10-12mm, the slot opening fillet r angle radius is 9-12mm, the side wall slope is 3-5°, and the slot depth (H) is 38-40mm.

[0014] Further, the rectangular flat steel error of the present application is controlled to be 30±0.5mm and 90±1mm.

[0015] The scheme of the present application is also suitable for rolling of the rectangular flat steel of (30-39) mm*90mm.

[0016] The key of the present application lies in controlling the reduction, slot width, slot bottom width, slot bottom fillet R angle and other parameters. Too small slot width and slot width gap will cause excessive wear of the roll, and even damage; the surface quality of the steel will decrease, such as indentation, scratch and the like. Too large slot width and slot width gap will affect the dimensional accuracy of the rolled steel, such as uneven thickness. At the same time, unreasonable design of the slot width and slot width gap will easily cause the twisted steel. Too small slot bottom fillet R angle will cause stress concentration between the steel and the roll during rolling, increase the risk of roll damage, and the surface quality of the steel may be affected, such as crack, indentation and the like. Too large R angle will cause the shape of the rolled steel not to meet the requirements, affecting the dimensional accuracy.

[0017] Principles and beneficial effects of the present application:

[0018] 1) The present application has low requirements for the semi-finished product round diameter, and each rolling mill can freely select according to its own equipment capacity and raw material blank section, and the semi-finished product round is controlled to be 90-100mm;

[0019] 2) The rectangular rolling system adopts the mode of flat roll 5-flat roll 4-K4-flat roll 3-flat roll 2-K2-flat roll 1, wherein the flat roll 5 and the flat roll 4 are a small system, and the reduction can be appropriately increased or decreased according to the actual situation. If the rolling groove wears too fast, the corresponding rolling mill can be opened to reduce the pressure of the rolling groove. The flat roll 3 and the flat roll 2 are a small system as above. At the same time, if any one of the flat roll 5, the flat roll 4, the flat roll 3 and the flat roll 2 corresponding to the rolling mill fails, it can be temporarily taken offline to quickly restore production;

[0020] 3) Controlling the reduction of each pass is beneficial to prolong the steel quantity of the rolling groove, improve the efficiency and reduce the cost;

[0021] 4) In the production process, the guide opening degree of the rolling mill plays a crucial role, and if the guide opening degree is too large, the rolled piece is prone to twisting, biting and deviation, thereby causing serious accidents such as steel stacking, steel running and the like, and causing significant damage to personnel and equipment. If the guide opening degree is too small, the guide roller is prone to wear, causing indentation and folding quality accidents. Therefore, the opening degree and the guide opening degree of the guide roller are standardized;

[0022] 5) Rectangular flat steel is prone to crack due to stress concentration at the corner during rolling, and the finished product r angle shape is difficult to control, because the pass distribution is uneven and the pass design is unreasonable. The R angle radius of the K4 design pass groove bottom is 17-19mm, the R angle radius of the K2 pass groove bottom is 10-12mm, and the R angle radius gradually decreases, which is beneficial to the control of the finished product R angle. At the same time, the K4 pass amount is greater than the K2, which is beneficial to the stress release of the finished product R angle, and at the same time, the very small pass amount of the finished product rolling mill further releases the corner stress while ensuring the shape of the R angle.

[0023] The beneficial effects of the present application are:

[0024] 1. The rectangular rolling system adopts the mode of flat roller 5-flat roller 4-K4-flat roller 3-flat roller 2-K2-flat roller 1, if any one of the flat roller 5, the flat roller 4, the flat roller 3 and the flat roller 2 corresponding to any one of the rolling mills fails, it can be temporarily taken offline to quickly restore production.

[0025] 2. The length of the rolling groove is extended, the efficiency is improved, and the cost is reduced.

[0026] 3. The finished product size is stable, meets the requirements of customers and national standards, and the corner has no stress crack. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a schematic diagram of the cross-sectional size of the spring flat steel in the present application;

[0028] Figure 2 It is a size diagram of the K4 pass in the present application;

[0029] Figure 3 It is a size diagram of the K2 pass in the present application;

[0030] Figure 4 It is a finished product diagram of the rectangular flat steel without corresponding defects obtained by the embodiment of the present application;

[0031] Figure 5 It is a physical picture of rotten steel and folding caused by unreasonable R angle design in the prior art;

[0032] Figure 6 It is a picture of twisting and stacking accidents caused by unreasonable design in the prior art. DETAILED DESCRIPTION

[0033] The application will be described in further detail below in connection with specific embodiments and drawings.

[0034] Example 1: 30mm x 90mm rectangular flat steel rolling

[0035] The 30mm x 90mm rectangular flat steel rolling method of the present embodiment has the following specific process parameters:

[0036] 1) The semi-finished product has a circular diameter of 96mm;

[0037] 2) The rectangular rolling system adopts a mode of flat roller 5-flat roller 4-K4-flat roller 3-flat roller 2-K2-flat roller 1, wherein K4 and K2 are special hole patterns for 30mm x 90mm rectangular flat steel;

[0038] 3) The reduction of flat roller 5 is 30mm, the reduction of flat roller 4 is 19.5mm, the reduction of K4 is 21mm, the reduction of flat roller 3 is 10mm, the reduction of flat roller 2 is 12.5mm, the reduction of K2 is 17.5mm, and the reduction of flat roller 1 is 5.7mm;

[0039] 4) The corresponding mill guide opening of flat roller 5, flat roller 4, flat roller 3, and flat roller 2 is 6mm larger than the material type; the corresponding mill guide opening of K4, K2, and flat roller 1 is 2mm larger than the material type;

[0040] 5) In order to ensure the stability of the rolled piece in the mill train, the guide roller hole pattern in step 4) is specified, and the guide roller R of flat roller 5 and flat roller 4 is 44mm, and the guide roller R of flat roller 3 and flat roller 2 is 40mm;

[0041] 6) Among them, the slot width (B) of K4 is designed to be 72mm, the slot bottom width (b) is 63mm, the K4 hole pattern slot bottom corner radius R is 18mm, the slot opening corner radius r is 10mm, the side wall slope is 6°, and the slot depth (H) is 43mm; the slot width (B) of K2 is designed to be 30mm, the slot bottom width (b) is 42mm, the K2 hole pattern slot bottom corner radius R is 12mm, the slot opening corner radius r is 10mm, the side wall slope is 4°, and the slot depth (H) is 40mm.

[0042] The 30mm x 90mm rectangular flat steel rolling parameters of the present embodiment are shown in Table 1 below:

[0043] Table 1

[0044] ;

[0045] The beneficial effects of the present embodiment are:

[0046] 1. The rectangular rolling system adopts the pattern of flat roll 5-flat roll 4-K4-flat roll 3-flat roll 2-K2-flat roll 1. If any of the rolling mills corresponding to flat roll 5, flat roll 4, flat roll 3, or flat roll 2 malfunctions, it can be temporarily taken offline and production can be quickly restored.

[0047] 2. Extend the steel passage in the rolling groove to improve efficiency while reducing costs.

[0048] 3. The finished product has stable dimensions, meets customer and national standards, and has no stress cracks at the corners.

Claims

1. A method for rolling 30mm×90mm rectangular flat steel, characterized in that, The specific process parameters are as follows: 1) The diameter of the semi-finished circle is 90-100mm; 2) The rectangular rolling system adopts the pattern of flat roll 5-flat roll 4-K4-flat roll 3-flat roll 2-K2-flat roll 1, where K4 and K2 are special die types for 30mm×90mm rectangular flat steel; 3) The pressing amount of flat roller 5 is 25-35mm, the pressing amount of flat roller 4 is 15-25mm, the pressing amount of K4 is 18-28mm, the pressing amount of flat roller 3 is 5-15mm, the pressing amount of flat roller 2 is 5-15mm, the pressing amount of K2 is 9-18mm, and the pressing amount of flat roller 1 is 2-7mm. 4) The opening degree of the mill guides corresponding to flat rolls 5, 4, 3, and 2 is 5-8mm larger than that of the material; the opening degree of the mill guides corresponding to K4, K2, and 1 is 1-3mm larger than that of the material. 5) To ensure the stability of the rolled piece in the unit, the guide roller profile in step 4) is standardized. The guide roller R in flat roll 5 and flat roll 4 is 42-46mm, and the guide roller R in flat roll 3 and flat roll 2 is 38-42mm. 6) The K4 slot has a width of 70-74mm, a bottom width of 62-65mm, a bottom radius of 17-19mm, a top radius of 9-12mm, a sidewall slope of 5-8°, and a depth of 40-43mm. The K2 slot has a width of 30-31mm, a bottom width of 40-44mm, a bottom radius of 10-12mm, a top radius of 9-12mm, a sidewall slope of 3-5°, and a depth of 38-40mm.

2. The method for rolling 30mm×90mm rectangular flat steel according to claim 1, characterized in that, The error control for rectangular flat steel is 30±0.5mm and 90±1mm.

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