CN116148001A

CN116148001A - Method for manufacturing hollow stabilizer bar

Info

Publication number: CN116148001A
Application number: CN202211089414.7A
Authority: CN
Inventors: 樊天荣; 董杰; 廖家正; 黄竹愉
Original assignee: Zhangyi Iron And Steel Works Co ltd; Dongguan Zhangtai Metal Products Co ltd
Current assignee: Zhangyi Iron And Steel Works Co ltd; Dongguan Zhangtai Metal Products Co ltd
Priority date: 2022-09-07
Filing date: 2022-09-07
Publication date: 2023-05-23

Abstract

A method for manufacturing a hollow stabilizer bar, relating to the preparation of a tube blank, comprising: selecting steel materials for tensile test; according to the target tensile strength, the tensile strength before drawing the pipe, the characteristic parameter, the target extension coefficient and the target sectional area reduction rate of the steel are obtained; obtaining the relation between the outer diameter and the thickness of the pipe blank; selecting a target pipe blank size; selecting the size of steel; high-frequency welding to obtain the target pipe blank.

Description

Method for manufacturing hollow stabilizer bar

Technical Field

The invention relates to a manufacturing method of an automobile hollow stabilizer bar, in particular to a manufacturing method of an automobile hollow stabilizer bar welded by a seam.

Background

The conventional process (CN 109423580 and CN 110038913) of the high-frequency welded pipe blank of the hollow stabilizer bar for the automobile comprises the following steps: tubulation- > annealing heat treatment- > heading- > pickling- > involucra saponification- > drawing tube (1-3 times according to the dimensions of the tube blank- > cutting head and tail- > normalizing heat treatment- > straightening- > flaw detection- > cutting). Wherein the annealing heat treatment after the tube making aims at improving the weld joint structure to enable the weld joint structure to be close to the base material so as to facilitate the subsequent tube drawing. Normalizing heat treatment after tube drawing aims at adjusting the material organization to meet the mechanical property requirement.

In the aspect of heat treatment technology, the hollow stabilizer bar has extremely high requirements on surface quality, and excessively thick decarburized layers and microcracks cannot exist so as to ensure the fatigue resistance. Conventional heat treatment uses a continuous or batch furnace, which is maintained at a temperature above the A1 or A3 transformation point temperature of the steel for a period of time to change the material structure. The higher the temperature or the longer the holding time, the more severe the decarburization and oxidation of the surface. The existing technology usually uses atmosphere protection to reduce the occurrence of decarburization and oxidation, and relatively increases the production cost.

In the aspect of surface treatment process, acid washing is carried out after traditional heat treatment, an oxide layer with overburning on the surface is removed, and saponification is carried out, so that a layer of meticulous lubricating film is generated on the surface of the surface, and the lubricating purpose in the process of pumping pipes is provided. The solution after phosphating and saponification treatment is neutralized and purified and then discharged, so that the pollution risk is reduced.

In the aspect of the tube drawing process, the traditional tube drawing method adopts multiple times of tube drawing, process annealing is needed between tube drawing each time, the tensile strength of the tube drawing is not easy to be improved, and higher production cost is needed.

Disclosure of Invention

In order to reduce the number of drawing tubes, one embodiment of the present invention provides a method for manufacturing a hollow stabilizer bar, which comprises:

selecting a steel material and a target tensile strength of the steel material;

obtaining a tensile relation between the reduction rate of the sectional area of the steel material and the tensile strength and a tensile strength a before drawing the pipe by using a tensile test;

performing curve fitting based on lnY = lna +n×lnx by the stretching relationship, wherein Y is a tensile strength of the steel material, and X is an elongation coefficient corresponding to the reduction rate of the cross-sectional area of the steel material, so as to obtain a characteristic parameter n of the steel material;

obtaining a target elongation coefficient of the steel material according to the target tensile strength, the front tensile strength a of the pumping pipe and the characteristic parameter n;

obtaining a cross-sectional area target reduction rate RA according to the target extension coefficient;

obtaining a relation of D0 to t0 according to a relation of thickness t (D-t) = (1-RA) t0 (D0-t 0), wherein D is a target outer diameter of the drawn tube after the steel is made into a tube blank, t is a target wall thickness of the tube blank after the tube blank is drawn, D0 is a tube blank outer diameter of the tube blank, and t0 is a tube blank thickness of the tube blank;

selecting a target blank size according to the relation between D0 and t 0;

selecting a target steel size according to the target pipe blank size, rolling the steel into a shape, and then welding the steel into the target pipe blank at high frequency.

Drawings

FIG. 1 is a flow chart of a method of manufacturing an automotive stabilizer bar according to an embodiment of the present invention.

FIG. 2 is a graph of reduction in cross-sectional area versus tensile strength for one embodiment of the present invention.

FIG. 3 is a graph showing the determination of steel characteristic parameters using curve fitting according to an embodiment of the present invention.

FIG. 4 is a flowchart of a method of manufacturing an automotive stabilizer bar according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of a high frequency soldering apparatus according to an embodiment of the present invention.

FIG. 6 is a schematic illustration of a preform, according to an embodiment of the present invention.

FIG. 7 is a table showing a comparison of mechanical properties of a preform before and after induction heat treatment, in accordance with one embodiment of the present invention.

Detailed Description

Referring to fig. 1, a method for manufacturing a hollow stabilizer bar for an automobile, with respect to the preparation of a preform, in one embodiment comprises: step 10, selecting steel, carrying out a tensile test after induction heat treatment; step 11, obtaining the tensile relation between the reduction rate of the sectional area of the steel and the tensile strength before pipe drawing; step 12, obtaining characteristic parameters of the steel material through curve fitting based on a governing equation; step 13, obtaining a target elongation coefficient of the steel; step 14, obtaining the target reduction rate of the cross-sectional area of the steel material; step 15, obtaining the relation of D0 to t0, D0 being the outer diameter of the tube blank and t0 being the thickness of the tube blank; step 16, selecting a target pipe blank size; step 17, selecting the size of steel; and 18, welding the target pipe blank at high frequency.

Step 10, selecting manganese boron steel as the steel material of the hollow stabilizer bar for the automobile and the target tensile strength of the steel material, wherein in one embodiment, the steel material comprises the following components in percentage by mass: 0.20-0.40% of C, 0.15-0.40% of Si, 1.1-1.5% of Mn, 0.01-0.06% of Al, 0.05-0.3% of Cr, 0.01-0.06% of Ti, 0.001-0.005% of B, less than 0.02% of P, less than 0.01% of S, less than 0.01% of N, and the balance of Fe and unavoidable impurities.

In one embodiment, the rolled steel material is welded into a tube by high frequency welding, and the tube blank is obtained. Referring to fig. 6, the preform includes a base material 1 and a weld bead 2. Referring to fig. 7, the pipe blank is subjected to induction heat treatment at two different temperature ranges of 700 to 830C and 830 to 960C, respectively, and then subjected to a tensile test. As can be seen from a comparison table of mechanical properties of the tube blank before and after the induction heat treatment in FIG. 7, the induction heat treatments in two different temperature ranges can lead the mechanical properties of the weld bead 2 and the base material 1, such as tensile strength, yield strength and elongation, to be consistent. Wherein, after induction heat treatment, the elongation of the welding bead 2 is greatly improved, and the extensibility is greatly improved. In one embodiment, after induction heat treatment, the tensile strength a before drawing the tube is obtained by a tensile test.

In steps 11 and 12, in one embodiment, the induction heat treated pipe blank is subjected to tensile test for different reduction rates of cross-sectional area, respectively, so as to obtain a tensile relationship between the reduction rate of cross-sectional area and the tensile strength, and the graph is shown in fig. 2.RA1, RA2, RA3, RA4, RA5 represent the reduction of the cross-sectional area from small to large, respectively. In fig. 2, the solid line indicates the data of the base material in the preform, and the broken line indicates the data of the weld bead. In one embodiment, when the reduction rate is 0, the intercept of the Y axis is the tensile strength a before the steel pipe is drawn out.

Using the governing equation y=a×x ⁿ Y is tensile strength, X is elongation coefficient of the pipe blank, X=1/(1-RA) is defined, RA is reduction rate of sectional area, and lnY = lna +n is lnX, and n is characteristic parameter of the pipe blank. For different reduction rates, the tensile strength and the elongation coefficient are respectively logarithmic, so that the experimental data (solid line) of fig. 3 are obtained, and then curve fitting (curve fitting) is performed on the experimental data. The slope of the fitted straight line (dotted line) is the characteristic parameter n of the pipe embryo.

And step 13, obtaining a target elongation coefficient by using lnY = lna +n.lnX, and obtaining the tensile strength a of the tube blank before tube drawing and the characteristic parameter n of the tube blank and also the target tensile strength according to curve fitting.

Step 14, using the elongation coefficient x=1/(1-RA) of the tube blank, the target reduction ratio of the cross-sectional area of the tube blank can be obtained.

Step 15, obtaining a relation of D0 to t0 according to a relation of thickness t (D-t) = (1-RA) = (D0-t 0), wherein D is a target outer diameter of the drawn tube after the steel is made into a tube blank, t is a target wall thickness of the drawn tube after the tube blank is drawn, D0 is a tube blank outer diameter of the tube blank, and t0 is a tube blank thickness of the tube blank. In one implementation, the steel and the target tensile strength after the steel pipe is drawn are selected, the tensile strength a before the steel pipe is drawn, the characteristic parameter n of the steel, the target elongation coefficient and the target sectional area reduction rate can be obtained through the above processes, then the target sectional area reduction rate is brought into RA in the relational expression, and then the relation of D0 to t0 can be obtained by matching with the target outer diameter D and the target wall thickness t.

And 16, selecting a target size of the pipe blank and a corresponding target steel size according to the relation of D0 and t 0. Possibly selecting t0, and then manufacturing a die according to the corresponding D0; or D0 is selected, and the steel thickness of the pipe blank is selected according to the corresponding t 0. Therefore, the pipe diameter of the high-frequency welded pipe can be deduced from the thickness of the steel belt, and a proper pipe making die is selected. The steel strip with proper thickness can be purchased from the pipe diameter corresponding to the existing pipe making mould. In one embodiment, the pipe diameter of the pipe blank is determined by the existing pipe making mold, the required steel coil plate thickness is ordered to the steel mill, or the plate thickness of the existing steel coil is determined, and then the pipe making mold is developed.

And 17, rolling and forming the steel material which meets the target steel material size, and then welding the steel material into a target pipe blank at high frequency. Thus, the dimensions of the preform can be obtained by reversing the desired dimensions and mechanical properties of the finished product.

Referring to fig. 4, a method of manufacturing a hollow stabilizer bar for an automobile, in one embodiment, includes: step 200, pipe making; step 201, a first induction heat treatment; step 202, heading; step 203, oil immersion lubrication; step 204, pumping the pipe; step 205, cutting; step 206, second induction heat treatment; step 207, straightening; step 208, flaw detection; step 209, short pipe; step 210, rust prevention.

Step 200, after the steel is rolled and formed, referring to fig. 5, the left side of the pipe blank 30 is an open pipe after being subjected to high-frequency induction heating by the induction coil 34, heat is concentrated on two sides of the open end due to skin effect and proximity effect, materials are fused and combined through extrusion of the right side roller dies 31, 32 and 33, and weld flash generated after extrusion is scraped by an inner scraping device and an outer scraping device respectively, so that the inner surface and the outer surface of a weld joint of the steel pipe are smooth and smooth, and the wall thickness is uniform. And rolling the welded pipe with the inner and outer scrapes by a roller die of the sizing section, and controlling the outer diameter size and straightness. The high-frequency welded pipe after sizing and forming is inspected for weld quality through an online detection device, so that no cracking or insufficient fusion phenomenon is ensured. Finally, the blanking length is obtained through flying saw cutting, and the flying saw cutting is conveyed to a blanking table for stacking and bundling, and the subsequent heat treatment is carried out.

And 201, performing first induction heat treatment to anneal the pipe blank, adopting an induction heating mode, wherein the number of turns of an induction coil is 1-3, the heating frequency is 3-30kHz, heating the steel pipe to the heat treatment temperature of 700-960 ℃ so that the steel pipe passes through the coil at a fixed speed, and performing natural air cooling. And after annealing, the pipe blank weld joint does not have a martensite iron structure, the structure is ferrite iron and corrugated iron, and the mechanical property is uniform. The heat treated material has the mechanical properties of 500-650MPa tensile strength, 350-500MPa yield strength, elongation of over 25%, and structural characteristics of superior grain size to 8 grade, surface decarburized layer below 40 microns and surface oxide layer below 10 microns. In one embodiment, the steel tube is heated to two different temperatures, one at 700-830 degrees C and the other at 830-960 degrees C. The test results show that after the heat treatment of the two groups of parameters, the mechanical properties of the weld joint are close to those of the base metal, and the weld joint optimization purpose can be achieved by the two groups of parameters.

Step 202, reducing the head of the steel pipe, so that the reduced head of the steel pipe can enter a drawing die, and the steel pipe is convenient to clamp during drawing and is prepared for drawing.

In step 203, the induction heat treatment is adopted, the heating time is extremely short, no surface overburning oxide layer exists, the drawing oil is directly immersed for lubrication before the drawing pipe is drawn, the phosphating and saponification treatment are not carried out, and the drawing pipe is directly drawn in an oil drawing mode.

And 204, in the tube drawing process, the steel tube with the finished head and lubrication after the tube blank is annealed is placed on horizontal tube drawing equipment, the length of the steel tube before tube drawing is 4-7 meters, and 1-3 steel tubes are drawn in a single time. The shrinkage rate is 25-35% by adopting one-time pipe drawing, the pipe drawing speed is 10-25m/min, and the length of the steel pipe after pipe drawing is 6-10 m. The straight pipe after the pipe is drawn out accords with the following dimensional precision that the outer diameter tolerance is +/-0.10mm, the wall thickness tolerance is +/-0.10mm, the roundness outer diameter tolerance is 0.08mm, the surface roughness Ra is 3.2, and the mechanical properties of the straight pipe include the tensile strength of 800-900MPa, the yield strength of 500-780MPa and the elongation rate of more than 8%. Flattening the straight pipe after pipe drawing to 86% of the original pipe diameter by flattening test to generate cracking; through flaring test, the flaring of the original pipe diameter is increased by 38 percent to generate cracking.

Step 205, cut to remove the length of the header end.

At step 206, a second induction heat treatment performs a refined extraction tube anneal. The straight pipe which accords with the size after being finely pumped is treated by adopting an induction heating mode, the heating frequency is 3-30kHz, and the annealing is carried out at the heat treatment temperature of 500-750 ℃ so that the annealed straight pipe has the mechanical properties of 550-750MPa of tensile strength, 350-500MPa of yield strength, more than 15% of elongation and the structural characteristics of grain size being superior to grade 8, surface decarburized layer being below 40um and surface oxide layer being below 10um, and the dimensional precision being within +/-0.10mm of outer diameter tolerance, +/-0.10mm of wall thickness tolerance, within 0.08mm of roundness outer diameter tolerance, within 1mm/1m of straightness and within Ra3.2 of surface roughness. Flattening the heat-treated straight pipe to 50% of the original pipe diameter by flattening test; through flaring test, the flaring rate reaches 32 percent, and cracking does not occur, thereby meeting the acceptable specification of 28 percent.

In step 207, in one embodiment, a plurality of roller dies are used for straightening.

In step 208, in one embodiment, eddy currents and ultrasonic waves are used to perform non-destructive inspection of the inner and outer surfaces of the steel pipe.

Step 209, cutting the steel tube to the final specified delivery length.

Step 210, performing rust prevention treatment.

Claims

1. A method of manufacturing a hollow stabilizer bar comprising:

selecting a steel material and a target tensile strength of the steel material;

obtaining a target elongation coefficient of the steel material according to the target tensile strength, the pull-out front tensile strength a and the characteristic parameter n;

selecting a target blank size according to the relation between D0 and t 0;

2. The method of claim 1, wherein selecting a billet size based on the relationship of D0 to t0 comprises selecting D0 and purchasing a product steel based on t 0.

3. The method of claim 1, wherein selecting a preform size based on the relationship of D0 to t0 comprises selecting t0 and creating a mold based on D0.

4. The method of claim 1, further comprising, after high frequency welding the blank: the pipe blank is subjected to first induction heat treatment, then is directly immersed in oil for lubrication, and then is subjected to pipe drawing.

5. The method of claim 4, wherein the first induction heat treatment step comprises providing a heating frequency of 3K-30KHz and a heating temperature of 700-960 degrees C.

6. The method of claim 4, wherein the first induction heat treatment step comprises forming a surface decarburized layer of less than 40um and a surface oxidized layer of less than 10um on the preform, and the following tissue properties: the grain size is better than grade 8, and the following mechanical properties are achieved: the tensile strength is 500-650MPa, and the elongation is more than 25%.

7. The method of claim 4, wherein the drawing step comprises drawing the tube once to achieve the target reduction rate RA of the cross-sectional area, a surface roughness Ra3.2, and mechanical properties as follows: the tensile strength is 800-900MPa, and the elongation is more than 8%.

8. The method of claim 4, further comprising performing a second induction heat treatment on the preform after the drawing step.

9. The method of claim 8, the second induction heat treatment step comprising providing a heating frequency of 3K-30KHz and a heating temperature of 500-750 degrees C.

10. The method of claim 8, wherein the second induction heat treatment step comprises forming a surface decarburized layer of less than 40um and a surface oxidized layer of less than 10um on the preform, and the following mechanical properties: 550-750MPa of tensile strength, 350-500MPa of yield strength, more than 15% of elongation and the following tissue characteristics: the grain size is better than grade 8.