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Method for producing improved stainless steel seamless steel pipe

A technology for seamless steel pipes and production methods, applied in forming tools, rolling mill control devices, metal rolling, etc., can solve the problems of high notch sensitivity, poor surface quality, and difficult processing, etc., to overcome the thin wall of steel pipes, The outer diameter and wall thickness tolerance is small, and the effect of improving the product qualification rate

Inactive Publication Date: 2009-03-04
JIANGSU HONGBAO GROUP CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, because the yield strength of this type of material is relatively high, it is difficult to process it. In the existing production methods of martensitic stainless steel seamless steel pipes, in the processes of piercing and rolling, hot piercing combined with hot rolling or Continuous casting and rolling, such as the methods disclosed in Chinese patents CN96116963.X, CN90109547.8, CN200510059854.8, CN200610038586.6, and these methods focus on the adjustment of trace elements in the material or quenching-tempering, etc. However, these existing production processes still have defects: the outer diameter and wall thickness tolerance of the steel pipe after processing is relatively large, and the surface quality is poor, usually manifested as rough surface, unevenness and cracks, etc.
[0003] In particular, the straightening steps in the prior art all adopt normal temperature straightening, but because martensitic stainless steel has the characteristics of high yield coefficient and high notch sensitivity, the traditional straightening at room temperature is either difficult to straighten to the required straightness level, Either be cracked, resulting in lower yield

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0028] The improved production method of stainless steel seamless steel pipe of the present invention includes the steps of heating the tube blank, piercing, rolling, pickling and straightening, wherein in the straightening step, before straightening, First heat the pipe fittings to 100-200°C. More specifically, before the pipe fittings enter the straightening machine, the pipe fittings are heated to 100-200° C. by an induction heating coil and then straightened. This kind of process makes the steel pipe not easy to straighten and crack, and the straightness of the steel pipe after straightening is better, and the bending degree is less than 1.5mm / m.

[0029] The inventor used 50 2Cr13, 73×6mm pipes and divided them into 5 groups for straightening, and obtained the results in the following table:

[0030] Specifications (mm) The number of heating temperature Curvature(mm / m) Surface Quality 73×6 10 room temperature, no heating 2.5、2.8、3.0、3.1、3.05 Th...

Embodiment 2

[0032] The main difference between this embodiment and the above embodiments lies in the piercing step and the rolling step. The piercing step is a continuous, equal-diameter hot piercing process, and the plug in the hot piercing process is a non-wearing plug, and immediately enters the cold rolling step after the hot piercing, and the cold rolling step adopts a large amount of deformation, That is, the single-pass deformation is 1.4-1.6mm, and the wall reduction and diameter reduction of the steel pipe are required to be greater than 1:3.

[0033] The inventor used a 90×7.5mm waste pipe to roll it into a 73×6mm seamless steel pipe, and the sample size was 5 pieces. The specific data are shown in the table below: Unit: mm

[0034] serial number Size before rolling Rolled products Outer diameter size (four points) Wall thickness tolerance (four points) 1 90×7.5 73×6 73.32，73.1，72.7，72.9 6.25，6.35，6.28，6.05 2 90×7.5 73×6 73.28，73.14，72.7，72.85 6...

Embodiment 3

[0036] The main difference between this embodiment and the above embodiments lies in the pickling step in the production process of seamless steel pipes. In the production method of the present invention, the pickling solution used in the pickling step is 20-30% sulfuric acid solution, and , 0.5-5% NaCl and 1-10% NaNO are also added to the pickling solution 3 As a sustained release agent, in addition, in the pickling step, the pickling solution is heated to a temperature of 50-80°C. This cleans the scale surface and leaves it smooth without over-pickling.

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Abstract

The invention relates to a method for producing an improved stainless steel seamless steel pipe, which comprises the steps of heating, piercing, rolling, acid cleaning and straightening a pipe blank, wherein the pipe blank is heated up to 100-200 DEG C before being straightened in the step of straightening; and before entering a straightening machine, the pipe blank is heated up through induction heating coils. The invention further adopts a mild straightening process in the step of straightening, and before entering a straightening machine, the pipe blank is heated up to 100-200 DEG C through the induction heating coils, thereby ensuring that the seamless steel pipe has little possibility in crack rectification and the produced steel pipe has fine straightness and degree of curve being less than 1.5mm / m. In addition, the invention adopts a continuous and equal-diameter hot piercing process and adopts a cold rolling process in the rolling process, thereby effectively preventing pipe materials from being unevenly deformed; and the produced steel pipe has the advantages of small tolerance between the outer diameter and the wall thickness, high accuracy, and better quality and more smooth surface.

Description

Technical field: [0001] The present invention relates to a production method of a seamless steel pipe, more particularly, relates to an improved production method of a martensitic stainless steel seamless steel pipe. Background technique: [0002] Martensitic stainless steel such as 1Cr13 and 1Cr12Mo has the advantages of good corrosion resistance, high toughness and good cold deformation performance, and it has good vibration damping properties, and is widely used in steam turbines, stationary blades, and compressors. Guide vanes and other corrosion-resistant parts, such as generator water tanks, water tank rings, center pipes, water joint flanges, etc., can also be used in important fields such as the nuclear industry. According to its thermal strength, it can be used below 450 °C. However, because the yield strength of this type of material is relatively high, it is difficult to process it. In the existing production methods of martensitic stainless steel seamless steel p...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B21B15/00B21D3/00B21D37/16B21B19/04B21B19/06B21B37/78C23G1/02C23G1/04
Inventor 王忠华
Owner JIANGSU HONGBAO GROUP CO LTD
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